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Sample records for niche modelling electronic

  1. Does niche divergence accompany allopatric divergence in Aphelocoma jays as predicted under ecological speciation? Insights from tests with niche models.

    Science.gov (United States)

    McCormack, John E; Zellmer, Amanda J; Knowles, L Lacey

    2010-05-01

    The role of ecology in the origin of species has been the subject of long-standing interest to evolutionary biologists. New sources of spatially explicit ecological data allow for large-scale tests of whether speciation is associated with niche divergence or whether closely related species tend to be similar ecologically (niche conservatism). Because of the confounding effects of spatial autocorrelation of environmental variables, we generate null expectations for niche divergence for both an ecological-niche modeling and a multivariate approach to address the question: do allopatrically distributed taxa occupy similar niches? In a classic system for the study of niche evolution--the Aphelocoma jays--we show that there is little evidence for niche divergence among Mexican Jay (A. ultramarina) lineages in the process of speciation, contrary to previous results. In contrast, Aphelocoma species that exist in partial sympatry in some regions show evidence for niche divergence. Our approach is widely applicable to the many cases of allopatric lineages in the beginning stages of speciation. These results do not support an ecological speciation model for Mexican Jay lineages because, in most cases, the allopatric environments they occupy are not significantly more divergent than expected under a null model.

  2. Advances and Limitations of Disease Biogeography Using Ecological Niche Modeling.

    Science.gov (United States)

    Escobar, Luis E; Craft, Meggan E

    2016-01-01

    Mapping disease transmission risk is crucial in public and animal health for evidence based decision-making. Ecology and epidemiology are highly related disciplines that may contribute to improvements in mapping disease, which can be used to answer health related questions. Ecological niche modeling is increasingly used for understanding the biogeography of diseases in plants, animals, and humans. However, epidemiological applications of niche modeling approaches for disease mapping can fail to generate robust study designs, producing incomplete or incorrect inferences. This manuscript is an overview of the history and conceptual bases behind ecological niche modeling, specifically as applied to epidemiology and public health; it does not pretend to be an exhaustive and detailed description of ecological niche modeling literature and methods. Instead, this review includes selected state-of-the-science approaches and tools, providing a short guide to designing studies incorporating information on the type and quality of the input data (i.e., occurrences and environmental variables), identification and justification of the extent of the study area, and encourages users to explore and test diverse algorithms for more informed conclusions. We provide a friendly introduction to the field of disease biogeography presenting an updated guide for researchers looking to use ecological niche modeling for disease mapping. We anticipate that ecological niche modeling will soon be a critical tool for epidemiologists aiming to map disease transmission risk, forecast disease distribution under climate change scenarios, and identify landscape factors triggering outbreaks.

  3. Framework for analyzing ecological trait-based models in multidimensional niche spaces

    Science.gov (United States)

    Biancalani, Tommaso; DeVille, Lee; Goldenfeld, Nigel

    2015-05-01

    We develop a theoretical framework for analyzing ecological models with a multidimensional niche space. Our approach relies on the fact that ecological niches are described by sequences of symbols, which allows us to include multiple phenotypic traits. Ecological drivers, such as competitive exclusion, are modeled by introducing the Hamming distance between two sequences. We show that a suitable transform diagonalizes the community interaction matrix of these models, making it possible to predict the conditions for niche differentiation and, close to the instability onset, the asymptotically long time population distributions of niches. We exemplify our method using the Lotka-Volterra equations with an exponential competition kernel.

  4. Ecological Niche Modelling of Bank Voles in Western Europe

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    Sara Amirpour Haredasht

    2013-01-01

    Full Text Available The bank vole (Myodes glareolus is the natural host of Puumala virus (PUUV in vast areas of Europe. PUUV is one of the hantaviruses which are transmitted to humans by infected rodents. PUUV causes a general mild form of hemorrhagic fever with renal syndrome (HFRS called nephropathia epidemica (NE. Vector-borne and zoonotic diseases generally display clear spatial patterns due to different space-dependent factors. Land cover influences disease transmission by controlling both the spatial distribution of vectors or hosts, as well as by facilitating the human contact with them. In this study the use of ecological niche modelling (ENM for predicting the geographical distribution of bank vole population on the basis of spatial climate information is tested. The Genetic Algorithm for Rule-set Prediction (GARP is used to model the ecological niche of bank voles in Western Europe. The meteorological data, land cover types and geo-referenced points representing the locations of the bank voles (latitude/longitude in the study area are used as the primary model input value. The predictive accuracy of the bank vole ecologic niche model was significant (training accuracy of 86%. The output of the GARP models based on the 50% subsets of points used for testing the model showed an accuracy of 75%. Compared with random models, the probability of such high predictivity was low (χ2 tests, p < 10−6. As such, the GARP models were predictive and the used ecologic niche model indeed indicates the ecologic requirements of bank voles. This approach successfully identified the areas of infection risk across the study area. The result suggests that the niche modelling approach can be implemented in a next step towards the development of new tools for monitoring the bank vole’s population.

  5. Ecological niche modelling of bank voles in Western Europe.

    Science.gov (United States)

    Amirpour Haredasht, Sara; Barrios, Miguel; Farifteh, Jamshid; Maes, Piet; Clement, Jan; Verstraeten, Willem W; Tersago, Katrien; Van Ranst, Marc; Coppin, Pol; Berckmans, Daniel; Aerts, Jean-Marie

    2013-01-28

    The bank vole (Myodes glareolus) is the natural host of Puumala virus (PUUV) in vast areas of Europe. PUUV is one of the hantaviruses which are transmitted to humans by infected rodents. PUUV causes a general mild form of hemorrhagic fever with renal syndrome (HFRS) called nephropathia epidemica (NE). Vector-borne and zoonotic diseases generally display clear spatial patterns due to different space-dependent factors. Land cover influences disease transmission by controlling both the spatial distribution of vectors or hosts, as well as by facilitating the human contact with them. In this study the use of ecological niche modelling (ENM) for predicting the geographical distribution of bank vole population on the basis of spatial climate information is tested. The Genetic Algorithm for Rule-set Prediction (GARP) is used to model the ecological niche of bank voles in Western Europe. The meteorological data, land cover types and geo-referenced points representing the locations of the bank voles (latitude/longitude) in the study area are used as the primary model input value. The predictive accuracy of the bank vole ecologic niche model was significant (training accuracy of 86%). The output of the GARP models based on the 50% subsets of points used for testing the model showed an accuracy of 75%. Compared with random models, the probability of such high predictivity was low (χ(2) tests, p < 10(-6)). As such, the GARP models were predictive and the used ecologic niche model indeed indicates the ecologic requirements of bank voles. This approach successfully identified the areas of infection risk across the study area. The result suggests that the niche modelling approach can be implemented in a next step towards the development of new tools for monitoring the bank vole's population.

  6. Improved Predictions of the Geographic Distribution of Invasive Plants Using Climatic Niche Models

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    Ramírez-Albores, Jorge E.; Bustamante, Ramiro O.

    2016-01-01

    Climatic niche models for invasive plants are usually constructed with occurrence records taken from literature and collections. Because these data neither discriminate among life-cycle stages of plants (adult or juvenile) nor the origin of individuals (naturally established or man-planted), the resulting models may mispredict the distribution ranges of these species. We propose that more accurate predictions could be obtained by modelling climatic niches with data of naturally established individuals, particularly with occurrence records of juvenile plants because this would restrict the predictions of models to those sites where climatic conditions allow the recruitment of the species. To test this proposal, we focused on the Peruvian peppertree (Schinus molle), a South American species that has largely invaded Mexico. Three climatic niche models were constructed for this species using high-resolution dataset gathered in the field. The first model included all occurrence records, irrespective of the life-cycle stage or origin of peppertrees (generalized niche model). The second model only included occurrence records of naturally established mature individuals (adult niche model), while the third model was constructed with occurrence records of naturally established juvenile plants (regeneration niche model). When models were compared, the generalized climatic niche model predicted the presence of peppertrees in sites located farther beyond the climatic thresholds that naturally established individuals can tolerate, suggesting that human activities influence the distribution of this invasive species. The adult and regeneration climatic niche models concurred in their predictions about the distribution of peppertrees, suggesting that naturally established adult trees only occur in sites where climatic conditions allow the recruitment of juvenile stages. These results support the proposal that climatic niches of invasive plants should be modelled with data of

  7. Introducing MERGANSER: A Flexible Framework for Ecological Niche Modeling

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    Klawonn, M.; Dow, E. M.

    2015-12-01

    Ecological Niche Modeling (ENM) is a collection of techniques to find a "fundamental niche", the range of environmental conditions suitable for a species' survival in the absence of inter-species interactions, given a set of environmental parameters. Traditional approaches to ENM face a number of obstacles including limited data accessibility, data management problems, computational costs, interface usability, and model validation. The MERGANSER system, which stands for Modeling Ecological Residency Given A Normalized Set of Environmental Records, addresses these issues through powerful data persistence and flexible data access, coupled with a clear presentation of results and fine-tuned control over model parameters. MERGANSER leverages data measuring 72 weather related phenomena, land cover, soil type, population, species occurrence, general species information, and elevation, totaling over 1.5 TB of data. To the best of the authors' knowledge, MERGANSER uses higher-resolution spatial data sets than previously published models. Since MERGANSER stores data in an instance of Apache SOLR, layers generated in support of niche models are accessible to users via simplified Apache Lucene queries. This is made even simpler via an HTTP front end that generates Lucene queries automatically. Specifically, a user need only enter the name of a place and a species to run a model. Using this approach to synthesizing model layers, the MERGANSER system has successfully reproduced previously published niche model results with a simplified user experience. Input layers for the model are generated dynamically using OpenStreetMap and SOLR's spatial search functionality. Models are then run using either user-specified or automatically determined parameters after normalizing them into a common grid. Finally, results are visualized in the web interface, which allows for quick validation. Model results and all surrounding metadata are also accessible to the user for further study.

  8. Range bagging: a new method for ecological niche modelling from presence-only data.

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    Drake, John M

    2015-06-06

    The ecological niche is the set of environments in which a population of a species can persist without introduction of individuals from other locations. A good mathematical or computational representation of the niche is a prerequisite to addressing many questions in ecology, biogeography, evolutionary biology and conservation. A particularly challenging question for ecological niche modelling is the problem of presence-only modelling. That is, can an ecological niche be identified from records drawn only from the set of niche environments without records from non-niche environments for comparison? Here, I introduce a new method for ecological niche modelling from presence-only data called range bagging. Range bagging draws on the concept of a species' environmental range, but was inspired by the empirical performance of ensemble learning algorithms in other areas of ecological research. This paper extends the concept of environmental range to multiple dimensions and shows that range bagging is computationally feasible even when the number of environmental dimensions is large. The target of the range bagging base learner is an environmental tolerance of the species in a projection of its niche and is therefore an ecologically interpretable property of a species' biological requirements. The computational complexity of range bagging is linear in the number of examples, which compares favourably with the main alternative, Qhull. In conclusion, range bagging appears to be a reasonable choice for niche modelling in applications in which a presence-only method is desired and may provide a solution to problems in other disciplines where one-class classification is required, such as outlier detection and concept learning.

  9. The inverse niche model for food webs with parasites

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    Warren, Christopher P.; Pascual, Mercedes; Lafferty, Kevin D.; Kuris, Armand M.

    2010-01-01

    Although parasites represent an important component of ecosystems, few field and theoretical studies have addressed the structure of parasites in food webs. We evaluate the structure of parasitic links in an extensive salt marsh food web, with a new model distinguishing parasitic links from non-parasitic links among free-living species. The proposed model is an extension of the niche model for food web structure, motivated by the potential role of size (and related metabolic rates) in structuring food webs. The proposed extension captures several properties observed in the data, including patterns of clustering and nestedness, better than does a random model. By relaxing specific assumptions, we demonstrate that two essential elements of the proposed model are the similarity of a parasite's hosts and the increasing degree of parasite specialization, along a one-dimensional niche axis. Thus, inverting one of the basic rules of the original model, the one determining consumers' generality appears critical. Our results support the role of size as one of the organizing principles underlying niche space and food web topology. They also strengthen the evidence for the non-random structure of parasitic links in food webs and open the door to addressing questions concerning the consequences and origins of this structure.

  10. Mechanistic species distribution modeling reveals a niche shift during invasion.

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    Chapman, Daniel S; Scalone, Romain; Štefanić, Edita; Bullock, James M

    2017-06-01

    Niche shifts of nonnative plants can occur when they colonize novel climatic conditions. However, the mechanistic basis for niche shifts during invasion is poorly understood and has rarely been captured within species distribution models. We quantified the consequence of between-population variation in phenology for invasion of common ragweed (Ambrosia artemisiifolia L.) across Europe. Ragweed is of serious concern because of its harmful effects as a crop weed and because of its impact on public health as a major aeroallergen. We developed a forward mechanistic species distribution model based on responses of ragweed development rates to temperature and photoperiod. The model was parameterized and validated from the literature and by reanalyzing data from a reciprocal common garden experiment in which native and invasive populations were grown within and beyond the current invaded range. It could therefore accommodate between-population variation in the physiological requirements for flowering, and predict the potentially invaded ranges of individual populations. Northern-origin populations that were established outside the generally accepted climate envelope of the species had lower thermal requirements for bud development, suggesting local adaptation of phenology had occurred during the invasion. The model predicts that this will extend the potentially invaded range northward and increase the average suitability across Europe by 90% in the current climate and 20% in the future climate. Therefore, trait variation observed at the population scale can trigger a climatic niche shift at the biogeographic scale. For ragweed, earlier flowering phenology in established northern populations could allow the species to spread beyond its current invasive range, substantially increasing its risk to agriculture and public health. Mechanistic species distribution models offer the possibility to represent niche shifts by varying the traits and niche responses of individual

  11. The influence of social niche on cultural niche construction: modelling changes in belief about marriage form in Taiwan

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    Lipatov, Mikhail; Brown, Melissa J.; Feldman, Marcus W.

    2011-01-01

    With introduction of social niche effects into a model of cultural change, the frequency of a practice cannot predict the frequency of its underlying belief. The combination of a general model with empirical data from a specific case illustrates the importance of collaboration between modellers and field researchers, and identifies the type of quantitative data necessary for analysing case studies. Demographic data from colonial-period household registers in Taiwan document a shift in marriage form within 40 years, from a mixture of uxorilocal marriages and virilocal marriages to the latter's dominance. Ethnographic data indicate marriage-related beliefs, costs, ethnic effects and colonial policies as well as the importance of horizontal cultural transmission. We present a formal model for the effects of moral beliefs about marriage and a population economic index on the decline of uxorilocal marriage. We integrate empirical marriage rates and an estimated economic index to produce five projections of the historical frequencies of one belief. These projections demonstrate how economic development may affect a cultural niche. They also indicate the need for future research on the relationship between wealth and cultural variability, the motivational force of cultural versus social factors, and the process of cultural niche construction. PMID:21320903

  12. Malaria in Africa: vector species' niche models and relative risk maps.

    Directory of Open Access Journals (Sweden)

    Alexander Moffett

    2007-09-01

    Full Text Available A central theoretical goal of epidemiology is the construction of spatial models of disease prevalence and risk, including maps for the potential spread of infectious disease. We provide three continent-wide maps representing the relative risk of malaria in Africa based on ecological niche models of vector species and risk analysis at a spatial resolution of 1 arc-minute (9 185 275 cells of approximately 4 sq km. Using a maximum entropy method we construct niche models for 10 malaria vector species based on species occurrence records since 1980, 19 climatic variables, altitude, and land cover data (in 14 classes. For seven vectors (Anopheles coustani, A. funestus, A. melas, A. merus, A. moucheti, A. nili, and A. paludis these are the first published niche models. We predict that Central Africa has poor habitat for both A. arabiensis and A. gambiae, and that A. quadriannulatus and A. arabiensis have restricted habitats in Southern Africa as claimed by field experts in criticism of previous models. The results of the niche models are incorporated into three relative risk models which assume different ecological interactions between vector species. The "additive" model assumes no interaction; the "minimax" model assumes maximum relative risk due to any vector in a cell; and the "competitive exclusion" model assumes the relative risk that arises from the most suitable vector for a cell. All models include variable anthrophilicity of vectors and spatial variation in human population density. Relative risk maps are produced from these models. All models predict that human population density is the critical factor determining malaria risk. Our method of constructing relative risk maps is equally general. We discuss the limits of the relative risk maps reported here, and the additional data that are required for their improvement. The protocol developed here can be used for any other vector-borne disease.

  13. Niche construction game cancer cells play.

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    Bergman, Aviv; Gligorijevic, Bojana

    2015-10-01

    Niche construction concept was originally defined in evolutionary biology as the continuous interplay between natural selection via environmental conditions and the modification of these conditions by the organism itself. Processes unraveling during cancer metastasis include construction of niches, which cancer cells use towards more efficient survival, transport into new environments and preparation of the remote sites for their arrival. Many elegant experiments were done lately illustrating, for example, the premetastatic niche construction, but there is practically no mathematical modeling done which would apply the niche construction framework. To create models useful for understanding niche construction role in cancer progression, we argue that a) genetic, b) phenotypic and c) ecological levels are to be included. While the model proposed here is phenomenological in its current form, it can be converted into a predictive outcome model via experimental measurement of the model parameters. Here we give an overview of an experimentally formulated problem in cancer metastasis and propose how niche construction framework can be utilized and broadened to model it. Other life science disciplines, such as host-parasite coevolution, may also benefit from niche construction framework adaptation, to satisfy growing need for theoretical considerations of data collected by experimental biology.

  14. Niche construction game cancer cells play

    Science.gov (United States)

    Bergman, Aviv; Gligorijevic, Bojana

    2015-10-01

    Niche construction concept was originally defined in evolutionary biology as the continuous interplay between natural selection via environmental conditions and the modification of these conditions by the organism itself. Processes unraveling during cancer metastasis include construction of niches, which cancer cells use towards more efficient survival, transport into new environments and preparation of the remote sites for their arrival. Many elegant experiments were done lately illustrating, for example, the premetastatic niche construction, but there is practically no mathematical modeling done which would apply the niche construction framework. To create models useful for understanding niche construction role in cancer progression, we argue that a) genetic, b) phenotypic and c) ecological levels are to be included. While the model proposed here is phenomenological in its current form, it can be converted into a predictive outcome model via experimental measurement of the model parameters. Here we give an overview of an experimentally formulated problem in cancer metastasis and propose how niche construction framework can be utilized and broadened to model it. Other life science disciplines, such as host-parasite coevolution, may also benefit from niche construction framework adaptation, to satisfy growing need for theoretical considerations of data collected by experimental biology.

  15. Toward a Periodic Table of Niches, or Exploring the Lizard Niche Hypervolume.

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    Pianka, Eric R; Vitt, Laurie J; Pelegrin, Nicolás; Fitzgerald, Daniel B; Winemiller, Kirk O

    2017-11-01

    Widespread niche convergence suggests that species can be organized according to functional trait combinations to create a framework analogous to a periodic table. We compiled ecological data for lizards to examine patterns of global and regional niche diversification, and we used multivariate statistical approaches to develop the beginnings for a periodic table of niches. Data (50+ variables) for five major niche dimensions (habitat, diet, life history, metabolism, defense) were compiled for 134 species of lizards representing 24 of the 38 extant families. Principal coordinates analyses were performed on niche dimensional data sets, and species scores for the first three axes were used as input for a principal components analysis to ordinate species in continuous niche space and for a regression tree analysis to separate species into discrete niche categories. Three-dimensional models facilitate exploration of species positions in relation to major gradients within the niche hypervolume. The first gradient loads on body size, foraging mode, and clutch size. The second was influenced by metabolism and terrestrial versus arboreal microhabitat. The third was influenced by activity time, life history, and diet. Natural dichotomies are activity time, foraging mode, parity mode, and habitat. Regression tree analysis identified 103 cases of extreme niche conservatism within clades and 100 convergences between clades. Extending this approach to other taxa should lead to a wider understanding of niche evolution.

  16. Insights from ecological niche modeling on the taxonomic distinction and niche differentiation between the black-spotted and red-spotted tokay geckoes (Gekko gecko).

    Science.gov (United States)

    Zhang, Yueyun; Chen, Chongtao; Li, Li; Zhao, Chengjian; Chen, Weicai; Huang, Yong

    2014-09-01

    The black-spotted tokay and the red-spotted tokay are morphologically distinct and have largely allopatric distributions. The black-spotted tokay is characterized by a small body size and dark skin with sundry spots, while the red-spotted tokay has a relatively large body size and red spots. Based on morphological, karyotypic, genetic, and distribution differences, recent studies suggested their species status; however, their classifications remain controversial, and additional data such as ecological niches are necessary to establish firm hypotheses regarding their taxonomic status. We reconstructed their ecological niches models using climatic and geographic data. We then performed niche similarity tests (niche identity and background tests) and point-based analyses to explore whether ecological differentiation has occurred, and whether such differences are sufficient to explain the maintenance of their separate segments of environmental ranges. We found that both niche models of the black- and the red-spotted tokay had a good fit and a robust performance, as indicated by the high area under the curve (AUC) values ("black" = 0.982, SD = ± 0.002, "red" = 0.966 ± 0.02). Significant ecological differentiation across the entire geographic range was found, indicating that the involvement of ecological differentiation is important for species differentiation. Divergence along the environmental axes is highly associated with climatic conditions, with isothermality being important for the "black" form, while temperature seasonality, precipitation of warmest quarter, and annual temperature range together being important for the "red" form. These factors are likely important factors in niche differentiation between the two forms, which result in morphological replacement. Overall, beside morphological and genetic differentiation information, our results contribute to additional insights into taxonomic distinction and niche differentiation between the black- and the red

  17. Divergence is not enough: the use of ecological niche models for the validation of taxon boundaries.

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    Dagnino, D; Minuto, L; Casazza, G

    2017-11-01

    Delimiting taxon boundaries is crucial for any evolutionary research and conservation regulation. In order to avoid mistaken description of species, the approach of integrative taxonomy recommends considering multidisciplinary lines of evidence, including ecology. Unfortunately, ecological data are often difficult to quantify objectively. Here we test and discuss the potential use of ecological niche models for validating taxon boundaries, using three pairs of closely related plant taxa endemic to the south-western Alps as a case study. We also discuss the application of ecological niche models for species delimitation and the implementation of different approaches. Niche overlap, niche equivalency and niche similarity were assessed both in multidimensional environmental space and in geographic space to look for differences in the niche of three pairs of closely related plant taxa. We detected a high degree of niche differentiation between taxa although this result seems not due to differences in habitat selection. The different statistical tests gave contrasting outcomes between environmental and geographic spaces. According to our results, niche divergence does not seem to support taxon boundaries at species level, but may have had important consequences for local adaptation and in generating phenotypic diversity at intraspecific level. Environmental space analysis should be preferred to geographic space as it provides more clear results. Even if the different analyses widely disagree in their conclusions about taxon boundaries, our study suggests that ecological niche models may help taxonomists to reach a decision. © 2017 German Botanical Society and The Royal Botanical Society of the Netherlands.

  18. Spatial distributions of niche-constructing populations

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    Xiaozhuo Han

    2015-12-01

    Full Text Available Niche construction theory regards organisms not only as the object of natural selection but also an active subject that can change their own selective pressure through eco-evolutionary feedbacks. Through reviewing the existing works on the theoretical models of niche construction, here we present the progress made on how niche construction influences genetic structure of spatially structured populations and the spatial-temporal dynamics of metapopulations, with special focuses on mathematical models and simulation methods. The majority of results confirmed that niche construction can significantly alter the evolutionary trajectories of structured populations. Organism-environmental interactions induced by niche construction can have profound influence on the dynamics, competition and diversity of metapopulations. It can affect fine-scale spatially distribution of species and spatial heterogeneity of the environment. We further propose a few research directions with potentials, such as applying adaptive dynamics or spatial game theory to explore the effect of niche construction on phenotypic evolution and diversification.

  19. Integrating life stages into ecological niche models: a case study on tiger beetles.

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    Taboada, Angela; von Wehrden, Henrik; Assmann, Thorsten

    2013-01-01

    Detailed understanding of a species' natural history and environmental needs across spatial scales is a primary requisite for effective conservation planning, particularly for species with complex life cycles in which different life stages occupy different niches and respond to the environment at different scales. However, niche models applied to conservation often neglect early life stages and are mostly performed at broad spatial scales. Using the endangered heath tiger beetle (Cicindela sylvatica) as a model species, we relate presence/absence and abundance data of locally dispersing adults and sedentary larvae to abiotic and biotic variables measured in a multiscale approach within the geographic extent relevant to active conservation management. At the scale of hundreds of meters, fine-grained abiotic conditions (i.e., vegetation structure) are fundamental determinants of the occurrence of both life stages, whereas the effect of biotic factors is mostly contained in the abiotic signature. The combination of dense heath vegetation and bare ground areas is thus the first requirement for the species' preservation, provided that accessibility to the suitable habitat is ensured. At a smaller scale (centimetres), the influence of abiotic factors on larval occurrence becomes negligible, suggesting the existence of important additional variables acting within larval proximity. Sustained significant correlations between neighbouring larvae in the models provide an indication of the potential impact of neighbourhood crowding on the larval niche within a few centimetres. Since the species spends the majority of its life cycle in the larval stage, it is essential to consider the hierarchical abiotic and biotic processes affecting the larvae when designing practical conservation guidelines for the species. This underlines the necessity for a more critical evaluation of the consequences of disregarding niche variation between life stages when estimating niches and

  20. Ecological niches of open ocean phytoplankton taxa

    DEFF Research Database (Denmark)

    Brun, Philipp Georg; Vogt, Meike; Payne, Mark

    2015-01-01

    We characterize the realized ecological niches of 133 phytoplankton taxa in the open ocean based on observations from the MAREDAT initiative and a statistical species distribution model (MaxEnt). The models find that the physical conditions (mixed layer depth, temperature, light) govern large...... conditions in the open ocean. Our estimates of the realized niches roughly match the predictions of Reynolds' C-S-R model for the global ocean, namely that taxa classified as nutrient stress tolerant have niches at lower nutrient and higher irradiance conditions than light stress tolerant taxa. Yet...

  1. Place prioritization for biodiversity content using species ecological niche modeling

    OpenAIRE

    Víctor Sánchez-Cordero; Verónica Cirelli; Mariana Munguial; Sahotra Sarkar

    2005-01-01

    Place prioritization for biodiversity representation is essential for conservation planning, particularly in megadiverse countries where high deforestation threatens biodiversity. Given the collecting biases and uneven sampling of biological inventories, there is a need to develop robust models of species’ distributions. By modeling species’ ecological niches using point occurrence data and digitized environmental feature maps, we can predict potential and extant distributions of species in u...

  2. Environmental niche models for riverine desert fishes and their similarity according to phylogeny and functionality

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    Whitney, James E.; Whittier, Joanna B.; Paukert, Craig P.

    2017-01-01

    Environmental filtering and competitive exclusion are hypotheses frequently invoked in explaining species' environmental niches (i.e., geographic distributions). A key assumption in both hypotheses is that the functional niche (i.e., species traits) governs the environmental niche, but few studies have rigorously evaluated this assumption. Furthermore, phylogeny could be associated with these hypotheses if it is predictive of functional niche similarity via phylogenetic signal or convergent evolution, or of environmental niche similarity through phylogenetic attraction or repulsion. The objectives of this study were to investigate relationships between environmental niches, functional niches, and phylogenies of fishes of the Upper (UCRB) and Lower (LCRB) Colorado River Basins of southwestern North America. We predicted that functionally similar species would have similar environmental niches (i.e., environmental filtering) and that closely related species would be functionally similar (i.e., phylogenetic signal) and possess similar environmental niches (i.e., phylogenetic attraction). Environmental niches were quantified using environmental niche modeling, and functional similarity was determined using functional trait data. Nonnatives in the UCRB provided the only support for environmental filtering, which resulted from several warmwater nonnatives having dam number as a common predictor of their distributions, whereas several cool- and coldwater nonnatives shared mean annual air temperature as an important distributional predictor. Phylogenetic signal was supported for both natives and nonnatives in both basins. Lastly, phylogenetic attraction was only supported for native fishes in the LCRB and for nonnative fishes in the UCRB. Our results indicated that functional similarity was heavily influenced by evolutionary history, but that phylogenetic relationships and functional traits may not always predict the environmental distribution of species. However, the

  3. Plant stem cell niches.

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    Aichinger, Ernst; Kornet, Noortje; Friedrich, Thomas; Laux, Thomas

    2012-01-01

    Multicellular organisms possess pluripotent stem cells to form new organs, replenish the daily loss of cells, or regenerate organs after injury. Stem cells are maintained in specific environments, the stem cell niches, that provide signals to block differentiation. In plants, stem cell niches are situated in the shoot, root, and vascular meristems-self-perpetuating units of organ formation. Plants' lifelong activity-which, as in the case of trees, can extend over more than a thousand years-requires that a robust regulatory network keep the balance between pluripotent stem cells and differentiating descendants. In this review, we focus on current models in plant stem cell research elaborated during the past two decades, mainly in the model plant Arabidopsis thaliana. We address the roles of mobile signals on transcriptional modules involved in balancing cell fates. In addition, we discuss shared features of and differences between the distinct stem cell niches of Arabidopsis.

  4. Cellular population dynamics control the robustness of the stem cell niche

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    Adam L. MacLean

    2015-11-01

    Full Text Available Within populations of cells, fate decisions are controlled by an indeterminate combination of cell-intrinsic and cell-extrinsic factors. In the case of stem cells, the stem cell niche is believed to maintain ‘stemness’ through communication and interactions between the stem cells and one or more other cell-types that contribute to the niche conditions. To investigate the robustness of cell fate decisions in the stem cell hierarchy and the role that the niche plays, we introduce simple mathematical models of stem and progenitor cells, their progeny and their interplay in the niche. These models capture the fundamental processes of proliferation and differentiation and allow us to consider alternative possibilities regarding how niche-mediated signalling feedback regulates the niche dynamics. Generalised stability analysis of these stem cell niche systems enables us to describe the stability properties of each model. We find that although the number of feasible states depends on the model, their probabilities of stability in general do not: stem cell–niche models are stable across a wide range of parameters. We demonstrate that niche-mediated feedback increases the number of stable steady states, and show how distinct cell states have distinct branching characteristics. The ecological feedback and interactions mediated by the stem cell niche thus lend (surprisingly high levels of robustness to the stem and progenitor cell population dynamics. Furthermore, cell–cell interactions are sufficient for populations of stem cells and their progeny to achieve stability and maintain homeostasis. We show that the robustness of the niche – and hence of the stem cell pool in the niche – depends only weakly, if at all, on the complexity of the niche make-up: simple as well as complicated niche systems are capable of supporting robust and stable stem cell dynamics.

  5. Ecological Niche Modelling of the Bacillus anthracis A1.a sub-lineage in Kazakhstan

    Science.gov (United States)

    2011-01-01

    Background Bacillus anthracis, the causative agent of anthrax, is a globally distributed zoonotic pathogen that continues to be a veterinary and human health problem in Central Asia. We used a database of anthrax outbreak locations in Kazakhstan and a subset of genotyped isolates to model the geographic distribution and ecological associations of B. anthracis in Kazakhstan. The aims of the study were to test the influence of soil variables on a previous ecological niche based prediction of B. anthracis in Kazakhstan and to determine if a single sub-lineage of B. anthracis occupies a unique ecological niche. Results The addition of soil variables to the previously developed ecological niche model did not appreciably alter the limits of the predicted geographic or ecological distribution of B. anthracis in Kazakhstan. The A1.a experiment predicted the sub-lineage to be present over a larger geographic area than did the outbreak based experiment containing multiple lineages. Within the geographic area predicted to be suitable for B. anthracis by all ten best subset models, the A1.a sub-lineage was associated with a wider range of ecological tolerances than the outbreak-soil experiment. Analysis of rule types showed that logit rules predominate in the outbreak-soil experiment and range rules in the A1.a sub-lineage experiment. Random sub-setting of locality points suggests that models of B. anthracis distribution may be sensitive to sample size. Conclusions Our analysis supports careful consideration of the taxonomic resolution of data used to create ecological niche models. Further investigations into the environmental affinities of individual lineages and sub-lineages of B. anthracis will be useful in understanding the ecology of the disease at large and small scales. With model based predictions serving as approximations of disease risk, these efforts will improve the efficacy of public health interventions for anthrax prevention and control. PMID:22152056

  6. A Trial of electronic surveillance feedback for quality improvement at Nurses Improving Care for Healthsystem Elders (NICHE) hospitals.

    Science.gov (United States)

    Wald, Heidi L; Bandle, Brian; Richard, Angela A; Min, Sung-Joon; Capezuti, Elizabeth

    2014-10-01

    Catheter-associated urinary tract infection (CAUTI) risk is directly related to duration of indwelling urinary catheters (IUCs), rising beyond 2 days of catheterization. We conducted a cluster randomized study in nonintensive care units of Nurses Improving Care for Healthsystem Elders (NICHE) hospitals. Electronic surveillance data were used in an audit and feedback intervention for frontline nurses to reduce IUC duration. Multivariable methods were used to identify the difference in average IUC duration and proportion of patients with IUC duration hospital characteristics. A total of 24 units at 19 NICHE hospitals reported 13,499 adult patients with IUCs over 18 months. Early and delayed intervention groups had important baseline differences in IUC utilization. Use of evidence-based CAUTI prevention measures increased during study participation. In multivariable analysis, the average IUC duration and proportion of patients with IUC duration Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

  7. Geological 3D model of the investigation niche in ONKALO, Olkiluoto, southwestern Finland

    Energy Technology Data Exchange (ETDEWEB)

    Koittola, N.

    2014-07-15

    The main goal of this Master of Science Thesis was to create a geological 3D-model of the investigation niche 3 and its surroundings. The model were created for the needs of the rock mechanical back analysis. This study is a part of Posiva's regional studies for characterization of the bedrock. Totally 4 models were created: lithological model, foliation model, fracture model, and physical rock property model. Besides the modeling, there was also made a study of the migmatite structures in the niche. Used geological and geophysical methods were drill core loggings, tunnel mapping, ground penetration radar, mise-a-la-masse and drill hole geophysics. Four rock types exist at the niche area: veined gneiss, pegmatite granite, diatexitic gneiss and quartz gneiss. The lithological units were modeled primary with the drill core loggings, tunnel mapping and ground penetrating radar. The major lithological units followed the main foliation direction (south dipping). So the continuations were fairly easy to model in the walls and roof, where the data was lacking. Foliation and fractures were modeled as discs, with mid-points at the measurement points of the structure. There were two main foliation directions 164/46 and 62/39. Fractures were more scattered but three fracture sets can be separated: 156/34, 270/85 and 342/83. The first set is mainly from the drill core loggings, second and third from tunnel mapping. Used methods in foliation model were drill core loggings, tunnel mapping and drill hole geophysics. In fracture model used data was from drill core loggings, tunnel mapping, mise-a-la-masse measurements and drill core geophysic. Four anomalous zones were detected with the drill hole geophysics. Three of these zones were associated with intensely fractured zones and one was connected to exceptionally high mica content in the gneiss. Rocks of Olkiluoto are divided into gneisses and magmatic rocks in the geological mapping. Actually almost all Olkiluoto

  8. Geological 3D model of the investigation niche in ONKALO, Olkiluoto, southwestern Finland

    International Nuclear Information System (INIS)

    Koittola, N.

    2014-07-01

    The main goal of this Master of Science Thesis was to create a geological 3D-model of the investigation niche 3 and its surroundings. The model were created for the needs of the rock mechanical back analysis. This study is a part of Posiva's regional studies for characterization of the bedrock. Totally 4 models were created: lithological model, foliation model, fracture model, and physical rock property model. Besides the modeling, there was also made a study of the migmatite structures in the niche. Used geological and geophysical methods were drill core loggings, tunnel mapping, ground penetration radar, mise-a-la-masse and drill hole geophysics. Four rock types exist at the niche area: veined gneiss, pegmatite granite, diatexitic gneiss and quartz gneiss. The lithological units were modeled primary with the drill core loggings, tunnel mapping and ground penetrating radar. The major lithological units followed the main foliation direction (south dipping). So the continuations were fairly easy to model in the walls and roof, where the data was lacking. Foliation and fractures were modeled as discs, with mid-points at the measurement points of the structure. There were two main foliation directions 164/46 and 62/39. Fractures were more scattered but three fracture sets can be separated: 156/34, 270/85 and 342/83. The first set is mainly from the drill core loggings, second and third from tunnel mapping. Used methods in foliation model were drill core loggings, tunnel mapping and drill hole geophysics. In fracture model used data was from drill core loggings, tunnel mapping, mise-a-la-masse measurements and drill core geophysic. Four anomalous zones were detected with the drill hole geophysics. Three of these zones were associated with intensely fractured zones and one was connected to exceptionally high mica content in the gneiss. Rocks of Olkiluoto are divided into gneisses and magmatic rocks in the geological mapping. Actually almost all Olkiluoto's rocks are

  9. Ecological and evolutionary consequences of niche construction for its agent.

    Science.gov (United States)

    Kylafis, Grigoris; Loreau, Michel

    2008-10-01

    Niche construction can generate ecological and evolutionary feedbacks that have been underinvestigated so far. We present an eco-evolutionary model that incorporates the process of niche construction to reveal its effects on the ecology and evolution of the niche-constructing agent. We consider a simple plant-soil nutrient ecosystem in which plants have the ability to increase the input of inorganic nutrient as an example of positive niche construction. On an ecological time scale, the model shows that niche construction allows the persistence of plants under infertile soil conditions that would otherwise lead to their extinction. This expansion of plants' niche, however, requires a high enough rate of niche construction and a high enough initial plant biomass to fuel the positive ecological feedback between plants and their soil environment. On an evolutionary time scale, we consider that the rates of niche construction and nutrient uptake coevolve in plants while a trade-off constrains their values. Different evolutionary outcomes are possible depending on the shape of the trade-off. We show that niche construction results in an evolutionary feedback between plants and their soil environment such that plants partially regulate soil nutrient content. The direct benefit accruing to plants, however, plays a crucial role in the evolutionary advantage of niche construction.

  10. Geographical parthenogenesis: General purpose genotypes and frozen niche variation

    DEFF Research Database (Denmark)

    Vrijenhoek, Robert C.; Parker, Dave

    2009-01-01

    hypotheses concerning the evolution of niche breadth in asexual species - the "general-purpose genotype" (GPG) and "frozen niche-variation" (FNV) models. The two models are often portrayed as mutually exclusive, respectively viewing clonal lineages as generalists versus specialists. Nonetheless...

  11. Modelling the meteorological forest fire niche in heterogeneous pyrologic conditions.

    Science.gov (United States)

    De Angelis, Antonella; Ricotta, Carlo; Conedera, Marco; Pezzatti, Gianni Boris

    2015-01-01

    Fire regimes are strongly related to weather conditions that directly and indirectly influence fire ignition and propagation. Identifying the most important meteorological fire drivers is thus fundamental for daily fire risk forecasting. In this context, several fire weather indices have been developed focussing mainly on fire-related local weather conditions and fuel characteristics. The specificity of the conditions for which fire danger indices are developed makes its direct transfer and applicability problematic in different areas or with other fuel types. In this paper we used the low-to-intermediate fire-prone region of Canton Ticino as a case study to develop a new daily fire danger index by implementing a niche modelling approach (Maxent). In order to identify the most suitable weather conditions for fires, different combinations of input variables were tested (meteorological variables, existing fire danger indices or a combination of both). Our findings demonstrate that such combinations of input variables increase the predictive power of the resulting index and surprisingly even using meteorological variables only allows similar or better performances than using the complex Canadian Fire Weather Index (FWI). Furthermore, the niche modelling approach based on Maxent resulted in slightly improved model performance and in a reduced number of selected variables with respect to the classical logistic approach. Factors influencing final model robustness were the number of fire events considered and the specificity of the meteorological conditions leading to fire ignition.

  12. Ecological niche transferability using invasive species as a case study.

    Directory of Open Access Journals (Sweden)

    Miguel Fernández

    Full Text Available Species distribution modeling is widely applied to predict invasive species distributions and species range shifts under climate change. Accurate predictions depend upon meeting the assumption that ecological niches are conserved, i.e., spatially or temporally transferable. Here we present a multi-taxon comparative analysis of niche conservatism using biological invasion events well documented in natural history museum collections. Our goal is to assess spatial transferability of the climatic niche of a range of noxious terrestrial invasive species using two complementary approaches. First we compare species' native versus invasive ranges in environmental space using two distinct methods, Principal Components Analysis and Mahalanobis distance. Second we compare species' native versus invaded ranges in geographic space as estimated using the species distribution modeling technique Maxent and the comparative index Hellinger's I. We find that species exhibit a range of responses, from almost complete transferability, in which the invaded niches completely overlap with the native niches, to a complete dissociation between native and invaded ranges. Intermediate responses included expansion of dimension attributable to either temperature or precipitation derived variables, as well as niche expansion in multiple dimensions. We conclude that the ecological niche in the native range is generally a poor predictor of invaded range and, by analogy, the ecological niche may be a poor predictor of range shifts under climate change. We suggest that assessing dimensions of niche transferability prior to standard species distribution modeling may improve the understanding of species' dynamics in the invaded range.

  13. Niche conservatism and the invasive potential of the wild boar.

    Science.gov (United States)

    Sales, Lilian Patrícia; Ribeiro, Bruno R; Hayward, Matt Warrington; Paglia, Adriano; Passamani, Marcelo; Loyola, Rafael

    2017-09-01

    Niche conservatism, i.e. the retention of a species' fundamental niche through evolutionary time, is cornerstone for biological invasion assessments. The fact that species tend to maintain their original climate niche allows predictive maps of invasion risk to anticipate potential invadable areas. Unravelling the mechanisms driving niche shifts can shed light on the management of invasive species. Here, we assessed niche shifts in one of the world's worst invasive species: the wild boar Sus scrofa. We also predicted potential invadable areas based on an ensemble of three ecological niche modelling methods, and evaluated the performance of models calibrated with native vs. pooled (native plus invaded) species records. By disentangling the drivers of change on the exotic wild boar population's niches, we found strong evidence for niche conservatism during biological invasion. Ecological niche models calibrated with both native and pooled range records predicted convergent areas. Also, observed niche shifts are mostly explained by niche unfilling, i.e. there are unoccupied areas in the exotic range where climate is analogous to the native range. Niche unfilling is expected as result of recent colonization and ongoing dispersal, and was potentially stronger for the Neotropics, where a recent wave of introductions for pig-farming and game-hunting has led to high wild boar population growth rates. The invasive potential of wild boar in the Neotropics is probably higher than in other regions, which has profound management implications if we are to prevent their invasion into species-rich areas, such as Amazonia, coupled with expansion of African swine fever and possibly great economic losses. Although the originally Eurasian-wide distribution suggests a pre-adaptation to a wide array of climates, the wild boar world-wide invasion does not exhibit evidence of niche evolution. The invasive potential of the wild boar therefore probably lies on the reproductive, dietary and

  14. Predicting Future Seed Sourcing of Platycladus orientalis (L. for Future Climates Using Climate Niche Models

    Directory of Open Access Journals (Sweden)

    Xian-Ge Hu

    2017-12-01

    Full Text Available Climate niche modeling has been widely used to assess the impact of climate change on forest trees at the species level. However, geographically divergent tree populations are expected to respond differently to climate change. Considering intraspecific local adaptation in modeling species responses to climate change will thus improve the credibility and usefulness of climate niche models, particularly for genetic resources management. In this study, we used five Platycladus orientalis (L. seed zones (Northwestern; Northern; Central; Southern; and Subtropical covering the entire species range in China. A climate niche model was developed and used to project the suitable climatic conditions for each of the five seed zones for current and various future climate scenarios (Representative Concentration Pathways: RCP2.6, RCP4.5, RCP6.0, and RCP8.5. Our results indicated that the Subtropical seed zone would show consistent reduction for all climate change scenarios. The remaining seed zones, however, would experience various degrees of expansion in suitable habitat relative to their current geographic distributions. Most of the seed zones would gain suitable habitats at their northern distribution margins and higher latitudes. Thus, we recommend adjusting the current forest management strategies to mitigate the negative impacts of climate change.

  15. Modeling the Ecological Niche of Bacillus anthracis to Map Anthrax Risk in Kyrgyzstan.

    Science.gov (United States)

    Blackburn, Jason K; Matakarimov, Saitbek; Kozhokeeva, Sabira; Tagaeva, Zhyldyz; Bell, Lindsay K; Kracalik, Ian T; Zhunushov, Asankadyr

    2017-03-01

    AbstractAnthrax, caused by the environmental bacterium Bacillus anthracis , is an important zoonosis nearly worldwide. In Central Asia, anthrax represents a major veterinary and public health concern. In the Republic of Kyrgyzstan, ongoing anthrax outbreaks have been reported in humans associated with handling infected livestock and contaminated animal by-products such as meat or hides. The current anthrax situation has prompted calls for improved insights into the epidemiology, ecology, and spatial distribution of the disease in Kyrgyzstan to better inform control and surveillance. Disease control for both humans and livestock relies on annual livestock vaccination ahead of outbreaks. Toward this, we used a historic database of livestock anthrax reported from 1932 to 2006 mapped at high resolution to develop an ecological niche model-based prediction of B. anthracis across Kyrgyzstan and identified spatial clusters of livestock anthrax using a cluster morphology statistic. We also defined the seasonality of outbreaks in livestock. Cattle were the most frequently reported across the time period, with the greatest number of cases in late summer months. Our niche models defined four areas as suitable to support pathogen persistence, the plateaus near Talas and Bishkek, the valleys of western Kyrgyzstan along the Fergana Valley, and the low-lying areas along the shore of Lake Isyk-Kul. These areas should be considered "at risk" for livestock anthrax and subsequent human cases. Areas defined by the niche models can be used to prioritize anthrax surveillance and inform efforts to target livestock vaccination campaigns.

  16. Ecologic Niche Modeling of Blastomyces dermatitidis in Wisconsin

    Science.gov (United States)

    Reed, Kurt D.; Meece, Jennifer K.; Archer, John R.; Peterson, A. Townsend

    2008-01-01

    Background Blastomycosis is a potentially fatal mycosis that is acquired by inhaling infectious spores of Blastomyces dermatitidis present in the environment. The ecology of this pathogen is poorly understood, in part because it has been extremely difficult to identify the niche(s) it occupies based on culture isolation of the organism from environmental samples. Methodology/Principal Findings We investigated the ecology of blastomycosis by performing maximum entropy modeling of exposure sites from 156 cases of human and canine blastomycosis to provide a regional-scale perspective of the geographic and ecologic distribution of B. dermatitidis in Wisconsin. Based on analysis with climatic, topographic, surface reflectance and other environmental variables, we predicted that ecologic conditions favorable for maintaining the fungus in nature occur predominantly within northern counties and counties along the western shoreline of Lake Michigan. Areas of highest predicted occurrence were often in proximity to waterways, especially in northcentral Wisconsin, where incidence of infection is highest. Ecologic conditions suitable for B. dermatitidis are present in urban and rural environments, and may differ at the extremes of distribution of the species in the state. Conclusions/Significance Our results provide a framework for a more informed search for specific environmental factors modulating B. dermatitidis occurrence and transmission and will be useful for improving public health awareness of relative exposure risks. PMID:18446224

  17. THE GERMLINE STEM CELL NICHE UNIT IN MAMMALIAN TESTES

    Science.gov (United States)

    Oatley, Jon M.; Brinster, Ralph L.

    2014-01-01

    This review addresses current understanding of the germline stem cell niche unit in mammalian testes. Spermatogenesis is a classic model of tissue-specific stem cell function relying on self-renewal and differentiation of spermatogonial stem cells (SSCs). These fate decisions are influenced by a niche microenvironment composed of a growth factor milieu that is provided by several testis somatic support cell populations. Investigations over the last two decades have identified key determinants of the SSC niche including cytokines that regulate SSC functions and support cells providing these factors, adhesion molecules that influence SSC homing, and developmental heterogeneity of the niche during postnatal aging. Emerging evidence suggests that Sertoli cells are a key support cell population influencing the formation and function of niches by secreting soluble factors and possibly orchestrating contributions of other support cells. Investigations with mice have shown that niche influence on SSC proliferation differs during early postnatal development and adulthood. Moreover, there is mounting evidence of an age-related decline in niche function, which is likely influenced by systemic factors. Defining the attributes of stem cell niches is key to developing methods to utilize these cells for regenerative medicine. The SSC population and associated niche comprise a valuable model system for study that provides fundamental knowledge about the biology of tissue-specific stem cells and their capacity to sustain homeostasis of regenerating tissue lineages. While the stem cell is essential for maintenance of all self-renewing tissues and has received considerable attention, the role of niche cells is at least as important and may prove to be more receptive to modification in regenerative medicine. PMID:22535892

  18. Characterization of the bone marrow adipocyte niche with three-dimensional electron microscopy.

    Science.gov (United States)

    Robles, Hero; Park, SungJae; Joens, Matthew S; Fitzpatrick, James A J; Craft, Clarissa S; Scheller, Erica L

    2018-01-27

    Unlike white and brown adipose tissues, the bone marrow adipocyte (BMA) exists in a microenvironment containing unique populations of hematopoietic and skeletal cells. To study this microenvironment at the sub-cellular level, we performed a three-dimensional analysis of the ultrastructure of the BMA niche with focused ion beam scanning electron microscopy (FIB-SEM). This revealed that BMAs display hallmarks of metabolically active cells including polarized lipid deposits, a dense mitochondrial network, and areas of endoplasmic reticulum. The distinct orientations of the triacylglycerol droplets suggest that fatty acids are taken up and/or released in three key areas - at the endothelial interface, into the hematopoietic milieu, and at the bone surface. Near the sinusoidal vasculature, endothelial cells send finger-like projections into the surface of the BMA which terminate near regions of lipid within the BMA cytoplasm. In some regions, perivascular cells encase the BMA with their flattened cellular projections, limiting contacts with other cells in the niche. In the hematopoietic milieu, BMAT adipocytes of the proximal tibia interact extensively with maturing cells of the myeloid/granulocyte lineage. Associations with erythroblast islands are also prominent. At the bone surface, the BMA extends organelle and lipid-rich cytoplasmic regions toward areas of active osteoblasts. This suggests that the BMA may serve to partition nutrient utilization between diverse cellular compartments, serving as an energy-rich hub of the stromal-reticular network. Lastly, though immuno-EM, we've identified a subset of bone marrow adipocytes that are innervated by the sympathetic nervous system, providing an additional mechanism for regulation of the BMA. In summary, this work reveals that the bone marrow adipocyte is a dynamic cell with substantial capacity for interactions with the diverse components of its surrounding microenvironment. These local interactions likely contribute to

  19. Niche conservatism in Gynandropaa frogs on the southeastern Qinghai-Tibetan Plateau.

    Science.gov (United States)

    Hu, Junhua; Broennimann, Olivier; Guisan, Antoine; Wang, Bin; Huang, Yan; Jiang, Jianping

    2016-09-07

    The role of ecological niche in lineage diversification has been the subject of long-standing interest of ecologists and evolutionary biologists. Gynandropaa frogs diversified into three independent clades endemic to the southeastern Qinghai-Tibetan Plateau. Here, we address the question whether these clades kept the same niche after separation, and what it tells us about possible diversification processes. We applied predictions in geographical (G)-space and tests of niche conservatism in environmental (E)-space. Niche models in G-space indicate separate regions with high suitability for the different clades, with some potential areas of sympatry. While the pair of central and eastern clades displayed the largest niche overlap for most variables, and strict niche equivalency was rejected for all clade-pairs, we found no strong evidence for niche divergence, but rather the signature of niche conservatism compared to null models in E-space. These results suggest a common ancestral ecological niche, and as such give good support to divergence through allopatric speciation, but alternative explanations are also possible. Our findings illustrate how testing for niche conservatism in lineage diversification can provide insights into underlying speciation processes, and how this information may guide further research and conservation practices, as illustrated here for amphibians on the Qinghai-Tibetan Plateau.

  20. The use of ecological niche modeling to infer potential risk areas of snakebite in the Mexican state of Veracruz.

    Directory of Open Access Journals (Sweden)

    Carlos Yañez-Arenas

    Full Text Available Many authors have claimed that snakebite risk is associated with human population density, human activities, and snake behavior. Here we analyzed whether environmental suitability of vipers can be used as an indicator of snakebite risk. We tested several hypotheses to explain snakebite incidence, through the construction of models incorporating both environmental suitability and socioeconomic variables in Veracruz, Mexico.Ecological niche modeling (ENM was used to estimate potential geographic and ecological distributions of nine viper species' in Veracruz. We calculated the distance to the species' niche centroid (DNC; this distance may be associated with a prediction of abundance. We found significant inverse relationships between snakebites and DNCs of common vipers (Crotalus simus and Bothrops asper, explaining respectively 15% and almost 35% of variation in snakebite incidence. Additionally, DNCs for these two vipers, in combination with marginalization of human populations, accounted for 76% of variation in incidence.Our results suggest that niche modeling and niche-centroid distance approaches can be used to mapping distributions of environmental suitability for venomous snakes; combining this ecological information with socioeconomic factors may help with inferring potential risk areas for snakebites, since hospital data are often biased (especially when incidences are low.

  1. The use of ecological niche modeling to infer potential risk areas of snakebite in the Mexican state of Veracruz.

    Science.gov (United States)

    Yañez-Arenas, Carlos; Peterson, A Townsend; Mokondoko, Pierre; Rojas-Soto, Octavio; Martínez-Meyer, Enrique

    2014-01-01

    Many authors have claimed that snakebite risk is associated with human population density, human activities, and snake behavior. Here we analyzed whether environmental suitability of vipers can be used as an indicator of snakebite risk. We tested several hypotheses to explain snakebite incidence, through the construction of models incorporating both environmental suitability and socioeconomic variables in Veracruz, Mexico. Ecological niche modeling (ENM) was used to estimate potential geographic and ecological distributions of nine viper species' in Veracruz. We calculated the distance to the species' niche centroid (DNC); this distance may be associated with a prediction of abundance. We found significant inverse relationships between snakebites and DNCs of common vipers (Crotalus simus and Bothrops asper), explaining respectively 15% and almost 35% of variation in snakebite incidence. Additionally, DNCs for these two vipers, in combination with marginalization of human populations, accounted for 76% of variation in incidence. Our results suggest that niche modeling and niche-centroid distance approaches can be used to mapping distributions of environmental suitability for venomous snakes; combining this ecological information with socioeconomic factors may help with inferring potential risk areas for snakebites, since hospital data are often biased (especially when incidences are low).

  2. Ecological niche of plant pathogens

    Directory of Open Access Journals (Sweden)

    Ecaterina Fodor

    2011-06-01

    Full Text Available Disease ecology is a new approach to the understanding of the spread and dynamics of pathogens in natural and man-made environments. Defining and describing the ecological niche of the pathogens is one of the major tasks for ecological theory, as well as for practitioners preoccupied with the control and forecasting of established and emerging diseases. Niche theory has been periodically revised, not including in an explicit way the pathogens. However, many progresses have been achieved in niche modeling of disease spread, but few attempts were made to construct a theoretical frame for the ecological niche of pathogens. The paper is a review of the knowledge accumulated during last decades in the niche theory of pathogens and proposes an ecological approach in research. It quest for new control methods in what concerns forest plant pathogens, with a special emphasis on fungi like organisms of the genus Phytophthora. Species of Phytophthora are the most successful plant pathogens of the moment, affecting forest and agricultural systems worldwide, many of them being invasive alien organisms in many ecosystems. The hyperspace of their ecological niche is defined by hosts, environment and human interference, as main axes. To select most important variables within the hyperspace, is important the understanding of the complex role of pathogens in the ecosystems as well as for control programs. Biotic relationships within ecosystem of host-pathogen couple are depicted by ecological network and specific metrics attached to this. The star shaped network is characterized by few high degree nodes, by short path lengths and relatively low connectivity, premises for a rapid disturbance spread. 

  3. Ecological niche of plant pathogens

    Directory of Open Access Journals (Sweden)

    Ecaterina Fodor

    2011-02-01

    Full Text Available Disease ecology is a new approach to the understanding of the spread and dynamics of pathogens in natural and man-made environments. Defining and describing the ecological niche of the pathogens is one of the major tasks for ecological theory, as well as for practitioners preoccupied with the control and forecasting of established and emerging diseases. Niche theory has been periodically revised, not including in an explicit way the pathogens. However, many progresses have been achieved in niche modeling of disease spread, but few attempts were made to construct a theoretical frame for the ecological niche of pathogens. The paper is a review of the knowledge accumulated during last decades in the niche theory of pathogens and proposes an ecological approach in research. It quest for new control methods in what concerns forest plant pathogens, with a special emphasis on fungi like organisms of the genus Phytophthora. Species of Phytophthora are the most successful plant pathogens of the moment, affecting forest and agricultural systems worldwide, many of them being invasive alien organisms in many ecosystems. The hyperspace of their ecological niche is defined by hosts, environment and human interference, as main axes. To select most important variables within the hyperspace, is important for the understanding of the complex role of pathogens in the ecosystems as well as for control programs. Biotic relationships within ecosystem of host-pathogen couple are depicted by ecological network and specific metrics attached to this. The star shaped network is characterized by few high degree nodes, by short path lengths and relatively low connectivity, premises for a rapid disturbance spread.

  4. Intestinal Stem Cell Niche Insights Gathered from Both In Vivo and Novel In Vitro Models

    Directory of Open Access Journals (Sweden)

    Nikolce Gjorevski

    2017-01-01

    Full Text Available Intestinal stem cells are located at the base of the crypts and are surrounded by a complex structure called niche. This environment is composed mainly of epithelial cells and stroma which provides signals that govern cell maintenance, proliferation, and differentiation. Understanding how the niche regulates stem cell fate by controlling developmental signaling pathways will help us to define how stem cells choose between self-renewal and differentiation and how they maintain their undifferentiated state. Tractable in vitro assay systems, which reflect the complexity of the in vivo situation but provide higher level of control, would likely be crucial in identifying new players and mechanisms controlling stem cell function. Knowledge of the intestinal stem cell niche gathered from both in vivo and novel in vitro models may help us improve therapies for tumorigenesis and intestinal damage and make autologous intestinal transplants a feasible clinical practice.

  5. Niche evolution and diversification in a Neotropical radiation of birds (Aves: Furnariidae).

    Science.gov (United States)

    Seeholzer, Glenn F; Claramunt, Santiago; Brumfield, Robb T

    2017-03-01

    Rapid diversification may be caused by ecological adaptive radiation via niche divergence. In this model, speciation is coupled with niche divergence and lineage diversification is predicted to be correlated with rates of niche evolution. Studies of the role of niche evolution in diversification have generally focused on ecomorphological diversification but climatic-niche evolution may also be important. We tested these alternatives using a phylogeny of 298 species of ovenbirds (Aves: Furnariidae). We found that within Furnariidae, variation in species richness and diversification rates of subclades were best predicted by rate of climatic-niche evolution than ecomorphological evolution. Although both are clearly important, univariate regression and multivariate model averaging more consistently supported the climatic-niche as the best predictor of lineage diversification. Our study adds to the growing body of evidence, suggesting that climatic-niche divergence may be an important driver of rapid diversification in addition to ecomorphological evolution. However, this pattern may depend on the phylogenetic scale at which rate heterogeneity is examined. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  6. Behavioural manipulation of insect hosts by Baculoviridae as a process of niche construction.

    Science.gov (United States)

    Hamblin, Steven; Tanaka, Mark M

    2013-08-16

    Niche construction has received increasing attention in recent years as a vital force in evolution and examples of niche construction have been identified in a wide variety of taxa, but viruses are conspicuously absent. In this study we explore how niche construction can lead to viruses engineering their hosts (including behavioural manipulation) with feedback on selective pressures for viral transmission and virulence. To illustrate this concept we focus on Baculoviridae, a family of invertebrate viruses that have evolved to modify the feeding behaviour of their lepidopteran hosts and liquefy their cadavers as part of the course of infection. We present a mathematical model showing how niche construction leads to feedback from the behavioural manipulation to the liquefaction of the host, linking the evolution of both of these traits, and show how this association arises from the action of niche construction. Model results show that niche construction is plausible in this system and delineates the conditions under which niche construction will occur. Niche construction in this system is also shown to be sensitive to parameter values that reflect ecological forces. Our model demonstrates that niche construction can be a potent force in viral evolution and can lead to the acquisition and maintenance of the behavioural manipulation and liquefaction traits in Baculoviridae via the niche constructing effects on the host. These results show the potential for niche construction theory to provide new insights into viral evolution.

  7. Why developmental niche construction is not selective niche construction: and why it matters.

    Science.gov (United States)

    Stotz, Karola

    2017-10-06

    In the last decade, niche construction has been heralded as the neglected process in evolution. But niche construction is just one way in which the organism's interaction with and construction of the environment can have potential evolutionary significance. The constructed environment does not just select for , it also produces new variation. Nearly 3 decades ago, and in parallel with Odling-Smee's article 'Niche-constructing phenotypes', West and King introduced the 'ontogenetic niche' to give the phenomena of exo genetic inheritance a formal name. Since then, a range of fields in the life sciences and medicine has amassed evidence that parents influence their offspring by means other than DNA (parental effects), and proposed mechanisms for how heritable variation can be environmentally induced and developmentally regulated. The concept of 'developmental niche construction' (DNC) elucidates how a diverse range of mechanisms contributes to the transgenerational transfer of developmental resources. My most central of claims is that whereas the selective niche of niche construction theory is primarily used to explain the active role of the organism in its selective environment, DNC is meant to indicate the active role of the organism in its developmental environment. The paper highlights the differences between the construction of the selective and the developmental niche, and explores the overall significance of DNC for evolutionary theory.

  8. Stitch the niche - a practical philosophy and visual schematic for the niche concept

    NARCIS (Netherlands)

    McInerny, Greg J.; Etienne, Rampal S.

    2012-01-01

    By over-focusing on precise definitions, ecology has produced a confused idea of the niche concept. This, our second paper, develops a practical philosophy for the niche that approaches the concept at the correct level of abstraction. We deconstruct the niche into effect and response components and

  9. Periarteriolar Glioblastoma Stem Cell Niches Express Bone Marrow Hematopoietic Stem Cell Niche Proteins

    NARCIS (Netherlands)

    Hira, Vashendriya V. V.; Wormer, Jill R.; Kakar, Hala; Breznik, Barbara; van der Swaan, Britt; Hulsbos, Renske; Tigchelaar, Wikky; Tonar, Zbynek; Khurshed, Mohammed; Molenaar, Remco J.; van Noorden, Cornelis J. F.

    2018-01-01

    In glioblastoma, a fraction of malignant cells consists of therapy-resistant glioblastoma stem cells (GSCs) residing in protective niches that recapitulate hematopoietic stem cell (HSC) niches in bone marrow. We have previously shown that HSC niche proteins stromal cell-derived factor-1α (SDF-1α),

  10. Intraspecific niche models for ponderosa pine (Pinus ponderosa) suggest potential variability in population-level response to climate change

    Science.gov (United States)

    Maguire, Kaitlin C.; Shinneman, Douglas; Potter, Kevin M.; Hipkins, Valerie D.

    2018-01-01

    Unique responses to climate change can occur across intraspecific levels, resulting in individualistic adaptation or movement patterns among populations within a given species. Thus, the need to model potential responses among genetically distinct populations within a species is increasingly recognized. However, predictive models of future distributions are regularly fit at the species level, often because intraspecific variation is unknown or is identified only within limited sample locations. In this study, we considered the role of intraspecific variation to shape the geographic distribution of ponderosa pine (Pinus ponderosa), an ecologically and economically important tree species in North America. Morphological and genetic variation across the distribution of ponderosa pine suggest the need to model intraspecific populations: the two varieties (var. ponderosa and var. scopulorum) and several haplotype groups within each variety have been shown to occupy unique climatic niches, suggesting populations have distinct evolutionary lineages adapted to different environmental conditions. We utilized a recently-available, geographically-widespread dataset of intraspecific variation (haplotypes) for ponderosa pine and a recently-devised lineage distance modeling approach to derive additional, likely intraspecific occurrence locations. We confirmed the relative uniqueness of each haplotype-climate relationship using a niche-overlap analysis, and developed ecological niche models (ENMs) to project the distribution for two varieties and eight haplotypes under future climate forecasts. Future projections of haplotype niche distributions generally revealed greater potential range loss than predicted for the varieties. This difference may reflect intraspecific responses of distinct evolutionary lineages. However, directional trends are generally consistent across intraspecific levels, and include a loss of distributional area and an upward shift in elevation. Our results

  11. Intraspecific niche models for ponderosa pine (Pinus ponderosa) suggest potential variability in population-level response to climate change.

    Science.gov (United States)

    Maguire, Kaitlin C; Shinneman, Douglas J; Potter, Kevin M; Hipkins, Valerie D

    2018-03-14

    Unique responses to climate change can occur across intraspecific levels, resulting in individualistic adaptation or movement patterns among populations within a given species. Thus, the need to model potential responses among genetically distinct populations within a species is increasingly recognized. However, predictive models of future distributions are regularly fit at the species level, often because intraspecific variation is unknown or is identified only within limited sample locations. In this study, we considered the role of intraspecific variation to shape the geographic distribution of ponderosa pine (Pinus ponderosa), an ecologically and economically important tree species in North America. Morphological and genetic variation across the distribution of ponderosa pine suggest the need to model intraspecific populations: the two varieties (var. ponderosa and var. scopulorum) and several haplotype groups within each variety have been shown to occupy unique climatic niches, suggesting populations have distinct evolutionary lineages adapted to different environmental conditions. We utilized a recently-available, geographically-widespread dataset of intraspecific variation (haplotypes) for ponderosa pine and a recently-devised lineage distance modeling approach to derive additional, likely intraspecific occurrence locations. We confirmed the relative uniqueness of each haplotype-climate relationship using a niche-overlap analysis, and developed ecological niche models (ENMs) to project the distribution for two varieties and eight haplotypes under future climate forecasts. Future projections of haplotype niche distributions generally revealed greater potential range loss than predicted for the varieties. This difference may reflect intraspecific responses of distinct evolutionary lineages. However, directional trends are generally consistent across intraspecific levels, and include a loss of distributional area and an upward shift in elevation. Our results

  12. Stem Cell Spheroids and Ex Vivo Niche Modeling: Rationalization and Scaling-Up.

    Science.gov (United States)

    Chimenti, Isotta; Massai, Diana; Morbiducci, Umberto; Beltrami, Antonio Paolo; Pesce, Maurizio; Messina, Elisa

    2017-04-01

    Improved protocols/devices for in vitro culture of 3D cell spheroids may provide essential cues for proper growth and differentiation of stem/progenitor cells (S/PCs) in their niche, allowing preservation of specific features, such as multi-lineage potential and paracrine activity. Several platforms have been employed to replicate these conditions and to generate S/PC spheroids for therapeutic applications. However, they incompletely reproduce the niche environment, with partial loss of its highly regulated network, with additional hurdles in the field of cardiac biology, due to debated resident S/PCs therapeutic potential and clinical translation. In this contribution, the essential niche conditions (metabolic, geometric, mechanical) that allow S/PCs maintenance/commitment will be discussed. In particular, we will focus on both existing bioreactor-based platforms for the culture of S/PC as spheroids, and on possible criteria for the scaling-up of niche-like spheroids, which could be envisaged as promising tools for personalized cardiac regenerative medicine, as well as for high-throughput drug screening.

  13. The Fluctuation Niche in Plants

    Directory of Open Access Journals (Sweden)

    Jaume Terradas

    2009-01-01

    Full Text Available Classical approaches to niche in coexisting plants have undervalued temporal fluctuations. We propose that fluctuation niche is an important dimension of the total niche and interacts with habitat and life-history niches to provide a better understanding of the multidimensional niche space where ecological interactions occur. To scale a fluctuation niche, it is necessary to relate environmental constrictions or species performance not only to the absolute values of the usual environmental and ecophysiological variables but also to their variances or other measures of variability. We use Mediterranean plant communities as examples, because they present characteristic large seasonal and interannual fluctuations in water and nutrient availabilities, along an episodic-constant gradient, and because the plant responses include a number of syndromes coupled to this gradient.

  14. The Fluctuation Niche in Plants

    International Nuclear Information System (INIS)

    Terradas, J.; Penuelas, J.; Lloret, F.; Penuelas, J.

    2009-01-01

    Classical approaches to niche in coexisting plants have undervalued temporal fluctuations. We propose that fluctuation niche is an important dimension of the total niche and interacts with habitat and life-history niches to provide a better understanding of the multidimensional niche space where ecological interactions occur. To scale a fluctuation niche, it is necessary to relate environmental constrictions or species performance not only to the absolute values of the usual environmental and eco physiological variables but also to their variances or other measures of variability. We use Mediterranean plant communities as examples, because they present characteristic large seasonal and inter annual fluctuations in water and nutrient availabilities, along an episodic-constant gradient, and because the plant responses include a number of syndromes coupled to this gradient.

  15. Niche entrepreneurs in urban systems integration : On the role of individuals in niche formation

    NARCIS (Netherlands)

    Pesch, U.; Vernay, A.L.; van Bueren, E.M.; Pandis Iveroth, S

    2017-01-01

    In many sustainable urban innovation projects, the efforts, endurance and enthusiasm of individuals at key positions are considered a crucial factor for success. This article studies the role of individual agency in sociotechnical niches by using Kingdon’s agenda-setting model. Although strategic

  16. Microhabitat and Climatic Niche Change Explain Patterns of Diversification among Frog Families.

    Science.gov (United States)

    Moen, Daniel S; Wiens, John J

    2017-07-01

    A major goal of ecology and evolutionary biology is to explain patterns of species richness among clades. Differences in rates of net diversification (speciation minus extinction over time) may often explain these patterns, but the factors that drive variation in diversification rates remain uncertain. Three important candidates are climatic niche position (e.g., whether clades are primarily temperate or tropical), rates of climatic niche change among species within clades, and microhabitat (e.g., aquatic, terrestrial, arboreal). The first two factors have been tested separately in several studies, but the relative importance of all three is largely unknown. Here we explore the correlates of diversification among families of frogs, which collectively represent ∼88% of amphibian species. We assemble and analyze data on phylogeny, climate, and microhabitat for thousands of species. We find that the best-fitting phylogenetic multiple regression model includes all three types of variables: microhabitat, rates of climatic niche change, and climatic niche position. This model explains 67% of the variation in diversification rates among frog families, with arboreal microhabitat explaining ∼31%, niche rates ∼25%, and climatic niche position ∼11%. Surprisingly, we show that microhabitat can have a much stronger influence on diversification than climatic niche position or rates of climatic niche change.

  17. An introduction to niche construction theory.

    Science.gov (United States)

    Laland, Kevin; Matthews, Blake; Feldman, Marcus W

    Niche construction refers to the modification of selective environments by organisms. Theoretical and empirical studies of niche construction are increasing in importance as foci in evolutionary ecology. This special edition presents theoretical and empirical research that illustrates the significance of niche construction to the field. Here we set the scene for the following papers by (1) discussing the history of niche construction research, (2) providing clear definitions that distinguish niche construction from related concepts such as ecosystem engineering and the extended phenotype, (3) providing a brief summary of the findings of niche construction research, (4) discussing the contribution of niche construction and ecological inheritance to (a) expanded notions of inheritance, and (b) the extended evolutionary synthesis, and (5) briefly touching on some of the issues that underlie the controversies over niche construction.

  18. Predicting the current and future potential distributions of lymphatic filariasis in Africa using maximum entropy ecological niche modelling.

    Directory of Open Access Journals (Sweden)

    Hannah Slater

    Full Text Available Modelling the spatial distributions of human parasite species is crucial to understanding the environmental determinants of infection as well as for guiding the planning of control programmes. Here, we use ecological niche modelling to map the current potential distribution of the macroparasitic disease, lymphatic filariasis (LF, in Africa, and to estimate how future changes in climate and population could affect its spread and burden across the continent. We used 508 community-specific infection presence data collated from the published literature in conjunction with five predictive environmental/climatic and demographic variables, and a maximum entropy niche modelling method to construct the first ecological niche maps describing potential distribution and burden of LF in Africa. We also ran the best-fit model against climate projections made by the HADCM3 and CCCMA models for 2050 under A2a and B2a scenarios to simulate the likely distribution of LF under future climate and population changes. We predict a broad geographic distribution of LF in Africa extending from the west to the east across the middle region of the continent, with high probabilities of occurrence in the Western Africa compared to large areas of medium probability interspersed with smaller areas of high probability in Central and Eastern Africa and in Madagascar. We uncovered complex relationships between predictor ecological niche variables and the probability of LF occurrence. We show for the first time that predicted climate change and population growth will expand both the range and risk of LF infection (and ultimately disease in an endemic region. We estimate that populations at risk to LF may range from 543 and 804 million currently, and that this could rise to between 1.65 to 1.86 billion in the future depending on the climate scenario used and thresholds applied to signify infection presence.

  19. Stem cell dynamics in the hair follicle niche

    Science.gov (United States)

    Rompolas, Panteleimon; Greco, Valentina

    2014-01-01

    Hair follicles are skin appendages of the mammalian skin that have the ability to periodically and stereotypically regenerate in order to continuously produce new hair over our lifetime. The ability of the hair follicle to regenerate is due to the presence of stem cells that along with other cell populations and non-cellular components, including molecular signals and extracellular material, make up a niche microenvironment. Mounting evidence suggests that the niche is critical for regulating stem cell behavior and thus the process of regeneration. Here we review the literature concerning past and current studies that have utilized mouse genetic models, combined with other approaches to dissect the molecular and cellular composition of the hair follicle niche. We also discuss our current understanding of how stem cells operate within the niche during the process of tissue regeneration and the factors that regulate their behavior. PMID:24361866

  20. Interpreting the process behind endemism in China by integrating the phylogeography and ecological niche models of the Stachyridopsis ruficeps.

    Directory of Open Access Journals (Sweden)

    Huatao Liu

    Full Text Available An area of endemism (AOE is a complex expression of the ecological and evolutionary history of a species. Here we aim to address the principal drivers of avian diversification in shaping patterns of endemism in China by integrating genetic, ecological, and distributional data on the Red-headed Tree Babbler (Stachyridopsis ruficeps, which is distributed across the eastern Himalayas and south China. We sequenced two mtDNA markers from 182 individuals representing all three of the primary AOEs in China. Phylogenetic inferences were used to reconstruct intraspecific phylogenetic relationships. Divergence time and population demography were estimated to gain insight into the evolutionary history of the species. We used Ecological niche modeling to predict species' distributions during the Last Glacial Maximum (LGM and in the present. Finally, we also used two quantitative tests, an identity test and background test to assess the similarity of ecological niche preferences between adjacent lineages. We found five primary reciprocally monophyletic clades, typically separated approximately 0.2-2.27 MYA, of which three were deeply isolated endemic lineages located in the three AOEs. All phylogroups were detected to have undergone population expansion during the past 0.3 MY. Niche models showed discontinuous habitats, and there were three barriers of less suitable habitat during the LGM and in modern times. Ecoclimatic niches may diverge significantly even over recent timescales, as each phylogroup had a unique distribution, and unique niche characteristics. Vicariant events associated with geographical and ecological barriers, glacial refuges and ecological differentiation may be the main drivers forming the pattern of endemism in China.

  1. Global thermal niche models of two European grasses show high invasion risks in Antarctica.

    Science.gov (United States)

    Pertierra, Luis R; Aragón, Pedro; Shaw, Justine D; Bergstrom, Dana M; Terauds, Aleks; Olalla-Tárraga, Miguel Ángel

    2017-07-01

    The two non-native grasses that have established long-term populations in Antarctica (Poa pratensis and Poa annua) were studied from a global multidimensional thermal niche perspective to address the biological invasion risk to Antarctica. These two species exhibit contrasting introduction histories and reproductive strategies and represent two referential case studies of biological invasion processes. We used a multistep process with a range of species distribution modelling techniques (ecological niche factor analysis, multidimensional envelopes, distance/entropy algorithms) together with a suite of thermoclimatic variables, to characterize the potential ranges of these species. Their native bioclimatic thermal envelopes in Eurasia, together with the different naturalized populations across continents, were compared next. The potential niche of P. pratensis was wider at the cold extremes; however, P. annua life history attributes enable it to be a more successful colonizer. We observe that particularly cold summers are a key aspect of the unique Antarctic environment. In consequence, ruderals such as P. annua can quickly expand under such harsh conditions, whereas the more stress-tolerant P. pratensis endures and persist through steady growth. Compiled data on human pressure at the Antarctic Peninsula allowed us to provide site-specific biosecurity risk indicators. We conclude that several areas across the region are vulnerable to invasions from these and other similar species. This can only be visualized in species distribution models (SDMs) when accounting for founder populations that reveal nonanalogous conditions. Results reinforce the need for strict management practices to minimize introductions. Furthermore, our novel set of temperature-based bioclimatic GIS layers for ice-free terrestrial Antarctica provide a mechanism for regional and global species distribution models to be built for other potentially invasive species. © 2017 John Wiley & Sons Ltd.

  2. Local-scale models reveal ecological niche variability in amphibian and reptile communities from two contrasting biogeographic regions

    Directory of Open Access Journals (Sweden)

    Alberto Muñoz

    2016-10-01

    Full Text Available Ecological Niche Models (ENMs are widely used to describe how environmental factors influence species distribution. Modelling at a local scale, compared to a large scale within a high environmental gradient, can improve our understanding of ecological species niches. The main goal of this study is to assess and compare the contribution of environmental variables to amphibian and reptile ENMs in two Spanish national parks located in contrasting biogeographic regions, i.e., the Mediterranean and the Atlantic area. The ENMs were built with maximum entropy modelling using 11 environmental variables in each territory. The contributions of these variables to the models were analysed and classified using various statistical procedures (Mann–Whitney U tests, Principal Components Analysis and General Linear Models. Distance to the hydrological network was consistently the most relevant variable for both parks and taxonomic classes. Topographic variables (i.e., slope and altitude were the second most predictive variables, followed by climatic variables. Differences in variable contribution were observed between parks and taxonomic classes. Variables related to water availability had the larger contribution to the models in the Mediterranean park, while topography variables were decisive in the Atlantic park. Specific response curves to environmental variables were in accordance with the biogeographic affinity of species (Mediterranean and non-Mediterranean species and taxonomy (amphibians and reptiles. Interestingly, these results were observed for species located in both parks, particularly those situated at their range limits. Our findings show that ecological niche models built at local scale reveal differences in habitat preferences within a wide environmental gradient. Therefore, modelling at local scales rather than assuming large-scale models could be preferable for the establishment of conservation strategies for herptile species in natural

  3. Local-scale models reveal ecological niche variability in amphibian and reptile communities from two contrasting biogeographic regions

    Science.gov (United States)

    Santos, Xavier; Felicísimo, Ángel M.

    2016-01-01

    Ecological Niche Models (ENMs) are widely used to describe how environmental factors influence species distribution. Modelling at a local scale, compared to a large scale within a high environmental gradient, can improve our understanding of ecological species niches. The main goal of this study is to assess and compare the contribution of environmental variables to amphibian and reptile ENMs in two Spanish national parks located in contrasting biogeographic regions, i.e., the Mediterranean and the Atlantic area. The ENMs were built with maximum entropy modelling using 11 environmental variables in each territory. The contributions of these variables to the models were analysed and classified using various statistical procedures (Mann–Whitney U tests, Principal Components Analysis and General Linear Models). Distance to the hydrological network was consistently the most relevant variable for both parks and taxonomic classes. Topographic variables (i.e., slope and altitude) were the second most predictive variables, followed by climatic variables. Differences in variable contribution were observed between parks and taxonomic classes. Variables related to water availability had the larger contribution to the models in the Mediterranean park, while topography variables were decisive in the Atlantic park. Specific response curves to environmental variables were in accordance with the biogeographic affinity of species (Mediterranean and non-Mediterranean species) and taxonomy (amphibians and reptiles). Interestingly, these results were observed for species located in both parks, particularly those situated at their range limits. Our findings show that ecological niche models built at local scale reveal differences in habitat preferences within a wide environmental gradient. Therefore, modelling at local scales rather than assuming large-scale models could be preferable for the establishment of conservation strategies for herptile species in natural parks. PMID

  4. Ecological niche modelling and nDNA sequencing support a new, morphologically cryptic beetle species unveiled by DNA barcoding.

    Science.gov (United States)

    Hawlitschek, Oliver; Porch, Nick; Hendrich, Lars; Balke, Michael

    2011-02-09

    DNA sequencing techniques used to estimate biodiversity, such as DNA barcoding, may reveal cryptic species. However, disagreements between barcoding and morphological data have already led to controversy. Species delimitation should therefore not be based on mtDNA alone. Here, we explore the use of nDNA and bioclimatic modelling in a new species of aquatic beetle revealed by mtDNA sequence data. The aquatic beetle fauna of Australia is characterised by high degrees of endemism, including local radiations such as the genus Antiporus. Antiporus femoralis was previously considered to exist in two disjunct, but morphologically indistinguishable populations in south-western and south-eastern Australia. We constructed a phylogeny of Antiporus and detected a deep split between these populations. Diagnostic characters from the highly variable nuclear protein encoding arginine kinase gene confirmed the presence of two isolated populations. We then used ecological niche modelling to examine the climatic niche characteristics of the two populations. All results support the status of the two populations as distinct species. We describe the south-western species as Antiporus occidentalis sp.n. In addition to nDNA sequence data and extended use of mitochondrial sequences, ecological niche modelling has great potential for delineating morphologically cryptic species.

  5. Hydrological-niche models predict water plant functional group distributions in diverse wetland types.

    Science.gov (United States)

    Deane, David C; Nicol, Jason M; Gehrig, Susan L; Harding, Claire; Aldridge, Kane T; Goodman, Abigail M; Brookes, Justin D

    2017-06-01

    Human use of water resources threatens environmental water supplies. If resource managers are to develop policies that avoid unacceptable ecological impacts, some means to predict ecosystem response to changes in water availability is necessary. This is difficult to achieve at spatial scales relevant for water resource management because of the high natural variability in ecosystem hydrology and ecology. Water plant functional groups classify species with similar hydrological niche preferences together, allowing a qualitative means to generalize community responses to changes in hydrology. We tested the potential for functional groups in making quantitative prediction of water plant functional group distributions across diverse wetland types over a large geographical extent. We sampled wetlands covering a broad range of hydrogeomorphic and salinity conditions in South Australia, collecting both hydrological and floristic data from 687 quadrats across 28 wetland hydrological gradients. We built hydrological-niche models for eight water plant functional groups using a range of candidate models combining different surface inundation metrics. We then tested the predictive performance of top-ranked individual and averaged models for each functional group. Cross validation showed that models achieved acceptable predictive performance, with correct classification rates in the range 0.68-0.95. Model predictions can be made at any spatial scale that hydrological data are available and could be implemented in a geographical information system. We show the response of water plant functional groups to inundation is consistent enough across diverse wetland types to quantify the probability of hydrological impacts over regional spatial scales. © 2017 by the Ecological Society of America.

  6. Inferring the past and present connectivity across the range of a North American leaf beetle: combining ecological niche modeling and a geographically explicit model of coalescence.

    Science.gov (United States)

    Dellicour, Simon; Fearnley, Shannon; Lombal, Anicée; Heidl, Sarah; Dahlhoff, Elizabeth P; Rank, Nathan E; Mardulyn, Patrick

    2014-08-01

    The leaf beetle Chrysomela aeneicollis occurs across Western North America, either at high elevation or in small, isolated populations along the coast, and thus has a highly fragmented distribution. DNA sequence data (three loci) were collected from five regions across the species range. Population connectivity was examined using traditional ecological niche modeling, which suggested that gene flow could occur among regions now and in the past. We developed geographically explicit coalescence models of sequence evolution that incorporated a two-dimensional representation of the hypothesized ranges suggested by the niche-modeling estimates. We simulated sequence data according to these models and compared them to observed sequences to identify most probable scenarios regarding the migration history of C. aeneicollis. Our results disagreed with initial niche-modeling estimates by clearly rejecting recent connectivity among regions, and were instead most consistent with a long period of range fragmentation, extending well beyond the last glacial maximum. This application of geographically explicit models of coalescence has highlighted some limitations of the use of climatic variables for predicting the present and past range of a species and has explained aspects of the Pleistocene evolutionary history of a cold-adapted organism in Western North America. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  7. To predict the niche, model colonization and extinction

    Science.gov (United States)

    Charles B. Yackulic; James D. Nichols; Janice Reid; Ricky Der

    2015-01-01

    Ecologists frequently try to predict the future geographic distributions of species. Most studies assume that the current distribution of a species reflects its environmental requirements (i.e., the species’ niche). However, the current distributions of many species are unlikely to be at equilibrium with the current distribution of environmental conditions, both...

  8. Niche energy markets in rural areas

    International Nuclear Information System (INIS)

    Walsh, M.; McCarthy, S.

    1996-01-01

    The objective of this project is the development of a standard methodology for integrating non-food crops in rural areas with niche energy markets. This has involved a number of steps including (i) identification of 3 niche markets for energy crops which are of common interest to the partners, (ii) application of the standard costing methodology to investigate these three niche markets and (iii) comparison of the results from this work in three workshops (one for each market). Three tightly defined niche markets were identified; these were chosen following an examination of the national energy marekts in each of the partners countries (Ireland, Germany, Netherlands, UK, Greece and Portugal). This paper gives an overview of the national energy markets which were examined. The three niche markets are introduced and the reasons for their selection given. The application of the methodology to each of the niche markets is presented along with the conclusions of the partners regarding the niche markets. (Author)

  9. Compatible ecological niche signals between biological and archaeological datasets for late-surviving Neandertals.

    Science.gov (United States)

    Bible, Rachael C; Peterson, A Townsend

    2018-04-17

    To assess ecological niche similarity for biological and archaeological samples representing late-surviving Neandertals in Europe to evaluate the validity of combining these two types of data in ecological niche modeling analyses. Tests of niche conservatism were used to assess niche similarity and niche identity of samples of morphologically diagnostic Neandertal remains and Middle Paleolithic (MP) archaeological sites dating to the time period leading up to Neandertal extinction. Paleoenvironmental reconstructions for the Pre-H4 (43.3-40.2 ky cal BP) were used as environmental space analyses. Null hypotheses of niche similarity and identity of the two types of samples could not be rejected. As primary and secondary evidence of Neandertal occurrence during the Pre-H4 show high levels of niche similarity and identity, combining the two types of occurrence data to create larger samples for niche analyses is justified without the concern that different environmental signals could complicate future research. © 2018 Wiley Periodicals, Inc.

  10. Niche conservatism of Eulophia alta, a trans-Atlantic orchid species

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    Marta Kolanowska

    2014-03-01

    Full Text Available The genus Eulophia embraces over 230 species distributed through the tropical and subtropical Africa, Asia, Australia and the Americas. In Neotropics it is represented by a sole species – E. alta. The aim of the presented study was to evaluate the difference between ecological niches occupied by American and African populations of this species based on the ecological niche modeling. The similarity between the glacial and present niches occupied by E. alta was calculated and the factors limiting the species occurrence were identified. Areas of seasonal tropical forest, tropical savanna and woodland served as refugia for the studied species during last glacial maximum and they were more widespread in Neotropics than in Africa. No significant niche shift after last glacial maximum was observed. The distribution of E. alta in its whole range is restricted mainly by temperature seasonality. The differences in the niches occupied by African and Neotropical populations of E. alta suggest preglacial disjunction of the species range and independent adaptation of both groups. Despite the significant range disjunction of E. alta the species is characterized by relatively high degree of niche conservatism.

  11. Niche players

    Science.gov (United States)

    Seandel, Marco; Falciatori, Ilaria; Shmelkov, Sergey V.; Kim, Jiyeon; James, Daylon; Rafii, Shahin

    2010-01-01

    The undifferentiated spermatogonia of adult mouse testes are composed of both true stem cells and committed progenitors. It is unclear what normally prevents these adult germ cells from manifesting multipotency. The critical elements of the spermatogonial stem cell niche, while poorly understood, are thought to be composed of Sertoli cells with several other somatic cell types in close proximity. We recently discovered a novel orphan G-protein coupled receptor (GPR125) that is restricted to undifferentiated spermatogonia within the testis. GPR125 expression was maintained when the progenitor cells were extracted from the in vivo niche and propagated under growth conditions that recapitulate key elements of the niche. Such conditions preserved the ability of the cells to generate multipotent derivatives, known as multipotent adult spermatogonial derived progenitor cells (MASCs). Upon differentiation, the latter produced a variety tissues including functional endothelium, illustrating the potential applications of such cells. Thus, GPR125 represents a novel target for purifying adult stem and progenitors from tissues, with the goal of developing autologous multipotent cell lines. PMID:18256534

  12. Current and future niche of North and Central American sand flies (Diptera: psychodidae in climate change scenarios.

    Directory of Open Access Journals (Sweden)

    David Moo-Llanes

    Full Text Available Ecological niche models are useful tools to infer potential spatial and temporal distributions in vector species and to measure epidemiological risk for infectious diseases such as the Leishmaniases. The ecological niche of 28 North and Central American sand fly species, including those with epidemiological relevance, can be used to analyze the vector's ecology and its association with transmission risk, and plan integrated regional vector surveillance and control programs. In this study, we model the environmental requirements of the principal North and Central American phlebotomine species and analyze three niche characteristics over future climate change scenarios: i potential change in niche breadth, ii direction and magnitude of niche centroid shifts, iii shifts in elevation range. Niche identity between confirmed or incriminated Leishmania vector sand flies in Mexico, and human cases were analyzed. Niche models were constructed using sand fly occurrence datapoints from Canada, USA, Mexico, Guatemala and Belize. Nine non-correlated bioclimatic and four topographic data layers were used as niche components using GARP in OpenModeller. Both B2 and A2 climate change scenarios were used with two general circulation models for each scenario (CSIRO and HadCM3, for 2020, 2050 and 2080. There was an increase in niche breadth to 2080 in both scenarios for all species with the exception of Lutzomyia vexator. The principal direction of niche centroid displacement was to the northwest (64%, while the elevation range decreased greatest for tropical, and least for broad-range species. Lutzomyia cruciata is the only epidemiologically important species with high niche identity with that of Leishmania spp. in Mexico. Continued landscape modification in future climate change will provide an increased opportunity for the geographic expansion of NCA sand flys' ENM and human exposure to vectors of Leishmaniases.

  13. Current and Future Niche of North and Central American Sand Flies (Diptera: Psychodidae) in Climate Change Scenarios

    Science.gov (United States)

    Moo-Llanes, David; Ibarra-Cerdeña, Carlos N.; Rebollar-Téllez, Eduardo A.; Ibáñez-Bernal, Sergio; González, Camila; Ramsey, Janine M.

    2013-01-01

    Ecological niche models are useful tools to infer potential spatial and temporal distributions in vector species and to measure epidemiological risk for infectious diseases such as the Leishmaniases. The ecological niche of 28 North and Central American sand fly species, including those with epidemiological relevance, can be used to analyze the vector's ecology and its association with transmission risk, and plan integrated regional vector surveillance and control programs. In this study, we model the environmental requirements of the principal North and Central American phlebotomine species and analyze three niche characteristics over future climate change scenarios: i) potential change in niche breadth, ii) direction and magnitude of niche centroid shifts, iii) shifts in elevation range. Niche identity between confirmed or incriminated Leishmania vector sand flies in Mexico, and human cases were analyzed. Niche models were constructed using sand fly occurrence datapoints from Canada, USA, Mexico, Guatemala and Belize. Nine non-correlated bioclimatic and four topographic data layers were used as niche components using GARP in OpenModeller. Both B2 and A2 climate change scenarios were used with two general circulation models for each scenario (CSIRO and HadCM3), for 2020, 2050 and 2080. There was an increase in niche breadth to 2080 in both scenarios for all species with the exception of Lutzomyia vexator. The principal direction of niche centroid displacement was to the northwest (64%), while the elevation range decreased greatest for tropical, and least for broad-range species. Lutzomyia cruciata is the only epidemiologically important species with high niche identity with that of Leishmania spp. in Mexico. Continued landscape modification in future climate change will provide an increased opportunity for the geographic expansion of NCA sand flys' ENM and human exposure to vectors of Leishmaniases. PMID:24069478

  14. Biodiversity influences plant productivity through niche-efficiency.

    Science.gov (United States)

    Liang, Jingjing; Zhou, Mo; Tobin, Patrick C; McGuire, A David; Reich, Peter B

    2015-05-05

    The loss of biodiversity is threatening ecosystem productivity and services worldwide, spurring efforts to quantify its effects on the functioning of natural ecosystems. Previous research has focused on the positive role of biodiversity on resource acquisition (i.e., niche complementarity), but a lack of study on resource utilization efficiency, a link between resource and productivity, has rendered it difficult to quantify the biodiversity-ecosystem functioning relationship. Here we demonstrate that biodiversity loss reduces plant productivity, other things held constant, through theory, empirical evidence, and simulations under gradually relaxed assumptions. We developed a theoretical model named niche-efficiency to integrate niche complementarity and a heretofore-ignored mechanism of diminishing marginal productivity in quantifying the effects of biodiversity loss on plant productivity. Based on niche-efficiency, we created a relative productivity metric and a productivity impact index (PII) to assist in biological conservation and resource management. Relative productivity provides a standardized measure of the influence of biodiversity on individual productivity, and PII is a functionally based taxonomic index to assess individual species' inherent value in maintaining current ecosystem productivity. Empirical evidence from the Alaska boreal forest suggests that every 1% reduction in overall plant diversity could render an average of 0.23% decline in individual tree productivity. Out of the 283 plant species of the region, we found that large woody plants generally have greater PII values than other species. This theoretical model would facilitate the integration of biological conservation in the international campaign against several pressing global issues involving energy use, climate change, and poverty.

  15. Domestic policy consequences of new implementation models. Consequences for industrial niches; Industripolitiske konsekvenser av nye gjennomfoeringsmodeller. Konsekvenser for nisjebedriftene

    Energy Technology Data Exchange (ETDEWEB)

    Johannessen, T.

    1995-12-31

    The paper relates to the consequences of domestic policy with the focus on new implementation models used for cost reduction of offshore development projects in Norway. The paper puts the attention to the consequences from implementation models on industrial niches (subcontractors)

  16. Division within the North American boreal forest: Ecological niche divergence between the Bicknell's Thrush (Catharus bicknelli) and Gray-cheeked Thrush (C. minimus).

    Science.gov (United States)

    FitzGerald, Alyssa M

    2017-07-01

    Sister species that diverged in allopatry in similar environments are expected to exhibit niche conservatism. Using ecological niche modeling and a multivariate analysis of climate and habitat data, I test the hypothesis that the Bicknell's Thrush ( Catharus bicknelli ) and Gray-cheeked Thrush ( C. mimimus ), sister species that breed in the North American boreal forest, show niche conservatism. Three tree species that are important components of breeding territories of both thrush species were combined with climatic variables to create niche models consisting of abiotic and biotic components. Abiotic-only, abiotic+biotic, and biotic-only models were evaluated using the area under the curve (AUC) criterion. Abiotic+biotic models had higher AUC scores and did not over-project thrush distributions compared to abiotic-only or biotic-only models. From the abiotic+biotic models, I tested for niche conservatism or divergence by accounting for the differences in the availability of niche components by calculating (1) niche overlap from ecological niche models and (2) mean niche differences of environmental values at occurrence points. Niche background similarity tests revealed significant niche divergence in 10 of 12 comparisons, and multivariate tests revealed niche divergence along 2 of 3 niche axes. The Bicknell's Thrush breeds in warmer and wetter regions with a high abundance of balsam fir ( Abies balsamea ), whereas Gray-cheeked Thrush often co-occurs with black spruce ( Picea mariana ). Niche divergence, rather than conservatism, was the predominant pattern for these species, suggesting that ecological divergence has played a role in the speciation of the Bicknell's Thrush and Gray-cheeked Thrush. Furthermore, because niche models were improved by the incorporation of biotic variables, this study validates the inclusion of relevant biotic factors in ecological niche modeling to increase model accuracy.

  17. Stem Cell Plasticity and Niche Dynamics in Cancer Progression.

    Science.gov (United States)

    Picco, Noemi; Gatenby, Robert A; Anderson, Alexander R A

    2017-03-01

    Cancer stem cells (CSCs) have been hypothesized to initiate and drive tumor growth and recurrence due to their self-renewal ability. If correct, this hypothesis implies that successful therapy must focus primarily on eradication of this CSC fraction. However, recent evidence suggests stemness is niche dependent and may represent one of many phenotypic states that can be accessed by many cancer genotypes when presented with specific environmental cues. A better understanding of the relationship of stemness to niche-related phenotypic plasticity could lead to alternative treatment strategies. Here, we investigate the role of environmental context in the expression of stem-like cell properties through in-silico simulation of ductal carcinoma. We develop a two-dimensional hybrid discrete-continuum cellular automata model to describe the single-cell scale dynamics of multicellular tissue formation. Through a suite of simulations, we investigate interactions between a phenotypically heterogeneous cancer cell population and a dynamic environment. We generate homeostatic ductal structures that consist of a mixture of stem and differentiated cells governed by both intracellular and environmental dynamics. We demonstrate that a wide spectrum of tumor-like histologies can result from these structures by varying microenvironmental parameters. Niche driven phenotypic plasticity offers a simple first-principle explanation for the diverse ductal structures observed in histological sections from breast cancer. Conventional models of carcinogenesis largely focus on mutational events. We demonstrate that variations in the environmental niche can produce intraductal cancers independent of genetic changes in the resident cells. Therapies targeting the microenvironmental niche may offer an alternative cancer prevention strategy.

  18. Assessing the potential for establishment of western cherry fruit fly using ecological niche modeling.

    Science.gov (United States)

    Kumar, Sunil; Neven, Lisa G; Yee, Wee L

    2014-06-01

    Sweet cherries, Prunus avium (L.) L., grown in the western United States are exported to many countries around the world. Some of these countries have enforced strict quarantine rules and trade restrictions owing to concerns about the potential establishment and subsequent spread of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), a major quarantine pest of sweet cherry. We used 1) niche models (CLIMEX and MaxEnt) to map the climatic suitability, 2) North Carolina State University-Animal and Plant Health Inspection Service Plant Pest Forecasting System to examine chilling requirement, and 3) host distribution and availability to assess the potential for establishment of R. indifferens in areas of western North America where it currently does not exist and eight current or potential fresh sweet cherry markets: Colombia, India, Indonesia, Malaysia, Taiwan, Thailand, Venezuela, and Vietnam. Results from niche models conformed well to the current distribution of R. indifferens in western North America. MaxEnt and CLIMEX models had high performance and predicted climatic suitability in some of the countries (e.g., Andean range in Colombia and Venezuela, northern and northeastern India, central Taiwan, and parts of Vietnam). However, our results showed no potential for establishment of R. indifferens in Colombia, Indonesia, Malaysia, Taiwan, Thailand, Venezuela, and Vietnam when the optimal chilling requirement to break diapause (minimum temperature policy makers.

  19. Matching global and regional distribution models of the recluse spider Loxosceles rufescens: to what extent do these reflect niche conservatism?

    Science.gov (United States)

    Taucare-Ríos, A; Nentwig, W; Bizama, G; Bustamante, R O

    2018-06-08

    The Mediterranean recluse spider, Loxosceles rufescens (Dufour, 1820) (Araneae: Sicariidae) is a cosmopolitan spider that has been introduced in many parts of the world. Its bite can be dangerous to humans. However, the potential distribution of this alien species, which is able to spread fairly quickly with human aid, is completely unknown. Using a combination of global and regional niche models, it is possible to analyse the spread of this species in relation to environmental conditions. This analysis found that the successful spreading of this species varies according to the region invaded. The majority of populations in Asia are stable and show niche conservatism, whereas in North America this spider is expected to be less successful in occupying niches that differ from those in its native region and that do not support its synanthropic way of living. © 2018 The Royal Entomological Society.

  20. A variational approach to niche construction.

    Science.gov (United States)

    Constant, Axel; Ramstead, Maxwell J D; Veissière, Samuel P L; Campbell, John O; Friston, Karl J

    2018-04-01

    In evolutionary biology, niche construction is sometimes described as a genuine evolutionary process whereby organisms, through their activities and regulatory mechanisms, modify their environment such as to steer their own evolutionary trajectory, and that of other species. There is ongoing debate, however, on the extent to which niche construction ought to be considered a bona fide evolutionary force, on a par with natural selection. Recent formulations of the variational free-energy principle as applied to the life sciences describe the properties of living systems, and their selection in evolution, in terms of variational inference. We argue that niche construction can be described using a variational approach. We propose new arguments to support the niche construction perspective, and to extend the variational approach to niche construction to current perspectives in various scientific fields. © 2018 The Authors.

  1. When does it pay to invest in a patch? The evolution of intentional niche construction.

    Science.gov (United States)

    Mohlenhoff, Kathryn A; Codding, Brian F

    2017-09-01

    Humans modify their environments in ways that significantly transform the earth's ecosystems. Recent research suggests that such niche-constructing behaviors are not passive human responses to environmental variation, but instead should be seen as active and intentional management of the environment. Although such research is useful in highlighting the interactive dynamics between humans and their natural world, the niche-construction framework, as currently applied, fails to explain why people would decide to modify their environments in the first place. To help resolve this problem, we use a model of technological intensification to analyze the cost-benefit trade-offs associated with niche construction as a form of patch investment. We use this model to assess the costs and benefits of three paradigmatic cases of intentional niche construction in Western North America: the application of fire in acorn groves, the manufacture of fishing weirs, and the adoption of maize agriculture. Intensification models predict that investing in patch modification (niche construction) only provides a net benefit when the amount of resources needed crosses a critical threshold that makes the initial investment worthwhile. From this, it follows that low-cost investments, such as burning in oak groves, should be quite common, while more costly investments, such as maize agriculture, should be less common and depend on the alternatives available in the local environment. We examine how patterns of mobility, risk management, territoriality, and private property also co-evolve with the costs and benefits of niche construction. This approach illustrates that explaining niche-constructing behavior requires understanding the economic trade-offs involved in patch investment. Integrating concepts from niche construction and technological intensification models within a behavioral ecological framework provides insights into the coevolution and active feedback between adaptive behaviors and

  2. Comparison of Hematopoietic and Spermatogonial Stem Cell Niches from the Regenerative Medicine Aspect.

    Science.gov (United States)

    Köse, Sevil; Yersal, Nilgün; Önen, Selin; Korkusuz, Petek

    2018-06-08

    Recent advances require a dual evaluation of germ and somatic stem cell niches with a regenerative medicine perspective. For a better point of view of the niche concept, it is needed to compare the microenvironments of those niches in respect to several components. The cellular environment of spermatogonial stem cells' niche consists of Sertoli cells, Leydig cells, vascular endothelial cells, epididymal fat cells, peritubular myoid cells while hematopoietic stem cells have mesenchymal stem cells, osteoblasts, osteoclasts, megacaryocytes, macrophages, vascular endothelial cells, pericytes and adipocytes in their microenvironment. Not only those cells', but also the effect of the other factors such as hormones, growth factors, chemokines, cytokines, extracellular matrix components, biomechanical forces (like shear stress, tension or compression) and physical environmental elements such as temperature, oxygen level and pH will be clarified during the chapter. Because it is known that the microenvironment has an important role in the stem cell homeostasis and disease conditions, it is crucial to understand the details of the microenvironment and to be able to compare the niche concepts of the different types of stem cells from each other, for the regenerative interventions. Indeed, the purpose of this chapter is to point out the usage of niche engineering within the further studies in the regenerative medicine field. Decellularized, synthetic or non-synthetic scaffolds may help to mimic the stem cell niche. However, the shared or different characteristics of germ and somatic stem cell microenvironments are necessary to constitute a proper niche model. When considered from this aspect, it is possible to produce some strategies on the personalized medicine by using those artificial models of stem cell microenvironment.

  3. Postglacial species displacement in Triturus newts deduced from asymmetrically introgressed mitochondrial DNA and ecological niche models

    Directory of Open Access Journals (Sweden)

    Wielstra Ben

    2012-08-01

    Full Text Available Abstract Background If the geographical displacement of one species by another is accompanied by hybridization, mitochondrial DNA can introgress asymmetrically, from the outcompeted species into the invading species, over a large area. We explore this phenomenon using the two parapatric crested newt species, Triturus macedonicus and T. karelinii, distributed on the Balkan Peninsula in south-eastern Europe, as a model. Results We first delimit a ca. 54,000 km2 area in which T. macedonicus contains T. karelinii mitochondrial DNA. This introgression zone bisects the range of T. karelinii, cutting off a T. karelinii enclave. The high similarity of introgressed mitochondrial DNA haplotypes with those found in T. karelinii suggests a recent transfer across the species boundary. We then use ecological niche modeling to explore habitat suitability of the location of the present day introgression zone under current, mid-Holocene and Last Glacial Maximum conditions. This area was inhospitable during the Last Glacial Maximum for both species, but would have been habitable at the mid-Holocene. Since the mid-Holocene, habitat suitability generally increased for T. macedonicus, whereas it decreased for T. karelinii. Conclusion The presence of a T. karelinii enclave suggests that T. karelinii was the first to colonize the area where the present day introgression zone is positioned after the Last Glacial Maximum. Subsequently, we propose T. karelinii was outcompeted by T. macedonicus, which captured T. karelinii mitochondrial DNA via introgressive hybridization in the process. Ecological niche modeling suggests that this replacement was likely facilitated by a shift in climate since the mid-Holocene. We suggest that the northwestern part of the current introgression zone was probably never inhabited by T. karelinii itself, and that T. karelinii mitochondrial DNA spread there through T. macedonicus exclusively. Considering the spatial distribution of the

  4. The United States pork niche market phenomenon.

    Science.gov (United States)

    Honeyman, M S; Pirog, R S; Huber, G H; Lammers, P J; Hermann, J R

    2006-08-01

    After the broad industrialization of the US pork industry, there has been a development of niche markets for export and domestic pork; that is, there is a pork niche market phenomenon. The US pork niche market phenomenon is characterized, and 2 of the major markets are explained in detail. With the Midwest's tradition of a diversified family-based agriculture and record low hog prices of the late 1990s, the conditions were conducive for this phenomenon to develop. Pork niche markets utilize various sales methods including Internet sales, local abattoir sales, direct marketing, farmer networks, and targeting to organized groups. In 2003, there were approximately 35 to 40 active pork niche marketing efforts in Iowa. The Berkshire breed is an example of a swine breed that has had a recent resurgence because of niche markets. Berkshire pork is known for tenderness and excellent quality. Berkshire registrations have increased 4-fold in the last 10 yr. One of the larger niche marketers of "natural pork" is Niman Ranch Pork, which has more than 400 farmer-producers and processes about 2,500 pigs weekly. Many US consumers of pork are interested in issues concerning the environment, food safety, pig welfare, and pig farm ownership and structure. These consumers may be willing to pay more for pork from farmers who are also concerned about these issues. Small- and medium-sized swine farmers are active in pork niche markets. Niche markets claim product differentiation by superior or unique product quality and social attributes. Quality attributes include certain swine breeds, and meat quality, freshness, taste or flavor, and tenderness. Social or credence attributes often are claimed and include freedom from antibiotics and growth promotants; local family farm production; natural, organic, outdoor, or bedded rearing; humane rearing; known origin; environmentally friendly production; and the absence of animal by-products in the feed. Niche pork markets and alternative swine

  5. Niche evolution and adaptive radiation: Testing the order of trait divergence

    Science.gov (United States)

    Ackerly, D.D.; Schwilk, D.W.; Webb, C.O.

    2006-01-01

    In the course of an adaptive radiation, the evolution of niche parameters is of particular interest for understanding modes of speciation and the consequences for coexistence of related species within communities. We pose a general question: In the course of an evolutionary radiation, do traits related to within-community niche differences (?? niche) evolve before or after differentiation of macrohabitat affinity or climatic tolerances (?? niche)? Here we introduce a new test to address this question, based on a modification of the method of independent contrasts. The divergence order test (DOT) is based on the average age of the nodes on a tree, weighted by the absolute magnitude of the contrast at each node for a particular trait. The comparison of these weighted averages reveals whether large divergences for one trait have occurred earlier or later in the course of diversification, relative to a second trait; significance is determined by bootstrapping from maximum-likelihood ancestral state reconstructions. The method is applied to the evolution of Ceanothus, a woody plant group in California, in which co-occurring species exhibit significant differences in a key leaf trait (specific leaf area) associated with contrasting physiological and life history strategies. Co-occurring species differ more for this trait than expected under a null model of community assembly. This ?? niche difference evolved early in the divergence of two major subclades within Ceanothus, whereas climatic distributions (?? niche traits) diversified later within each of the subclades. However, rapid evolution of climate parameters makes inferences of early divergence events highly uncertain, and differentiation of the ?? niche might have taken place throughout the evolution of the group, without leaving a clear phylogenetic signal. Similar patterns observed in several plant and animal groups suggest that early divergence of ?? niche traits might be a common feature of niche evolution in

  6. Ecological niche models reveal the importance of climate variability for the biogeography of protosteloid amoebae.

    Science.gov (United States)

    Aguilar, María; Lado, Carlos

    2012-08-01

    Habitat availability and environmental preferences of species are among the most important factors in determining the success of dispersal processes and therefore in shaping the distribution of protists. We explored the differences in fundamental niches and potential distributions of an ecological guild of slime moulds-protosteloid amoebae-in the Iberian Peninsula. A large set of samples collected in a north-east to south-west transect of approximately 1000 km along the peninsula was used to test the hypothesis that, together with the existence of suitable microhabitats, climate conditions may determine the probability of survival of species. Although protosteloid amoebae share similar morphologies and life history strategies, canonical correspondence analyses showed that they have varied ecological optima, and that climate conditions have an important effect in niche differentiation. Maxent environmental niche models provided consistent predictions of the probability of presence of the species based on climate data, and they were used to generate maps of potential distribution in an 'everything is everywhere' scenario. The most important climatic factors were, in both analyses, variables that measure changes in conditions throughout the year, confirming that the alternation of fruiting bodies, cysts and amoeboid stages in the life cycles of protosteloid amoebae constitutes an advantage for surviving in a changing environment. Microhabitat affinity seems to be influenced by climatic conditions, which suggests that the micro-environment may vary at a local scale and change together with the external climate at a larger scale.

  7. THE NICHE CONSTRUCTION PERSPECTIVE: A CRITICAL APPRAISAL*

    Science.gov (United States)

    Scott-Phillips, Thomas C; Laland, Kevin N; Shuker, David M; Dickins, Thomas E; West, Stuart A

    2014-01-01

    Niche construction refers to the activities of organisms that bring about changes in their environments, many of which are evolutionarily and ecologically consequential. Advocates of niche construction theory (NCT) believe that standard evolutionary theory fails to recognize the full importance of niche construction, and consequently propose a novel view of evolution, in which niche construction and its legacy over time (ecological inheritance) are described as evolutionary processes, equivalent in importance to natural selection. Here, we subject NCT to critical evaluation, in the form of a collaboration between one prominent advocate of NCT, and a team of skeptics. We discuss whether niche construction is an evolutionary process, whether NCT obscures or clarifies how natural selection leads to organismal adaptation, and whether niche construction and natural selection are of equivalent explanatory importance. We also consider whether the literature that promotes NCT overstates the significance of niche construction, whether it is internally coherent, and whether it accurately portrays standard evolutionary theory. Our disagreements reflect a wider dispute within evolutionary theory over whether the neo-Darwinian synthesis is in need of reformulation, as well as different usages of some key terms (e.g., evolutionary process). PMID:24325256

  8. The niche party concept and its measurement

    OpenAIRE

    Meyer, Thomas M; Miller, Bernhard

    2015-01-01

    The concept of the niche party has become increasingly popular in analyses of party competition. Yet, existing approaches vary in their definitions and their measurement approaches. We propose using a minimal definition that allows us to compare political parties in terms of their ?nicheness?. We argue that the conceptual core of the niche party concept is based on issue emphasis and that a niche party emphasizes policy areas neglected by its rivals. Based on this definition, we propose a con...

  9. Plant stem cell niches.

    Science.gov (United States)

    Stahl, Yvonne; Simon, Rüdiger

    2005-01-01

    Stem cells are required to support the indeterminate growth style of plants. Meristems are a plants stem cell niches that foster stem cell survival and the production of descendants destined for differentiation. In shoot meristems, stem cell fate is decided at the populational level. The size of the stem cell domain at the meristem tip depends on signals that are exchanged with cells of the organizing centre underneath. In root meristems, individual stem cells are controlled by direct interaction with cells of the quiescent centre that lie in the immediate neighbourhood. Analysis of the interactions and signaling processes in the stem cell niches has delivered some insights into the molecules that are involved and revealed that the two major niches for plant stem cells are more similar than anticipated.

  10. Bone Marrow Vascular Niche: Home for Hematopoietic Stem Cells

    Directory of Open Access Journals (Sweden)

    Ningning He

    2014-01-01

    Full Text Available Though discovered later than osteoblastic niche, vascular niche has been regarded as an alternative indispensable niche operating regulation on hematopoietic stem cells (HSCs. As significant progresses gained on this type niche, it is gradually clear that the main work of vascular niche is undertaking to support hematopoiesis. However, compared to what have been defined in the mechanisms through which the osteoblastic niche regulates hematopoiesis, we know less in vascular niche. In this review, based on research data hitherto we will focus on component foundation and various functions of vascular niche that guarantee the normal hematopoiesis process within bone marrow microenvironments. And the possible pathways raised by various research results through which this environment undergoes its function will be discussed as well.

  11. Niche-specific cognitive strategies

    DEFF Research Database (Denmark)

    Hulgard, K.; Ratcliffe, J. M.

    2014-01-01

    Related species with different diets are predicted to rely on different cognitive strategies: those best suited for locating available and appropriate foods. Here we tested two predictions of the niche-specific cognitive strategies hypothesis in bats, which suggests that predatory species should...... the niche-specific cognitive strategies hypothesis and suggest that for gleaning and clutter-resistant aerial hawking bats, learning to associate shape with food interferes with subsequent spatial memory learning....

  12. Functional traits, convergent evolution, and periodic tables of niches.

    Science.gov (United States)

    Winemiller, Kirk O; Fitzgerald, Daniel B; Bower, Luke M; Pianka, Eric R

    2015-08-01

    Ecology is often said to lack general theories sufficiently predictive for applications. Here, we examine the concept of a periodic table of niches and feasibility of niche classification schemes from functional trait and performance data. Niche differences and their influence on ecological patterns and processes could be revealed effectively by first performing data reduction/ordination analyses separately on matrices of trait and performance data compiled according to logical associations with five basic niche 'dimensions', or aspects: habitat, life history, trophic, defence and metabolic. Resultant patterns then are integrated to produce interpretable niche gradients, ordinations and classifications. Degree of scheme periodicity would depend on degrees of niche conservatism and convergence causing species clustering across multiple niche dimensions. We analysed a sample data set containing trait and performance data to contrast two approaches for producing niche schemes: species ordination within niche gradient space, and niche categorisation according to trait-value thresholds. Creation of niche schemes useful for advancing ecological knowledge and its applications will depend on research that produces functional trait and performance datasets directly related to niche dimensions along with criteria for data standardisation and quality. As larger databases are compiled, opportunities will emerge to explore new methods for data reduction, ordination and classification. © 2015 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd.

  13. Species-specific ecological niche modelling predicts different range contractions for Lutzomyia intermedia and a related vector of Leishmania braziliensis following climate change in South America.

    Science.gov (United States)

    McIntyre, Shannon; Rangel, Elizabeth F; Ready, Paul D; Carvalho, Bruno M

    2017-03-24

    Before 1996 the phlebotomine sand fly Lutzomyia neivai was usually treated as a synonym of the morphologically similar Lutzomyia intermedia, which has long been considered a vector of Leishmania braziliensis, the causative agent of much cutaneous leishmaniasis in South America. This report investigates the likely range changes of both sand fly species in response to a stabilisation climate change scenario (RCP4.5) and a high greenhouse gas emissions one (RCP8.5). Ecological niche modelling was used to identify areas of South America with climates currently suitable for each species, and then the future distributions of these climates were predicted based on climate change scenarios. Compared with the previous ecological niche model of L. intermedia (sensu lato) produced using the GARP algorithm in 2003, the current investigation modelled the two species separately, making use of verified presence records and additional records after 2001. Also, the new ensemble approach employed ecological niche modelling algorithms (including Maximum Entropy, Random Forests and Support Vector Machines) that have been widely adopted since 2003 and perform better than GARP, as well as using a more recent climate change model (HadGEM2) considered to have better performance at higher resolution than the earlier one (HadCM2). Lutzomyia intermedia was shown to be the more tropical of the two species, with its climatic niche defined by higher annual mean temperatures and lower temperature seasonality, in contrast to the more subtropical L. neivai. These different latitudinal ranges explain the two species' predicted responses to climate change by 2050, with L. intermedia mostly contracting its range (except perhaps in northeast Brazil) and L. neivai mostly shifting its range southwards in Brazil and Argentina. This contradicts the findings of the 2003 report, which predicted more range expansion. The different findings can be explained by the improved data sets and modelling methods. Our

  14. The niche construction perspective: a critical appraisal.

    Science.gov (United States)

    Scott-Phillips, Thomas C; Laland, Kevin N; Shuker, David M; Dickins, Thomas E; West, Stuart A

    2014-05-01

    Niche construction refers to the activities of organisms that bring about changes in their environments, many of which are evolutionarily and ecologically consequential. Advocates of niche construction theory (NCT) believe that standard evolutionary theory fails to recognize the full importance of niche construction, and consequently propose a novel view of evolution, in which niche construction and its legacy over time (ecological inheritance) are described as evolutionary processes, equivalent in importance to natural selection. Here, we subject NCT to critical evaluation, in the form of a collaboration between one prominent advocate of NCT, and a team of skeptics. We discuss whether niche construction is an evolutionary process, whether NCT obscures or clarifies how natural selection leads to organismal adaptation, and whether niche construction and natural selection are of equivalent explanatory importance. We also consider whether the literature that promotes NCT overstates the significance of niche construction, whether it is internally coherent, and whether it accurately portrays standard evolutionary theory. Our disagreements reflect a wider dispute within evolutionary theory over whether the neo-Darwinian synthesis is in need of reformulation, as well as different usages of some key terms (e.g., evolutionary process). © 2013 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

  15. Prediction of the niche effect for single flat panels with or without attached sound absorbing materials.

    Science.gov (United States)

    Sgard, Franck; Atalla, Noureddine; Nélisse, Hugues

    2015-01-01

    The sound transmission loss (STL) of a test sample measured in sound transmission facilities is affected by the opening in which it is located. This is called the niche effect. This paper uses a modal approach to study the STL of a rectangular plate with or without an attached porous material located inside a box-shaped niche. The porous material is modeled as a limp equivalent fluid. The proposed model is validated by comparison with finite element/boundary element computations. Using a condensation of the pressure fields in the niche, the niche effect is interpreted in terms of a modification of the modal blocked pressure fields acting on the panel induced by the front cavity and by a modification of the radiation efficiency of the panel modes due to the presence of the back cavity. The modal approach is then used to investigate the impact of (1) the presence of a porous material attached to the panel on the niche effect and (2) the niche effect on the assessment of the porous material insertion loss. A simplified model for the porous material based on a transfer matrix approach is also proposed to predict the STL of the system and its validity is discussed.

  16. Predicting fundamental and realized distributions based on thermal niche: A case study of a freshwater turtle

    Science.gov (United States)

    Rodrigues, João Fabrício Mota; Coelho, Marco Túlio Pacheco; Ribeiro, Bruno R.

    2018-04-01

    Species distribution models (SDM) have been broadly used in ecology to address theoretical and practical problems. Currently, there are two main approaches to generate SDMs: (i) correlative, which is based on species occurrences and environmental predictor layers and (ii) process-based models, which are constructed based on species' functional traits and physiological tolerances. The distributions estimated by each approach are based on different components of species niche. Predictions of correlative models approach species realized niches, while predictions of process-based are more akin to species fundamental niche. Here, we integrated the predictions of fundamental and realized distributions of the freshwater turtle Trachemys dorbigni. Fundamental distribution was estimated using data of T. dorbigni's egg incubation temperature, and realized distribution was estimated using species occurrence records. Both types of distributions were estimated using the same regression approaches (logistic regression and support vector machines), both considering macroclimatic and microclimatic temperatures. The realized distribution of T. dorbigni was generally nested in its fundamental distribution reinforcing theoretical assumptions that the species' realized niche is a subset of its fundamental niche. Both modelling algorithms produced similar results but microtemperature generated better results than macrotemperature for the incubation model. Finally, our results reinforce the conclusion that species realized distributions are constrained by other factors other than just thermal tolerances.

  17. Rainwater Harvesting and Social Networks: Visualising Interactions for Niche Governance, Resilience and Sustainability

    Directory of Open Access Journals (Sweden)

    Sarah Ward

    2016-11-01

    Full Text Available Visualising interactions across urban water systems to explore transition and change processes requires the development of methods and models at different scales. This paper contributes a model representing the network interactions of rainwater harvesting (RWH infrastructure innovators and other organisations in the UK RWH niche to identify how resilience and sustainability feature within niche governance in practice. The RWH network interaction model was constructed using a modified participatory social network analysis (SNA. The SNA was further analysed through the application of a two-part analytical framework based on niche management and the safe, resilient and sustainable (‘Safe and SuRe’ framework. Weak interactions between some RWH infrastructure innovators and other organisations highlighted reliance on a limited number of persuaders to influence the regime and landscape, which were underrepresented. Features from niche creation and management were exhibited by the RWH network interaction model, though some observed characteristics were not represented. Additional Safe and SuRe features were identified covering diverse innovation, responsivity, no protection, unconverged expectations, primary influencers, polycentric or adaptive governance and multiple learning-types. These features enable RWH infrastructure innovators and other organisations to reflect on improving resilience and sustainability, though further research in other sectors would be useful to verify and validate observation of the seven features.

  18. The niche party concept and its measurement.

    Science.gov (United States)

    Meyer, Thomas M; Miller, Bernhard

    2015-03-01

    The concept of the niche party has become increasingly popular in analyses of party competition. Yet, existing approaches vary in their definitions and their measurement approaches. We propose using a minimal definition that allows us to compare political parties in terms of their 'nicheness'. We argue that the conceptual core of the niche party concept is based on issue emphasis and that a niche party emphasizes policy areas neglected by its rivals. Based on this definition, we propose a continuous measure that allows for more fine-grained measurement of a party's 'nicheness' than the dominant, dichotomous approaches and thereby limits the risk of measurement error. Drawing on data collected by the Comparative Manifesto Project, we show that (1) our measure has high face validity and (2) exposes differences among parties that are not captured by alternative, static or dichotomous measures.

  19. Mammalian niche conservation through deep time.

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    Larisa R G DeSantis

    Full Text Available Climate change alters species distributions, causing plants and animals to move north or to higher elevations with current warming. Bioclimatic models predict species distributions based on extant realized niches and assume niche conservation. Here, we evaluate if proxies for niches (i.e., range areas are conserved at the family level through deep time, from the Eocene to the Pleistocene. We analyze the occurrence of all mammalian families in the continental USA, calculating range area, percent range area occupied, range area rank, and range polygon centroids during each epoch. Percent range area occupied significantly increases from the Oligocene to the Miocene and again from the Pliocene to the Pleistocene; however, mammalian families maintain statistical concordance between rank orders across time. Families with greater taxonomic diversity occupy a greater percent of available range area during each epoch and net changes in taxonomic diversity are significantly positively related to changes in percent range area occupied from the Eocene to the Pleistocene. Furthermore, gains and losses in generic and species diversity are remarkably consistent with ~2.3 species gained per generic increase. Centroids demonstrate southeastern shifts from the Eocene through the Pleistocene that may correspond to major environmental events and/or climate changes during the Cenozoic. These results demonstrate range conservation at the family level and support the idea that niche conservation at higher taxonomic levels operates over deep time and may be controlled by life history traits. Furthermore, families containing megafauna and/or terminal Pleistocene extinction victims do not incur significantly greater declines in range area rank than families containing only smaller taxa and/or only survivors, from the Pliocene to Pleistocene. Collectively, these data evince the resilience of families to climate and/or environmental change in deep time, the absence of

  20. Ecological Niche Modeling of Risk Factors for H7N9 Human Infection in China

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    Min Xu

    2016-06-01

    Full Text Available China was attacked by a serious influenza A (H7N9 virus in 2013. The first human infection case was confirmed in Shanghai City and soon spread across most of eastern China. Using the methods of Geographic Information Systems (GIS and ecological niche modeling (ENM, this research quantitatively analyzed the relationships between the H7N9 occurrence and the main environmental factors, including meteorological variables, human population density, bird migratory routes, wetland distribution, and live poultry farms, markets, and processing factories. Based on these relationships the probability of the presence of H7N9 was predicted. Results indicated that the distribution of live poultry processing factories, farms, and human population density were the top three most important determinants of the H7N9 human infection. The relative contributions to the model of live poultry processing factories, farms and human population density were 39.9%, 17.7% and 17.7%, respectively, while the maximum temperature of the warmest month and mean relative humidity had nearly no contribution to the model. The paper has developed an ecological niche model (ENM that predicts the spatial distribution of H7N9 cases in China using environmental variables. The area under the curve (AUC values of the model were greater than 0.9 (0.992 for the training samples and 0.961 for the test data. The findings indicated that most of the high risk areas were distributed in the Yangtze River Delta. These findings have important significance for the Chinese government to enhance the environmental surveillance at multiple human poultry interfaces in the high risk area.

  1. The niche construction of cultural complexity: interactions between innovations, population size and the environment.

    Science.gov (United States)

    Fogarty, Laurel; Creanza, Nicole

    2017-12-05

    Niche construction is a process through which organisms alter their environments and, in doing so, influence or change the selective pressures to which they are subject. 'Cultural niche construction' refers specifically to the effect of cultural traits on the selective environments of other biological or cultural traits and may be especially important in human evolution. In addition, the relationship between population size and cultural accumulation has been the subject of extensive debate, in part because anthropological studies have demonstrated a significant association between population size and toolkit complexity in only a subset of studied cultures. Here, we review the role of cultural innovation in constructing human evolutionary niches and introduce a new model to describe the accumulation of human cultural traits that incorporates the effects of cultural niche construction. We consider the results of this model in light of available data on human toolkit sizes across populations to help elucidate the important differences between food-gathering societies and food-producing societies, in which niche construction may be a more potent force. These results support the idea that a population's relationship with its environment, represented here by cultural niche construction, should be considered alongside population size in studies of cultural complexity.This article is part of the themed issue 'Process and pattern in innovations from cells to societies'. © 2017 The Author(s).

  2. The evolution of climatic niches in squamate reptiles.

    Science.gov (United States)

    Pie, Marcio R; Campos, Leonardo L F; Meyer, Andreas L S; Duran, Andressa

    2017-07-12

    Despite the remarkable diversity found in squamate reptiles, most of their species tend to be found in warm/dry environments, suggesting that climatic requirements played a crucial role in their diversification, yet little is known about the evolution of their climatic niches. In this study, we integrate climatic information associated with the geographical distribution of 1882 squamate species and their phylogenetic relationships to investigate the tempo and mode of climatic niche evolution in squamates, both over time and among lineages. We found that changes in climatic niche dynamics were pronounced over their recent squamate evolutionary history, and we identified extensive evidence for rate heterogeneity in squamate climatic niche evolution. Most rate shifts involved accelerations, particularly over the past 50 Myr. Most squamates occupy similar regions of the climatic niche space, with only a few lineages diversifying into colder and humid climatic conditions. The changes from arid to mesic conditions in some regions of the globe may have provided opportunities for climatic niche evolution, although most lineages tended to remain near their ancestral niche. Variation in rates of climatic niche evolution seems common, particularly in response to the availability of new climatic conditions over evolutionary time. © 2017 The Author(s).

  3. Identification of hepatic niche harboring human acute lymphoblastic leukemic cells via the SDF-1/CXCR4 axis.

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    Itaru Kato

    Full Text Available In acute lymphoblastic leukemia (ALL patients, the bone marrow niche is widely known to be an important element of treatment response and relapse. Furthermore, a characteristic liver pathology observed in ALL patients implies that the hepatic microenvironment provides an extramedullary niche for leukemic cells. However, it remains unclear whether the liver actually provides a specific niche. The mechanism underlying this pathology is also poorly understood. Here, to answer these questions, we reconstituted the histopathology of leukemic liver by using patients-derived primary ALL cells into NOD/SCID/Yc (null mice. The liver pathology in this model was similar to that observed in the patients. By using this model, we clearly demonstrated that bile duct epithelial cells form a hepatic niche that supports infiltration and proliferation of ALL cells in the liver. Furthermore, we showed that functions of the niche are maintained by the SDF-1/CXCR4 axis, proposing a novel therapeutic approach targeting the extramedullary niche by inhibition of the SDF-1/CXCR4 axis. In conclusion, we demonstrated that the liver dissemination of leukemia is not due to nonselective infiltration, but rather systematic invasion and proliferation of leukemic cells in hepatic niche. Although the contribution of SDF-1/CXCR4 axis is reported in some cancer cells or leukemic niches such as bone marrow, we demonstrated that this axis works even in the extramedullary niche of leukemic cells. Our findings form the basis for therapeutic approaches that target the extramedullary niche by inhibiting the SDF-1/CXCR4 axis.

  4. The HysNiche trial: hysteroscopic resection of uterine caesarean scar defect (niche) in patients with abnormal bleeding, a randomised controlled trial.

    Science.gov (United States)

    Vervoort, A J M W; Van der Voet, L F; Witmer, M; Thurkow, A L; Radder, C M; van Kesteren, P J M; Quartero, H W P; Kuchenbecker, W K H; Bongers, M Y; Geomini, P M A J; de Vleeschouwer, L H M; van Hooff, M H A; van Vliet, H A A M; Veersema, S; Renes, W B; van Meurs, H S; Bosmans, J; Oude Rengerink, K; Brölmann, H A M; Mol, B W J; Huirne, J A F

    2015-11-12

    A caesarean section (CS) can cause a defect or disruption of the myometrium at the site of the uterine scar, called a niche. In recent years, an association between a niche and postmenstrual spotting after a CS has been demonstrated. Hysteroscopic resection of these niches is thought to reduce spotting and menstrual pain. However, there are no randomised trials assessing the effectiveness of a hysteroscopic niche resection. We planned a multicentre randomised trial comparing hysteroscopic niche resection to no intervention. We study women with postmenstrual spotting after a CS and a niche with a residual myometrium of at least 3 mm during sonohysterography. After informed consent is obtained, eligible women will be randomly allocated to hysteroscopic resection of the niche or expectant management for 6 months. The primary outcome is the number of days with postmenstrual spotting during one menstrual cycle 6 months after randomisation. Secondary outcomes are menstrual characteristics, menstruation related pain and experienced discomfort due to spotting or menstrual pain, quality of life, patient satisfaction, sexual function, urological symptoms, medical consultations, medication use, complications, lost productivity and medical costs. Measurements will be performed at baseline and at 3 and 6 months after randomisation. A cost-effectiveness analysis will be performed from a societal perspective at 6 months after randomisation. This trial will provide insight in the (cost)effectiveness of hysteroscopic resection of a niche versus expectant management in women who have postmenstrual spotting and a niche with sufficient residual myometrium to perform a hysteroscopic niche resection. Dutch Trial Register NTR3269 . Registered 1 February 2012. ZonMw Grant number 80-82305-97-12030.

  5. Not all renal stem cell niches are the same: anatomy of an evolution

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    Clara Gerosa

    2016-08-01

    Full Text Available The renal stem cell niche represents the most important structure of the developing kidney, responsible for nephrogenesis. Recently, some Authors have reported, at ultrastructural level, a previously unknown complexity of the architecture of renal stem cell niche in experimental models. This study was aimed at studying, at histological level, the anatomy of renal stem cell niches in the human fetal kidney. To this end, ten fetal kidneys, whose gestational ages ranged from 11 up to 24 weeks, were studied. H&E-stained sections were observed at high power. The study of the anatomy of renal stem cell niches in the human kidney revealed a previously unreported complexity: some niches appeared as a roundish arrangement of mesenchymal cells; others showed the initial phases of induction by ureteric buds; in other niches the process of mesenchymal epithelial transition was more evident; finally, in other stem cell niches the first signs of nephron origin were detectable. These findings suggest the existence of niches with different anatomy in the same kidney, indicating different stages of evolution even in adjacent niches. All stem cell niches were in strict contact with the capsular cells, suggesting a major role of the renal capsule in nephrogenesis. Finally, our study confirms the existence of a strict contact between the bud tip cells and the surrounding mesenchyme in the human developing kidney, giving a morphological support to the theory of intercellular channels allowing the passage of transcription factors from the epithelial to the mesenchymal stem/progenitors cells.Proceedings of the 2nd International Course on Perinatal Pathology (part of the 11th International Workshop on Neonatology · October 26th-31st, 2015 · Cagliari (Italy · October 31st, 2015 · Stem cells: present and future Guest Editors: Gavino Faa, Vassilios Fanos, Antonio Giordano

  6. OMWS: A Web Service Interface for Ecological Niche Modelling

    Directory of Open Access Journals (Sweden)

    Renato De Giovanni

    2015-09-01

    Full Text Available Ecological niche modelling (ENM experiments often involve a high number of tasks to be performed. Such tasks may consume a significant amount of computing resources and take a long time to complete, especially when using personal computers. OMWS is a Web service interface that allows more powerful computing back-ends to be remotely exploited by other applications to carry out ENM tasks. Its latest version includes a new operation that can be used to specify complex workflows in a single request, adding the possibility of using workflow management systems on parallel computing back-end. In this paper we describe the OMWS protocol and compare its most recent version with the previous one by running the same ENM experiment using two functionally equivalent clients, each designed for one of the OMWS interface versions. Different back-end configurations were used to investigate how the performance scales for each protocol version when more processing power is made available. Results show that the new version outperforms (in a factor of 2 the previous one when more computing resources are used.

  7. Using ecological niche modeling to determine avian richness hotspots

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    R. Mirzaei

    2017-04-01

    Full Text Available Understanding distributions of wildlife species is a key step towards identifying biodiversity hotspots and designing effective conservation strategies. In this paper, the spatial pattern of diversity of birds in Golestan Province, Iran was estimated. Ecological niche modeling was used to determine distributions of 144 bird species across the province using a maximum entropy algorithm. Richness maps across all birds, and separately for rare and threatened species, were prepared as approximations to hotspots. Results showed close similarity between hotspots for all birds and those for rare birds; hotspots were concentrated in the southern and especially the southwestern parts of the province. Hotspots for threatened birds tended more to the central and especially the western parts of the province, which include coastal habitats. Based on three criteria, it is clear that the western part is the most important area of the province in terms of bird Faunas. Despite some shortcomings, hotspot analysis for birds could be applied to guide conservation efforts and provide useful tool towards efficient conservation action.

  8. Macrophytes shape trophic niche variation among generalist fishes.

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    Ivana Vejříková

    Full Text Available Generalist species commonly have a fundamental role in ecosystems as they can integrate spatially distinct habitats and food-web compartments, as well as control the composition, abundance and behavior of organisms at different trophic levels. Generalist populations typically consist of specialized individuals, but the potential for and hence degree of individual niche variation can be largely determined by habitat complexity. We compared individual niche variation within three generalist fishes between two comparable lakes in the Czech Republic differing in macrophyte cover, i.e. macrophyte-rich Milada and macrophyte-poor Most. We tested the hypothesis that large individual niche variation among generalist fishes is facilitated by the presence of macrophytes, which provides niches and predation shelter for fish and their prey items. Based on results from stable nitrogen (δ15N and carbon (δ13C isotopic mixing models, perch (Perca fluviatilis L. and rudd (Scardinius erythrophthalmus (L. showed larger individual variation (i.e., variance in trophic position in Milada as compared to Most, whereas no significant between-lake differences were observed for roach (Rutilus rutilus (L.. Contrary to our hypothesis, all the three species showed significantly lower individual variation in the relative reliance on littoral food resources in Milada than in Most. Rudd relied significantly more whereas perch and roach relied less on littoral food resources in Milada than in Most, likely due to prevalent herbivory by rudd and prevalent zooplanktivory by perch and roach in the macrophyte-rich Milada as compared to macrophyte-poor Most. Our study demonstrates how the succession of macrophyte vegetation, via its effects on the physical and biological complexity of the littoral zone and on the availability of small prey fish and zooplankton, can strongly influence individual niche variation among generalist fishes with different ontogenetic trajectories, and hence

  9. Macrophytes shape trophic niche variation among generalist fishes

    Science.gov (United States)

    Vejřík, Lukáš; Šmejkal, Marek; Čech, Martin; Sajdlová, Zuzana; Frouzová, Jaroslava; Kiljunen, Mikko; Peterka, Jiří

    2017-01-01

    Generalist species commonly have a fundamental role in ecosystems as they can integrate spatially distinct habitats and food-web compartments, as well as control the composition, abundance and behavior of organisms at different trophic levels. Generalist populations typically consist of specialized individuals, but the potential for and hence degree of individual niche variation can be largely determined by habitat complexity. We compared individual niche variation within three generalist fishes between two comparable lakes in the Czech Republic differing in macrophyte cover, i.e. macrophyte-rich Milada and macrophyte-poor Most. We tested the hypothesis that large individual niche variation among generalist fishes is facilitated by the presence of macrophytes, which provides niches and predation shelter for fish and their prey items. Based on results from stable nitrogen (δ15N) and carbon (δ13C) isotopic mixing models, perch (Perca fluviatilis L.) and rudd (Scardinius erythrophthalmus (L.)) showed larger individual variation (i.e., variance) in trophic position in Milada as compared to Most, whereas no significant between-lake differences were observed for roach (Rutilus rutilus (L.)). Contrary to our hypothesis, all the three species showed significantly lower individual variation in the relative reliance on littoral food resources in Milada than in Most. Rudd relied significantly more whereas perch and roach relied less on littoral food resources in Milada than in Most, likely due to prevalent herbivory by rudd and prevalent zooplanktivory by perch and roach in the macrophyte-rich Milada as compared to macrophyte-poor Most. Our study demonstrates how the succession of macrophyte vegetation, via its effects on the physical and biological complexity of the littoral zone and on the availability of small prey fish and zooplankton, can strongly influence individual niche variation among generalist fishes with different ontogenetic trajectories, and hence the overall

  10. Modulating the stem cell niche for tissue regeneration

    Science.gov (United States)

    Lane, Steven W; Williams, David A; Watt, Fiona M

    2015-01-01

    The field of regenerative medicine holds considerable promise for treating diseases that are currently intractable. Although many researchers are adopting the strategy of cell transplantation for tissue repair, an alternative approach to therapy is to manipulate the stem cell microenvironment, or niche, to facilitate repair by endogenous stem cells. The niche is highly dynamic, with multiple opportunities for intervention. These include administration of small molecules, biologics or biomaterials that target specific aspects of the niche, such as cell-cell and cell–extracellular matrix interactions, to stimulate expansion or differentiation of stem cells, or to cause reversion of differentiated cells to stem cells. Nevertheless, there are several challenges in targeting the niche therapeutically, not least that of achieving specificity of delivery and responses. We envisage that successful treatments in regenerative medicine will involve different combinations of factors to target stem cells and niche cells, applied at different times to effect recovery according to the dynamics of stem cell–niche interactions. PMID:25093887

  11. Drosophila Glypicans Regulate Follicle Stem Cell Maintenance and Niche Competition.

    Science.gov (United States)

    Su, Tsu-Yi; Nakato, Eriko; Choi, Pui Yee; Nakato, Hiroshi

    2018-04-09

    Adult stem cells reside in specialized microenvironments, called niches, which provide signals for stem cells to maintain their undifferentiated and self-renewing state. To maintain stem cell quality, several types of stem cells are known to be regularly replaced by progenitor cells through niche competition. However, the cellular and molecular bases for stem cell competition for niche occupancy are largely unknown. Here, we show that two Drosophila members of the glypican family of heparan sulfate proteoglycans (HSPGs), Dally and Dally-like (Dlp), differentially regulate follicle stem cell (FSC) maintenance and FSC competitiveness for niche occupancy. Lineage analyses of glypican mutant FSC clones showed that dally is essential for normal FSC maintenance. In contrast, dlp is a hyper-competitive mutation: dlp mutant FSC progenitors often eventually occupy the entire epithelial sheet. RNAi knockdown experiments showed that Dally and Dlp play both partially redundant and distinct roles in regulating Jak/Stat, Wg and Hh signaling in FSCs. The Drosophila FSC system offers a powerful genetic model to study the mechanisms by which HSPGs exert specific functions in stem cell replacement and competition. Copyright © 2018, Genetics.

  12. [Mesenchymal stroma cells and their niche].

    Science.gov (United States)

    Schneider, R K

    2013-11-01

    Stem cells reside in a highly specialized, complex microenvironment that is known as the stem cell niche. The stem cell niche can be described as an anatomically defined space where the stem cell is localized and nourished and stem cell quiescence, proliferation and differentiation are maintained. Tissue engineering aims to imitate the stem cell niche to (I) induce a directed differentiation, (II) maintain the self-renewal capacity or (III) find a regulated balance between self-renewal and differentiation. Mesenchymal stem or stromal cells (MSC) can differentiate in three-dimensional collagen gels into functional osteoblasts when subjected to a phosphate-rich cultivation medium. Furthermore, they acquire a prosynthetic, matrix remodeling, contractile phenotype. Medial artery calcification in patients with chronic kidney disease also proceeds through intramembranous ossification resulting from osteoblast-induced calcification of the collagen extracellular matrix. Thus, the influence of uremic cultivation conditions as a pathophysiological stimulus on MSC and endothelial cells was analyzed with special regards to matrix remodeling, vascularization and calcification. The results showed that BMP-2/4 mediated MSC (mal)differentiation into osteoblasts with acquired matrix remodeling phenotype and loss of proangiogenic capacity. These studies have led to the conclusion that uremia has detrimental effects on the stem cell niche and promotes the continuous calcification by osteogenic (mal)differentiation. In summary, recent studies have shown the conducting and regulating effect of the stem cell niche under physiological conditions that can be applied and mimicked for tissue engineering applications. However, under pathological conditions the stem cell niche can have detrimental effects on stem cell function and can promote disease progression.

  13. Use of ecological niche modeling as a tool for predicting the potential distribution of Microcystis sp (cyanobacteria in the Aguamilpa Dam, Nayarit, Mexico

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    Enrique Martinez-Meyer

    2012-04-01

    Full Text Available Ecological niche modeling is an important tool to evaluate the spatial distribution of terrestrial species, however, its applicability has been little explored in the aquatic environment. Microcystis sp., a species of cyanobacteria, is widely recognized for its ability to produce a group of toxins known as microcystins, which can cause death of animals as fish, birds and mammals depending on the amount of toxin absorbed. Like any taxonomic group, cyanobacteria has environmental thresholds, therefore, a suitable ecological niche will define their distribution. This study was conducted in Aguamilpa Hydroelectric Reservoir, an artificial ecosystem that started operations in 1994. In this system we evaluated the potential distribution of Microcystis sp., by generating a prediction model based on the concept of ecological niche MAXENT, using a Digital Elevation Model in cells of 100 m x 100 m (1 ha spatial resolution and monitoring eleven physicochemical and biological variables and nutrients in water. The distribution maps were developed using ArcMap 9.2®. The results indicated that Microcystis sp., is distributed mainly in the upper tributary basin (Huaynamota basin during the dry season. There was less chance to find cyanobacteria in the entire system during the cold dry season, while during the warm dry season cyanobacteria was recognized at the confluence of two rivers. During the rainfall season there were no reports of cyanobacteria presence. This species is often associated with arising trophic processes of anthropogenic origin; therefore, attention is required in specific areas that have been identified in this work to improve Aguamilpa’s watershed management and restoration. It was also recognized the importance of phosphorus and nitrogen interaction, which determines the distribution of Microcystis sp., in the Aguamilpa Reservoir. The results of this study demonstrated that ecological niche modeling was a suitable tool to assess the

  14. Phylogenetic climatic niche conservatism and evolution of climatic suitability in Neotropical Angraecinae (Vandeae, Orchidaceae) and their closest African relatives

    Czech Academy of Sciences Publication Activity Database

    Kolanowska, Marta; Grochocka, E.; Konowalik, K.

    2017-01-01

    Roč. 5, may (2017), č. článku e3328. ISSN 2167-8359 R&D Projects: GA ČR GB14-36098G Institutional support: RVO:86652079 Keywords : campylocentrum orchidaceae * molecular phylogenetics * environmental niches * costa-rica * diversity * models * speciation * ecology * pollination * divergence * Angraecinae * Ecological niche modeling * Orchidaceae * Phylogenetic niche conservatism * Angraecum * Campylocentrum * Dendrophylax Subject RIV: EH - Ecology, Behaviour OBOR OECD: Biodiversity conservation Impact factor: 2.177, year: 2016

  15. Vascular and perivascular niches, but not the osteoblastic niche, are numerically restored following allogeneic hematopoietic stem cell transplantation in patients with aplastic anemia.

    Science.gov (United States)

    Wu, Liangliang; Mo, Wenjian; Zhang, Yuping; Zhou, Ming; Li, Yumiao; Zhou, Ruiqing; Xu, Shiling; Pan, Shiyi; Deng, Hui; Mao, Ping; Wang, Shunqing

    2017-07-01

    Bone marrow (BM) niches, including the osteoblastic, vascular, and perivascular niches, are numerically impaired in patients with aplastic anemia (AA). It remains unclear whether these niches are numerically restored in AA patients after allogenic hematopoietic stem cell transplantation (allo-HSCT). To investigate changes in BM niches, we monitored 52 patients with AA who had undergone allo-HSCT and performed immunohistochemical studies of BM niches using antibodies against CD34, CD146, and osteopontin. After allo-HSCT, patients with AA exhibited a remarkable increase in the number of cellular elements in the BM niches, including the vascular and perivascular cells. However, no significant differences in endosteal cells were detected. We explored the cause of this restoration by analyzing the origin of BM mesenchymal stem cells (BM-MSCs) and the expression of cytokines in BM plasma. STR-PCR revealed that the BM-MSCs were derived from the host, not the donor. In addition, significantly elevated levels of vascular endothelial growth factor (VEGF) were found after allo-HSCT. Our data indicates that vascular and perivascular niches are numerically restored, but the endosteal niche remains numerically impaired in patients with AA after allo-HSCT, and that levels of VEGF, but not donor-derived BM-MSCs, may correlate with the restoration of BM niches.

  16. To predict the niche, model colonization and extinction

    Science.gov (United States)

    Yackulic, Charles B.; Nichols, James D.; Reid, Janice; Der, Ricky

    2015-01-01

    Ecologists frequently try to predict the future geographic distributions of species. Most studies assume that the current distribution of a species reflects its environmental requirements (i.e., the species' niche). However, the current distributions of many species are unlikely to be at equilibrium with the current distribution of environmental conditions, both because of ongoing invasions and because the distribution of suitable environmental conditions is always changing. This mismatch between the equilibrium assumptions inherent in many analyses and the disequilibrium conditions in the real world leads to inaccurate predictions of species' geographic distributions and suggests the need for theory and analytical tools that avoid equilibrium assumptions. Here, we develop a general theory of environmental associations during periods of transient dynamics. We show that time-invariant relationships between environmental conditions and rates of local colonization and extinction can produce substantial temporal variation in occupancy–environment relationships. We then estimate occupancy–environment relationships during three avian invasions. Changes in occupancy–environment relationships over time differ among species but are predicted by dynamic occupancy models. Since estimates of the occupancy–environment relationships themselves are frequently poor predictors of future occupancy patterns, research should increasingly focus on characterizing how rates of local colonization and extinction vary with environmental conditions.

  17. The HysNiche trial: hysteroscopic resection of uterine caesarean scar defect (niche) in patients with abnormal bleeding, a randomised controlled trial

    NARCIS (Netherlands)

    Vervoort, A. J. M. W.; van der Voet, L. F.; Witmer, M.; Thurkow, A. L.; Radder, C. M.; van Kesteren, P. J. M.; Quartero, H. W. P.; Kuchenbecker, W. K. H.; Bongers, M. Y.; Geomini, P. M. A. J.; de Vleeschouwer, L. H. M.; van Hooff, M. H. A.; van Vliet, H. A. A. M.; Veersema, S.; Renes, W. B.; van Meurs, H. S.; Bosmans, J.; Oude Rengerink, K.; Brölmann, H. A. M.; Mol, B. W. J.; Huirne, J. A. F.

    2015-01-01

    A caesarean section (CS) can cause a defect or disruption of the myometrium at the site of the uterine scar, called a niche. In recent years, an association between a niche and postmenstrual spotting after a CS has been demonstrated. Hysteroscopic resection of these niches is thought to reduce

  18. Competition influence in the segregation of the trophic niche of otariids: a case study using isotopic Bayesian mixing models in Galapagos pinnipeds.

    Science.gov (United States)

    Páez-Rosas, Diego; Rodríguez-Pérez, Mónica; Riofrío-Lazo, Marjorie

    2014-12-15

    The feeding success of predators is associated with the competition level for resources, and, thus, sympatric species are exposed to a potential trophic overlap. Isotopic Bayesian mixing models should provide a better understanding of the contribution of preys to the diet of predators and the feeding behavior of a species over time. The carbon and nitrogen isotopic signatures from pup hair samples of 93 Galapagos sea lions and 48 Galapagos fur seals collected between 2003 and 2009 in different regions (east and west) of the archipelago were analyzed. A PDZ Europa ANCA-GSL elemental analyzer interfaced with a PDZ Europa 20-20 continuous flow gas source mass spectrometer was employed. Bayesian models, SIAR and SIBER, were used to estimate the contribution of prey to the diet of predators, the niche breadth, and the trophic overlap level between the populations. Statistical differences in the isotopic values of both predators were observed over the time. The mixing model determined that Galapagos fur seals had a primarily teutophagous diet, whereas the Galapagos sea lions fed exclusively on fish in both regions of the archipelago. The SIBER analysis showed differences in the trophic niche between the two sea lion populations, with the western rookery of the Galapagos sea lion being the population with the largest trophic niche area. A trophic niche partitioning between Galapagos fur seals and Galapagos sea lions in the west of the archipelago is suggested by our results. At intraspecific level, the western population of the Galapagos sea lion (ZwW) showed higher trophic breadth than the eastern population, a strategy adopted by the ZwW to decrease the interspecific competition levels in the western region. Copyright © 2014 John Wiley & Sons, Ltd.

  19. Diet and trophic niche of Lithobates catesbeianus (Amphibia: Anura

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    Peterson T. Leivas

    2012-10-01

    Full Text Available Lithobates catesbeianus (Shaw, 1802 is an invasive anuran introduced in Brazil that is associated with the displacement and the decline of populations of native species worldwide. There is evidence that biological invasions are facilitated by certain attributes of the invading species, for instance niche breath, and that invasive species have a broader ecological niche with respect to native ones. We designed a study to ascertain the temporal, ontogenetic, and sex differences in the niche dynamics of the American bullfrog. We sampled monthly from June 2008 to May 2009 in the state of Paraná, southern Brazil. For each individual, we gathered biometric and stomach content data. We then estimated the niche breath of the juveniles and adults, and compared it between the sexes. A total of 104 females and 77 males were sampled. Lithobates catesbeianus has a generalist diet, preying upon invertebrates and vertebrates. Even though the diet of the studied population varied seasonally, it did not differ between the sexes nor did it respond to biometric variables. Niche breadth was more restricted in the winter than in the autumn. The trophic niche of juveniles and adults did not overlap much when compared with the trophic niche overlap between males and females. Adult males and females had a considerable niche overlap, but females had a broader trophic niche than males in the winter and in the spring. These niche characteristics point to an opportunistic predation strategy that may have facilitated the process of invasion and establishment of this species in the study area.

  20. Niche conservatism and phylogenetic clustering in a tribe of arid-adapted marsupial mice, the Sminthopsini.

    Science.gov (United States)

    García-Navas, Vicente; Westerman, Michael

    2018-05-28

    The progressive expansion of the Australian arid zone during the last 20 Ma appears to have spurred the diversification of several families of plants, vertebrates and invertebrates, yet such taxonomic groups appear to show limited niche radiation. Here, we test whether speciation is associated with niche conservatism (constraints on ecological divergence) or niche divergence in a tribe of marsupial mice (Sminthopsini; 23 taxa) that includes the most speciose genus of living dasyurids, the sminthopsins. To that end, we integrated phylogenetic data with ecological niche modelling, to enable us to reconstruct the evolution of climatic suitability within Sminthopsini. Niche overlap among species was low-moderate (but generally higher than expected given environmental background similarity), and the degree of phylogenetic clustering increased with aridity. Climatic niche reconstruction illustrates that there has been little apparent evolution of climatic tolerance within clades. Accordingly, climatic disparity tends to be accumulated among clades, suggesting considerable niche conservatism. Our results also indicate that evolution of climatic tolerances has been heterogeneous across different dimensions of climate (temperature vs. precipitation) and across phylogenetic clusters (Sminthopsis murina group vs. other groups). Although some results point to the existence of shifts in climatic niches during the speciation of sminthopsins, our study provides evidence for substantial phylogenetic niche conservatism in the group. We conclude that niche diversification had a low impact on the speciation of this tribe of small, but highly mobile marsupials. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology.

  1. Modeling of Iranian Cheetah Habitat using Ecological Niche Factor Analysis (Case Study: Dare Anjir Wildlife Refuge

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    N. Zamani

    2016-03-01

    Full Text Available Evaluation of habitat sustainability indexes is essential in wildlife management and conservation of rare species. Suitable habitats are required in wildlife managements and conservation also, they increase reproduction and survival rate of species. In this study in order to mapping habitat sustainability and recognizing habitat requirements of Iranian Cheetah (Acinonyx jubatus venaticus, field data from Dare Anjir  wildlife refuge were collected since autumn 2009 until summer 2011. Ecological Niche Factor Analysis approach has been used to develop habitat suitability model. In this method primary maps of  habitat variables including elevation, slope, aspect, vegetation cover, distance from water sources and environmental monitoring stations have been produced by Idrisi and Biomapper software and imported in Biomapper. The output scores obtained from the analysis showed that Iranian cheetah tends to mountain areas where has more topographical features for camouflage in order to hunting, and northern aspects which have more humidity, denser vegetation cover and more preys . Our result showed that the Iranian cheetah has medium niche width and prefer marginal habitats.

  2. Trophic niche shifts driven by phytoplankton in sandy beach ecosystems

    Science.gov (United States)

    Bergamino, Leandro; Martínez, Ana; Han, Eunah; Lercari, Diego; Defeo, Omar

    2016-10-01

    Stable isotopes (δ13C and δ15N) together with chlorophyll a and densities of surf diatoms were used to analyze changes in trophic niches of species in two sandy beaches of Uruguay with contrasting morphodynamics (i.e. dissipative vs. reflective). Consumers and food sources were collected over four seasons, including sediment organic matter (SOM), suspended particulate organic matter (POM) and the surf zone diatom Asterionellopsis guyunusae. Circular statistics and a Bayesian isotope mixing model were used to quantify food web differences between beaches. Consumers changed their trophic niche between beaches in the same direction of the food web space towards higher reliance on surf diatoms in the dissipative beach. Mixing models indicated that A. guyunusae was the primary nutrition source for suspension feeders in the dissipative beach, explaining their change in dietary niche compared to the reflective beach where the proportional contribution of surf diatoms was low. The high C/N ratios in A. guyunusae indicated its high nutritional value and N content, and may help to explain the high assimilation by suspension feeders at the dissipative beach. Furthermore, density of A. guyunusae was higher in the dissipative than in the reflective beach, and cell density was positively correlated with chlorophyll a only in the dissipative beach. Therefore, surf diatoms are important drivers in the dynamics of sandy beach food webs, determining the trophic niche space and productivity. Our study provides valuable insights on shifting foraging behavior by beach fauna in response to changes in resource availability.

  3. Global Habitat Suitability and Ecological Niche Separation in the Phylum Placozoa.

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    Omid Paknia

    Full Text Available The enigmatic placozoans, which hold a key position in the metazoan Tree of Life, have attracted substantial attention in many areas of biological and biomedical research. While placozoans have become an emerging model system, their ecology and particularly biogeography remain widely unknown. In this study, we use modelling approaches to explore habitat preferences, and distribution pattern of the placozoans phylum. We provide hypotheses for discrete ecological niche separation between genetic placozoan lineages, which may also help to understand biogeography patterns in other small marine invertebrates. We, here, used maximum entropy modelling to predict placozoan distribution using 20 environmental grids of 9.2 km2 resolution. In addition, we used recently developed metrics of niche overlap to compare habitat suitability models of three genetic clades. The predicted distributions range from 55°N to 44°S and are restricted to regions of intermediate to warm sea surface temperatures. High concentrations of salinity and low nutrient concentrations appear as secondary factors. Tests of niche equivalency reveal the largest differences between placozoan clades I and III. Interestingly, the genetically well-separated clades I and V appear to be ecologically very similar. Our habitat suitability models predict a wider latitudinal distribution for placozoans, than currently described, especially in the northern hemisphere. With respect to biogeography modelling, placozoans show patterns somewhere between higher metazoan taxa and marine microorganisms, with the first group usually showing complex biogeographies and the second usually showing "no biogeography."

  4. Market niche analysis in the casino gaming industry.

    Science.gov (United States)

    Dandurand, L

    1990-03-01

    This article discusses the nature of market niche analysis in the casino gaming industry. It presents four approaches for conducting market niche analysis. An an example of one approach, the Las Vegas Visitor Profile Study is used to identify a premium niche in the Las Vegas Slot Target Market. A detailed examination of the premium niche profile provides a description of the typical premium slot player. The description of the typical premium player leads to hypotheses regarding needs (the unique preference set) of the premium player. An analysis of the unique preference set suggests an appropriate enhanced marketing program.

  5. Primer and interviews: The dynamic stem cell niche.

    Science.gov (United States)

    Kiefer, Julie C

    2011-03-01

    A stem cell niche is a microenvironment that supports self-renewal of a population of stem cells, and their production of differentiated cells. While the definition evokes images of a stem cell Shangri-La-where a serene stem cell pool nestles within a niche that shelters and sustains it-the reality is much more tumultuous. Niches are subject to an ever-changing maelstrom of environmental factors, the ravages of old age, and the sly tactics of disease. Presented here is a basic overview of the different ways in which stem cell niches respond to local and systemic environments, and their impact on stem cell behavior. The primer culminates with a discussion of the topic with stem cell and niche biologists D. Leanne Jones, Ph.D., and Tudorita Tumbar, Ph.D. Copyright © 2011 Wiley-Liss, Inc.

  6. The crosstalk between hematopoietic stem cells and their niches.

    Science.gov (United States)

    Durand, Charles; Charbord, Pierre; Jaffredo, Thierry

    2018-07-01

    Hematopoietic stem cells (HSCs) reside in specific microenvironments also called niches that regulate HSC functions. Understanding the molecular and cellular mechanisms involved in the crosstalk between HSCs and niche cells is a major issue in stem cell biology and regenerative medicine. The purpose of this review is to discuss recent advances in this field with particular emphasis on the transcriptional landscape of HSC niche cells and the roles of extracellular vesicles (EVs) in the dialog between HSCs and their microenvironments. The development of high-throughput technologies combined with computational methods has considerably improved our knowledge on the molecular identity of HSC niche cells. Accumulating evidence strongly suggest that the dialog between HSCs and their niches is bidirectional and that EVs play an important role in this process. These advances bring a unique conceptual and methodological framework for understanding the molecular complexity of the HSC niche and identifying novel HSC regulators. They are also promising for exploring the reciprocal influence of HSCs on niche cells and delivering specific molecules to HSCs in regenerative medicine.

  7. Shifts in the ecological niche of Lutzomyia peruensis under climate change scenarios in Peru.

    Science.gov (United States)

    Moo-Llanes, D A; Arque-Chunga, W; Carmona-Castro, O; Yañez-Arenas, C; Yañez-Trujillano, H H; Cheverría-Pacheco, L; Baak-Baak, C M; Cáceres, A G

    2017-06-01

    The Peruvian Andes presents a climate suitable for many species of sandfly that are known vectors of leishmaniasis or bartonellosis, including Lutzomyia peruensis (Diptera: Psychodidae), among others. In the present study, occurrences data for Lu. peruensis were compiled from several items in the scientific literature from Peru published between 1927 and 2015. Based on these data, ecological niche models were constructed to predict spatial distributions using three algorithms [Support vector machine (SVM), the Genetic Algorithm for Rule-set Prediction (GARP) and Maximum Entropy (MaxEnt)]. In addition, the environmental requirements of Lu. peruensis and three niche characteristics were modelled in the context of future climate change scenarios: (a) potential changes in niche breadth; (b) shifts in the direction and magnitude of niche centroids, and (c) shifts in elevation range. The model identified areas that included environments suitable for Lu. peruensis in most regions of Peru (45.77%) and an average altitude of 3289 m a.s.l. Under climate change scenarios, a decrease in the distribution areas of Lu. peruensis was observed for all representative concentration pathways. However, the centroid of the species' ecological niche showed a northwest direction in all climate change scenarios. The information generated in this study may help health authorities responsible for the supervision of strategies to control leishmaniasis to coordinate, plan and implement appropriate strategies for each area of risk, taking into account the geographic distribution and potential dispersal of Lu. peruensis. © 2017 The Royal Entomological Society.

  8. Astrocitary niches in human adult medulla oblongata.

    Science.gov (United States)

    Rusu, Mugurel Constantin; Dermengiu, Dan; Loreto, Carla; Motoc, Andrei Gheorghe Marius; Pop, Elena

    2013-04-01

    Astrocytes are considered as neuromodulators of the CNS. Whereas experimental studies on astrocitary functions are gaining importance, the anatomy of the astrocitary niches in the human CNS has been overlooked. The study was performed on the brainstem of 10 adult cadavers. We aimed to determine astrocitary niches in the human medulla oblongata using immunohistochemical labeling with vimentin and also CD34 immunostaining to accurately diagnose associated microvessels. Niches rich in astrocytes were identified as follows: (a) the superficial layer of astrocytes, ventral and ventrolateral, in the rostral medulla oblongata; (b) the median raphe; (c) medullary nuclei: arcuate nucleus, area postrema, nucleus of the solitary tract; (d) the subependymal zone (SEZ, caudal medulla) and subventricular zone (SVZ, rostral medulla). Astrocytes were scarce in the ventrolateral medulla, and mostly present within the pyramidal tract and the olivary nucleus. Apart from the SEZ and SVZ, the brainstem niches of astrocytes mostly overlap those regions known to perform roles as central respiratory chemoreceptors. The astrocytes of the SEZ and SVZ, which are known as stem cell niches, are related to an increased microvascular density. Copyright © 2012 Elsevier GmbH. All rights reserved.

  9. Glioblastoma niches: from the concept to the phenotypical reality.

    Science.gov (United States)

    Schiffer, Davide; Mellai, Marta; Bovio, Enrica; Bisogno, Ilaria; Casalone, Cristina; Annovazzi, Laura

    2018-05-08

    Recently, the concept of niches as sites of tumor progression, invasion, and angiogenesis in glioblastoma (GB) has been extensively debated. Niches, considered the sites in which glioblastoma stem cells (GSCs) reside, have been classified as perivascular, perinecrotic, and invasive. However, from a neuropathological point of view, it is not easy to establish when a tumor structure can be considered a niche. The relevant literature has been reviewed in the light of our recent experience on the subject. As for perinecrotic niches, the occurrence of GSCs around necrosis is interpreted as triggered by hypoxia through HIF-1α. Our alternative hypothesis is that, together with progenitors, they are the cell constituents of hyper-proliferative areas of GB, where perinecrotic niches have developed, and they would, therefore, represent the remnants of GSCs/progenitors spared by the developing necrosis. Perivascular structures originate from both transport vessels and exchange vessels, i.e., venules, arterioles, or the undefinable neo-formed small vessels, but only those in which a direct contact between GSCs/progenitors and endothelial cells occurs can be called niches. Both pericytes and microglia/macrophages play a role in niche function: Macrophages of blood origin invade GB only after the appearance of "mother vessels" with consequent blood-brain barrier disruption. Not all vessel/tumor cell structures can be considered niches, that is, crucial sites of tumor progression, invasion, and angiogenesis.

  10. Habitat niche breadth predicts invasiveness in solitary ascidians.

    Science.gov (United States)

    Granot, Itai; Shenkar, Noa; Belmaker, Jonathan

    2017-10-01

    A major focus of invasion biology is understanding the traits associated with introduction success. Most studies assess these traits in the invaded region, while only few compare nonindigenous species to the pool of potential invaders in their native region. We focused on the niche breadth hypothesis , commonly evoked but seldom tested, which states that generalist species are more likely to become introduced as they are capable of thriving under a wide set of conditions. Based on the massive introduction of tropical species into the Mediterranean via the Suez Canal (Lessepsian migration), we defined ascidians in the Red Sea as the pool of potential invaders. We constructed unique settlement plates, each representing six different niches, to assess ascidian niche breadth, and deployed them in similar habitats in the native and invaded regions. For each species found on plates, we evaluated its abundance, relative abundance across successional stages, and niche breadth, and then compared (1) species in the Red Sea known to have been introduced into the Mediterranean (Lessepsian species) and those not known from the Mediterranean (non-Lessepsian); and (2) nonindigenous and indigenous species in the Mediterranean. Lessepsian species identified on plates in the Red Sea demonstrated wider niche breadth than non-Lessepsian species, supporting the niche breadth hypothesis within the native region. No differences were found between Lessepsian and non-Lessepsian species in species abundance and successional stages. In the Mediterranean, nonindigenous species numerically dominated the settlement plates. This precluded robust comparisons of niche breadth between nonindigenous and indigenous species in the invaded region. In conclusion, using Red Sea ascidians as the pool of potential invaders, we found clear evidence supporting the niche breadth hypothesis in the native region. We suggest that such patterns may often be obscured when conducting trait-based studies in the

  11. Reconstitution of bone-like matrix in osteogenically differentiated mesenchymal stem cell–collagen constructs: A three-dimensional in vitro model to study hematopoietic stem cell niche

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    WY Lai

    2013-10-01

    Full Text Available Mesenchymal stem/stromal cells (MSCs and osteoblasts are important niche cells for hematopoietic stem cells (HSCs in bone marrow osteoblastic niche. Here, we aim to partially reconstitute the bone marrow HSC niche in vitro using collagen microencapsulation for investigation of the interactions between HSCs and MSCs. Mouse MSCs (mMSCs microencapsulated in collagen were osteogenically differentiated to derive a bone-like matrix consisting of osteocalcin, osteopontin, and calcium deposits and secreted bone morphogenic protein 2 (BMP2. Decellularized bone-like matrix was seeded with fluorescence-labeled human MSCs and HSCs. Comparing with pure collagen scaffold, significantly more HSCs and HSC–MSC pairs per unit area were found in the decellularized bone-like matrix. Moreover, incubation with excess neutralizing antibody of BMP2 resulted in a significantly higher number of HSC per unit area than that without in the decellularized matrix. This work suggests that the osteogenic differentiated MSC–collagen microsphere is a valuable three-dimensional in vitro model to elucidate cell–cell and cell–matrix interactions in HSC niche.

  12. Supply Chain Development: Insights from Strategic Niche Management

    Science.gov (United States)

    Caniels, Marjolein C. J.; Romijn, Henny A.

    2008-01-01

    Purpose: The purpose of this paper is to contribute to the study of supply chain design from the perspective of complex dynamic systems. Unlike extant studies that use formal simulation modelling and associated methodologies rooted in the physical sciences, it adopts a framework rooted in the social sciences, strategic niche management, which…

  13. Stem cell autotomy and niche interaction in different systems.

    Science.gov (United States)

    Dorn, David C; Dorn, August

    2015-07-26

    The best known cases of cell autotomy are the formation of erythrocytes and thrombocytes (platelets) from progenitor cells that reside in special niches. Recently, autotomy of stem cells and its enigmatic interaction with the niche has been reported from male germline stem cells (GSCs) in several insect species. First described in lepidopterans, the silkmoth, followed by the gipsy moth and consecutively in hemipterans, foremost the milkweed bug. In both, moths and the milkweed bug, GSCs form finger-like projections toward the niche, the apical cells (homologs of the hub cells in Drosophila). Whereas in the milkweed bug the projection terminals remain at the surface of the niche cells, in the gipsy moth they protrude deeply into the singular niche cell. In both cases, the projections undergo serial retrograde fragmentation with progressing signs of autophagy. In the gipsy moth, the autotomized vesicles are phagocytized and digested by the niche cell. In the milkweed bug the autotomized vesicles accumulate at the niche surface and disintegrate. Autotomy and sprouting of new projections appears to occur continuously. The significance of the GSC-niche interactions, however, remains enigmatic. Our concept on the signaling relationship between stem cell-niche in general and GSC and niche (hub cells and cyst stem cells) in particular has been greatly shaped by Drosophila melanogaster. In comparing the interactions of GSCs with their niche in Drosophila with those in species exhibiting GSC autotomy it is obvious that additional or alternative modes of stem cell-niche communication exist. Thus, essential signaling pathways, including niche-stem cell adhesion (E-cadherin) and the direction of asymmetrical GSC division - as they were found in Drosophila - can hardly be translated into the systems where GSC autotomy was reported. It is shown here that the serial autotomy of GSC projections shows remarkable similarities with Wallerian axonal destruction, developmental axon

  14. Stem cell autotomy and niche interaction in different systems

    Science.gov (United States)

    Dorn, David C; Dorn, August

    2015-01-01

    The best known cases of cell autotomy are the formation of erythrocytes and thrombocytes (platelets) from progenitor cells that reside in special niches. Recently, autotomy of stem cells and its enigmatic interaction with the niche has been reported from male germline stem cells (GSCs) in several insect species. First described in lepidopterans, the silkmoth, followed by the gipsy moth and consecutively in hemipterans, foremost the milkweed bug. In both, moths and the milkweed bug, GSCs form finger-like projections toward the niche, the apical cells (homologs of the hub cells in Drosophila). Whereas in the milkweed bug the projection terminals remain at the surface of the niche cells, in the gipsy moth they protrude deeply into the singular niche cell. In both cases, the projections undergo serial retrograde fragmentation with progressing signs of autophagy. In the gipsy moth, the autotomized vesicles are phagocytized and digested by the niche cell. In the milkweed bug the autotomized vesicles accumulate at the niche surface and disintegrate. Autotomy and sprouting of new projections appears to occur continuously. The significance of the GSC-niche interactions, however, remains enigmatic. Our concept on the signaling relationship between stem cell-niche in general and GSC and niche (hub cells and cyst stem cells) in particular has been greatly shaped by Drosophila melanogaster. In comparing the interactions of GSCs with their niche in Drosophila with those in species exhibiting GSC autotomy it is obvious that additional or alternative modes of stem cell-niche communication exist. Thus, essential signaling pathways, including niche-stem cell adhesion (E-cadherin) and the direction of asymmetrical GSC division - as they were found in Drosophila - can hardly be translated into the systems where GSC autotomy was reported. It is shown here that the serial autotomy of GSC projections shows remarkable similarities with Wallerian axonal destruction, developmental axon

  15. Innovations in electronic services

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    Dagmara Wach

    2011-12-01

    Full Text Available Summarry Existence in electronic business has become increasingly difficult. High competition and considerable financial resources needed to enter electronic market are the problems of most micro and small sized enterprises, starting or developing their business. Nevertheless, there is a market niche for them, which can ensure success and grant partial financing of the business. This niche are small web projects, providing the customer with personalized service, hitting his tastes and meeting immediate needs. A projects that large websites are unable to perform. Financial sourcing of those projects comes from EU subsidies, in the framework of the Działanie 8.1. PO IG, 2007-2013.

  16. Effects of global changes on the climatic niche of the tick Ixodes ricinus inferred by species distribution modelling.

    Science.gov (United States)

    Porretta, Daniele; Mastrantonio, Valentina; Amendolia, Sara; Gaiarsa, Stefano; Epis, Sara; Genchi, Claudio; Bandi, Claudio; Otranto, Domenico; Urbanelli, Sandra

    2013-09-19

    Global climate change can seriously impact on the epidemiological dynamics of vector-borne diseases. In this study we investigated how future climatic changes could affect the climatic niche of Ixodes ricinus (Acari, Ixodida), among the most important vectors of pathogens of medical and veterinary concern in Europe. Species Distribution Modelling (SDM) was used to reconstruct the climatic niche of I. ricinus, and to project it into the future conditions for 2050 and 2080, under two scenarios: a continuous human demographic growth and a severe increase of gas emissions (scenario A2), and a scenario that proposes lower human demographic growth than A2, and a more sustainable gas emissions (scenario B2). Models were reconstructed using the algorithm of "maximum entropy", as implemented in the software Maxent 3.3.3e; 4,544 occurrence points and 15 bioclimatic variables were used. In both scenarios an increase of climatic niche of about two times greater than the current area was predicted as well as a higher climatic suitability under the scenario B2 than A2. Such an increase occurred both in a latitudinal and longitudinal way, including northern Eurasian regions (e.g. Sweden and Russia), that were previously unsuitable for the species. Our models are congruent with the predictions of range expansion already observed in I. ricinus at a regional scale and provide a qualitative and quantitative assessment of the future climatically suitable areas for I. ricinus at a continental scale. Although the use of SDM at a higher resolution should be integrated by a more refined analysis of further abiotic and biotic data, the results presented here suggest that under future climatic scenarios most of the current distribution area of I. ricinus could remain suitable and significantly increase at a continental geographic scale. Therefore disease outbreaks of pathogens transmitted by this tick species could emerge in previous non-endemic geographic areas. Further studies will

  17. Application of a niche-based model for forest cover classification

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    Amici V

    2012-05-01

    Full Text Available In recent years, a surge of interest in biodiversity conservation have led to the development of new approaches to facilitate ecologically-based conservation policies and management plans. In particular, image classification and predictive distribution modeling applied to forest habitats, constitute a crucial issue as forests constitute the most widespread vegetation type and play a key role for ecosystem functioning. Then, the general purpose of this study is to develop a framework that in the absence of large amounts of field data for large areas may allow to select the most appropriate classification. In some cases, a hard division of classes is required, especially as support to environmental policies; despite this it is necessary to take into account problems which derive from a crisp view of ecological entities being mapped, since habitats are expected to be structurally complex and continuously vary within a landscape. In this paper, a niche model (MaxEnt, generally used to estimate species/habitat distribution, has been applied to classify forest cover in a complex Mediterranean area and to estimate the probability distribution of four forest types, producing continuous maps of forest cover. The use of the obtained models as validation of model for crisp classifications, highlighted that crisp classification, which is being continuously used in landscape research and planning, is not free from drawbacks as it is showing a high degree of inner variability. The modeling approach followed by this study, taking into account the uncertainty proper of the natural ecosystems and the use of environmental variables in land cover classification, may represent an useful approach to making more efficient and effective field inventories and to developing effective forest conservation policies.

  18. Ten Niche Strategies To Commercialize New High-Tech Products

    NARCIS (Netherlands)

    Ortt, J.R.; Langley, D.J.; Pals, N.

    2013-01-01

    There are serious gaps in the scientific literature relating to niche strategies as a means for commercializing new high-tech products. In particular, there is no clarity about what types of niche strategies can be distinguished, or how a niche strategy can be selected to suit a certain ituation. In

  19. Thermal Niche Tracking and Future Distribution of Atlantic Mackerel Spawning in response to Ocean Warming

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    Antoine eBruge

    2016-06-01

    Full Text Available North-east Atlantic mackerel spawning distribution has shifted northward in the last three decades probably in response to global sea warming. Yet, uncertainties subsist regarding on the shift rate, causalities, and how this species will respond to future conditions. Using egg surveys, we explored the influence of temperature change on mackerel’s spawning distribution (western and southern spawning components of the stock between 1992 and 2013, and projected how it may change under future climate change scenarios. We developed three generalized additive models: (i a spatiotemporal model to reconstruct the spawning distribution for the north-east Atlantic stock over the period 1992-2013, to estimate the rate of shift; (ii a thermal habitat model to assess if spawning mackerel have tracked their thermal spawning-niche; and (iii a niche-based model to project future spawning distribution under two predicted climate change scenarios. Our findings showed that mackerel spawning activity has shifted northward at a rate of 15.9 ± 0.9 km/decade between 1992 and 2013. Similarly, using the thermal habitat model, we detected a northward shift of the thermal spawning-niche. This indicates that mackerel has spawned at higher latitudes to partially tracking their thermal spawning-niche, at a rate of 28.0 ± 9.0 km/°C of sea warming. Under future scenarios (mid and end of the century, the extrapolation of the niche-based model to coupled hydroclimatic and biogeochemical models indicates that centre of gravity of mackerel spawning distribution is expected to shift westward (32 to 117 km and northward (0.5 to 328 km, but with high variability according to scenarios and time frames. The future of the overall egg production in the area is uncertain (change from -9.3% to 12%. With the aim to allow the fishing industry to anticipate the future distribution of mackerel shoals during the spawning period, future research should focus on reducing uncertainty in

  20. Evolution is a cooperative process: the biodiversity-related niches differentiation theory (BNDT) can explain why.

    Science.gov (United States)

    Gatti, Roberto Cazzolla

    2011-01-01

    A. McFayden and G.E. Hutchinson defined a niche as a multidimensional space or hypervolume within the environment that allows an individual or a species to survive, we consider niches as a fundamental ecological variable that regulate species' composition and relation in ecosystems. Successively the niche concept has been associated to the genetic term "phenotype" by MacArthurstressing the importance on what a species or a genome can show outside, either in the environmental functions or in body characteristics. Several indexes have been developed to evaluate the grade of overlapping and similarities of species' niches, even utilizing the theory of information. However, which are the factors that determine the number of species that can coexist in a determinate environment and why a generalist species do not compete until the exclusion of the remaining species to maximize its fitness, is still quite unknown. Moreover, there are few studies and theories that clearly explain why the number of niches is so variable through ecosystems and how can several species live in the same basal niche, intended in a comprehensive sense as the range of basic conditions (temperature, humidity, food-guild, etc.). Here I show that the number of niches in an ecosystem depends on the number of species present in a particular moment and that the species themselves allow the enhancement of niches in terms of space and number. I found that using a three-dimensional model as hypervolume and testing the theory on a Mediterranean, temperate and tropical forest ecosystem it is possible to demonstrate that each species plays a fundamental role in facilitating the colonization by other species by simply modifying the environment and exponentially increasing the available niches' space and number. I resumed these hypothesis, after some preliminary empiric tests, in the Biodiversity-related Niches Differentiation Theory (BNDT), stressing with these definition that the process of niches

  1. Exosomes as novel regulators of adult neurogenic niches

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    Luis Federico Batiz

    2016-01-01

    Full Text Available Adult neurogenesis has been convincingly demonstrated in two regions of the mammalian brain: the sub-granular zone (SGZ of the dentate gyrus (DG in the hippocampus, and the sub-ventricular zone (SVZ of the lateral ventricles. SGZ newborn neurons are destined to the granular cell layer of the DG, while new neurons from the SVZ neurons migrate rostrally into the olfactory bulb. The process of adult neurogenesis persists throughout life and is supported by a pool of neural stem cells (NSCs, which reside in a unique and specialized microenvironment known as neurogenic niche. Neurogenic niches are structured by a complex organization of different cell types, including the NSC-neuron lineage, glial cells and vascular cells. Thus, cell-to-cell communication plays a key role in the dynamic modulation of homeostasis and plasticity of the adult neurogenic process. Specific cell-cell contacts and extracellular signals originated locally provide the necessary support and regulate the balance between self-renewal and differentiation of NSCs. Furthermore, extracellular signals originated at distant locations, including other brain regions or systemic organs, may reach the niche through the cerebrospinal fluid or the vasculature and influence its nature. The role of several secreted molecules, such as cytokines, growth factors, neurotransmitters, and hormones, in the biology of adult NSCs, has been systematically addressed. Interestingly, in addition to these well-recognized signals, a novel type of intercellular messengers has been identified recently: the extracellular vesicles (EVs. EVs, and particularly exosomes, are implicated in the transfer of mRNAs, microRNAs (miRNAs, proteins and lipids between cells and thus are able to modify the function of recipient cells. Exosomes appear to play a significant role in different stem cell niches such as the mesenchymal stem cell niche, cancer stem cell niche and pre-metastatic niche; however, their roles in adult

  2. Neutral theory and the species abundance distribution: recent developments and prospects for unifying niche and neutral perspectives

    Science.gov (United States)

    Matthews, Thomas J; Whittaker, Robert J

    2014-01-01

    Published in 2001, The Unified Neutral Theory of Biodiversity and Biogeography (UNTB) emphasizes the importance of stochastic processes in ecological community structure, and has challenged the traditional niche-based view of ecology. While neutral models have since been applied to a broad range of ecological and macroecological phenomena, the majority of research relating to neutral theory has focused exclusively on the species abundance distribution (SAD). Here, we synthesize the large body of work on neutral theory in the context of the species abundance distribution, with a particular focus on integrating ideas from neutral theory with traditional niche theory. First, we summarize the basic tenets of neutral theory; both in general and in the context of SADs. Second, we explore the issues associated with neutral theory and the SAD, such as complications with fitting and model comparison, the underlying assumptions of neutral models, and the difficultly of linking pattern to process. Third, we highlight the advances in understanding of SADs that have resulted from neutral theory and models. Finally, we focus consideration on recent developments aimed at unifying neutral- and niche-based approaches to ecology, with a particular emphasis on what this means for SAD theory, embracing, for instance, ideas of emergent neutrality and stochastic niche theory. We put forward the argument that the prospect of the unification of niche and neutral perspectives represents one of the most promising future avenues of neutral theory research. PMID:25360266

  3. Neutral theory and the species abundance distribution: recent developments and prospects for unifying niche and neutral perspectives.

    Science.gov (United States)

    Matthews, Thomas J; Whittaker, Robert J

    2014-06-01

    Published in 2001, The Unified Neutral Theory of Biodiversity and Biogeography (UNTB) emphasizes the importance of stochastic processes in ecological community structure, and has challenged the traditional niche-based view of ecology. While neutral models have since been applied to a broad range of ecological and macroecological phenomena, the majority of research relating to neutral theory has focused exclusively on the species abundance distribution (SAD). Here, we synthesize the large body of work on neutral theory in the context of the species abundance distribution, with a particular focus on integrating ideas from neutral theory with traditional niche theory. First, we summarize the basic tenets of neutral theory; both in general and in the context of SADs. Second, we explore the issues associated with neutral theory and the SAD, such as complications with fitting and model comparison, the underlying assumptions of neutral models, and the difficultly of linking pattern to process. Third, we highlight the advances in understanding of SADs that have resulted from neutral theory and models. Finally, we focus consideration on recent developments aimed at unifying neutral- and niche-based approaches to ecology, with a particular emphasis on what this means for SAD theory, embracing, for instance, ideas of emergent neutrality and stochastic niche theory. We put forward the argument that the prospect of the unification of niche and neutral perspectives represents one of the most promising future avenues of neutral theory research.

  4. Imaging-Based Screen Identifies Laminin 411 as a Physiologically Relevant Niche Factor with Importance for i-Hep Applications

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    John Ong

    2018-03-01

    Full Text Available Summary: Use of hepatocytes derived from induced pluripotent stem cells (i-Heps is limited by their functional differences in comparison with primary cells. Extracellular niche factors likely play a critical role in bridging this gap. Using image-based characterization (high content analysis; HCA of freshly isolated hepatocytes from 17 human donors, we devised and validated an algorithm (Hepatocyte Likeness Index; HLI for comparing the hepatic properties of cells against a physiological gold standard. The HLI was then applied in a targeted screen of extracellular niche factors to identify substrates driving i-Heps closer to the standard. Laminin 411, the top hit, was validated in two additional induced pluripotent stem cell (iPSC lines, primary tissue, and an in vitro model of α1-antitrypsin deficiency. Cumulatively, these data provide a reference method to control and screen for i-Hep differentiation, identify Laminin 411 as a key niche protein, and underscore the importance of combining substrates, soluble factors, and HCA when developing iPSC applications. : Rashid and colleagues demonstrate the utility of a high-throughput imaging platform for identification of physiologically relevant extracellular niche factors to advance i-Heps closer to their primary tissue counterparts. The extracellular matrix (ECM protein screen identified Laminin 411 as an important niche factor facilitating i-Hep-based disease modeling in vitro. Keywords: iPS hepatocytes, extracellular niche, image-based screening, disease modeling, laminin

  5. Niche construction, sources of selection and trait coevolution.

    Science.gov (United States)

    Laland, Kevin; Odling-Smee, John; Endler, John

    2017-10-06

    Organisms modify and choose components of their local environments. This 'niche construction' can alter ecological processes, modify natural selection and contribute to inheritance through ecological legacies. Here, we propose that niche construction initiates and modifies the selection directly affecting the constructor, and on other species, in an orderly, directed and sustained manner. By dependably generating specific environmental states, niche construction co-directs adaptive evolution by imposing a consistent statistical bias on selection. We illustrate how niche construction can generate this evolutionary bias by comparing it with artificial selection. We suggest that it occupies the middle ground between artificial and natural selection. We show how the perspective leads to testable predictions related to: (i) reduced variance in measures of responses to natural selection in the wild; (ii) multiple trait coevolution, including the evolution of sequences of traits and patterns of parallel evolution; and (iii) a positive association between niche construction and biodiversity. More generally, we submit that evolutionary biology would benefit from greater attention to the diverse properties of all sources of selection.

  6. Niche divergence builds the case for ecological speciation in skinks of the Plestiodon skiltonianus species complex

    Science.gov (United States)

    Wogan, Guinevere O.U.; Richmond, Jonathan Q.

    2015-01-01

    Adaptation to different thermal environments has the potential to cause evolutionary changes that are sufficient to drive ecological speciation. Here, we examine whether climate-based niche divergence in lizards of the Plestiodon skiltonianus species complex is consistent with the outcomes of such a process. Previous work on this group shows that a mechanical sexual barrier has evolved between species that differ mainly in body size and that the barrier may be a by-product of selection for increased body size in lineages that have invaded xeric environments; however, baseline information on niche divergence among members of the group is lacking. We quantified the climatic niche using mechanistic physiological and correlative niche models and then estimated niche differences among species using ordination techniques and tests of niche overlap and equivalency. Our results show that the thermal niches of size-divergent, reproductively isolated morphospecies are significantly differentiated and that precipitation may have been as important as temperature in causing increased shifts in body size in xeric habitats. While these findings alone do not demonstrate thermal adaptation or identify the cause of speciation, their integration with earlier genetic and behavioral studies provides a useful test of phenotype–environment associations that further support the case for ecological speciation in these lizards.

  7. Climatic niche conservatism and biogeographical non-equilibrium in Eschscholzia californica (Papaveraceae), an invasive plant in the Chilean Mediterranean region.

    Science.gov (United States)

    Peña-Gómez, Francisco T; Guerrero, Pablo C; Bizama, Gustavo; Duarte, Milén; Bustamante, Ramiro O

    2014-01-01

    Species climate requirements are useful for predicting their geographic distribution. It is often assumed that the niche requirements for invasive plants are conserved during invasion, especially when the invaded regions share similar climate conditions. California and central Chile have a remarkable degree of convergence in their vegetation structure, and a similar Mediterranean climate. Such similarities make these geographic areas an interesting natural experiment for testing climatic niche dynamics and the equilibrium of invasive species in a new environment. We tested to see if the climatic niche of Eschscholzia californica is conserved in the invaded range (central Chile), and we assessed whether the invasion process has reached a biogeographical equilibrium, i.e., occupy all the suitable geographic locations that have suitable conditions under native niche requirements. We compared the climatic niche in the native and invaded ranges as well as the projected potential geographic distribution in the invaded range. In order to compare climatic niches, we conducted a Principal Component Analysis (PCA) and Species Distribution Models (SDMs), to estimate E. californica's potential geographic distribution. We also used SDMs to predict altitudinal distribution limits in central Chile. Our results indicated that the climatic niche occupied by E. californica in the invaded range is firmly conserved, occupying a subset of the native climatic niche but leaving a substantial fraction of it unfilled. Comparisons of projected SDMs for central Chile indicate a similarity, yet the projection from native range predicted a larger geographic distribution in central Chile compared to the prediction of the model constructed for central Chile. The projected niche occupancy profile from California predicted a higher mean elevation than that projected from central Chile. We concluded that the invasion process of E. californica in central Chile is consistent with climatic niche

  8. Target Article with Commentaries: Developmental Niche Construction

    Science.gov (United States)

    Flynn, Emma G.; Laland, Kevin N.; Kendal, Rachel L.; Kendal, Jeremy R.

    2013-01-01

    Niche construction is the modification of components of the environment through an organism's activities. Humans modify their environments mainly through ontogenetic and cultural processes, and it is this reliance on learning, plasticity and culture that lends human niche construction a special potency. In this paper we aim to facilitate…

  9. The shared preference niche of sympatric Asiatic black bears and sun bears in a tropical forest mosaic.

    Science.gov (United States)

    Steinmetz, Robert; Garshelis, David L; Chutipong, Wanlop; Seuaturien, Naret

    2011-01-20

    Ecologically similar species often coexist by partitioning use of habitats or resources. Such partitioning can occur through divergent or shared niches. We investigated overlap in habitat use and spatial co-occurrence by sympatric Asiatic black bears and sun bears in three habitats in Thailand, and thereby assessed which niche model best accounts for their coexistence. We used density of species-specific signs to assess habitat use. Signs of both bear species occurred in all three habitats, and on >60% of sampling transects. Both species fed mostly on fruit; insect feeding signs were uncommon, and were mostly from sun bears. Significant differences in habitat use occurred only in montane forest, the habitat in which fruit was most abundant; incidence of black bear sign there was six times higher than that of sun bears. Habitat use was similar between the two species in the other habitats, which comprised 85% of the area. Of 10 habitat attributes examined, fruiting tree density was the best predictor of occurrence for both species. Models that included interspecific competition (fresh foraging activity of the other species) were less supported than the top models without competition. Bear species co-occurrence at both coarse and fine spatial scales and use of the same resources (fruit trees) indicated common niche preferences. However, their habitat use differed in ways expected from their physical differences: larger black bears dominated in the most fruit-rich habitat, and smaller sun bears used less-preferred insects. These results indicate broadly overlapping fundamental niches combined with asymmetric competition-features consistent with the concept of shared preference niches. This model of the niche has received little attention in ecology, but appears to be relatively common in nature.

  10. The shared preference niche of sympatric Asiatic black bears and sun bears in a tropical forest mosaic.

    Directory of Open Access Journals (Sweden)

    Robert Steinmetz

    2011-01-01

    Full Text Available Ecologically similar species often coexist by partitioning use of habitats or resources. Such partitioning can occur through divergent or shared niches. We investigated overlap in habitat use and spatial co-occurrence by sympatric Asiatic black bears and sun bears in three habitats in Thailand, and thereby assessed which niche model best accounts for their coexistence.We used density of species-specific signs to assess habitat use. Signs of both bear species occurred in all three habitats, and on >60% of sampling transects. Both species fed mostly on fruit; insect feeding signs were uncommon, and were mostly from sun bears. Significant differences in habitat use occurred only in montane forest, the habitat in which fruit was most abundant; incidence of black bear sign there was six times higher than that of sun bears. Habitat use was similar between the two species in the other habitats, which comprised 85% of the area. Of 10 habitat attributes examined, fruiting tree density was the best predictor of occurrence for both species. Models that included interspecific competition (fresh foraging activity of the other species were less supported than the top models without competition.Bear species co-occurrence at both coarse and fine spatial scales and use of the same resources (fruit trees indicated common niche preferences. However, their habitat use differed in ways expected from their physical differences: larger black bears dominated in the most fruit-rich habitat, and smaller sun bears used less-preferred insects. These results indicate broadly overlapping fundamental niches combined with asymmetric competition-features consistent with the concept of shared preference niches. This model of the niche has received little attention in ecology, but appears to be relatively common in nature.

  11. Chironomidae larvae (Diptera) of Neotropical floodplain: overlap niche in different habitats.

    Science.gov (United States)

    Butakka, C M M; Ragonha, F H; Takeda, A M

    2014-05-01

    The niche overlap between trophic groups of Chironomidae larvae in different habitats was observed between trophic groups and between different environments in Neotropical floodplain. For the evaluation we used the index of niche overlap (CXY) and analysis of trophic networks, both from the types and amount of food items identified in the larval alimentary canal. In all environments, the larvae fed on mainly organic matter such as plants fragments and algae, but there were many omnivore larvae. Species that have high values of food items occurred in diverse environments as generalists with great overlap niche and those with a low amount of food items with less overlap niche were classified as specialists. The largest number of trophic niche overlap was observed among collector-gatherers in connected floodplain lakes. The lower values of index niche overlap were predators. The similarity in the diet of different taxa in the same niche does not necessarily imply competition between them, but coexistence when the food resource is not scarce in the environment even in partially overlapping niches.

  12. Potential for spread of the white-nose fungus (Pseudogymnoascus destructans in the Americas: use of Maxent and NicheA to assure strict model transference

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    Luis E. Escobar

    2014-11-01

    Full Text Available Emerging infectious diseases can present serious threats to wildlife, even to the point of causing extinction. White- nose fungus (Pseudogymnoascus destructans is causing an epizootic in bats that is expanding rapidly, both geographically and taxonomically. Little is known of the ecology and distributional potential of this intercontinental pathogen. We address this gap via ecological niche models that characterise coarse resolution niche differences between fungus populations on dif- ferent continents, identifying areas potentially vulnerable to infection in South America. Here we explore a novel approach to identifying areas of potential distribution across novel geographic regions that avoids perilious extrapolation into novel environments. European and North American fungus populations show differential use of environmental space, but rather than niche differentiation, we find that changes are best attributed to climatic differences between the two continents. Suitable areas for spread of the pathogen were identified across southern South America; however caution should be taken to avoid underestimating the potential for spread of this pathogen in South America.

  13. Potential for spread of the white-nose fungus (Pseudogymnoascus destructans) in the Americas: use of Maxent and NicheA to assure strict model transference.

    Science.gov (United States)

    Escobar, Luis E; Lira-Noriega, Andrés; Medina-Vogel, Gonzalo; Townsend Peterson, A

    2014-11-01

    Emerging infectious diseases can present serious threats to wildlife, even to the point of causing extinction. Whitenose fungus (Pseudogymnoascus destructans) is causing an epizootic in bats that is expanding rapidly, both geographically and taxonomically. Little is known of the ecology and distributional potential of this intercontinental pathogen. We address this gap via ecological niche models that characterise coarse resolution niche differences between fungus populations on different continents, identifying areas potentially vulnerable to infection in South America. Here we explore a novel approach to identifying areas of potential distribution across novel geographic regions that avoids perilious extrapolation into novel environments. European and North American fungus populations show differential use of environmental space, but rather than niche differentiation, we find that changes are best attributed to climatic differences between the two continents. Suitable areas for spread of the pathogen were identified across southern South America; however caution should be taken to avoid underestimating the potential for spread of this pathogen in South America.

  14. Evolution of climatic niche specialization: a phylogenetic analysis in amphibians.

    Science.gov (United States)

    Bonetti, Maria Fernanda; Wiens, John J

    2014-11-22

    The evolution of climatic niche specialization has important implications for many topics in ecology, evolution and conservation. The climatic niche reflects the set of temperature and precipitation conditions where a species can occur. Thus, specialization to a limited set of climatic conditions can be important for understanding patterns of biogeography, species richness, community structure, allopatric speciation, spread of invasive species and responses to climate change. Nevertheless, the factors that determine climatic niche width (level of specialization) remain poorly explored. Here, we test whether species that occur in more extreme climates are more highly specialized for those conditions, and whether there are trade-offs between niche widths on different climatic niche axes (e.g. do species that tolerate a broad range of temperatures tolerate only a limited range of precipitation regimes?). We test these hypotheses in amphibians, using phylogenetic comparative methods and global-scale datasets, including 2712 species with both climatic and phylogenetic data. Our results do not support either hypothesis. Rather than finding narrower niches in more extreme environments, niches tend to be narrower on one end of a climatic gradient but wider on the other. We also find that temperature and precipitation niche breadths are positively related, rather than showing trade-offs. Finally, our results suggest that most amphibian species occur in relatively warm and dry environments and have relatively narrow climatic niche widths on both of these axes. Thus, they may be especially imperilled by anthropogenic climate change. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  15. The thermal niche of Neotropical nectar-feeding bats: Its evolution and application to predict responses to global warming.

    Science.gov (United States)

    Ortega-García, Stephanie; Guevara, Lázaro; Arroyo-Cabrales, Joaquín; Lindig-Cisneros, Roberto; Martínez-Meyer, Enrique; Vega, Ernesto; Schondube, Jorge E

    2017-09-01

    The thermal niche of a species is one of the main determinants of its ecology and biogeography. In this study, we determined the thermal niche of 23 species of Neotropical nectar-feeding bats of the subfamily Glossophaginae (Chiroptera, Phyllostomidae). We calculated their thermal niches using temperature data obtained from collection records, by generating a distribution curve of the maximum and minimum temperatures per locality, and using the inflection points of the temperature distributions to estimate the species optimal (STZ) and suboptimal (SRZ) zones of the thermal niche. Additionally, by mapping the values of the STZ and SRZ on a phylogeny of the group, we generated a hypothesis of the evolution of the thermal niches of this clade of nectar-feeding bats. Finally, we used the characteristics of their thermal niches to predict the responses of these organisms to climate change. We found a large variation in the width and limits of the thermal niches of nectar-feeding bats. Additionally, while the upper limits of the thermal niches varied little among species, their lower limits differ wildly. The ancestral reconstruction of the thermal niche indicated that this group of Neotropical bats evolved under cooler temperatures. The two clades inside the Glossophaginae differ in the evolution of their thermal niches, with most members of the clade Choeronycterines evolving "colder" thermal niches, while the majority of the species in the clade Glossophagines evolving "warmer" thermal niches. By comparing thermal niches with climate change models, we found that all species could be affected by an increase of 1°C in temperature at the end of this century. This suggests that even nocturnal species could suffer important physiological costs from global warming. Our study highlights the value of scientific collections to obtain ecologically significant physiological data for a large number of species.

  16. Innovative business models within niche tourist markets: shared identity, authenticity and flexibile networks. The case of three italian SMEs

    Directory of Open Access Journals (Sweden)

    Federica Montaguti

    2016-07-01

    Full Text Available Innovative business models within niche tourist markets: shared identity, authenticity and flexibile networks. The case of three italian SMEs The evolution of business models is a crucial challenge for tourism companies, which should understand how they can stimulate their creativity and introduce innovation. However for many firms, in particular for SMEs, this process is not so easy to be adopted. Even more difficult it is to understand how the business model should change to be successful in solving what appears to be one of the main problems for SMEs, especially within mature, tourist destinations, i.e. targeting new profitable segments. The paper discusses the main findings of a research project carried out by the authors about changes in the business models of Italian tourism companies, underlining in particular three case-studies of interest in terms of the innovation put in place and that relate to SMEs. The analysis, based on the business model canvas, the value constellation and the storytelling, found out that these three firms are flexible companies that have characteristics emblematic of the knowledge and information economy business models. They successfully answer the needs of specific niches, finding new opportunities within a mature tourism market and famous destinations, thanks to their ability to develop wide flexible networks, where customers are an active part, and thanks to the value proposed to the clients, centred on the idea of a shared identity between the clients and the company’s founders and of an authenticity guaranteed by the life story of the founders themselves.

  17. Classification and comparison of niche services for developing strategy of medical tourism in Asian countries.

    Science.gov (United States)

    Chen, Hung-chi; Kuo, Hsin-chih; Chung, Kuo-Piao; Chang, Sophia; Su, Syi; Yang, Ming-chin

    2010-01-01

    Medical tourism is a new trend in medical service. It is booming not only in Asian countries but also in European and South American countries. Worldwide competition of medical service is expected in the future, and niche service will be a "trademark" for the promotion of global medicine. Niche service also functions for market segmentation. Niche services are usually surgical procedures. A study was carried out to compare different strategies for developing medical tourism in Asian countries. The role of a niche service is evaluated in the initiation and further development of medical tourism for individual countries. From this study, a general classification was proposed in terms of treatment procedures. It can be used as a useful guideline for additional studies in medical tourism. Niche service plays the following roles in the development of medical tourism: (1) It attracts attention in the mass media and helps in subsequent promotion of business, (2) it exerts pressure on the hospital, which must improve the quality of health care provided in treating foreign patients, especially the niche services, and (3) it is a tool for setting up the business model. E-Da Hospital is an example for developing medical tourism in Taiwan. A side effect is that niche service brings additional foreign patients, which will contribute to the benefit of the hospital, but this leaves less room for treating domestic patients. A niche service is a means of introduction for entry into the market of medical tourism. How to create a successful story is important for the development of a niche service. When a good reputation has been established, the information provided on the Internet can last for a long time and can spread internationally to form a distinguished mark for further development. Niche services can be classified into 3 categories: (1) Low-risk procedures with large price differences and long stay after retirement; (2) high-risk procedures with less of a price difference

  18. The extraocular muscle stem cell niche is resistant to ageing and disease

    Directory of Open Access Journals (Sweden)

    Luigi eFormicola

    2014-12-01

    Full Text Available Specific muscles are spared in many degenerative myopathies. Most notably, the extraocular muscles (EOMs do not show clinical signs of late stage myopathies including the accumulation of fibrosis and fat. It has been proposed that an altered stem cell niche underlies the resistance of EOMs in these pathologies, however, to date, no reports have provided a detailed characterization of the EOM stem cell niche. PW1/Peg3 is expressed in progenitor cells in all adult tissues including satellite cells and a subset of interstitial non-satellite cell progenitors in muscle. These PW1-positive interstitial cells (PICs include a fibroadipogenic progenitor population (FAPs that give rise to fat and fibrosis in late stage myopathies. PICs/FAPs are mobilized following injury and FAPs exert a promyogenic role upon myoblasts in vitro but require the presence of a minimal population of satellite cells in vivo. We and others recently described that FAPs express promyogenic factors while satellite cells express antimyogenic factors suggesting that PICs/FAPs act as support niche cells in skeletal muscle through paracrine interactions. We analyzed the EOM stem cell niche in young adult and aged wild-type mice and found that the balance between PICs and satellite cells within the EOM stem cell niche is maintained throughout life. Moreover, in the adult mdx mouse model for Duchenne muscular dystrophy, the EOM stem cell niche is unperturbed compared to normal mice, in contrast to Tibialis Anterior (TA muscle, which displays signs of ongoing degeneration/regeneration. Regenerating mdx TA shows increased levels of both PICs and satellite cells, comparable to normal unaffected EOMs. We propose that the increase in PICs that we observe in normal EOMs contributes to preserving the integrity of the myofibers and satellite cells. Our data suggest that molecular cues regulating muscle regeneration are intrinsic properties of EOMs.

  19. Tracking niche variation over millennial timescales in sympatric killer whale lineages.

    Science.gov (United States)

    Foote, Andrew D; Newton, Jason; Ávila-Arcos, María C; Kampmann, Marie-Louise; Samaniego, Jose A; Post, Klaas; Rosing-Asvid, Aqqalu; Sinding, Mikkel-Holger S; Gilbert, M Thomas P

    2013-10-07

    Niche variation owing to individual differences in ecology has been hypothesized to be an early stage of sympatric speciation. Yet to date, no study has tracked niche width over more than a few generations. In this study, we show the presence of isotopic niche variation over millennial timescales and investigate the evolutionary outcomes. Isotopic ratios were measured from tissue samples of sympatric killer whale Orcinus orca lineages from the North Sea, spanning over 10 000 years. Isotopic ratios spanned a range similar to the difference in isotopic values of two known prey items, herring Clupea harengus and harbour seal Phoca vitulina. Two proxies of the stage of speciation, lineage sorting of mitogenomes and genotypic clustering, were both weak to intermediate indicating that speciation has made little progress. Thus, our study confirms that even with the necessary ecological conditions, i.e. among-individual variation in ecology, it is difficult for sympatric speciation to progress in the face of gene flow. In contrast to some theoretical models, our empirical results suggest that sympatric speciation driven by among-individual differences in ecological niche is a slow process and may not reach completion. We argue that sympatric speciation is constrained in this system owing to the plastic nature of the behavioural traits under selection when hunting either mammals or fish.

  20. Niche construction drives social dependence in hermit crabs.

    Science.gov (United States)

    Laidre, Mark E

    2012-10-23

    Organisms can receive not only a genetic inheritance from their ancestors but also an ecological inheritance, involving modifications their ancestors made to the environment through niche construction. Ecological inheritances may persist as a legacy, potentially generating selection pressures that favor sociality. Yet, most proposed cases of sociality being impacted by an ecological inheritance come from organisms that live among close kin and were highly social before their niche construction began. Here, I show that in terrestrial hermit crabs (Coenobita compressus)--organisms that do not live with kin and reside alone, each in its own shell--niche-construction drives social dependence, such that individuals can only survive in remodeled shells handed down from conspecifics. These results suggest that niche construction can be an important initiator of evolutionary pressures to socialize, even among unrelated and otherwise asocial organisms. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Niche tracking and rapid establishment of distributional equilibrium in the house sparrow show potential responsiveness of species to climate change.

    Directory of Open Access Journals (Sweden)

    William B Monahan

    changes to the realized environmental space. Such insights may be used to conceptualize mechanistic climatic niche models in birds and other taxa.

  2. Ecological niche modelling of Rift Valley fever virus vectors in Baringo, Kenya

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    Alfred O. Ochieng

    2016-11-01

    Full Text Available Background: Rift Valley fever (RVF is a vector-borne zoonotic disease that has an impact on human health and animal productivity. Here, we explore the use of vector presence modelling to predict the distribution of RVF vector species under climate change scenario to demonstrate the potential for geographic spread of Rift Valley fever virus (RVFV. Objectives: To evaluate the effect of climate change on RVF vector distribution in Baringo County, Kenya, with an aim of developing a risk map for spatial prediction of RVF outbreaks. Methodology: The study used data on vector presence and ecological niche modelling (MaxEnt algorithm to predict the effect of climatic change on habitat suitability and the spatial distribution of RVF vectors in Baringo County. Data on species occurrence were obtained from longitudinal sampling of adult mosquitoes and larvae in the study area. We used present (2000 and future (2050 Bioclim climate databases to model the vector distribution. Results: Model results predicted potential suitable areas with high success rates for Culex quinquefasciatus, Culex univitattus, Mansonia africana, and Mansonia uniformis. Under the present climatic conditions, the lowlands were found to be highly suitable for all the species. Future climatic conditions indicate an increase in the spatial distribution of Cx. quinquefasciatus and M. africana. Model performance was statistically significant. Conclusion: Soil types, precipitation in the driest quarter, precipitation seasonality, and isothermality showed the highest predictive potential for the four species.

  3. Synergistic selection between ecological niche and mate preference primes diversification.

    Science.gov (United States)

    Boughman, Janette W; Svanbäck, Richard

    2017-01-01

    The ecological niche and mate preferences have independently been shown to be important for the process of speciation. Here, we articulate a novel mechanism by which ecological niche use and mate preference can be linked to promote speciation. The degree to which individual niches are narrow and clustered affects the strength of divergent natural selection and population splitting. Similarly, the degree to which individual mate preferences are narrow and clustered affects the strength of divergent sexual selection and assortative mating between diverging forms. This novel perspective is inspired by the literature on ecological niches; it also explores mate preferences and how they may contribute to speciation. Unlike much comparative work, we do not search for evolutionary patterns using proxies for adaptation and sexual selection, but rather we elucidate how ideas from niche theory relate to mate preference, and how this relationship can foster speciation. Recognizing that individual and population niches are conceptually and ecologically linked to individual and population mate preference functions will significantly increase our understanding of rapid evolutionary diversification in nature. It has potential to help solve the difficult challenge of testing the role of sexual selection in the speciation process. We also identify ecological factors that are likely to affect individual niche and individual mate preference in synergistic ways and as a consequence to promote speciation. The ecological niche an individual occupies can directly affect its mate preference. Clusters of individuals with narrow, differentiated niches are likely to have narrow, differentiated mate preference functions. Our approach integrates ecological and sexual selection research to further our understanding of diversification processes. Such integration may be necessary for progress because these processes seem inextricably linked in the natural world. © 2016 The Author(s). Evolution

  4. Development and molecular composition of the hepatic progenitor cell niche.

    Science.gov (United States)

    Vestentoft, Peter Siig

    2013-05-01

    End-stage liver diseases represent major health problems that are currently treated by liver transplantation. However, given the world-wide shortage of donor livers novel strategies are needed for therapeutic treatment. Adult stem cells have the ability to self-renew and differentiate into the more specialized cell types of a given organ and are found in tissues throughout the body. These cells, whose progeny are termed progenitor cells in human liver and oval cells in rodents, have the potential to treat patients through the generation of hepatic parenchymal cells, even from the patient's own tissue. Little is known regarding the nature of the hepatic progenitor cells. Though they are suggested to reside in the most distal part of the biliary tree, the canal of Hering, the lack of unique surface markers for these cells has hindered their isolation and characterization. Upon activation, they proliferate and form ductular structures, termed "ductular reactions", which radiate into the hepatic parenchyma. The ductular reactions contain activated progenitor cells that not only acquire a phenotype resembling that observed in developing liver but also display markers of differentiation shared with the cholangiocytic or hepatocytic lineages, the two parenchymal hepatic cell types. Interactions between the putative progenitor cells, the surrounding support cells and the extracellular matrix scaffold, all constituting the progenitor cell niche, are likely to be important for regulating progenitor cell activity and differentiation. Therefore, identifying novel progenitor cell markers and deciphering their microenvironment could facilitate clinical use. The aims of the present PhD thesis were to expand knowledge of the hepatic progenitor cell niche and characterize it both during development and in disease. Several animal models of hepatic injury are known to induce activation of the progenitor cells. In order to identify possible progenitor cell markers and niche components

  5. The vasculature as a neural stem cell niche.

    Science.gov (United States)

    Otsuki, Leo; Brand, Andrea H

    2017-11-01

    Neural stem cells (NSCs) are multipotent, self-renewing progenitors that generate progeny that differentiate into neurons and glia. NSCs in the adult mammalian brain are generally quiescent. Environmental stimuli such as learning or exercise can activate quiescent NSCs, inducing them to proliferate and produce new neurons and glia. How are these behaviours coordinated? The neurovasculature, the circulatory system of the brain, is a key component of the NSC microenvironment, or 'niche'. Instructive signals from the neurovasculature direct NSC quiescence, proliferation, self-renewal and differentiation. During ageing, a breakdown in the niche accompanies NSC dysfunction and cognitive decline. There is much interest in reversing these changes and enhancing NSC activity by targeting the neurovasculature therapeutically. Here we discuss principles of neurovasculature-NSC crosstalk, and the implications for the design of NSC-based therapies. We also consider the emerging contributions to this field of the model organism Drosophila melanogaster. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Reproductive Interference and Niche Partitioning in Aphidophagous Insects

    Directory of Open Access Journals (Sweden)

    Suzuki Noriyuki

    2016-01-01

    Full Text Available The range and quality of prey species differ greatly among closely related species of predators. However, the factors responsible for this diversified niche utilization are unclear. This is because the predation and resource competition do not always prevent species coexistence. In this paper, we present evidence in support of reproductive interference as a driver of niche partitioning, focusing on aphidophagous insect. Firstly, we present closely related generalist and specialist species pairs in aphidophagous lacewings to compare the reproductive interference hypothesis with two other hypotheses that have been proposed to explain niche partitioning in lacewings and sympatric speciation through host race formation and sexual selection. Secondly, we present a case study that shows how reproductive interference can drive niche partitioning in sibling ladybird species. Thirdly, we show that many ladybird genera include species inhabiting the same region but having different food and habitat preferences, raising the possibility that reproductive interference might occur in these groups. Finally, we show that intraguild predation cannot always explain the niche partitioning in aphidophagous insects including hoverflies and parasitoids. On the basis of the evidence presented, we urge that future studies investigating predator communities should take account of the role of reproductive interference.

  7. Foxl1-Expressing Mesenchymal Cells Constitute the Intestinal Stem Cell NicheSummary

    Directory of Open Access Journals (Sweden)

    Reina Aoki

    2016-03-01

    Full Text Available Background & Aims: Intestinal epithelial stem cells that express leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5 and/or B cell specific Moloney murine leukemia virus integration site 1 (Bmi1 continuously replicate and generate differentiated cells throughout life. Previously, Paneth cells were suggested to constitute an epithelium-intrinsic niche that regulates the behavior of these stem cells. However, ablating Paneth cells has no effect on the maintenance of functional stem cells. Here, we show definitively that a small subset of mesenchymal subepithelial cells expressing the winged-helix transcription factor forkhead box l1 (Foxl1 are a critical component of the intestinal stem cell niche. Methods: We genetically ablated Foxl1+ mesenchymal cells in adult mice using 2 separate models by expressing either the human or simian diphtheria toxin receptor under Foxl1 promoter control. Conclusions: Killing Foxl1+ cells by diphtheria toxin administration led to an abrupt cessation of proliferation of both epithelial stem- and transit-amplifying progenitor cell populations that was associated with a loss of active Wnt signaling to the intestinal epithelium. Therefore, Foxl1-expressing mesenchymal cells constitute the fundamental niche for intestinal stem cells. Keywords: Intestinal Stem Cell Niche, Wnt, Mesenchyme

  8. Are species' responses to global change predicted by past niche evolution?

    Science.gov (United States)

    Lavergne, Sébastien; Evans, Margaret E. K.; Burfield, Ian J.; Jiguet, Frederic; Thuiller, Wilfried

    2013-01-01

    Predicting how and when adaptive evolution might rescue species from global change, and integrating this process into tools of biodiversity forecasting, has now become an urgent task. Here, we explored whether recent population trends of species can be explained by their past rate of niche evolution, which can be inferred from increasingly available phylogenetic and niche data. We examined the assemblage of 409 European bird species for which estimates of demographic trends between 1970 and 2000 are available, along with a species-level phylogeny and data on climatic, habitat and trophic niches. We found that species' proneness to demographic decline is associated with slow evolution of the habitat niche in the past, in addition to certain current-day life-history and ecological traits. A similar result was found at a higher taxonomic level, where families prone to decline have had a history of slower evolution of climatic and habitat niches. Our results support the view that niche conservatism can prevent some species from coping with environmental change. Thus, linking patterns of past niche evolution and contemporary species dynamics for large species samples may provide insights into how niche evolution may rescue certain lineages in the face of global change. PMID:23209172

  9. Haematopoietic stem cell niches: new insights inspire new questions

    Science.gov (United States)

    Ugarte, Fernando; Forsberg, E Camilla

    2013-01-01

    Haematopoietic stem cell (HSC) niches provide an environment essential for life-long HSC function. Intense investigation of HSC niches both feed off and drive technology development to increase our capability to assay functionally defined cells with high resolution. A major driving force behind the desire to understand the basic biology of HSC niches is the clear implications for clinical therapies. Here, with particular emphasis on cell type-specific deletion of SCL and CXCL12, we focus on unresolved issues on HSC niches, framed around some very recent advances and novel discoveries on the extrinsic regulation of HSC maintenance. We also provide ideas for possible paths forward, some of which are clearly within reach while others will require both novel tools and vision. PMID:24022369

  10. Reconciling phylogeography and ecological niche models for New Zealand beetles looking beyond glacial refugia

    DEFF Research Database (Denmark)

    Marske, Katharine Ann; Leschen, Richard; Buckley, Thomas

    2011-01-01

    stochastic search variable selection incorporated in BEAST to identify historical dispersal patterns via ancestral state reconstruction. Ecological niche models (ENMs) were incorporated to reconstruct the potential geographic distribution of each species during the Last Glacial Maximum (LGM). Coalescent...... analyses suggest a North Island origin for E. lawsoni, with gene flow predominately north–south between adjacent regions. ENMs for E. lawsoni indicated glacial refugia in coastal regions of both main islands, consistent with phylogenetic patterns but at odds with the coalescent dates, which implicate much...... on both main islands is evident. Divergence dates for both species are consistent with the topographic evolution of New Zealand over the last 10 Ma, whereas the signature of the LGM is less apparent in the time-scaled phylogeny....

  11. The use of climatic niches in screening procedures for introduced species to evaluate risk of spread: a case with the American Eastern grey squirrel.

    Directory of Open Access Journals (Sweden)

    Mirko Di Febbraro

    Full Text Available Species introduction represents one of the most serious threats for biodiversity. The realized climatic niche of an invasive species can be used to predict its potential distribution in new areas, providing a basis for screening procedures in the compilation of black and white lists to prevent new introductions. We tested this assertion by modeling the realized climatic niche of the Eastern grey squirrel Sciurus carolinensis. Maxent was used to develop three models: one considering only records from the native range (NRM, a second including records from native and invasive range (NIRM, a third calibrated with invasive occurrences and projected in the native range (RCM. Niche conservatism was tested considering both a niche equivalency and a niche similarity test. NRM failed to predict suitable parts of the currently invaded range in Europe, while RCM underestimated the suitability in the native range. NIRM accurately predicted both the native and invasive range. The niche equivalency hypothesis was rejected due to a significant difference between the grey squirrel's niche in native and invasive ranges. The niche similarity test yielded no significant results. Our analyses support the hypothesis of a shift in the species' climatic niche in the area of introductions. Species Distribution Models (SDMs appear to be a useful tool in the compilation of black lists, allowing identifying areas vulnerable to invasions. We advise caution in the use of SDMs based only on the native range of a species for the compilation of white lists for other geographic areas, due to the significant risk of underestimating its potential invasive range.

  12. Phylogeny and niche conservatism in North and Central American triatomine bugs (Hemiptera: Reduviidae: Triatominae), vectors of Chagas' disease.

    Science.gov (United States)

    Ibarra-Cerdeña, Carlos N; Zaldívar-Riverón, Alejandro; Peterson, A Townsend; Sánchez-Cordero, Víctor; Ramsey, Janine M

    2014-10-01

    The niche conservatism hypothesis states that related species diverge in niche characteristics at lower rates than expected, given their lineage divergence. Here we analyze whether niche conservatism is a common pattern among vector species (Hemiptera: Reduviidae: Triatominae) of Trypanosoma cruzi that inhabit North and Central America, a highly heterogeneous landmass in terms of environmental gradients. Mitochondrial and nuclear loci were used in a multi-locus phylogenetic framework to reconstruct phylogenetic relationships among species and estimate time of divergence of selected clades to draw biogeographic inferences. Then, we estimated similarity between the ecological niche of sister species and tested the niche conservatism hypothesis using our best estimate of phylogeny. Triatoma is not monophyletic. A primary clade with all North and Central American (NCA) triatomine species from the genera Triatoma, Dipetalogaster, and Panstrongylus, was consistently recovered. Nearctic species within the NCA clade (T. p. protracta, T. r. rubida) diverged during the Pliocene, whereas the Neotropical species (T. phyllosoma, T. longipennis, T. dimidiata complex) are estimated to have diverged more recently, during the Pleistocene. The hypothesis of niche conservatism could not be rejected for any of six sister species pairs. Niche similarity between sister species best fits a retention model. While this framework is used here to infer niche evolution, it has a direct impact on spatial vector dynamics driven by human population movements, expansion of transportation networks and climate change scenarios.

  13. Evolution under changing climates: climatic niche stasis despite rapid evolution in a non-native plant.

    Science.gov (United States)

    Alexander, Jake M

    2013-09-22

    A topic of great current interest is the capacity of populations to adapt genetically to rapidly changing climates, for example by evolving the timing of life-history events, but this is challenging to address experimentally. I use a plant invasion as a model system to tackle this question by combining molecular markers, a common garden experiment and climatic niche modelling. This approach reveals that non-native Lactuca serriola originates primarily from Europe, a climatic subset of its native range, with low rates of admixture from Asia. It has rapidly refilled its climatic niche in the new range, associated with the evolution of flowering phenology to produce clines along climate gradients that mirror those across the native range. Consequently, some non-native plants have evolved development times and grow under climates more extreme than those found in Europe, but not among populations from the native range as a whole. This suggests that many plant populations can adapt rapidly to changed climatic conditions that are already within the climatic niche space occupied by the species elsewhere in its range, but that evolution to conditions outside of this range is more difficult. These findings can also help to explain the prevalence of niche conservatism among non-native species.

  14. Time-specific ecological niche modeling predicts spatial dynamics of vector insects and human dengue cases.

    Science.gov (United States)

    Peterson, A Townsend; Martínez-Campos, Carmen; Nakazawa, Yoshinori; Martínez-Meyer, Enrique

    2005-09-01

    Numerous human diseases-malaria, dengue, yellow fever and leishmaniasis, to name a few-are transmitted by insect vectors with brief life cycles and biting activity that varies in both space and time. Although the general geographic distributions of these epidemiologically important species are known, the spatiotemporal variation in their emergence and activity remains poorly understood. We used ecological niche modeling via a genetic algorithm to produce time-specific predictive models of monthly distributions of Aedes aegypti in Mexico in 1995. Significant predictions of monthly mosquito activity and distributions indicate that predicting spatiotemporal dynamics of disease vector species is feasible; significant coincidence with human cases of dengue indicate that these dynamics probably translate directly into transmission of dengue virus to humans. This approach provides new potential for optimizing use of resources for disease prevention and remediation via automated forecasting of disease transmission risk.

  15. A hypothesis-testing framework for studies investigating ontogenetic niche shifts using stable isotope ratios.

    Directory of Open Access Journals (Sweden)

    Caroline M Hammerschlag-Peyer

    Full Text Available Ontogenetic niche shifts occur across diverse taxonomic groups, and can have critical implications for population dynamics, community structure, and ecosystem function. In this study, we provide a hypothesis-testing framework combining univariate and multivariate analyses to examine ontogenetic niche shifts using stable isotope ratios. This framework is based on three distinct ontogenetic niche shift scenarios, i.e., (1 no niche shift, (2 niche expansion/reduction, and (3 discrete niche shift between size classes. We developed criteria for identifying each scenario, as based on three important resource use characteristics, i.e., niche width, niche position, and niche overlap. We provide an empirical example for each ontogenetic niche shift scenario, illustrating differences in resource use characteristics among different organisms. The present framework provides a foundation for future studies on ontogenetic niche shifts, and also can be applied to examine resource variability among other population sub-groupings (e.g., by sex or phenotype.

  16. Niche as a determinant of word fate in online groups.

    Directory of Open Access Journals (Sweden)

    Eduardo G Altmann

    2011-05-01

    Full Text Available Patterns of word use both reflect and influence a myriad of human activities and interactions. Like other entities that are reproduced and evolve, words rise or decline depending upon a complex interplay between their intrinsic properties and the environments in which they function. Using Internet discussion communities as model systems, we define the concept of a word niche as the relationship between the word and the characteristic features of the environments in which it is used. We develop a method to quantify two important aspects of the size of the word niche: the range of individuals using the word and the range of topics it is used to discuss. Controlling for word frequency, we show that these aspects of the word niche are strong determinants of changes in word frequency. Previous studies have already indicated that word frequency itself is a correlate of word success at historical time scales. Our analysis of changes in word frequencies over time reveals that the relative sizes of word niches are far more important than word frequencies in the dynamics of the entire vocabulary at shorter time scales, as the language adapts to new concepts and social groupings. We also distinguish endogenous versus exogenous factors as additional contributors to the fates of words, and demonstrate the force of this distinction in the rise of novel words. Our results indicate that short-term nonstationarity in word statistics is strongly driven by individual proclivities, including inclinations to provide novel information and to project a distinctive social identity.

  17. From GenBank to GBIF: Phylogeny-Based Predictive Niche Modeling Tests Accuracy of Taxonomic Identifications in Large Occurrence Data Repositories.

    Science.gov (United States)

    Smith, B Eugene; Johnston, Mark K; Lücking, Robert

    2016-01-01

    Accuracy of taxonomic identifications is crucial to data quality in online repositories of species occurrence data, such as the Global Biodiversity Information Facility (GBIF), which have accumulated several hundred million records over the past 15 years. These data serve as basis for large scale analyses of macroecological and biogeographic patterns and to document environmental changes over time. However, taxonomic identifications are often unreliable, especially for non-vascular plants and fungi including lichens, which may lack critical revisions of voucher specimens. Due to the scale of the problem, restudy of millions of collections is unrealistic and other strategies are needed. Here we propose to use verified, georeferenced occurrence data of a given species to apply predictive niche modeling that can then be used to evaluate unverified occurrences of that species. Selecting the charismatic lichen fungus, Usnea longissima, as a case study, we used georeferenced occurrence records based on sequenced specimens to model its predicted niche. Our results suggest that the target species is largely restricted to a narrow range of boreal and temperate forest in the Northern Hemisphere and that occurrence records in GBIF from tropical regions and the Southern Hemisphere do not represent this taxon, a prediction tested by comparison with taxonomic revisions of Usnea for these regions. As a novel approach, we employed Principal Component Analysis on the environmental grid data used for predictive modeling to visualize potential ecogeographical barriers for the target species; we found that tropical regions conform a strong barrier, explaining why potential niches in the Southern Hemisphere were not colonized by Usnea longissima and instead by morphologically similar species. This approach is an example of how data from two of the most important biodiversity repositories, GenBank and GBIF, can be effectively combined to remotely address the problem of inaccuracy of

  18. Trophic specialization influences the rate of environmental niche evolution in damselfishes (Pomacentridae).

    Science.gov (United States)

    Litsios, Glenn; Pellissier, Loïc; Forest, Félix; Lexer, Christian; Pearman, Peter B; Zimmermann, Niklaus E; Salamin, Nicolas

    2012-09-22

    The rate of environmental niche evolution describes the capability of species to explore the available environmental space and is known to vary among species owing to lineage-specific factors. Trophic specialization is a main force driving species evolution and is responsible for classical examples of adaptive radiations in fishes. We investigate the effect of trophic specialization on the rate of environmental niche evolution in the damselfish, Pomacentridae, which is an important family of tropical reef fishes. First, phylogenetic niche conservatism is not detected in the family using a standard test of phylogenetic signal, and we demonstrate that the environmental niches of damselfishes that differ in trophic specialization are not equivalent while they still overlap at their mean values. Second, we estimate the relative rates of niche evolution on the phylogenetic tree and show the heterogeneity among rates of environmental niche evolution of the three trophic groups. We suggest that behavioural characteristics related to trophic specialization can constrain the evolution of the environmental niche and lead to conserved niches in specialist lineages. Our results show the extent of influence of several traits on the evolution of the environmental niche and shed new light on the evolution of damselfishes, which is a key lineage in current efforts to conserve biodiversity in coral reefs.

  19. Probabilistic and spatially variable niches inferred from demography

    Science.gov (United States)

    Jeffrey M. Diez; Itamar Giladi; Robert Warren; H. Ronald. Pulliam

    2014-01-01

    Summary 1. Mismatches between species distributions and habitat suitability are predicted by niche theory and have important implications for forecasting how species may respond to environmental changes. Quantifying these mismatches is challenging, however, due to the high dimensionality of species niches and the large spatial and temporal variability in population...

  20. Niche Marketing Potentials for Farm Entrepreneurs in Nigeria https ...

    African Journals Online (AJOL)

    User

    . Niche marketing involves targetting a product or service to a small but specific well ... Table 1: Examples of possible niche markets for entrepreneurs in Nigeria. Farm Business .... Concepts, Principles and Decisions, 2nd Edition. Afritowers ...

  1. Asymmetric biotic interactions and abiotic niche differences revealed by a dynamic joint species distribution model.

    Science.gov (United States)

    Lany, Nina K; Zarnetske, Phoebe L; Schliep, Erin M; Schaeffer, Robert N; Orians, Colin M; Orwig, David A; Preisser, Evan L

    2018-05-01

    A species' distribution and abundance are determined by abiotic conditions and biotic interactions with other species in the community. Most species distribution models correlate the occurrence of a single species with environmental variables only, and leave out biotic interactions. To test the importance of biotic interactions on occurrence and abundance, we compared a multivariate spatiotemporal model of the joint abundance of two invasive insects that share a host plant, hemlock woolly adelgid (HWA; Adelges tsugae) and elongate hemlock scale (EHS; Fiorina externa), to independent models that do not account for dependence among co-occurring species. The joint model revealed that HWA responded more strongly to abiotic conditions than EHS. Additionally, HWA appeared to predispose stands to subsequent increase of EHS, but HWA abundance was not strongly dependent on EHS abundance. This study demonstrates how incorporating spatial and temporal dependence into a species distribution model can reveal the dependence of a species' abundance on other species in the community. Accounting for dependence among co-occurring species with a joint distribution model can also improve estimation of the abiotic niche for species affected by interspecific interactions. © 2018 by the Ecological Society of America.

  2. Average niche breadths of species in lake macrophyte communities respond to ecological gradients variably in four regions on two continents.

    Science.gov (United States)

    Alahuhta, Janne; Virtala, Antti; Hjort, Jan; Ecke, Frauke; Johnson, Lucinda B; Sass, Laura; Heino, Jani

    2017-05-01

    Different species' niche breadths in relation to ecological gradients are infrequently examined within the same study and, moreover, species niche breadths have rarely been averaged to account for variation in entire ecological communities. We investigated how average environmental niche breadths (climate, water quality and climate-water quality niches) in aquatic macrophyte communities are related to ecological gradients (latitude, longitude, altitude, species richness and lake area) among four distinct regions (Finland, Sweden and US states of Minnesota and Wisconsin) on two continents. We found that correlations between the three different measures of average niche breadths and ecological gradients varied considerably among the study regions, with average climate and average water quality niche breadth models often showing opposite trends. However, consistent patterns were also found, such as widening of average climate niche breadths and narrowing of average water quality niche breadths of aquatic macrophytes along increasing latitudinal and altitudinal gradients. This result suggests that macrophyte species are generalists in relation to temperature variations at higher latitudes and altitudes, whereas species in southern, lowland lakes are more specialised. In contrast, aquatic macrophytes growing in more southern nutrient-rich lakes were generalists in relation to water quality, while specialist species are adapted to low-productivity conditions and are found in highland lakes. Our results emphasise that species niche breadths should not be studied using only coarse-scale data of species distributions and corresponding environmental conditions, but that investigations on different kinds of niche breadths (e.g., climate vs. local niches) also require finer resolution data at broad spatial extents.

  3. In a niche of time: do specialty hospitals outperform general services hospitals?

    Science.gov (United States)

    Poole, LeJon; Davis, Jullet A; Gunby, Norris W

    2013-01-01

    Niche hospitals represent a growing segment in the health care industry. Niche facilities are primarily engaged in the treatment of cardiac or orthopedic conditions. The effectiveness of this strategy is of interest because niche hospitals focus on only the most profitable services. The purpose of this research was to assess the financial effectiveness of the niche strategy. We theorize that firm and market-level factors concomitantly with the strategy of the hospital-niche versus traditional-are associated with financial performance. This research used 2 data sources, the 2003 Medicare Cost Report and the 2003 Area Resource File. The sample was limited to only for-profit, urban, nongovernmental hospitals (n = 995). The data were analyzed using hierarchical least squares regression. Financial performance was operationalized using the hospital's return on assets. The principal finding of this project is that niche hospitals had significantly higher performance than traditional facilities. From the organizational perspective, the niche strategy leads to better financial performance. From a societal perspective, the niche strategy provides increased focus and efficiencies through repetition. Despite the limited focus of this strategy, patients who can access these providers may experience better outcomes than patients in more traditional hospitals.

  4. Analysis of Alcove 8/Niche 3 Flow and Transport Tests

    International Nuclear Information System (INIS)

    H.H. Liu

    2006-01-01

    The purpose of this report is to document analyses of the Alcove 8/Niche 3 flow and transport tests, with a focus on the large-infiltration-plot tests and compare pre-test model predictions with the actual test observations. The tests involved infiltration that originated from the floor of Alcove 8 (located in the Enhanced Characterization of Repository Block (ECRB) Cross Drift) and observations of seepage and tracer transport at Niche 3 (located in the Main Drift of the Exploratory Studies Facility (ESF)). The test results are relevant to drift seepage and solute transport in the unsaturated zone (UZ) of Yucca Mountain. The main objective of this analysis was to evaluate the modeling approaches used and the importance of the matrix diffusion process by comparing simulation and actual test observations. The pre-test predictions for the large plot test were found to differ from the observations and the reasons for the differences were documented in this report to partly address CR 6783, which concerns unexpected test results. These unexpected results are discussed and assessed with respect to the current baseline unsaturated zone radionuclide transport model in Sections 6.2.4, 6.3.2, and 6.4

  5. Pleistocene niche stability and lineage diversification in the subtropical spider Araneus omnicolor (Araneidae.

    Directory of Open Access Journals (Sweden)

    Elen A Peres

    Full Text Available The influence of Quaternary climate oscillations on the diversification of the South American fauna is being increasingly explored. However, most of these studies have focused on taxa that are endemic to tropical environments, and relatively few have treated organisms restricted to subtropical biomes. Here we used an integrative phylogeographical framework to investigate the effects of these climate events on the ecological niche and genetic patterns of the subtropical orb-weaver spider Araneus omnicolor (Araneidae. We analyzed the mitochondrial (Cytochrome Oxidase I, COI and nuclear (Internal Transcribed Subunit II, ITS2 DNA of 130 individuals throughout the species' range, and generated distribution models in three different climate scenarios [present, Last Glacial Maximum (LGM, and Last Interglacial Maximum (LIG]. Additionally, we used an Approximate Bayesian Computation (ABC approach to compare possible demographic scenarios and select the hypothesis that better explains the genetic patterns of A. omnicolor. We obtained high haplotype diversity but low nucleotide variation among sequences. The population structure and demographic analyses showed discrepancies between markers, suggesting male-biased dispersal in the species. The time-calibrated COI phylogenetic inference showed a recent diversification of lineages (Middle/Late Pleistocene, while the paleoclimate modeling indicated niche stability since ~120 Kya. The ABC results agreed with the niche models, supporting a panmictic population as the most likely historical scenario for the species. These results indicate that A. omnicolor experienced no niche or population reductions during the Late Pleistocene, despite the intense landscape modifications that occurred in the subtropical region, and that other factors beside LGM and LIG climate oscillations might have contributed to the demographic history of this species. This pattern may be related to the high dispersal ability and wide

  6. Spontaneous Cognition and Epistemic Agency in the Cognitive Niche

    Science.gov (United States)

    Fabry, Regina E.

    2018-01-01

    According to Thomas Metzinger, many human cognitive processes in the waking state are spontaneous and are deprived of the experience of epistemic agency. He considers mind wandering as a paradigm example of our recurring loss of epistemic agency. I will enrich this view by extending the scope of the concept of epistemic agency to include cases of depressive rumination and creative cognition, which are additional types of spontaneous cognition. Like mind wandering, they are characterized by unique phenomenal and functional properties that give rise to varying degrees of epistemic agency. The main claim of this paper will be that the experience of being an epistemic agent within a certain time frame is a relational phenomenon that emerges from the organism’s capacity to interact with its cognitive niche. To explore this relation, I develop a new framework that integrates phenomenological considerations on epistemic agency with a functional account of the reciprocal coupling of the embodied organism with its cognitive niche. This account rests upon dynamical accounts of strong embodied and embedded cognition and recent work on cognitive niche construction. Importantly, epistemic agency and organism-niche coupling are gradual phenomena ranging from weak to strong realizations. The emerging framework will be employed to analyze mind wandering, depressive rumination, and creative cognition as well as their commonalities and differences. Mind wandering and depressive rumination are cases of weak epistemic agency and organism-niche coupling. However, there are also important phenomenological, functional, and neuronal differences. In contrast, creative cognition is a case of strong epistemic agency and organism-niche coupling. By providing a phenomenological and functional analysis of these distinct types of spontaneous cognition, we can gain a better understanding of the importance of organism-niche interaction for the realization of epistemic agency.

  7. Climatic niche conservatism and the evolutionary dynamics in species range boundaries

    DEFF Research Database (Denmark)

    Olalla-Tárraga1, Miguel Á.; McInnes, Linsey; Bini, Luis M.

    2011-01-01

    Aim Comparative evidence for phylogenetic niche conservatism – the tendency for lineages to retain their ancestral niches over long time scales – has so far been mixed, depending on spatial and taxonomic scale. We quantify and compare conservatism in the climatic factors defining range boundaries...... conservatism, as expected from their greater physiological sensitivity and lower dispersal abilities. Location Global; continental land masses excluding Antarctica. Methods We used nearly complete global distributional databases to estimate the climatic niche conservatism in extant continental mammals...... and amphibians. We characterized the climatic niche of each species by using a suite of variables and separately investigate conservatism in each variable using both taxonomic and phylogenetic approaches. Finally, we explored the spatial, taxonomic and phylogenetic patterns in recent climatic niche evolution...

  8. Development of a laboratory niche Web site.

    Science.gov (United States)

    Dimenstein, Izak B; Dimenstein, Simon I

    2013-10-01

    This technical note presents the development of a methodological laboratory niche Web site. The "Grossing Technology in Surgical Pathology" (www.grossing-technology.com) Web site is used as an example. Although common steps in creation of most Web sites are followed, there are particular requirements for structuring the template's menu on methodological laboratory Web sites. The "nested doll principle," in which one object is placed inside another, most adequately describes the methodological approach to laboratory Web site design. Fragmentation in presenting the Web site's material highlights the discrete parts of the laboratory procedure. An optimally minimal triad of components can be recommended for the creation of a laboratory niche Web site: a main set of media, a blog, and an ancillary component (host, contact, and links). The inclusion of a blog makes the Web site a dynamic forum for professional communication. By forming links and portals, cloud computing opens opportunities for connecting a niche Web site with other Web sites and professional organizations. As an additional source of information exchange, methodological laboratory niche Web sites are destined to parallel both traditional and new forms, such as books, journals, seminars, webinars, and internal educational materials. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Change of niche in guanaco (Lama guanicoe): the effects of climate change on habitat suitability and lineage conservatism in Chile.

    Science.gov (United States)

    Castillo, Andrea G; Alò, Dominique; González, Benito A; Samaniego, Horacio

    2018-01-01

    The main goal of this contribution was to define the ecological niche of the guanaco ( Lama guanicoe ), to describe potential distributional changes, and to assess the relative importance of niche conservatism and divergence processes between the two lineages described for the species ( L.g. cacsilensis and L.g. guanicoe ). We used maximum entropy to model lineage's climate niche from 3,321 locations throughout continental Chile, and developed future niche models under climate change for two extreme greenhouse gas emission scenarios (RCP2.6 and RCP8.5). We evaluated changes of the environmental niche and future distribution of the largest mammal in the Southern Cone of South America. Evaluation of niche conservatism and divergence were based on identity and background similarity tests. We show that: (a) the current geographic distribution of lineages is associated with different climatic requirements that are related to the geographic areas where these lineages are located; (b) future distribution models predict a decrease in the distribution surface under both scenarios; (c) a 3% decrease of areal protection is expected if the current distribution of protected areas is maintained, and this is expected to occur at the expense of a large reduction of high quality habitats under the best scenario; (d) current and future distribution ranges of guanaco mostly adhere to phylogenetic niche divergence hypotheses between lineages. Associating environmental variables with species ecological niche seems to be an important aspect of unveiling the particularities of, both evolutionary patterns and ecological features that species face in a changing environment. We report specific descriptions of how these patterns may play out under the most extreme climate change predictions and provide a grim outlook of the future potential distribution of guanaco in Chile. From an ecological perspective, while a slightly smaller distribution area is expected, this may come with an important

  10. Change of niche in guanaco (Lama guanicoe: the effects of climate change on habitat suitability and lineage conservatism in Chile

    Directory of Open Access Journals (Sweden)

    Andrea G. Castillo

    2018-05-01

    Full Text Available Background The main goal of this contribution was to define the ecological niche of the guanaco (Lama guanicoe, to describe potential distributional changes, and to assess the relative importance of niche conservatism and divergence processes between the two lineages described for the species (L.g. cacsilensis and L.g. guanicoe. Methods We used maximum entropy to model lineage’s climate niche from 3,321 locations throughout continental Chile, and developed future niche models under climate change for two extreme greenhouse gas emission scenarios (RCP2.6 and RCP8.5. We evaluated changes of the environmental niche and future distribution of the largest mammal in the Southern Cone of South America. Evaluation of niche conservatism and divergence were based on identity and background similarity tests. Results We show that: (a the current geographic distribution of lineages is associated with different climatic requirements that are related to the geographic areas where these lineages are located; (b future distribution models predict a decrease in the distribution surface under both scenarios; (c a 3% decrease of areal protection is expected if the current distribution of protected areas is maintained, and this is expected to occur at the expense of a large reduction of high quality habitats under the best scenario; (d current and future distribution ranges of guanaco mostly adhere to phylogenetic niche divergence hypotheses between lineages. Discussion Associating environmental variables with species ecological niche seems to be an important aspect of unveiling the particularities of, both evolutionary patterns and ecological features that species face in a changing environment. We report specific descriptions of how these patterns may play out under the most extreme climate change predictions and provide a grim outlook of the future potential distribution of guanaco in Chile. From an ecological perspective, while a slightly smaller distribution

  11. Widespread correlations between climatic niche evolution and species diversification in birds.

    Science.gov (United States)

    Cooney, Christopher R; Seddon, Nathalie; Tobias, Joseph A

    2016-07-01

    The adaptability of species' climatic niches can influence the dynamics of colonization and gene flow across climatic gradients, potentially increasing the likelihood of speciation or reducing extinction in the face of environmental change. However, previous comparative studies have tested these ideas using geographically, taxonomically and ecologically restricted samples, yielding mixed results, and thus the processes linking climatic niche evolution with diversification remain poorly understood. Focusing on birds, the largest and most widespread class of terrestrial vertebrates, we test whether variation in species diversification among clades is correlated with rates of climatic niche evolution and the extent to which these patterns are modified by underlying gradients in biogeography and species' ecology. We quantified climatic niches, latitudinal distribution and ecological traits for 7657 (˜75%) bird species based on geographical range polygons and then used Bayesian phylogenetic analyses to test whether niche evolution was related to species richness and rates of diversification across genus- and family-level clades. We found that the rate of climatic niche evolution has a positive linear relationship with both species richness and diversification rate at two different taxonomic levels (genus and family). Furthermore, this positive association between labile climatic niches and diversification was detected regardless of variation in clade latitude or key ecological traits. Our findings suggest either that rapid adaptation to unoccupied areas of climatic niche space promotes avian diversification, or that diversification promotes adaptation. Either way, we propose that climatic niche evolution is a fundamental process regulating the link between climate and biodiversity at global scales, irrespective of the geographical and ecological context of speciation and extinction. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

  12. Adaptation and niche construction in human prehistory: a case study from the southern Scandinavian Late Glacial.

    Science.gov (United States)

    Riede, Felix

    2011-03-27

    The niche construction model postulates that human bio-social evolution is composed of three inheritance domains, genetic, cultural and ecological, linked by feedback selection. This paper argues that many kinds of archaeological data can serve as proxies for human niche construction processes, and presents a method for investigating specific niche construction hypotheses. To illustrate this method, the repeated emergence of specialized reindeer (Rangifer tarandus) hunting/herding economies during the Late Palaeolithic (ca 14.7-11.5 kyr BP) in southern Scandinavia is analysed from a niche construction/triple-inheritance perspective. This economic relationship resulted in the eventual domestication of Rangifer. The hypothesis of whether domestication was achieved as early as the Late Palaeolithic, and whether this required the use of domesticated dogs (Canis familiaris) as hunting, herding or transport aids, is tested via a comparative analysis using material culture-based phylogenies and ecological datasets in relation to demographic/genetic proxies. Only weak evidence for sustained niche construction behaviours by prehistoric hunter-gatherer in southern Scandinavia is found, but this study nonetheless provides interesting insights into the likely processes of dog and reindeer domestication, and into processes of adaptation in Late Glacial foragers.

  13. A family business: stem cell progeny join the niche to regulate homeostasis.

    Science.gov (United States)

    Hsu, Ya-Chieh; Fuchs, Elaine

    2012-01-23

    Stem cell niches, the discrete microenvironments in which the stem cells reside, play a dominant part in regulating stem cell activity and behaviours. Recent studies suggest that committed stem cell progeny become indispensable components of the niche in a wide range of stem cell systems. These unexpected niche inhabitants provide versatile feedback signals to their stem cell parents. Together with other heterologous cell types that constitute the niche, they contribute to the dynamics of the microenvironment. As progeny are often located in close proximity to stem cell niches, similar feedback regulations may be the underlying principles shared by different stem cell systems.

  14. A niche marketing guide for lamb cooperatives

    OpenAIRE

    Kazmierczak, Tamra Kirkpatrick; Bell, James B.

    1995-01-01

    The two types of niche markets targeted by lamb marketing cooperatives are described in this guide. The first type includes specialty middlemen outlets that cooperatives used to market lamb to specialized niches within the traditional meat marketing system of retail food stores, restaurants, food service outlets, and specialty distributors. The second type includes those outlets that cooperatives used to market lamb directly to the consumer, such as freezer markets, farmers' markets, mobile m...

  15. Different Motile Behaviors of Human Hematopoietic Stem versus Progenitor Cells at the Osteoblastic Niche

    Directory of Open Access Journals (Sweden)

    Katie Foster

    2015-11-01

    Full Text Available Despite advances in our understanding of interactions between mouse hematopoietic stem cells (HSCs and their niche, little is known about communication between human HSCs and the microenvironment. Using a xenotransplantation model and intravital imaging, we demonstrate that human HSCs display distinct motile behaviors to their hematopoietic progenitor cell (HPC counterparts, and the same pattern can be found between mouse HSCs and HPCs. HSCs become significantly less motile after transplantation, while progenitor cells remain motile. We show that human HSCs take longer to find their niche than previously expected and suggest that the niche be defined as the position where HSCs stop moving. Intravital imaging is the only technique to determine where in the bone marrow stem cells stop moving, and future analyses should focus on the environment surrounding the HSC at this point.

  16. UNTANGLING THE FUNGAL NICHE: A TRAIT-BASED APPROACH

    Directory of Open Access Journals (Sweden)

    Thomas W Crowther

    2014-10-01

    Full Text Available Fungi are prominent components of most terrestrial ecosystems, both in terms of biomass and ecosystem functioning, but the hyper-diverse nature of most communities has obscured the search for unifying principles governing community organization. In particular, unlike plants and animals, observational studies provide little evidence for the existence of niche processes in structuring fungal communities at broad spatial scales. This limits our capacity to predict how communities, and their functioning, vary across landscapes. We outline how a shift in focus, from taxonomy towards functional traits, might prove to be valuable in the search for general patterns in fungal ecology. We build on theoretical advances in plant and animal ecology to provide an empirical framework for a trait-based approach in fungal community ecology. Drawing upon specific characteristics of the fungal system, we highlight the significance of drought stress and combat in structuring free-living fungal communities. We propose a conceptual model to formalize how trade-offs between stress-tolerance and combative dominance are likely to organize communities across environmental gradients. Given that the survival of a fungus in a given environment is contingent on its ability to tolerate antagonistic competitors, measuring variation in combat trait expression along environmental gradients provides a means of elucidating realized, from fundamental niche spaces. We conclude that, using a trait-based understanding of how niche processes structure fungal communities across time and space, we can ultimately link communities with ecosystem functioning. Our trait-based framework highlights fundamental uncertainties that require testing in the fungal system, given their potential to uncover general mechanisms in fungal ecology.

  17. Regulatory System for Stem/Progenitor Cell Niches in the Adult Rodent Pituitary

    Science.gov (United States)

    Yoshida, Saishu; Kato, Takako; Kato, Yukio

    2016-01-01

    The anterior lobe of the pituitary gland is a master endocrine tissue composed of five types of endocrine cells. Although the turnover rate of pituitary endocrine cells is as low as about 1.6% per day, recent studies have demonstrated that Sex-determining region Y-box 2 (SOX2)+-cells exist as pituitary stem/progenitor cells in the adult anterior lobe and contribute to cell regeneration. Notably, SOX2+-pituitary stem/progenitor cells form two types of niches in this tissue: the marginal cell layer (MCL-niche) and the dense cell clusters scattering in the parenchyma (parenchymal-niche). However, little is known about the mechanisms and factors for regulating the pituitary stem/progenitor cell niches, as well as the functional differences between the two types of niches. Elucidation of the regulatory mechanisms in the niches might enable us to understand the cell regeneration system that acts in accordance with physiological demands in the adult pituitary. In this review, so as to reveal the regulatory mechanisms of the two types of niche, we summarize the regulatory factors and their roles in the adult rodent pituitary niches by focusing on three components: soluble factors, cell surface proteins and extracellular matrixes. PMID:26761002

  18. Regulatory System for Stem/Progenitor Cell Niches in the Adult Rodent Pituitary

    Directory of Open Access Journals (Sweden)

    Saishu Yoshida

    2016-01-01

    Full Text Available The anterior lobe of the pituitary gland is a master endocrine tissue composed of five types of endocrine cells. Although the turnover rate of pituitary endocrine cells is as low as about 1.6% per day, recent studies have demonstrated that Sex-determining region Y-box 2 (SOX2+-cells exist as pituitary stem/progenitor cells in the adult anterior lobe and contribute to cell regeneration. Notably, SOX2+-pituitary stem/progenitor cells form two types of niches in this tissue: the marginal cell layer (MCL-niche and the dense cell clusters scattering in the parenchyma (parenchymal-niche. However, little is known about the mechanisms and factors for regulating the pituitary stem/progenitor cell niches, as well as the functional differences between the two types of niches. Elucidation of the regulatory mechanisms in the niches might enable us to understand the cell regeneration system that acts in accordance with physiological demands in the adult pituitary. In this review, so as to reveal the regulatory mechanisms of the two types of niche, we summarize the regulatory factors and their roles in the adult rodent pituitary niches by focusing on three components: soluble factors, cell surface proteins and extracellular matrixes.

  19. The making of an immigrant niche.

    Science.gov (United States)

    Waldinger, R

    1994-01-01

    "This article speaks to the conceptual and methodological issues in research on the making of an immigrant niche through a case study of immigrant professionals in New York City government." The author argues that "the growth of this immigrant niche resulted from changes in the relative supply of native workers and in the structure of employment, which opened the bureaucracy to immigrants and reduced native/immigrant competition. These shifts opened hiring portals; given the advantages of network hiring for workers and managers, and an immigrant propensity for government employment, network recruitment led to a rapid buildup in immigrant ranks." excerpt

  20. Stem cell niche-specific Ebf3 maintains the bone marrow cavity.

    Science.gov (United States)

    Seike, Masanari; Omatsu, Yoshiki; Watanabe, Hitomi; Kondoh, Gen; Nagasawa, Takashi

    2018-03-01

    Bone marrow is the tissue filling the space between bone surfaces. Hematopoietic stem cells (HSCs) are maintained by special microenvironments known as niches within bone marrow cavities. Mesenchymal cells, termed CXC chemokine ligand 12 (CXCL12)-abundant reticular (CAR) cells or leptin receptor-positive (LepR + ) cells, are a major cellular component of HSC niches that gives rise to osteoblasts in bone marrow. However, it remains unclear how osteogenesis is prevented in most CAR/LepR + cells to maintain HSC niches and marrow cavities. Here, using lineage tracing, we found that the transcription factor early B-cell factor 3 (Ebf3) is preferentially expressed in CAR/LepR + cells and that Ebf3-expressing cells are self-renewing mesenchymal stem cells in adult marrow. When Ebf3 is deleted in CAR/LepR + cells, HSC niche function is severely impaired, and bone marrow is osteosclerotic with increased bone in aged mice. In mice lacking Ebf1 and Ebf3 , CAR/LepR + cells exhibiting a normal morphology are abundantly present, but their niche function is markedly impaired with depleted HSCs in infant marrow. Subsequently, the mutants become progressively more osteosclerotic, leading to the complete occlusion of marrow cavities in early adulthood. CAR/LepR + cells differentiate into bone-producing cells with reduced HSC niche factor expression in the absence of Ebf1/Ebf3 Thus, HSC cellular niches express Ebf3 that is required to create HSC niches, to inhibit their osteoblast differentiation, and to maintain spaces for HSCs. © 2018 Seike et al.; Published by Cold Spring Harbor Laboratory Press.

  1. Single-cell and coupled GRN models of cell patterning in the Arabidopsis thaliana root stem cell niche

    Directory of Open Access Journals (Sweden)

    Alvarez-Buylla Elena R

    2010-10-01

    Full Text Available Abstract Background Recent experimental work has uncovered some of the genetic components required to maintain the Arabidopsis thaliana root stem cell niche (SCN and its structure. Two main pathways are involved. One pathway depends on the genes SHORTROOT and SCARECROW and the other depends on the PLETHORA genes, which have been proposed to constitute the auxin readouts. Recent evidence suggests that a regulatory circuit, composed of WOX5 and CLE40, also contributes to the SCN maintenance. Yet, we still do not understand how the niche is dynamically maintained and patterned or if the uncovered molecular components are sufficient to recover the observed gene expression configurations that characterize the cell types within the root SCN. Mathematical and computational tools have proven useful in understanding the dynamics of cell differentiation. Hence, to further explore root SCN patterning, we integrated available experimental data into dynamic Gene Regulatory Network (GRN models and addressed if these are sufficient to attain observed gene expression configurations in the root SCN in a robust and autonomous manner. Results We found that an SCN GRN model based only on experimental data did not reproduce the configurations observed within the root SCN. We developed several alternative GRN models that recover these expected stable gene configurations. Such models incorporate a few additional components and interactions in addition to those that have been uncovered. The recovered configurations are stable to perturbations, and the models are able to recover the observed gene expression profiles of almost all the mutants described so far. However, the robustness of the postulated GRNs is not as high as that of other previously studied networks. Conclusions These models are the first published approximations for a dynamic mechanism of the A. thaliana root SCN cellular pattering. Our model is useful to formally show that the data now available are not

  2. Neural Crossroads in the Hematopoietic Stem Cell Niche.

    Science.gov (United States)

    Agarwala, Sobhika; Tamplin, Owen J

    2018-05-29

    The hematopoietic stem cell (HSC) niche supports steady-state hematopoiesis and responds to changing needs during stress and disease. The nervous system is an important regulator of the niche, and its influence is established early in development when stem cells are specified. Most research has focused on direct innervation of the niche, however recent findings show there are different modes of neural control, including globally by the central nervous system (CNS) and hormone release, locally by neural crest-derived mesenchymal stem cells, and intrinsically by hematopoietic cells that express neural receptors and neurotransmitters. Dysregulation between neural and hematopoietic systems can contribute to disease, however new therapeutic opportunities may be found among neuroregulator drugs repurposed to support hematopoiesis. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. Fibrocytes and the tissue niche in lung repair

    Directory of Open Access Journals (Sweden)

    Bjermer Leif

    2011-06-01

    Full Text Available Abstract Human fibrocytes are bone marrow-derived mesenchymal progenitor cells that express a variety of markers related to leukocytes, hematopoietic stem cells and a diverse set of fibroblast phenotypes. Fibrocytes can be recruited from the circulation to the tissue where they further can differentiate and proliferate into various mesenchymal cell types depending on the tissue niche. This local tissue niche is important because it modulates the fibrocytes and coordinates their role in tissue behaviour and repair. However, plasticity of a niche may be co-opted in chronic airway diseases such as asthma, idiopathic pulmonary fibrosis and obliterative bronchiolitis. This review will therefore focus on a possible role of fibrocytes in pathological tissue repair processes in those diseases.

  4. Niche dimensions in fishes: an integrative view.

    Science.gov (United States)

    Pörtner, H O; Schulte, P M; Wood, C M; Schiemer, F

    2010-01-01

    Current shifts in ecosystem composition and function emphasize the need for an understanding of the links between environmental factors and organism fitness and tolerance. The examples discussed here illustrate how recent progress in the field of comparative physiology may provide a better mechanistic understanding of the ecological concepts of the fundamental and realized niches and thus provide insights into the impacts of anthropogenic disturbance. Here we argue that, as a link between physiological and ecological indicators of organismal performance, the mechanisms shaping aerobic scope and passive tolerance set the dimensions of an animal's niche, here defined as its capacity to survive, grow, behave, and interact with other species. We demonstrate how comparative studies of cod or killifish populations in a latitudinal cline have unraveled mitochondrial mechanisms involved in establishing a species' niche, performance, and energy budget. Riverine fish exemplify how the performance windows of various developmental stages follow the dynamic regimes of both seasonal temperatures and river hydrodynamics, as synergistic challenges. Finally, studies of species in extreme environments, such as the tilapia of Lake Magadi, illustrate how on evolutionary timescales functional and morphological shifts can occur, associated with new specializations. We conclude that research on the processes and time course of adaptations suitable to overcome current niche limits is urgently needed to assess the resilience of species and ecosystems to human impact, including the challenges of global climate change.

  5. Phylogenetic climatic niche conservatism and evolution of climatic suitability in Neotropical Angraecinae (Vandeae, Orchidaceae) and their closest African relatives.

    Science.gov (United States)

    Kolanowska, Marta; Grochocka, Elżbieta; Konowalik, Kamil

    2017-01-01

    In the present study we investigate the concept of phylogenetic niche conservatism (PNC) within the American species of angraecoid orchids ( Campylocentrum and Dendrophylax ) and their closest relatives in the Old World ( Angraecum ) using ecological niche modelling (ENM). The predicted niche occupancy profiles were matched with the outcomes of previous phylogenetic studies to reconstruct the evolution of climatic suitability within the orchid group studied and evaluate the role of niche differentiation in the speciation of Angraecinae. No correlation between preferred niches and taxonomic relationships within the orchid group studied was revealed. The climatic suitability of the majority of the species overlapped each other, either fully or partially. This pattern is also present in the species of other orchid genera. Our research confirms a significant level of PNC in Orchidaceae, even within taxa exhibiting a transatlantic disjunction. The analysis of the evolution of climatic suitability indicated that the adaptation to various climatic conditions is not a factor that has driven speciation within orchids studied.

  6. Predicting geographic distributions of Phacellodomus species (Aves: Furnariidae in South America based on ecological niche modeling

    Directory of Open Access Journals (Sweden)

    Maria da Salete Gurgel Costa

    2014-08-01

    Full Text Available Phacellodomus Reichenbach, 1853, comprises nine species of Furnariids that occur in South America in open and generally dry areas. This study estimated the geographic distributions of Phacellodomus species in South America by ecological niche modeling. Applying maximum entropy method, models were produced for eight species based on six climatic variables and 949 occurrence records. Since highest climatic suitability for Phacellodomus species has been estimated in open and dry areas, the Amazon rainforest areas are not very suitable for these species. Annual precipitation and minimum temperature of the coldest month are the variables that most influence the models. Phacellodomus species occurred in 35 ecoregions of South America. Chaco and Uruguayan savannas were the ecoregions with the highest number of species. Despite the overall connection of Phacellodomus species with dry areas, species such as P. ruber, P. rufifrons, P. ferrugineigula and P. erythrophthalmus occurred in wet forests and wetland ecoregions.

  7. Interactions between structural and chemical biomimetism in synthetic stem cell niches

    International Nuclear Information System (INIS)

    Nava, Michele M; Raimondi, Manuela T; Credi, Caterina; De Marco, Carmela; Turri, Stefano; Cerullo, Giulio; Osellame, Roberto

    2015-01-01

    Advancements in understanding stem cell functions and differentiation are of key importance for the clinical success of stem-cell-based therapies. 3D structural niches fabricated by two-photon polymerization are a powerful platform for controlling stem cell growth and differentiation. In this paper, we investigate the possibility of further controlling stem cell fate by tuning the mechanical properties of such niches through coating with thin layers of biomimetic hyaluronan-based and gelatin-based hydrogels. We first assess the biocompatibility of chemical coatings and then study the interactions between structural and chemical biomimetism on the response of MSCs in terms of proliferation and differentiation. We observed a clear effect of the hydrogel coating on otherwise identical 3D scaffolds. In particular, in gelatin-coated niches we observed a stronger metabolic activity and commitment toward the osteo-chondral lineage with respect to hyaluronan-coated niches. Conversely, a reduction in the homing effect was observed in all the coated niches, especially in gelatin-coated niches. This study demonstrates the feasibility of controlling independently different mechanical cues, in bioengineered stem cell niches, i.e. the 3D scaffold geometry and the surface stiffness. This will allow, on the one hand, understanding their specific role in stem cell proliferation and differentiation and, on the other hand, finely tuning their synergistic effect. (paper)

  8. Evaluation of the impacts of climate change on disease vectors through ecological niche modelling.

    Science.gov (United States)

    Carvalho, B M; Rangel, E F; Vale, M M

    2017-08-01

    Vector-borne diseases are exceptionally sensitive to climate change. Predicting vector occurrence in specific regions is a challenge that disease control programs must meet in order to plan and execute control interventions and climate change adaptation measures. Recently, an increasing number of scientific articles have applied ecological niche modelling (ENM) to study medically important insects and ticks. With a myriad of available methods, it is challenging to interpret their results. Here we review the future projections of disease vectors produced by ENM, and assess their trends and limitations. Tropical regions are currently occupied by many vector species; but future projections indicate poleward expansions of suitable climates for their occurrence and, therefore, entomological surveillance must be continuously done in areas projected to become suitable. The most commonly applied methods were the maximum entropy algorithm, generalized linear models, the genetic algorithm for rule set prediction, and discriminant analysis. Lack of consideration of the full-known current distribution of the target species on models with future projections has led to questionable predictions. We conclude that there is no ideal 'gold standard' method to model vector distributions; researchers are encouraged to test different methods for the same data. Such practice is becoming common in the field of ENM, but still lags behind in studies of disease vectors.

  9. Manipulation of signaling thresholds in "engineered stem cell niches" identifies design criteria for pluripotent stem cell screens.

    Directory of Open Access Journals (Sweden)

    Raheem Peerani

    Full Text Available In vivo, stem cell fate is regulated by local microenvironmental parameters. Governing parameters in this stem cell niche include soluble factors, extra-cellular matrix, and cell-cell interactions. The complexity of this in vivo niche limits analyses into how individual niche parameters regulate stem cell fate. Herein we use mouse embryonic stem cells (mESC and micro-contact printing (microCP to investigate how niche size controls endogenous signaling thresholds. microCP is used to restrict colony diameter, separation, and degree of clustering. We show, for the first time, spatial control over the activation of the Janus kinase/signal transducer and activator of transcription pathway (Jak-Stat. The functional consequences of this niche-size-dependent signaling control are confirmed by demonstrating that direct and indirect transcriptional targets of Stat3, including members of the Jak-Stat pathway and pluripotency-associated genes, are regulated by colony size. Modeling results and empirical observations demonstrate that colonies less than 100 microm in diameter are too small to maximize endogenous Stat3 activation and that colonies separated by more than 400 microm can be considered independent from each other. These results define parameter boundaries for the use of ESCs in screening studies, demonstrate the importance of context in stem cell responsiveness to exogenous cues, and suggest that niche size is an important parameter in stem cell fate control.

  10. Phylogenetic signals in the climatic niches of the world's amphibians

    DEFF Research Database (Denmark)

    Hof, Christian; Rahbek, Carsten; Araújo, Miguel B.

    2010-01-01

    amphibian orders and across biogeographical regions. To our knowledge, this is the first study providing a comprehensive analysis of the phylogenetic signal in species climatic niches for an entire clade across the world. Even though our results do not provide a strong test of the niche conservatism......The question of whether closely related species share similar ecological requirements has attracted increasing attention, because of its importance for understanding global diversity gradients and the impacts of climate change on species distributions. In fact, the assumption that related species...... are also ecologically similar has often been made, although the prevalence of such a phylogenetic signal in ecological niches remains heavily debated. Here, we provide a global analysis of phylogenetic niche relatedness for the world's amphibians. In particular, we assess which proportion of the variance...

  11. Hanging drop cultures of human testis and testis cancer samples: a model used to investigate activin treatment effects in a preserved niche.

    Science.gov (United States)

    Jørgensen, A; Young, J; Nielsen, J E; Joensen, U N; Toft, B G; Rajpert-De Meyts, E; Loveland, K L

    2014-05-13

    Testicular germ cell tumours of young adults, seminoma or non-seminomas, are preceded by a pre-invasive precursor, carcinoma in situ (CIS), understood to arise through differentiation arrest of embryonic germ cells. Knowledge about the malignant transformation of germ cells is currently limited by the lack of experimental models. The aim of this study was to establish an experimental tissue culture model to maintain normal and malignant germ cells within their niche and allow investigation of treatment effects. Human testis and testis cancer specimens from orchidectomies were cultured in 'hanging drops' and effects of activin A and follistatin treatment were investigated in seminoma cultures. Testis fragments with normal spermatogenesis or CIS cells were cultured for 14 days with sustained proliferation of germ cells and CIS cells and without increased apoptosis. Seminoma cultures survived 7 days, with proliferating cells detectable during the first 5 days. Activin A treatment significantly reduced KIT transcript and protein levels in seminoma cultures, thereby demonstrating a specific treatment response. Hanging drop cultures of human testis and testis cancer samples can be employed to delineate mechanisms governing growth of normal, CIS and tumorigenic germ cells retained within their niche.

  12. The Satellite Cell Niche Regulates the Balance between Myoblast Differentiation and Self-Renewal via p53.

    Science.gov (United States)

    Flamini, Valentina; Ghadiali, Rachel S; Antczak, Philipp; Rothwell, Amy; Turnbull, Jeremy E; Pisconti, Addolorata

    2018-03-13

    Satellite cells are adult muscle stem cells residing in a specialized niche that regulates their homeostasis. How niche-generated signals integrate to regulate gene expression in satellite cell-derived myoblasts is poorly understood. We undertook an unbiased approach to study the effect of the satellite cell niche on satellite cell-derived myoblast transcriptional regulation and identified the tumor suppressor p53 as a key player in the regulation of myoblast quiescence. After activation and proliferation, a subpopulation of myoblasts cultured in the presence of the niche upregulates p53 and fails to differentiate. When satellite cell self-renewal is modeled ex vivo in a reserve cell assay, myoblasts treated with Nutlin-3, which increases p53 levels in the cell, fail to differentiate and instead become quiescent. Since both these Nutlin-3 effects are rescued by small interfering RNA-mediated p53 knockdown, we conclude that a tight control of p53 levels in myoblasts regulates the balance between differentiation and return to quiescence. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  13. Language and other artifacts: socio-cultural dynamics of niche construction.

    Science.gov (United States)

    Sinha, Chris

    2015-01-01

    Niche construction theory is a relatively new approach in evolutionary biology that seeks to integrate an ecological dimension into the Darwinian theory of evolution by natural selection. It is regarded by many evolutionary biologists as providing a significant revision of the Neo-Darwinian modern synthesis that unified Darwin's theory of natural and sexual selection with 20th century population genetics. Niche construction theory has been invoked as a processual mediator of social cognitive evolution and of the emergence and evolution of language. I argue that language itself can be considered as a biocultural niche and evolutionary artifact. I provide both a general analysis of the cognitive and semiotic status of artifacts, and a formal analysis of language as a social and semiotic institution, based upon a distinction between the fundamental semiotic relations of "counting as" and "standing for." I explore the consequences for theories of language and language learning of viewing language as a biocultural niche. I suggest that not only do niches mediate organism-organism interactions, but also that organisms mediate niche-niche interactions in ways that affect evolutionary processes, with the evolution of human infancy and childhood as a key example. I argue that language as a social and semiotic system is not only grounded in embodied engagements with the material and social-interactional world, but also grounds a sub-class of artifacts of particular significance in the cultural history of human cognition. Symbolic cognitive artifacts materially and semiotically mediate human cognition, and are not merely informational repositories, but co-agentively constitutive of culturally and historically emergent cognitive domains. I provide examples of the constitutive cognitive role of symbolic cognitive artifacts drawn from my research with my colleagues on cultural and linguistic conceptualizations of time, and their cultural variability. I conclude by reflecting on

  14. Phylogenetic niche conservatism and the evolutionary basis of ecological speciation.

    Science.gov (United States)

    Pyron, R Alexander; Costa, Gabriel C; Patten, Michael A; Burbrink, Frank T

    2015-11-01

    Phylogenetic niche conservatism (PNC) typically refers to the tendency of closely related species to be more similar to each other in terms of niche than they are to more distant relatives. This has been implicated as a potential driving force in speciation and other species-richness patterns, such as latitudinal gradients. However, PNC has not been very well defined in most previous studies. Is it a pattern or a process? What are the underlying endogenous (e.g. genetic) and exogenous (e.g. ecological) factors that cause niches to be conserved? What degree of similarity is necessary to qualify as PNC? Is it possible for the evolutionary processes causing niches to be conserved to also result in niche divergence in different habitats? Here, we revisit these questions, codifying a theoretical and operational definition of PNC as a mechanistic evolutionary process resulting from several factors. We frame this both from a macroevolutionary and population-genetic perspective. We discuss how different axes of physical (e.g. geographic) and environmental (e.g. climatic) heterogeneity interact with the fundamental process of PNC to produce different outcomes of ecological speciation. We also review tests for PNC, and suggest ways that these could be improved or better utilized in future studies. Ultimately, PNC as a process has a well-defined mechanistic basis in organisms, and future studies investigating ecological speciation would be well served to consider this, and frame hypothesis testing in terms of the processes and expected patterns described herein. The process of PNC may lead to patterns where niches are conserved (more similar than expected), constrained (divergent within a limited subset of available niches), or divergent (less similar than expected), based on degree of phylogenetic relatedness between species. © 2014 Cambridge Philosophical Society.

  15. Language and other artifacts: socio-cultural dynamics of niche construction.

    Directory of Open Access Journals (Sweden)

    Chris eSinha

    2015-10-01

    Full Text Available Niche construction theory is a relatively new approach in evolutionary biology that seeks to integrate an ecological dimension into the Darwinian theory of evolution by natural selection. It is regarded by many evolutionary biologists as providing a significant revision of the Neo-Darwinian modern synthesis that unified Darwin’s theory of natural and sexual selection with 20th century population genetics. Niche construction theory has been invoked as a processual mediator of social cognitive evolution and of the emergence and evolution of language. I argue that language itself can be considered as a biocultural niche and evolutionary artifact. I provide both a general analysis of the cognitive and semiotic status of artifacts, and a formal analysis of language as a social and semiotic institution, based upon a distinction between the fundamental semiotic relations of counting as and standing for. I explore the consequences for theories of language and language learning of viewing language as a biocultural niche. I suggest that not only do niches mediate organism-organism interactions, but also that organisms mediate niche-niche interactions in ways that affect evolutionary processes, with the evolution of human infancy and childhood as a key example. I argue that language as a social and semiotic system is not only grounded in embodied engagements with the material and social-interactional world, but also grounds a sub-class of artifacts of particular significance in the cultural history of human cognition. Symbolic cognitive artifacts materially and semiotically mediate human cognition, and are not merely informational repositories, but co-agentively constitutive of culturally and historically emergent cognitive domains. I provide examples of the constitutive cognitive role of symbolic cognitive artifacts drawn from my research with my colleagues on cultural and linguistic conceptualizations of time, and their cultural variability. I conclude

  16. A practical guideline for examining a uterine niche using ultrasonography in non-pregnant women

    DEFF Research Database (Denmark)

    Jordans, I P M; de Leeuw, R; Stegwee, S I

    2018-01-01

    OBJECTIVES: To generate a uniform, internationally recognized guideline for detailed uterine niche evaluation by ultrasonography in non-pregnant women using a modified Delphi method amongst international experts. METHODS: Fifteen international gynecological experts were recruited...... definitions, relevance, method of measurement and tips for visualization of the niche. All experts agreed on the proposed guideline for niche evaluation in non-pregnant women as presented in this paper. CONCLUSION: Consensus between niche experts was achieved on all items regarding ultrasonographic niche...

  17. Correlated evolution of thermal niches and functional physiology in tropical freshwater fishes.

    Science.gov (United States)

    Culumber, Zachary W; Tobler, Michael

    2018-05-01

    The role of ecology in phenotypic and species diversification is widely documented. Nonetheless, numerous nonadaptive processes can shape realized niches and phenotypic variation in natural populations, complicating inferences about adaptive evolution at macroevolutionary scales. We tested for evolved differences in thermal tolerances and their association with the realized thermal niche (including metrics describing diurnal and seasonal patterns of temperature extremes and variability) across a genus of tropical freshwater fishes reared in a standardized environment. There was limited evolution along the thermal niche axis associated with variation in maximum temperature and in upper thermal limits. In contrast, there was considerable diversification along the first major axis of the thermal niche associated with minimum temperatures and in lower thermal limits. Across our adaptive landscape analyses, 70% of species exhibited evidence of divergence in thermal niches. Most importantly, the first two major axes of thermal niche variation were significantly correlated with variation in lower thermal limits. Our results indicate adaptation to divergent thermal niches and adaptive evolution of related functional traits, and highlight the importance of divergence in lower thermal limits for the evolution of tropical biodiversity. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology.

  18. Ontogenetic niche shifts and evolutionary branching in size-structured populations

    NARCIS (Netherlands)

    Claessen, D.; Dieckmann, U.

    2002-01-01

    There are many examples of size-structured populations where individuals sequentially exploit several niches in the course of their life history. Efficient exploitation of such ontogenetic niches generally requires specific morphological adaptations. Here, we study the evolutionary implications of

  19. Stochastic dynamics for two biological species and ecological niches

    Science.gov (United States)

    Ruziska, Flávia M.; Arashiro, Everaldo; Tomé, Tânia

    2018-01-01

    We consider an ecological system in which two species interact with two niches. To this end we introduce a stochastic model with four states. Our analysis is founded in three approaches: Monte Carlo simulations of the model on a square lattice, mean-field approximation, and birth and death master equation. From this last approach we obtain a description in terms of Langevin equations which show in an explicit way the role of noise in population biology. We focus mainly on the description of time oscillations of the species population and the alternating dominance between them. The model treated here may provide insights on these properties.

  20. Biogeographic ranges do not support niche theory in radiating Canary Island plant clades

    DEFF Research Database (Denmark)

    Steinbauer, Manuel; Field, Richard; Fernández-Palacios, José María

    2016-01-01

    in allopatry. Main conclusions: The expectations from niche conservatism were frequently not met; instead our results suggest considerable climatic niche lability. All significant differences in climatic niche differentiation were opposite to the predictions from competitive displacement. These forces may...

  1. Donor Satellite Cell Engraftment is Significantly Augmented When the Host Niche is Preserved and Endogenous Satellite Cells are Incapacitated

    Science.gov (United States)

    Boldrin, Luisa; Neal, Alice; Zammit, Peter S; Muntoni, Francesco; Morgan, Jennifer E

    2012-01-01

    Stem cell transplantation is already in clinical practice for certain genetic diseases and is a promising therapy for dystrophic muscle. We used the mdx mouse model of Duchenne muscular dystrophy to investigate the effect of the host satellite cell niche on the contribution of donor muscle stem cells (satellite cells) to muscle regeneration. We found that incapacitation of the host satellite cells and preservation of the muscle niche promote donor satellite cell contribution to muscle regeneration and functional reconstitution of the satellite cell compartment. But, if the host niche is not promptly refilled, or is filled by competent host satellite cells, it becomes nonfunctional and donor engraftment is negligible. Application of this regimen to aged host muscles also promotes efficient regeneration from aged donor satellite cells. In contrast, if the niche is destroyed, yet host satellite cells remain proliferation-competent, donor-derived engraftment is trivial. Thus preservation of the satellite cell niche, concomitant with functional impairment of the majority of satellite cells within dystrophic human muscles, may improve the efficiency of stem cell therapy. Stem Cells2012;30:1971–1984 PMID:22730231

  2. Ecological-niche modeling and prioritization of conservation-area networks for Mexican herpetofauna.

    Science.gov (United States)

    Urbina-Cardona, J Nicolás; Flores-Villela, Oscar

    2010-08-01

    One of the most important tools in conservation biology is information on the geographic distribution of species and the variables determining those patterns. We used maximum-entropy niche modeling to run distribution models for 222 amphibian and 371 reptile species (49% endemics and 27% threatened) for which we had 34,619 single geographic records. The planning region is in southeastern Mexico, is 20% of the country's area, includes 80% of the country's herpetofauna, and lacks an adequate protected-area system. We used probabilistic data to build distribution models of herpetofauna for use in prioritizing conservation areas for three target groups (all species and threatened and endemic species). The accuracy of species-distribution models was better for endemic and threatened species than it was for all species. Forty-seven percent of the region has been deforested and additional conservation areas with 13.7% to 88.6% more native vegetation (76% to 96% of the areas are outside the current protected-area system) are needed. There was overlap in 26 of the main selected areas in the conservation-area network prioritized to preserve the target groups, and for all three target groups the proportion of vegetation types needed for their conservation was constant: 30% pine and oak forests, 22% tropical evergreen forest, 17% low deciduous forest, and 8% montane cloud forests. The fact that different groups of species require the same proportion of habitat types suggests that the pine and oak forests support the highest proportion of endemic and threatened species and should therefore be given priority over other types of vegetation for inclusion in the protected areas of southeastern Mexico.

  3. Overlap and partitioning of the ecological and isotopic niches

    Science.gov (United States)

    Elizabeth A. Flaherty; Merav Ben-David

    2010-01-01

    Recently, it was proposed that stable isotope patterns can be used to quantify the width of the ecological niche of animals. However, the potential effects of habitat use on isotopic patterns of consumers have not been fully explored and consequently isotopic patterns may yield deceptive estimates of niche width. Here, we simulated four different scenarios of a...

  4. Human niche, human behaviour, human nature.

    Science.gov (United States)

    Fuentes, Agustin

    2017-10-06

    The concept of a 'human nature' or 'human natures' retains a central role in theorizing about the human experience. In Homo sapiens it is clear that we have a suite of capacities generated via our evolutionary past, and present, and a flexible capacity to create and sustain particular kinds of cultures and to be shaped by them. Regardless of whether we label these capacities 'human natures' or not, humans occupy a distinctive niche and an evolutionary approach to examining it is critical. At present we are faced with a few different narratives as to exactly what such an evolutionary approach entails. There is a need for a robust and dynamic theoretical toolkit in order to develop a richer, and more nuanced, understanding of the cognitively sophisticated genus Homo and the diverse sorts of niches humans constructed and occupied across the Pleistocene, Holocene, and into the Anthropocene. Here I review current evolutionary approaches to 'human nature', arguing that we benefit from re-framing our investigations via the concept of the human niche and in the context of the extended evolutionary synthesis (EES). While not a replacement of standard evolutionary approaches, this is an expansion and enhancement of our toolkit. I offer brief examples from human evolution in support of these assertions.

  5. Environmental niche conservatism explains the accumulation of species richness in Mediterranean-hotspot plant genera.

    Science.gov (United States)

    Skeels, Alexander; Cardillo, Marcel

    2017-03-01

    The causes of exceptionally high plant diversity in Mediterranean-climate biodiversity hotspots are not fully understood. We asked whether a mechanism similar to the tropical niche conservatism hypothesis could explain the diversity of four large genera (Protea, Moraea, Banksia, and Hakea) with distributions within and adjacent to the Greater Cape Floristic Region (South Africa) or the Southwest Floristic Region (Australia). Using phylogenetic and spatial data we estimated the environmental niche of each species, and reconstructed the mode and dynamics of niche evolution, and the geographic history, of each genus. For three genera, there were strong positive relationships between the diversity of clades within a region and their inferred length of occupation of that region. Within genera, there was evidence for strong evolutionary constraint on niche axes associated with climatic seasonality and aridity, with different niche optima for hotspot and nonhotspot clades. Evolutionary transitions away from hotspots were associated with increases in niche breadth and elevated rates of niche evolution. Our results point to a process of "hotspot niche conservatism" whereby the accumulation of plant diversity in Mediterranean-type ecosystems results from longer time for speciation, with dispersal away from hotspots limited by narrow and phylogenetically conserved environmental niches. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  6. Unveiling current Guanaco distribution in chile based upon niche structure of phylogeographic lineages: Andean puna to subpolar forests.

    Science.gov (United States)

    González, Benito A; Samaniego, Horacio; Marín, Juan Carlos; Estades, Cristián F

    2013-01-01

    Niche description and differentiation at broad geographic scales have been recent major topics in ecology and evolution. Describing the environmental niche structure of sister taxa with known evolutionary trajectories stands out as a useful exercise in understanding niche requirements. Here we model the environmental niche structure and distribution of the recently resolved phylogeography of guanaco (Lama guanicoe) lineages on the western slope of the southern Andes. Using a maximum entropy framework, field data, and information on climate, topography, human density, and vegetation cover, we identify differences between the two subspecies (L.g.cacsilensis, L.g.guanicoe) and their intermediate-hybrid lineage, that most likely determine the distribution of this species. While aridity seems to be a major factor influencing the distribution at the species-level (annual precipitation ecological and/or evolutionary processes are shaping the niche of guanacos in Chile, producing discrepancies when comparing range distribution at the species-level (81,756 km(2)) with lineages-level (65,321 km(2)). The subspecies-specific description of niche structure is provided here based upon detailed spatial distribution of the lineages of guanacos in Chile. Such description provides a scientific tool to further develop large scale plans for habitat conservation and preservation of intraspecific genetic variability for this far ranging South American camelid, which inhabits a diversity of ecoregion types from Andean puna to subpolar forests.

  7. Identifying niche-mediated regulatory factors of stem cell phenotypic state: a systems biology approach.

    Science.gov (United States)

    Ravichandran, Srikanth; Del Sol, Antonio

    2017-02-01

    Understanding how the cellular niche controls the stem cell phenotype is often hampered due to the complexity of variegated niche composition, its dynamics, and nonlinear stem cell-niche interactions. Here, we propose a systems biology view that considers stem cell-niche interactions as a many-body problem amenable to simplification by the concept of mean field approximation. This enables approximation of the niche effect on stem cells as a constant field that induces sustained activation/inhibition of specific stem cell signaling pathways in all stem cells within heterogeneous populations exhibiting the same phenotype (niche determinants). This view offers a new basis for the development of single cell-based computational approaches for identifying niche determinants, which has potential applications in regenerative medicine and tissue engineering. © 2017 The Authors. FEBS Letters published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

  8. Using Geographic Information System-based Ecologic Niche Models to Forecast the Risk of Hantavirus Infection in Shandong Province, China

    Science.gov (United States)

    Wei, Lan; Qian, Quan; Wang, Zhi-Qiang; Glass, Gregory E.; Song, Shao-Xia; Zhang, Wen-Yi; Li, Xiu-Jun; Yang, Hong; Wang, Xian-Jun; Fang, Li-Qun; Cao, Wu-Chun

    2011-01-01

    Hemorrhagic fever with renal syndrome (HFRS) is an important public health problem in Shandong Province, China. In this study, we combined ecologic niche modeling with geographic information systems (GIS) and remote sensing techniques to identify the risk factors and affected areas of hantavirus infections in rodent hosts. Land cover and elevation were found to be closely associated with the presence of hantavirus-infected rodent hosts. The averaged area under the receiver operating characteristic curve was 0.864, implying good performance. The predicted risk maps based on the model were validated both by the hantavirus-infected rodents' distribution and HFRS human case localities with a good fit. These findings have the applications for targeting control and prevention efforts. PMID:21363991

  9. Invasion of Old World Phragmites australis in the New World: precipitation and temperature patterns combined with human influences redesign the invasive niche

    DEFF Research Database (Denmark)

    Guo, Wen-Yong; Lambertini, Carla; Li, Xiu-Zhen

    2013-01-01

    niches. We suggest that an increase in precipitation in the 20(th) century, global warming and human-made habitats have shaped the invasive niches of the two lineages in the New World. However, as the invasions are on-going and human and natural disturbances occur concomitantly, the future distribution....... australis (Haplotype M and Med) in both their native and introduced ranges using environmental niche models (ENMs) to assess (i) whether a niche shift accompanied the invasions in the New World; (ii) the role of biologically relevant climatic variables and human influence in the process of invasion...... for temperature fluctuations and increased precipitation. The introduced Med lineage has enlarged its original subtropical niche to the tropics-subtropics, invading regions with a high annual mean temperature (> c. 10 °C) and high precipitation in the driest period. Human influence is an important factor for both...

  10. Evidence of niche partitioning under ontogenetic influences among three morphologically similar siluriformes in small subtropical streams.

    Directory of Open Access Journals (Sweden)

    Karine Orlandi Bonato

    Full Text Available Ontogenetic influences in patterns of niche breadth and feeding overlap were investigated in three species of Siluriformes (Heptapterus sp., Rhamdia quelen and Trichomycterus poikilos aiming at understanding the species coexistence. Samplings were conducted bimonthly by electrofishing technique from June/2012 to June/2013 in ten streams of the northwestern state of Rio Grande do Sul, Brazil. The stomach contents of 1,948 individuals were analyzed by volumetric method, with 59 food items identified. In general Heptapterus sp. consumed a high proportion of Aegla sp., terrestrial plant remains and Megaloptera; R. quelen consumed fish, and Oligochaeta, followed by Aegla sp.; while the diet of T. poikilos was based on Simuliidae, Ephemeroptera and Trichoptera. Specie segregation was observed in the NMDS. Through PERMANOVA analysis feeding differences among species, and between a combination of species plus size classes were observed. IndVal showed which items were indicators of these differences. Niche breadth values were high for all species. The niche breadth values were low only for the larger size of R. quelen and Heptapterus sp. while T. poikilos values were more similar. Overall the species were a low feeding overlap values. The higher frequency of high feeding overlap was observed for interaction between Heptapterus sp. and T. poikilos. The null model confirmed the niche partitioning between the species. The higher frequency of high and intermediate feeding overlap values were reported to smaller size classes. The null model showed resource sharing between the species/size class. Therefore, overall species showed a resource partitioning because of the use of occasional items. However, these species share resources mainly in the early ontogenetic stages until the emphasized change of morphological characteristics leading to trophic niche expansion and the apparent segregation observed.

  11. The human and murine hematopoietic stem cell niches: are they comparable?

    Science.gov (United States)

    van Pel, Melissa; Fibbe, Willem E; Schepers, Koen

    2016-04-01

    Hematopoietic stem cells (HSCs) reside in specific niches that provide various instructive cues that regulate HSC self-renewal and their development into all mature cells of the peripheral blood. Progress in this research field has largely been guided by mouse studies. However, parallel studies with human subjects, tissues, and cells, in combination with xenotransplantation experiments in immunodeficient mice, have contributed to our increased understanding of the human HSC niche. Here, we summarize our current knowledge of the various specialized subsets of both stromal and hematopoietic cells that support HSCs through cell-cell interactions and secreted factors, and the many parallels between the murine and human HSC niches. Furthermore, we discuss recent technological advances that are likely to improve our understanding of the human HSC niche, a better understanding of which may allow further identification of unique molecular and cellular pathways in the HSC niche. This information may help to further improve the outcome of HSC transplantation and refine the treatment of hematopoietic diseases. © 2015 New York Academy of Sciences.

  12. A practioner's view on Strategic Niche Management

    International Nuclear Information System (INIS)

    Mourik, R.; Raven, R.P.J.M.

    2006-11-01

    Strategic Niche Management (SNM) is a tool to support the societal introduction of radical sustainable innovations. However, it has been mainly used in retrospective to analyse historical case studies. This report discusses SNM from a practioner's perspective with the main aim to articulate questions that should be addressed for translating SNM from an ex-post to an ex-ante tool. The main conclusion is that an SNM tool should focus on the level of 'niches' rather than single projects, i.e. SNM should aim to support (program) managers who aim at orchestrating the interaction between multiple experiments

  13. Lizard assemblage from a sand dune habitat from southeastern Brazil: a niche overlap analysis.

    Science.gov (United States)

    Winck, Gisele R; Hatano, Fabio; Vrcibradic, Davor; VAN Sluys, Monique; Rocha, Carlos F D

    2016-01-01

    Communities are structured by interactions of historical and ecological factors, which influence the use of different resources in time and space. We acquired data on time of activity, microhabitat use and diet of a lizard assemblage from a sand dune habitat in a coastal area, southeastern Brazil (Restinga de Jurubatiba). We analyzed the data of niche overlap among species in these three axes (temporal, spatial and trophic) using null models. We found a significant overlap within the trophic niche, whereas the overlap for the other axes did not differ from the expected. Based on this result, we discuss the factors acting on the structure of the local lizard community.

  14. Optimization of Femtosecond Laser Polymerized Structural Niches to Control Mesenchymal Stromal Cell Fate in Culture

    Directory of Open Access Journals (Sweden)

    Manuela T. Raimondi

    2014-06-01

    Full Text Available We applied two-photon polymerization to fabricate 3D synthetic niches arranged in complex patterns to study the effect of mechano-topological parameters on morphology, renewal and differentiation of rat mesenchymal stromal cells. Niches were formed in a photoresist with low auto-fluorescence, which enabled the clear visualization of the fluorescence emission of the markers used for biological diagnostics within the internal niche structure. The niches were structurally stable in culture up to three weeks. At three weeks of expansion in the niches, cell density increased by almost 10-fold and was 67% greater than in monolayer culture. Evidence of lineage commitment was observed in monolayer culture surrounding the structural niches, and within cell aggregates, but not inside the niches. Thus, structural niches were able not only to direct stem cell homing and colony formation, but also to guide aggregate formation, providing increased surface-to-volume ratios and space for stem cells to adhere and renew, respectively.

  15. Language and other artifacts: socio-cultural dynamics of niche construction

    Science.gov (United States)

    Sinha, Chris

    2015-01-01

    Niche construction theory is a relatively new approach in evolutionary biology that seeks to integrate an ecological dimension into the Darwinian theory of evolution by natural selection. It is regarded by many evolutionary biologists as providing a significant revision of the Neo-Darwinian modern synthesis that unified Darwin’s theory of natural and sexual selection with 20th century population genetics. Niche construction theory has been invoked as a processual mediator of social cognitive evolution and of the emergence and evolution of language. I argue that language itself can be considered as a biocultural niche and evolutionary artifact. I provide both a general analysis of the cognitive and semiotic status of artifacts, and a formal analysis of language as a social and semiotic institution, based upon a distinction between the fundamental semiotic relations of “counting as” and “standing for.” I explore the consequences for theories of language and language learning of viewing language as a biocultural niche. I suggest that not only do niches mediate organism-organism interactions, but also that organisms mediate niche-niche interactions in ways that affect evolutionary processes, with the evolution of human infancy and childhood as a key example. I argue that language as a social and semiotic system is not only grounded in embodied engagements with the material and social-interactional world, but also grounds a sub-class of artifacts of particular significance in the cultural history of human cognition. Symbolic cognitive artifacts materially and semiotically mediate human cognition, and are not merely informational repositories, but co-agentively constitutive of culturally and historically emergent cognitive domains. I provide examples of the constitutive cognitive role of symbolic cognitive artifacts drawn from my research with my colleagues on cultural and linguistic conceptualizations of time, and their cultural variability. I conclude by

  16. Electron-plasmon model in the electron liquid theory

    Directory of Open Access Journals (Sweden)

    M.V.Vavrukh

    2005-01-01

    Full Text Available Here we propose an accurate approach to the description of the electron liquid model in the electron and plasmon terms. Our ideas in the present paper are close to the conception of the collective variables which was developed in the papers of Bohm and Pines. However we use another body of mathematics in the transition to the expanded space of variable particles and plasmons realized by the transition operator. It is evident that in the Random Phase Approximation (RPA, the model which consists of two interactive subsystems of electrons and plasmons is equivalent to the electron liquid model with Coulomb interaction.

  17. Environmental niche divergence among three dune shrub sister species with parapatric distributions.

    Science.gov (United States)

    Chozas, Sergio; Chefaoui, Rosa M; Correia, Otília; Bonal, Raúl; Hortal, Joaquín

    2017-05-01

    The geographical distributions of species are constrained by their ecological requirements. The aim of this work was to analyse the effects of environmental conditions, historical events and biogeographical constraints on the diversification of the three species of the western Mediterranean shrub genus Stauracanthus , which have a parapatric distribution in the Iberian Peninsula. Ecological niche factor analysis and generalized linear models were used to measure the response of all Stauracanthus species to the environmental gradients and map their potential distributions in the Iberian Peninsula. The bioclimatic niche overlap between the three species was determined by using Schoener's index. The genetic differentiation of the Iberian and northern African populations of Stauracanthus species was characterized with GenalEx. The effects on genetic distances of the most important environmental drivers were assessed through Mantel tests and non-metric multidimensional scaling. The three Stauracanthus species show remarkably similar responses to climatic conditions. This supports the idea that all members of this recently diversified clade retain common adaptations to climate and consequently high levels of climatic niche overlap. This contrasts with the diverse edaphic requirements of Stauracanthus species. The populations of the S. genistoides-spectabilis clade grow on Miocene and Pliocene fine-textured sedimentary soils, whereas S. boivinii , the more genetically distant species, occurs on older and more coarse-textured sedimentary substrates. These patterns of diversification are largely consistent with a stochastic process of geographical range expansion and fragmentation coupled with niche evolution in the context of spatially complex environmental fluctuations. : The combined analysis of the distribution, realized environmental niche and phylogeographical relationships of parapatric species proposed in this work allows integration of the biogeographical

  18. Geographic Distribution of Chagas Disease Vectors in Brazil Based on Ecological Niche Modeling

    Directory of Open Access Journals (Sweden)

    Rodrigo Gurgel-Gonçalves

    2012-01-01

    Full Text Available Although Brazil was declared free from Chagas disease transmission by the domestic vector Triatoma infestans, human acute cases are still being registered based on transmission by native triatomine species. For a better understanding of transmission risk, the geographic distribution of Brazilian triatomines was analyzed. Sixteen out of 62 Brazilian species that both occur in >20 municipalities and present synanthropic tendencies were modeled based on their ecological niches. Panstrongylus geniculatus and P. megistus showed broad ecological ranges, but most of the species sort out by the biome in which they are distributed: Rhodnius pictipes and R. robustus in the Amazon; R. neglectus, Triatoma sordida, and T. costalimai in the Cerrado; R. nasutus, P. lutzi, T. brasiliensis, T. pseudomaculata, T. melanocephala, and T. petrocchiae in the Caatinga; T. rubrovaria in the southern pampas; T. tibiamaculata and T. vitticeps in the Atlantic Forest. Although most occurrences were recorded in open areas (Cerrado and Caatinga, our results show that all environmental conditions in the country are favorable to one or more of the species analyzed, such that almost nowhere is Chagas transmission risk negligible.

  19. Competition in a technological niche: the cars of the future

    NARCIS (Netherlands)

    Bakker, S.; Lente, H. van; Engels, R.

    2012-01-01

    The notion of ‘niche’has proved to be useful to account for the emergence of radical innovations. Most studies, however, deal with the development of single emerging technologies. In this paper we address the competition between multiple niche technologies.Within the niche of the ‘car of the future’

  20. Effective electron-electron and electron-phonon interactions in the Hubbard-Holstein model

    International Nuclear Information System (INIS)

    Aprea, G.; Di Castro, C.; Grilli, M. . E-mail marco.grilli@roma1.infn.it; Lorenzana, J.

    2006-01-01

    We investigate the interplay between the electron-electron and the electron-phonon interaction in the Hubbard-Holstein model. We implement the flow-equation method to investigate within this model the effect of correlation on the electron-phonon effective coupling and, conversely, the effect of phonons in the effective electron-electron interaction. Using this technique we obtain analytical momentum-dependent expressions for the effective couplings and we study their behavior for different physical regimes. In agreement with other works on this subject, we find that the electron-electron attraction mediated by phonons in the presence of Hubbard repulsion is peaked at low transferred momenta. The role of the characteristic energies involved is also analyzed

  1. Testing the niche variation hypothesis with a measure of body condition

    Science.gov (United States)

    Individual variation and fitness are cornerstones of evolution by natural selection. The niche variation hypothesis (NVH) posits that when interspecific competition is relaxed, intraspecific competition should drive niche expansion by selection favoring use of novel resources. Po...

  2. Evidence of niche shift and invasion potential of Lithobates catesbeianus in the habitat of Mexican endemic frogs.

    Directory of Open Access Journals (Sweden)

    Jorge Luis Becerra López

    Full Text Available Invasive alien species are one of most severe threats to biodiversity and natural resources. These biological invasions have been studied from the niche conservatism and niche shifts perspective. Niche differentiation may result from changes in fundamental niche or realized niche or both; in biological invasions, niche differences between native and non-native ranges can appear through niche expansion, niche unfilling and niche stability. The American bullfrog Lithobates catesbeianus is an invasive species that can have negative impacts on native amphibian populations. This research examines the climate niche shifts of this frog, its potential range of expansion in Mexico and the risk of invasion by bullfrog in the habitats of 82 frog species endemic to Mexico, that based on their climatic niche similarity were divided in four ecological groups. The results indicate that species in two ecological groups were the most vulnerable to invasion by bullfrog. However, the climate niche shifts of L. catesbeianus may allow it to adapt to new environmental conditions, so species from the two remaining groups cannot be dismissed as not vulnerable. This information is valuable for decision making in prioritizing areas for conservation of Mexican endemic frogs.

  3. Hypoxia-Activated Prodrug TH-302 Targets Hypoxic Bone Marrow Niches in Preclinical Leukemia Models.

    Science.gov (United States)

    Benito, Juliana; Ramirez, Marc S; Millward, Niki Zacharias; Velez, Juliana; Harutyunyan, Karine G; Lu, Hongbo; Shi, Yue-Xi; Matre, Polina; Jacamo, Rodrigo; Ma, Helen; Konoplev, Sergej; McQueen, Teresa; Volgin, Andrei; Protopopova, Marina; Mu, Hong; Lee, Jaehyuk; Bhattacharya, Pratip K; Marszalek, Joseph R; Davis, R Eric; Bankson, James A; Cortes, Jorge E; Hart, Charles P; Andreeff, Michael; Konopleva, Marina

    2016-04-01

    To characterize the prevalence of hypoxia in the leukemic bone marrow, its association with metabolic and transcriptional changes in the leukemic blasts and the utility of hypoxia-activated prodrug TH-302 in leukemia models. Hyperpolarized magnetic resonance spectroscopy was utilized to interrogate the pyruvate metabolism of the bone marrow in the murine acute myeloid leukemia (AML) model. Nanostring technology was used to evaluate a gene set defining a hypoxia signature in leukemic blasts and normal donors. The efficacy of the hypoxia-activated prodrug TH-302 was examined in the in vitro and in vivo leukemia models. Metabolic imaging has demonstrated increased glycolysis in the femur of leukemic mice compared with healthy control mice, suggesting metabolic reprogramming of hypoxic bone marrow niches. Primary leukemic blasts in samples from AML patients overexpressed genes defining a "hypoxia index" compared with samples from normal donors. TH-302 depleted hypoxic cells, prolonged survival of xenograft leukemia models, and reduced the leukemia stem cell pool in vivo In the aggressive FLT3/ITD MOLM-13 model, combination of TH-302 with tyrosine kinase inhibitor sorafenib had greater antileukemia effects than either drug alone. Importantly, residual leukemic bone marrow cells in a syngeneic AML model remain hypoxic after chemotherapy. In turn, administration of TH-302 following chemotherapy treatment to mice with residual disease prolonged survival, suggesting that this approach may be suitable for eliminating chemotherapy-resistant leukemia cells. These findings implicate a pathogenic role of hypoxia in leukemia maintenance and chemoresistance and demonstrate the feasibility of targeting hypoxic cells by hypoxia cytotoxins. ©2015 American Association for Cancer Research.

  4. How do habitat filtering and niche conservatism affect community composition at different taxonomic resolutions?

    Science.gov (United States)

    Munoz, François; Ramesh, B R; Couteron, Pierre

    2014-08-01

    Understanding how local species assembly depends on the regional biogeographic and environmental context is a challenging task in community ecology. In spatially implicit neutral models, a single immigration parameter, I(k), represents the flux of immigrants from a regional pool that compete with local offspring for establishment in communities. This flux counterbalances the effect of local stochastic extinctions to maintain local species diversity. If some species within the regional pool are not adapted to the local environment (habitat filtering), the migrant flux is reduced beyond that of the neutral model, such that habitat filtering influences the value of I(k) in non-neutral situations. Here, we propose a novel model in which immigrants from the regional pool are filtered according to their habitat preferences and the local environment, while taxa potentially retain habitat preferences from their ancestors (niche conservatism). Using both analytical reasoning and simulations, we demonstrate that I(k) is expected to be constant when estimated based on the community composition at several taxonomic levels, not only under neutral assumptions, but also when habitat filtering occurs, unless there is substantial niche conservatism. In the latter case, I(k) is expected to decrease when estimated based on the composition at species to genus and family levels, thus allowing a signature of niche conservatism to be detected by simply comparing I(k) estimates across taxonomic levels. We applied this approach to three rain forest data sets from South India and Central America and found no significant signature of niche conservatism when I(k) was compared across taxonomic levels, except at the family level in South India. We further observed more limited immigration in South Indian forests, supporting the hypothesis of a greater impact of habitat filtering and heterogeneity there than in Central America. Our results highlight the relevance of studying variations of I

  5. Biogeochemical and Ecomorphological Niche Segregation of Mediterranean Woody Species along a Local Gradient

    Directory of Open Access Journals (Sweden)

    Enrique G. de la Riva

    2017-07-01

    Full Text Available According with niche theory the species are specialized in different ecological niches, being able to coexist as result of a differential use of resources. In this context, the biogeochemical niche hypothesis proposes that species have an optimal elemental composition which results from the link between the chemical and morphological traits for the optimum plant functioning. Thus, and attending to the limiting similarity concept, different elemental composition and plant structure among co-occurring species may reduce competition, promoting different functional niches. Different functional habits associated with leaf life-span or growth forms are associated with different strategies for resource uptake, which could promote niche partitioning. In the present study, based on the biogeochemical niche concept and the use of resources in different proportions, we have focused on leaf traits (morphological and chemical associated with resource uptake, and explored the niche partitioning among functional habits: leaf life-span (deciduous, evergreen, and semideciduous and growth (tree, shrub, and arborescent-shrub. To this end, we have quantified the hypervolume of the leaf functional trait space (both structure and chemical composition in a sample of 45 Mediterranean woody species from Sierra Morena Mountains (Spain growing along a local soil resource gradient. Our results show consistent variation in functional space for woody communities distributed along the environmental gradient. Thus, communities dominated by deciduous trees with faster growth and a predominant acquisitive strategy were characteristic of bottom forests and showed highest leaf biogeochemical space. While semideciduous shrubs and evergreen (arborescent, trees species, characterized by a conservative strategy, dominated ridge forests and showed smaller functional space. In addition, within each topographical zone or environment type, the foliar biogeochemical niche partitioning

  6. Biogeochemical and Ecomorphological Niche Segregation of Mediterranean Woody Species along a Local Gradient.

    Science.gov (United States)

    de la Riva, Enrique G; Marañón, Teodoro; Violle, Cyrille; Villar, Rafael; Pérez-Ramos, Ignacio M

    2017-01-01

    According with niche theory the species are specialized in different ecological niches, being able to coexist as result of a differential use of resources. In this context, the biogeochemical niche hypothesis proposes that species have an optimal elemental composition which results from the link between the chemical and morphological traits for the optimum plant functioning. Thus, and attending to the limiting similarity concept, different elemental composition and plant structure among co-occurring species may reduce competition, promoting different functional niches. Different functional habits associated with leaf life-span or growth forms are associated with different strategies for resource uptake, which could promote niche partitioning. In the present study, based on the biogeochemical niche concept and the use of resources in different proportions, we have focused on leaf traits (morphological and chemical) associated with resource uptake, and explored the niche partitioning among functional habits: leaf life-span (deciduous, evergreen, and semideciduous) and growth (tree, shrub, and arborescent-shrub). To this end, we have quantified the hypervolume of the leaf functional trait space (both structure and chemical composition) in a sample of 45 Mediterranean woody species from Sierra Morena Mountains (Spain) growing along a local soil resource gradient. Our results show consistent variation in functional space for woody communities distributed along the environmental gradient. Thus, communities dominated by deciduous trees with faster growth and a predominant acquisitive strategy were characteristic of bottom forests and showed highest leaf biogeochemical space. While semideciduous shrubs and evergreen (arborescent, trees) species, characterized by a conservative strategy, dominated ridge forests and showed smaller functional space. In addition, within each topographical zone or environment type, the foliar biogeochemical niche partitioning would underlie the

  7. The Neogene rise of the tropical Andes facilitated diversification of wax palms (Ceroxylon: Arecaceae) through geographical colonization and climatic niche separation

    DEFF Research Database (Denmark)

    Sanín, María José; Kissling, W. Daniel; Bacon, Christine D.

    2016-01-01

    The tropical Andes are a biodiversity hotspot, partly due to their rich and complex floristic composition. A fundamental question regarding this outstanding biodiversity is what role the Andean orogeny has played in species diversification. Ceroxylon is a genus of endemic Andean palms that stands...... gradients. Ancestral areas were reconstructed under a model allowing for founder-event speciation and climatic niches were inferred from climatic variables at present-day occurrences of all species. Niche evolution in a phylogenetic framework was evaluated by testing differences between the climatic niches...... of clades. Our analyses identified four main clades, with a general pattern of diversification through geographical colonization from south to north after the Pliocene uplift of the northern Andes. Adaptation to low temperatures was conserved at the generic level, with climatic niche differentiation among...

  8. Intersexual trophic niche partitioning in an ant-eating spider (Araneae: Zodariidae.

    Directory of Open Access Journals (Sweden)

    Stano Pekár

    2011-01-01

    Full Text Available Divergence in trophic niche between the sexes may function to reduce competition between the sexes ("intersexual niche partitioning hypothesis", or may be result from differential selection among the sexes on maximizing reproductive output ("sexual selection hypothesis". The latter may lead to higher energy demands in females driven by fecundity selection, while males invest in mate searching. We tested predictions of the two hypotheses underlying intersexual trophic niche partitioning in a natural population of spiders. Zodarion jozefienae spiders specialize on Messor barbarus ants that are polymorphic in body size and hence comprise potential trophic niches for the spider, making this system well-suited to study intersexual trophic niche partitioning.Comparative analysis of trophic morphology (the chelicerae and body size of males, females and juveniles demonstrated highly female biased SSD (Sexual Size Dimorphism in body size, body weight, and in the size of chelicerae, the latter arising from sex-specific growth patterns in trophic morphology. In the field, female spiders actively selected ant sub-castes that were larger than the average prey size, and larger than ants captured by juveniles and males. Female fecundity was highly positively correlated with female body mass, which reflects foraging success during the adult stage. Females in laboratory experiments preferred the large ant sub-castes and displayed higher capture efficiency. In contrast, males occupied a different trophic niche and showed reduced foraging effort and reduced prey capture and feeding efficiency compared with females and juveniles.Our data indicate that female-biased dimorphism in trophic morphology and body size correlate with sex-specific reproductive strategies. We propose that intersexual trophic niche partitioning is shaped primarily by fecundity selection in females, and results from sex-differences in the route to successful reproduction where females are

  9. Trophic Niche Differentiation in Rodents and Marsupials Revealed by Stable Isotopes.

    Directory of Open Access Journals (Sweden)

    Mauro Galetti

    Full Text Available Tropical rainforests support the greatest diversity of small mammals in the world, yet we have little understanding about the mechanisms that promote the coexistence of species. Diet partitioning can favor coexistence by lessening competition, and interspecific differences in body size and habitat use are usually proposed to be associated with trophic divergence. However, the use of classic dietary methods (e.g. stomach contents is challenging in small mammals, particularly in community-level studies, thus we used stable isotopes (δ13C and δ15N to infer about trophic niche. We investigated i how trophic niche is partitioned among rodent and marsupial species in three Atlantic forest sites and ii if interspecific body size and locomotor habit inequalities can constitute mechanisms underlying the isotopic niche partitioning. We found that rodents occupied a broad isotopic niche space with species distributed in different trophic levels and relying on diverse basal carbon sources (C3 and C4 plants. Surprisingly, on the other hand, marsupials showed a narrow isotopic niche, both in δ13C and δ15N dimensions, which is partially overlapped with rodents, contradicting their description as omnivores and generalists proposed classic dietary studies. Although body mass differences did not explained the divergence in isotopic values among species, groups of species with different locomotor habit presented clear differences in the position of the isotopic niche space, indicating that the use of different forest strata can favor trophic niche partitioning in small mammals communities. We suggest that anthropogenic impacts, such as habitat modification (logging, harvesting, can simplify the vertical structure of ecosystems and collapse the diversity of basal resources, which might affect negatively small mammals communities in Atlantic forests.

  10. Time- and depth-wise trophic niche shifts in Antarctic benthos.

    Science.gov (United States)

    Calizza, Edoardo; Careddu, Giulio; Sporta Caputi, Simona; Rossi, Loreto; Costantini, Maria Letizia

    2018-01-01

    Climate change is expected to affect resource-consumer interactions underlying stability in polar food webs. Polar benthic organisms have adapted to the marked seasonality characterising their habitats by concentrating foraging and reproductive activity in summer months, when inputs from sympagic and pelagic producers increase. While this enables the persistence of biodiverse food webs, the mechanisms underlying changes in resource use and nutrient transfer are poorly understood. Thus, our understanding of how temporal and spatial variations in the supply of resources may affect food web structure and functioning is limited. By means of C and N isotopic analyses of two key Antarctic benthic consumers (Adamussium colbecki, Bivalvia, and Sterechinus neumayeri, Echinoidea) and Bayesian mixing models, we describe changes in trophic niche and nutrient transfer across trophic levels associated with the long- and short-term diet and body size of specimens sampled in midsummer in both shallow and deep waters. Samplings occurred soon after the sea-ice broke up at Tethys Bay, an area characterised by extreme seasonality in sea-ice coverage and productivity in the Ross Sea. In the long term, the trophic niche was broader and variation between specimens was greater, with intermediate-size specimens generally consuming a higher number of resources than small and large specimens. The coupling of energy channels in the food web was consequently more direct than in the short term. Sediment and benthic algae were more frequently consumed in the long term, before the sea-ice broke up, while consumers specialised on sympagic algae and plankton in the short term. Regardless of the time scale, sympagic algae were more frequently consumed in shallow waters, while plankton was more frequently consumed in deep waters. Our results suggest a strong temporal relationship between resource availability and the trophic niche of benthic consumers in Antarctica. Potential climate-driven changes

  11. Commodifying snow, taming the waters. Socio-ecological niche construction in an Alpine village.

    Science.gov (United States)

    Gross, Robert; Winiwarter, Verena

    White belts of snow clad mountains all over the world each winter. Even if there is no snow, the tourism industry is able to produce the white finery at the push of the button, thereby consuming large amounts of water. Studying Damüls, a well-known ski resort in Austria's westernmost province Vorarlberg, we can show that the development of a service sector within agro-pastoral landscapes was connected with novel water uses and massive interventions into Alpine landscapes. Human niche construction theory offers a unique avenue for studying the development of Alpine communities, but also highlights side effects accompanying the change from agrarian to tourism livelihoods. One aim of this paper is to broaden the scope of human niche construction theory. Inceptive, counteractive and relocational niche construction activities were coupled to the differentiation of actor groups. To incorporate social dynamics, indispensable for studies in environmental history, we propose the concept of socio-ecological niche construction. The paper investigates how villagers balanced resource limitations typical for an agrarian society with the differentiation of sub-niches, mediating selective forces on the population. When the valleys were industrialized, Damüls was almost given up as a permanent settlement. Then, tourists entered the stage, by and by turning the wheel of local development into a different direction. A tourism niche based on natural snow evolved from the 1930s onwards. While the socio-ecological niches of agriculture and tourism coexisted in the interwar years, this changed when ski lifts were built, embedded into a debt-based economy that made the tourism niche vulnerable to snow availability. Snow-dependency became a powerful selective force. It was mediated by the ski lift companies through a range of niche construction activities that turned water into an important resource of snowmaking systems.

  12. Tug of war in the haematopoietic stem cell niche: do myeloma plasma cells compete for the HSC niche?

    Science.gov (United States)

    Noll, J E; Williams, S A; Purton, L E; Zannettino, A C W

    2012-09-14

    In the adult mammal, normal haematopoiesis occurs predominantly in the bone marrow, where primitive haematopoietic stem cells (HSC) and their progeny reside in specialised microenvironments. The bone marrow microenvironment contains specific anatomical areas (termed niches) that are highly specialised for the development of certain blood cell types, for example HSCs. The HSC niche provides important cell-cell interactions and signalling molecules that regulate HSC self-renewal and differentiation processes. These same signals and interactions are also important in the progression of haematological malignancies, such as multiple myeloma (MM). This review provides an overview of the bone marrow microenvironment and its involvement in normal, physiological HSC maintenance and plasma cell growth throughout MM disease progression.

  13. Socializing with the neighbors: stem cells and their niche.

    Science.gov (United States)

    Fuchs, Elaine; Tumbar, Tudorita; Guasch, Geraldine

    2004-03-19

    The potential of stem cells in regenerative medicine relies upon removing them from their natural habitat, propagating them in culture, and placing them into a foreign tissue environment. To do so, it is essential to understand how stem cells interact with their microenvironment, the so-called stem cell niche, to establish and maintain their properties. In this review, we examine adult stem cell niches and their impact on stem cell biology.

  14. Citizen-science, Geoethics and Human Niche

    Science.gov (United States)

    Bohle, Martin

    2017-04-01

    The anthropogenic biogeosphere or 'human niche' is the intersection of the biogeosphere and the sphere of human activities of social, economic, cultural and political nature. The application case for geoethics, namely "appropriate behaviours and practices, wherever human activities interact with the Earth system" [1], is about niche building. Geoethics is about the conduct of people and geoscientists, respectively their ordinary lifestyles and professional activities. Geoscience professionals notice the diverse economic, social and cultural living conditions of people, and the application cases of geosciences mirror the diversity of the global social sphere. Subsequently it is argued: A) when considering the ethical dimensions of global niche building then geosciences should feature 'citizen geoscience'; and B) when considering the functioning of a knowledge-based society under conditions of anthropogenic global change then 'citizen geoscience' facilitates applying that knowledge base. (A) Regarding 'niche building': The design of production systems and consumption patterns embeds geoscience know-how and relates it to the everyday life. Any citizen's activities purposefully interconnect to the biogeosphere for well-being, care-taking, and reproduction, although habitually without involving a geoscientist in professional capacity. In that implicit manner the everyday behaviours and practices of people influence Earth system dynamic. This renders their inherent geoscience know-how a public good as it makes their ignorance a public risk. A comfortable human niche for billions of people requires a global biogeosphere that is disrupted little by citizens' activities and exposes them to hazards that can be tamed. Quite the reverse, anthropogenic global change will disturb living conditions for many citizen. Much geoscience know-how will have to be deployed to tame disturbances in a socially sustainable manner. Sustainability in turn needs involvement of citizens in

  15. Pre-metastatic niches

    DEFF Research Database (Denmark)

    Peinado, Héctor; Zhang, Haiying; Matei, Irina R.

    2017-01-01

    It is well established that organs of future metastasis are not passive receivers of circulating tumour cells, but are instead selectively and actively modified by the primary tumour before metastatic spread has even occurred. Sowing the 'seeds' of metastasis requires the action of tumour......-secreted factors and tumour-shed extracellular vesicles that enable the 'soil' at distant metastatic sites to encourage the outgrowth of incoming cancer cells. In this Review, we summarize the main processes and new mechanisms involved in the formation of the pre-metastatic niche....

  16. Lizard assemblage from a sand dune habitat from southeastern Brazil: a niche overlap analysis

    Directory of Open Access Journals (Sweden)

    GISELE R. WINCK

    2016-01-01

    Full Text Available ABSTRACT Communities are structured by interactions of historical and ecological factors, which influence the use of different resources in time and space. We acquired data on time of activity, microhabitat use and diet of a lizard assemblage from a sand dune habitat in a coastal area, southeastern Brazil (Restinga de Jurubatiba. We analyzed the data of niche overlap among species in these three axes (temporal, spatial and trophic using null models. We found a significant overlap within the trophic niche, whereas the overlap for the other axes did not differ from the expected. Based on this result, we discuss the factors acting on the structure of the local lizard community.

  17. Modeling of the ecological niches of the anopheles spp in Ecuador by the use of geo-informatic tools.

    Science.gov (United States)

    Padilla, Oswaldo; Rosas, Pablo; Moreno, Wilson; Toulkeridis, Theofilos

    2017-06-01

    Ecuador in the northwestern edge of South America is struggling by vector-borne diseases with an endemic-epidemic behavior leading to an enormous public health problem. Malaria, which has a cyclicality in its dynamics, is closely related to climatic, ecological and socio-economic phenomena. The main objective of this research has been to compare three different prediction species models, the so-called Maxent, logistic regression and multi criteria evaluation with fuzzy logic, in order to determine the model which best describes the ecological niche of the Anopheles spp species, which transmits malaria within Ecuador. After performing a detailed data collection and data processing, we applied the mentioned models and validated them with a statistical analysis in order to discover that the Maxent model has been the model that best defines the distribution of Anopheles spp within the territory. The determined sites, which are of high strategic value and important for the increasing national development, will now be able to initiate preventive countermeasures based on this study. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. The multi-niche crowding genetic algorithm: Analysis and applications

    Energy Technology Data Exchange (ETDEWEB)

    Cedeno, Walter [Univ. of California, Davis, CA (United States)

    1995-09-01

    The ability of organisms to evolve and adapt to the environment has provided mother nature with a rich and diverse set of species. Only organisms well adapted to their environment can survive from one generation to the next, transferring on the traits, that made them successful, to their offspring. Competition for resources and the ever changing environment drives some species to extinction and at the same time others evolve to maintain the delicate balance in nature. In this disertation we present the multi-niche crowding genetic algorithm, a computational metaphor to the survival of species in ecological niches in the face of competition. The multi-niche crowding genetic algorithm maintains stable subpopulations of solutions in multiple niches in multimodal landscapes. The algorithm introduces the concept of crowding selection to promote mating among members with qirnilar traits while allowing many members of the population to participate in mating. The algorithm uses worst among most similar replacement policy to promote competition among members with similar traits while allowing competition among members of different niches as well. We present empirical and theoretical results for the success of the multiniche crowding genetic algorithm for multimodal function optimization. The properties of the algorithm using different parameters are examined. We test the performance of the algorithm on problems of DNA Mapping, Aquifer Management, and the File Design Problem. Applications that combine the use of heuristics and special operators to solve problems in the areas of combinatorial optimization, grouping, and multi-objective optimization. We conclude by presenting the advantages and disadvantages of the algorithm and describing avenues for future investigation to answer other questions raised by this study.

  19. Intraspecific ecological niche divergence and reproductive shifts foster cytotype displacement and provide ecological opportunity to polyploids.

    Science.gov (United States)

    Karunarathne, Piyal; Schedler, Mara; Martínez, Eric J; Honfi, Ana I; Novichkova, Anastasiia; Hojsgaard, Diego

    2018-05-11

    Niche divergence between polyploids and their lower ploidy progenitors is one of the primary mechanisms fostering polyploid establishment and adaptive divergence. However, within-species chromosomal and reproductive variability have usually been neglected in community ecology and biodiversity analyses even though they have been recognized to play a role in the adaptive diversification of lineages. We used Paspalum intermedium, a grass species with diverging genetic systems (diploidy vs. autopolyploidy, allogamy vs. autogamy and sexuality vs. apomixis), to recognize the causality of biogeographic patterns, adaptation and ecological flexibility of cytotypes. Chromosome counts and flow cytometry were used to characterize within-species genetic systems diversity. Environmental niche modelling was used to evaluate intraspecific ecological attributes associated with environmental and climatic factors and to assess correlations among ploidy, reproductive modes and ecological conditions ruling species' population dynamics, range expansion, adaptation and evolutionary history. Two dominant cytotypes non-randomly distributed along local and regional geographical scales displayed niche differentiation, a directional shift in niche optima and signs of disruptive selection on ploidy-related ecological aptitudes for the exploitation of environmental resources. Ecologically specialized allogamous sexual diploids were found in northern areas associated with higher temperature, humidity and productivity, while generalist autogamous apomictic tetraploids occurred in southern areas, occupying colder and less productive environments. Four localities with a documented shift in ploidy and four mixed populations in a zone of ecological transition revealed an uneven replacement between cytotypes. Polyploidy and contrasting reproductive traits between cytotypes have promoted shifts in niche optima, and increased ecological tolerance and niche divergence. Ecologically specialized diploids

  20. Renewable energies and the poor: niche or nexus?

    International Nuclear Information System (INIS)

    Bhattacharyya, Subhes C.

    2006-01-01

    Renewable energies are considered as an essential element of any strategy for sustainable energy development. The poor in the developing world without access to modern energies are regarded as a major market for renewable energies. This short paper attempts to analyse whether such a niche is backed by any economic logic and whether renewable energy and the poor nexus could be a strategy for success. The paper suggests that contrary to the common belief, the economic logic behind the niche is unsound and that the nexus is not a recipe for success

  1. Evolution of the Jatropha Biofuel Niche in Ghana

    DEFF Research Database (Denmark)

    Nygaard, Ivan; Bolwig, Simon

    spanning the period 1995–2004 and including detailed company case studies. Relating to the MLP framework the factors analysed influencing internal niche processes are alignment of expectations, network formation, and learning and knowledge sharing, while those relating to the GVC framework are value chain......, which contributed to the collapse of the jatropha sector in Ghana and thus to the failure to capitalise on the initially high expectations of biofuel production. We also found a low level of learning and knowledgesharing between jatropha niche actors in Ghana, which, alongside weak public R&D support...

  2. AN ANALYSIS OF FUNDING DECISIONS FOR NICHE AGRICULTURAL PRODUCTS

    OpenAIRE

    HOWARD VAN AUKEN; SHAWN CARRAHER

    2012-01-01

    This paper examines the flow of funds from providers of capital to niche agricultural users of capital. Various programs through the US government, state/local economic development and private agencies work to improve the flow of capital to the niche agricultural sector. However, despite the expansion of programs aimed at providing financial resources to the agricultural sector, many sectors remain poorly served. Previous studies have suggested that agencies need to facilitate the flow of cap...

  3. Unveiling current Guanaco distribution in chile based upon niche structure of phylogeographic lineages: Andean puna to subpolar forests.

    Directory of Open Access Journals (Sweden)

    Benito A González

    Full Text Available Niche description and differentiation at broad geographic scales have been recent major topics in ecology and evolution. Describing the environmental niche structure of sister taxa with known evolutionary trajectories stands out as a useful exercise in understanding niche requirements. Here we model the environmental niche structure and distribution of the recently resolved phylogeography of guanaco (Lama guanicoe lineages on the western slope of the southern Andes. Using a maximum entropy framework, field data, and information on climate, topography, human density, and vegetation cover, we identify differences between the two subspecies (L.g.cacsilensis, L.g.guanicoe and their intermediate-hybrid lineage, that most likely determine the distribution of this species. While aridity seems to be a major factor influencing the distribution at the species-level (annual precipitation <900 mm, we also document important differences in niche specificity for each subspecies, where distribution of Northern lineage is explained mainly by elevation (mean = 3,413 m and precipitation seasonality (mean = 161 mm, hybrid lineage by annual precipitation (mean = 139 mm, and Southern subspecies by annual precipitation (mean = 553 mm, precipitation seasonality (mean = 21 mm and grass cover (mean = 8.2%. Among lineages, we detected low levels of niche overlap: I (Similarity Index = 0.06 and D (Schoener's Similarity Index = 0.01; and higher levels when comparing Northern and Southern subspecies with hybrids lineage ( I = 0.32-0.10 and D = 0.12-0.03, respectively. This suggests that important ecological and/or evolutionary processes are shaping the niche of guanacos in Chile, producing discrepancies when comparing range distribution at the species-level (81,756 km(2 with lineages-level (65,321 km(2. The subspecies-specific description of niche structure is provided here based upon detailed spatial distribution of the lineages of guanacos in Chile. Such description

  4. Exploring Climate Niches of Ponderosa Pine (Pinus ponderosa Douglas ex Lawson) Haplotypes in the Western United States: Implications for Evolutionary History and Conservation.

    Science.gov (United States)

    Shinneman, Douglas J; Means, Robert E; Potter, Kevin M; Hipkins, Valerie D

    2016-01-01

    Ponderosa pine (Pinus ponderosa Douglas ex Lawson) occupies montane environments throughout western North America, where it is both an ecologically and economically important tree species. A recent study using mitochondrial DNA analysis demonstrated substantial genetic variation among ponderosa pine populations in the western U.S., identifying 10 haplotypes with unique evolutionary lineages that generally correspond spatially with distributions of the Pacific (P. p. var. ponderosa) and Rocky Mountain (P. p. var. scopulorum) varieties. To elucidate the role of climate in shaping the phylogeographic history of ponderosa pine, we used nonparametric multiplicative regression to develop predictive climate niche models for two varieties and 10 haplotypes and to hindcast potential distribution of the varieties during the last glacial maximum (LGM), ~22,000 yr BP. Our climate niche models performed well for the varieties, but haplotype models were constrained in some cases by small datasets and unmeasured microclimate influences. The models suggest strong relationships between genetic lineages and climate. Particularly evident was the role of seasonal precipitation balance in most models, with winter- and summer-dominated precipitation regimes strongly associated with P. p. vars. ponderosa and scopulorum, respectively. Indeed, where present-day climate niches overlap between the varieties, introgression of two haplotypes also occurs along a steep clinal divide in western Montana. Reconstructed climate niches for the LGM suggest potentially suitable climate existed for the Pacific variety in the California Floristic province, the Great Basin, and Arizona highlands, while suitable climate for the Rocky Mountain variety may have existed across the southwestern interior highlands. These findings underscore potentially unique phylogeographic origins of modern ponderosa pine evolutionary lineages, including potential adaptations to Pleistocene climates associated with discrete

  5. Exploring Climate Niches of Ponderosa Pine (Pinus ponderosa Douglas ex Lawson Haplotypes in the Western United States: Implications for Evolutionary History and Conservation.

    Directory of Open Access Journals (Sweden)

    Douglas J Shinneman

    Full Text Available Ponderosa pine (Pinus ponderosa Douglas ex Lawson occupies montane environments throughout western North America, where it is both an ecologically and economically important tree species. A recent study using mitochondrial DNA analysis demonstrated substantial genetic variation among ponderosa pine populations in the western U.S., identifying 10 haplotypes with unique evolutionary lineages that generally correspond spatially with distributions of the Pacific (P. p. var. ponderosa and Rocky Mountain (P. p. var. scopulorum varieties. To elucidate the role of climate in shaping the phylogeographic history of ponderosa pine, we used nonparametric multiplicative regression to develop predictive climate niche models for two varieties and 10 haplotypes and to hindcast potential distribution of the varieties during the last glacial maximum (LGM, ~22,000 yr BP. Our climate niche models performed well for the varieties, but haplotype models were constrained in some cases by small datasets and unmeasured microclimate influences. The models suggest strong relationships between genetic lineages and climate. Particularly evident was the role of seasonal precipitation balance in most models, with winter- and summer-dominated precipitation regimes strongly associated with P. p. vars. ponderosa and scopulorum, respectively. Indeed, where present-day climate niches overlap between the varieties, introgression of two haplotypes also occurs along a steep clinal divide in western Montana. Reconstructed climate niches for the LGM suggest potentially suitable climate existed for the Pacific variety in the California Floristic province, the Great Basin, and Arizona highlands, while suitable climate for the Rocky Mountain variety may have existed across the southwestern interior highlands. These findings underscore potentially unique phylogeographic origins of modern ponderosa pine evolutionary lineages, including potential adaptations to Pleistocene climates associated

  6. Ontogenetic specialism in predators with multiple niche shifts prevents predator population recovery and establishment

    NARCIS (Netherlands)

    van Leeuwen, A.; Huss, M.; Gårdmark, A.; de Roos, A.M.

    2014-01-01

    The effects of ontogenetic niche shifts on community structure and dynamics are underexplored, despite the occurrence of such shifts in the majority of animal species. We studied the form of niche shifts in a predator that exhibits multiple ontogenetic niche shifts, and analyzed how this life

  7. ECOLOGICAL NICHE MODELING AND WILDLIFE MANAGEMENT UNITS (UMAS: AN APPLICATION TO DEER IN CAMPECHE, MÉXICO

    Directory of Open Access Journals (Sweden)

    Tania Escalante

    2013-08-01

    Full Text Available The Units for the Conservation, Management and Sustainable Use of Wildlife (UMAs are instruments of conservation and management of specific species in Mexico. UMAs represent in southeastern Mexico an important way for deer management, but they have major problems related to the monitoring of species. In this paper, we propose a methodology based on the use of a ‘niche centroid approach’ for estimating ecological distances to the niche centroid in order to produce distribution maps containing information on the potential relative abundance of species to evaluate the capability of UMAs to maintain populations of deers. We modeled the abundance for Mazama temama, M. pandora and Odocoileus virginianus on the state of Campeche, Mexico. Our predictions of areas with most abundance of deer coincided with reports from literature. We identified the UMAs “Ik Balam” and “Ejido Carlos Cano Cruz” as areas with high proportion of suitable environment, while UMAs “Betito y Lupita”, “El Huanal”, “Puh”, “Refugio faunístico Jalotum”, “Ría Lagartos-Ría Celestun” and “Yocol Cab Balam” have not environmental conditions adequate to maintain deer populations. Although this is a preliminary study, it can be a starting point to establish institutional standards for the management of species.

  8. Mapping the zoonotic niche of Ebola virus disease in Africa

    Science.gov (United States)

    Pigott, David M; Golding, Nick; Mylne, Adrian; Huang, Zhi; Henry, Andrew J; Weiss, Daniel J; Brady, Oliver J; Kraemer, Moritz UG; Smith, David L; Moyes, Catherine L; Bhatt, Samir; Gething, Peter W; Horby, Peter W; Bogoch, Isaac I; Brownstein, John S; Mekaru, Sumiko R; Tatem, Andrew J; Khan, Kamran; Hay, Simon I

    2014-01-01

    Ebola virus disease (EVD) is a complex zoonosis that is highly virulent in humans. The largest recorded outbreak of EVD is ongoing in West Africa, outside of its previously reported and predicted niche. We assembled location data on all recorded zoonotic transmission to humans and Ebola virus infection in bats and primates (1976–2014). Using species distribution models, these occurrence data were paired with environmental covariates to predict a zoonotic transmission niche covering 22 countries across Central and West Africa. Vegetation, elevation, temperature, evapotranspiration, and suspected reservoir bat distributions define this relationship. At-risk areas are inhabited by 22 million people; however, the rarity of human outbreaks emphasises the very low probability of transmission to humans. Increasing population sizes and international connectivity by air since the first detection of EVD in 1976 suggest that the dynamics of human-to-human secondary transmission in contemporary outbreaks will be very different to those of the past. DOI: http://dx.doi.org/10.7554/eLife.04395.001 PMID:25201877

  9. The muscle stem cell niche : regulation of satellite cells during regeneration

    NARCIS (Netherlands)

    Boonen, K.J.M.; Post, M.J.

    2008-01-01

    Satellite cells are considered to be adult skeletal muscle stem cells. Their ability to regenerate large muscle defects is highly dependent on their specific niche. When these cells are cultured in vitro, the loss of this niche leads to a loss of proliferative capacity and defective regeneration

  10. CROSS DRIFT ALCOVE/NICHE UTILITIES ANALYSIS

    International Nuclear Information System (INIS)

    S. Goodin

    1999-01-01

    The purpose of this analysis is to provide the design basis and general arrangement requirements of the non-potable water, waste water, compressed air and ventilation (post excavation) utilities required in support of the Cross Drift alcoves and niches

  11. Making Blood: The Haematopoietic Niche throughout Ontogeny

    Directory of Open Access Journals (Sweden)

    Mohammad A. Al-Drees

    2015-01-01

    Full Text Available Approximately one-quarter of all cells in the adult human body are blood cells. The haematopoietic system is therefore massive in scale and requires exquisite regulation to be maintained under homeostatic conditions. It must also be able to respond when needed, such as during infection or following blood loss, to produce more blood cells. Supporting cells serve to maintain haematopoietic stem and progenitor cells during homeostatic and pathological conditions. This coalition of supportive cell types, organised in specific tissues, is termed the haematopoietic niche. Haematopoietic stem and progenitor cells are generated in a number of distinct locations during mammalian embryogenesis. These stem and progenitor cells migrate to a variety of anatomical locations through the conceptus until finally homing to the bone marrow shortly before birth. Under stress, extramedullary haematopoiesis can take place in regions that are typically lacking in blood-producing activity. Our aim in this review is to examine blood production throughout the embryo and adult, under normal and pathological conditions, to identify commonalities and distinctions between each niche. A clearer understanding of the mechanism underlying each haematopoietic niche can be applied to improving ex vivo cultures of haematopoietic stem cells and potentially lead to new directions for transplantation medicine.

  12. Macroevolutionary diversification with limited niche disparity in a species-rich lineage of cold-climate lizards.

    Science.gov (United States)

    Reaney, Ashley M; Saldarriaga-Córdoba, Mónica; Pincheira-Donoso, Daniel

    2018-02-06

    Life diversifies via adaptive radiation when natural selection drives the evolution of ecologically distinct species mediated by their access to novel niche space, or via non-adaptive radiation when new species diversify while retaining ancestral niches. However, while cases of adaptive radiation are widely documented, examples of non-adaptively radiating lineages remain rarely observed. A prolific cold-climate lizard radiation from South America (Phymaturus), sister to a hyper-diverse adaptive radiation (Liolaemus), has extensively diversified phylogenetically and geographically, but with exceptionally minimal ecological and life-history diversification. This lineage, therefore, may offer unique opportunities to investigate the non-adaptive basis of diversification, and in combination with Liolaemus, to cover the whole spectrum of modes of diversification predicted by theory, from adaptive to non-adaptive. Using phylogenetic macroevolutionary modelling performed on a newly created 58-species molecular tree, we establish the tempo and mode of diversification in the Phymaturus radiation. Lineage accumulation in Phymaturus opposes a density-dependent (or 'niche-filling') process of diversification. Concurrently, we found that body size diversification is better described by an Ornstein-Uhlenbeck evolutionary model, suggesting stabilizing selection as the mechanism underlying niche conservatism (i.e., maintaining two fundamental size peaks), and which has predominantly evolved around two major adaptive peaks on a 'Simpsonian' adaptive landscape. Lineage diversification of the Phymaturus genus does not conform to an adaptive radiation, as it is characterised by a constant rate of species accumulation during the clade's history. Their strict habitat requirements (rocky outcrops), predominantly invariant herbivory, and especially the constant viviparous reproduction across species have likely limited their opportunities for adaptive diversifications throughout novel

  13. Novel therapeutic strategies to target leukemic cells that hijack compartmentalized continuous hematopoietic stem cell niches.

    Science.gov (United States)

    Hira, Vashendriya V V; Van Noorden, Cornelis J F; Carraway, Hetty E; Maciejewski, Jaroslaw P; Molenaar, Remco J

    2017-08-01

    Acute myeloid leukemia and acute lymphoblastic leukemia cells hijack hematopoietic stem cell (HSC) niches in the bone marrow and become leukemic stem cells (LSCs) at the expense of normal HSCs. LSCs are quiescent and resistant to chemotherapy and can cause relapse of the disease. HSCs in niches are needed to generate blood cell precursors that are committed to unilineage differentiation and eventually production of mature blood cells, including red blood cells, megakaryocytes, myeloid cells and lymphocytes. Thus far, three types of HSC niches are recognized: endosteal, reticular and perivascular niches. However, we argue here that there is only one type of HSC niche, which consists of a periarteriolar compartment and a perisinusoidal compartment. In the periarteriolar compartment, hypoxia and low levels of reactive oxygen species preserve the HSC pool. In the perisinusoidal compartment, hypoxia in combination with higher levels of reactive oxygen species enables proliferation of progenitor cells and their mobilization into the circulation. Because HSC niches offer protection to LSCs against chemotherapy, we review novel therapeutic strategies to inhibit homing of LSCs in niches for the prevention of dedifferentiation of leukemic cells into LSCs and to stimulate migration of leukemic cells out of niches. These strategies enhance differentiation and proliferation and thus sensitize leukemic cells to chemotherapy. Finally, we list clinical trials of therapies that tackle LSCs in HSC niches to circumvent their protection against chemotherapy. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  14. Self-organized amniogenesis by human pluripotent stem cells in a biomimetic implantation-like niche

    Science.gov (United States)

    Shao, Yue; Taniguchi, Kenichiro; Gurdziel, Katherine; Townshend, Ryan F.; Xue, Xufeng; Yong, Koh Meng Aw; Sang, Jianming; Spence, Jason R.; Gumucio, Deborah L.; Fu, Jianping

    2017-04-01

    Amniogenesis--the development of amnion--is a critical developmental milestone for early human embryogenesis and successful pregnancy. However, human amniogenesis is poorly understood due to limited accessibility to peri-implantation embryos and a lack of in vitro models. Here we report an efficient biomaterial system to generate human amnion-like tissue in vitro through self-organized development of human pluripotent stem cells (hPSCs) in a bioengineered niche mimicking the in vivo implantation environment. We show that biophysical niche factors act as a switch to toggle hPSC self-renewal versus amniogenesis under self-renewal-permissive biochemical conditions. We identify a unique molecular signature of hPSC-derived amnion-like cells and show that endogenously activated BMP-SMAD signalling is required for the amnion-like tissue development by hPSCs. This study unveils the self-organizing and mechanosensitive nature of human amniogenesis and establishes the first hPSC-based model for investigating peri-implantation human amnion development, thereby helping advance human embryology and reproductive medicine.

  15. Environmental filtering drives the shape and breadth of the seed germination niche in coastal plant communities.

    Science.gov (United States)

    Fernández-Pascual, Eduardo; Pérez-Arcoiza, Adrián; Prieto, José Alberto; Díaz, Tomás E

    2017-05-01

    A phylogenetic comparative analysis of the seed germination niche was conducted in coastal plant communities of western Europe. Two hypotheses were tested, that (1) the germination niche shape (i.e. the preference for a set of germination cues as opposed to another) would differ between beaches and cliffs to prevent seedling emergence in the less favourable season (winter and summer, respectively); and (2) the germination niche breadth (i.e. the amplitude of germination cues) would be narrower in the seawards communities, where environmental filtering is stronger. Seeds of 30 specialist species of coastal plant communities were collected in natural populations of northern Spain. Their germination was measured in six laboratory treatments based on field temperatures. Germination niche shape was estimated as the best germination temperature. Germination niche breadth was calculated using Pielou's evenness index. Differences between plant communities in their germination niche shape and breadth were tested using phylogenetic generalized least squares regression (PGLS). Germination niche shape differed between communities, being warm-cued in beaches (best germination temperature = 20 °C) and cold-cued in cliffs (14 °C). Germination niche was narrowest in seawards beaches (Pielou's index = 0·89) and broadest in landwards beaches (0·99). Cliffs had an intermediate germination niche breadth (0·95). The relationship between niche and plant community had a positive phylogenetic signal for shape (Pagel's λ = 0·64) and a negative one for breadth (Pagel's λ = -1·71). Environmental filters shape the germination niche to prevent emergence in the season of highest threat for seedling establishment. The germination niche breadth is narrower in the communities with stronger environmental filters, but only in beaches. This study provides empirical support to a community-level generalization of the hypotheses about the environmental drivers of the germination

  16. Occupy the Financial Niche: Saturation and Crisis

    Science.gov (United States)

    Purica, Ionut

    The model presented is one theoretical approach within a broader research program that could verify the nonlinear conjectures made, such that to quantify and predict potential discontinuous behaviour. In this case, the crisis behaviour associated with financial funds reallocation among various credit instruments, described as memes with the sense of Dawkins, is shown to be of discontinuous nature stemming from a logistic penetration in the behaviour niche. Actually the logistic penetration is typical in creating cyclic behaviour of economic structures as shown by Marchetti and others from IIASA. A Fokker-Planck equation description results in a stationary solution having a bifurcation like solution with evolution trajectories on a `cusp' type catastrophe that may describe discontinuous decision behaviour.

  17. Differential cytokine contributions of perivascular haematopoietic stem cell niches.

    Science.gov (United States)

    Asada, Noboru; Kunisaki, Yuya; Pierce, Halley; Wang, Zichen; Fernandez, Nicolas F; Birbrair, Alexander; Ma'ayan, Avi; Frenette, Paul S

    2017-03-01

    Arterioles and sinusoids of the bone marrow (BM) are accompanied by stromal cells that express nerve/glial antigen 2 (NG2) and leptin receptor (LepR), and constitute specialized niches that regulate quiescence and proliferation of haematopoietic stem cells (HSCs). However, how niche cells differentially regulate HSC functions remains unknown. Here, we show that the effects of cytokines regulating HSC functions are dependent on the producing cell sources. Deletion of chemokine C-X-C motif ligand 12 (Cxcl12) or stem cell factor (Scf) from all perivascular cells marked by nestin-GFP dramatically depleted BM HSCs. Selective Cxcl12 deletion from arteriolar NG2 + cells, but not from sinusoidal LepR + cells, caused HSC reductions and altered HSC localization in BM. By contrast, deletion of Scf in LepR + cells, but not NG2 + cells, led to reductions in BM HSC numbers. These results uncover distinct contributions of cytokines derived from perivascular cells in separate vascular niches to HSC maintenance.

  18. Biogeochemical and Ecomorphological Niche Segregation of Mediterranean Woody Species along a Local Gradient

    OpenAIRE

    Enrique G. de la Riva; Enrique G. de la Riva; Teodoro Marañón; Cyrille Violle; Rafael Villar; Ignacio M. Pérez-Ramos

    2017-01-01

    According with niche theory the species are specialized in different ecological niches, being able to coexist as result of a differential use of resources. In this context, the biogeochemical niche hypothesis proposes that species have an optimal elemental composition which results from the link between the chemical and morphological traits for the optimum plant functioning. Thus, and attending to the limiting similarity concept, different elemental composition and plant structure among co-oc...

  19. Niche suitability affects development: skull asymmetry increases in less suitable areas.

    Directory of Open Access Journals (Sweden)

    Renan Maestri

    Full Text Available For conservation purposes, it is important to take into account the suitability of a species to particular habitats; this information may predict the long-term survival of a species. In this sense, morphological measures of developmental stress, such as fluctuating asymmetry, can be proxies for an individual's performance in different regions. In this study, we conducted tests to determine whether areas with different levels of suitability for a species (generated by ecological niche models were congruent with morphological markers that reflect environmental stress and morphological variance. We generated a Maxent niche model and compared the suitability assessments of several areas with the skull morphology data (fluctuating asymmetry and morphological disparity of populations of the Atlantic forest endemic to Brazil rodent Akodon cursor. Our analyses showed a significant negative relationship between suitability levels and fluctuating asymmetry levels, which indicates that in less suitable areas, the individuals experience numerous disturbances during skull ontogeny. We have not found an association between morphological variance and environmental suitability. As expected, these results suggest that in environments with a lower suitability, developmental stress is increased. Such information is helpful in the understanding of the species evolution and in the selection of priority areas for the conservation of species.

  20. Protection from UV light is an evolutionarily conserved feature of the haematopoietic niche

    Science.gov (United States)

    Kapp, Friedrich G.; Perlin, Julie R.; Hagedorn, Elliott J.; Gansner, John M.; Schwarz, Daniel E.; O'Connell, Lauren A.; Johnson, Nicholas; Amemiya, Chris; Fisher, David E.; Wolfle, Ute; Trompouki, Eirini; Niemeyer, Charlotte M.; Driever, Wolfgang; Zon, Leonard I.

    2018-01-01

    Haematopoietic stem and progenitor cells (HSPCs) require a specific microenvironment, the haematopoietic niche, which regulates HSPC behaviour. The location of this niche varies across species, but the evolutionary pressures that drive HSPCs to different microenvironments remain unknown. The niche is located in the bone marrow in adult mammals, whereas it is found in other locations in non-mammalian vertebrates, for example, in the kidney marrow in teleost fish. Here we show that a melanocyte umbrella above the kidney marrow protects HSPCs against ultraviolet light in zebrafish. Because mutants that lack melanocytes have normal steady-state haematopoiesis under standard laboratory conditions, we hypothesized that melanocytes above the stem cell niche protect HSPCs against ultraviolet-light-induced DNA damage. Indeed, after ultraviolet-light irradiation, unpigmented larvae show higher levels of DNA damage in HSPCs, as indicated by staining of cyclobutane pyrimidine dimers and have reduced numbers of HSPCs, as shown by cmyb (also known as myb) expression. The umbrella of melanocytes associated with the haematopoietic niche is highly evolutionarily conserved in aquatic animals, including the sea lamprey, a basal vertebrate. During the transition from an aquatic to a terrestrial environment, HSPCs relocated into the bone marrow, which is protected from ultraviolet light by the cortical bone around the marrow. Our studies reveal that melanocytes above the haematopoietic niche protect HSPCs from ultraviolet-light-induced DNA damage in aquatic vertebrates and suggest that during the transition to terrestrial life, ultraviolet light was an evolutionary pressure affecting the location of the haematopoietic niche.

  1. Evolutionary dynamics of ecological niche in three Rhinogobio fishes from the upper Yangtze River inferred from morphological traits

    Science.gov (United States)

    Wang, Meirong; Liu, Fei; Lin, Pengcheng; Yang, Shaorong; Liu, Huanzhang

    2015-01-01

    In the past decades, it has been debated whether ecological niche should be conserved among closely related species (phylogenetic niche conservatism, PNC) or largely divergent (traditional ecological niche theory and ecological speciation) and whether niche specialist and generalist might remain in equilibrium or niche generalist could not appear. In this study, we employed morphological traits to describe ecological niche and test whether different niche dimensions exhibit disparate evolutionary patterns. We conducted our analysis on three Rhinogobio fish species (R. typus,R. cylindricus, and R. ventralis) from the upper Yangtze River, China. Among the 32 measured morphological traits except body length, PCA extracted the first four principal components with their loading scores >1.000. To find the PNC among species, Mantel tests were conducted with the Euclidean distances calculated from the four principal components (representing different niche dimensions) against the pairwise distances calculated from mitochondrial cytochrome b sequence variations. The results showed that the second and the third niche dimension, both related to swimming ability and behavior, exhibited phylogenetic conservatism. Further comparison on niche breadth among these three species revealed that the fourth dimension of R. typus showed the greatest width, indicating that this dimension exhibited niche generalism. In conclusion, our results suggested that different niche dimensions could show different evolutionary dynamic patterns: they may exhibit PNC or not, and some dimensions may evolve generalism. PMID:25691981

  2. Time- and depth-wise trophic niche shifts in Antarctic benthos.

    Directory of Open Access Journals (Sweden)

    Edoardo Calizza

    Full Text Available Climate change is expected to affect resource-consumer interactions underlying stability in polar food webs. Polar benthic organisms have adapted to the marked seasonality characterising their habitats by concentrating foraging and reproductive activity in summer months, when inputs from sympagic and pelagic producers increase. While this enables the persistence of biodiverse food webs, the mechanisms underlying changes in resource use and nutrient transfer are poorly understood. Thus, our understanding of how temporal and spatial variations in the supply of resources may affect food web structure and functioning is limited. By means of C and N isotopic analyses of two key Antarctic benthic consumers (Adamussium colbecki, Bivalvia, and Sterechinus neumayeri, Echinoidea and Bayesian mixing models, we describe changes in trophic niche and nutrient transfer across trophic levels associated with the long- and short-term diet and body size of specimens sampled in midsummer in both shallow and deep waters. Samplings occurred soon after the sea-ice broke up at Tethys Bay, an area characterised by extreme seasonality in sea-ice coverage and productivity in the Ross Sea. In the long term, the trophic niche was broader and variation between specimens was greater, with intermediate-size specimens generally consuming a higher number of resources than small and large specimens. The coupling of energy channels in the food web was consequently more direct than in the short term. Sediment and benthic algae were more frequently consumed in the long term, before the sea-ice broke up, while consumers specialised on sympagic algae and plankton in the short term. Regardless of the time scale, sympagic algae were more frequently consumed in shallow waters, while plankton was more frequently consumed in deep waters. Our results suggest a strong temporal relationship between resource availability and the trophic niche of benthic consumers in Antarctica. Potential

  3. Niche restriction and conservatism in a neotropical psittacine: the case of the Puerto Rican parrot

    Science.gov (United States)

    White, Thomas H.; Collazo, Jaime A.; Dinsmore, Stephen J.; Llerandi-Roman, I. C.

    2014-01-01

    The factors which govern species‘ distribution and abundance are myriad, and together constitute the ecological niche of a given species. Because abiotic factors are arguably the most profound of the factors influencing niche boundaries and thus, species distributions, substantial changes in either climatic or habitat-related parameters can be expected to produce interrelated and profound niche shifts. Habitat loss and degradation can also effectively induce a de facto climate change by forcing populations to relocate to environmentally suboptimal habitats. Populations experiencing niche shifts due to range restrictions and geographic isolation become subject to a suite of factors that may act synergistically to amplify deleterious ecological effects of habitat loss. These factors tend to exert a greater influence on populations of rare or endemic species with inherently restricted ranges. The Puerto Rican parrot (Amazona vittata) is an example of a tropical, insular, endemic and critically-endangered species that has suffered from extensive habitat loss and degradation over the past century, resulting in a single relict wild population restricted for more than 70 years to the montane rainforest of the Luquillo Mountains in northeastern Puerto Rico. In this chapter, we examine the current ecological situation of this geographically and demographically isolated parrot population by reviewing the history of landscape-level changes in and around the Luquillo Mountains, and concurrent biotic and abiotic limiting factors in relation to both historical population trajectory and current prognosis for species recovery. We used a decade (2000-2009) of empirical data on parrot fledgling survival together with long-term climatological data to model effects of local climate on fledgling survival and gain insights into its influence on population growth. We also modeled hypothetical survival of parrot fledglings in the lowlands surrounding the Luquillo Mountains, areas

  4. Using niche-based modelling to assess the impact of climate change on tree functional diversity in Europe

    DEFF Research Database (Denmark)

    Thuiller, Wilfried; Lavorel, Sandra; Sykes, Martin T.

    2006-01-01

    Rapid anthropogenic climate change is already affecting species distributions and ecosystem functioning worldwide. We applied niche-based models to analyse the impact of climate change on tree species and functional diversity in Europe. Present-day climate was used to predict the distributions...... of 122 tree species from different functional types (FT). We then explored projections of future distributions under one climate scenario for 2080, considering two alternative dispersal assumptions: no dispersal and unlimited dispersal. The species-rich broadleaved deciduous group appeared to play a key...... role in the future of different European regions. Temperate areas were projected to lose both species richness and functional diversity due to the loss of broadleaved deciduous trees. These were projected to migrate to boreal forests, thereby increasing their species richness and functional diversity...

  5. Notch signaling mediates the age-associated decrease in adhesion of germline stem cells to the niche.

    Directory of Open Access Journals (Sweden)

    Chen-Yuan Tseng

    2014-12-01

    Full Text Available Stem cells have an innate ability to occupy their stem cell niche, which in turn, is optimized to house stem cells. Organ aging is associated with reduced stem cell occupancy in the niche, but the mechanisms involved are poorly understood. Here, we report that Notch signaling is increased with age in Drosophila female germline stem cells (GSCs, and this results in their removal from the niche. Clonal analysis revealed that GSCs with low levels of Notch signaling exhibit increased adhesiveness to the niche, thereby out-competing their neighbors with higher levels of Notch; adhesiveness is altered through regulation of E-cadherin expression. Experimental enhancement of Notch signaling in GSCs hastens their age-dependent loss from the niche, and such loss is at least partially mediated by Sex lethal. However, disruption of Notch signaling in GSCs does not delay GSC loss during aging, and nor does it affect BMP signaling, which promotes self-renewal of GSCs. Finally, we show that in contrast to GSCs, Notch activation in the niche (which maintains niche integrity, and thus mediates GSC retention is reduced with age, indicating that Notch signaling regulates GSC niche occupancy both intrinsically and extrinsically. Our findings expose a novel role of Notch signaling in controlling GSC-niche adhesion in response to aging, and are also of relevance to metastatic cancer cells, in which Notch signaling suppresses cell adhesion.

  6. Geometrical model for the electron

    International Nuclear Information System (INIS)

    El-Sherbini, T.M.

    1985-07-01

    A model for an electron of finite dimensions is proposed. This model disregards the concept of electronic charge and leads to Bohr's frequency formula for the hydrogen atom and to Maxwell's equations for electromagnetic fields. The stability of a free electron under the action of centrifugal and transverse forces is discussed. (author)

  7. Individual diet variation in a marine fish assemblage: Optimal Foraging Theory, Niche Variation Hypothesis and functional identity

    Science.gov (United States)

    Cachera, M.; Ernande, B.; Villanueva, M. C.; Lefebvre, S.

    2017-02-01

    Individual diet variation (i.e. diet variation among individuals) impacts intra- and inter-specific interactions. Investigating its sources and relationship with species trophic niche organization is important for understanding community structure and dynamics. Individual diet variation may increase with intra-specific phenotypic (or "individual state") variation and habitat variability, according to Optimal Foraging Theory (OFT), and with species trophic niche width, according to the Niche Variation Hypothesis (NVH). OFT proposes "proximate sources" of individual diet variation such as variations in habitat or size whereas NVH relies on "ultimate sources" related to the competitive balance between intra- and inter-specific competitions. The latter implies as a corollary that species trophic niche overlap, taken as inter-specific competition measure, decreases as species niche width and individual niche variation increase. We tested the complementary predictions of OFT and NVH in a marine fish assemblage using stomach content data and associated trophic niche metrics. The NVH predictions were tested between species of the assemblage and decomposed into a between- and a within-functional group component to assess the potential influence of species' ecological function. For most species, individual diet variation and niche overlap were consistently larger than expected. Individual diet variation increased with intra-specific variability in individual state and habitat, as expected from OFT. It also increased with species niche width but in compliance with the null expectation, thus not supporting the NVH. In contrast, species niche overlap increased significantly less than null expectation with both species niche width and individual diet variation, supporting NVH corollary. The between- and within-functional group components of the NVH relationships were consistent with those between species at the assemblage level. Changing the number of prey categories used to

  8. Individual and species-specific traits explain niche size and functional role in spiders as generalist predators.

    Science.gov (United States)

    Sanders, Dirk; Vogel, Esther; Knop, Eva

    2015-01-01

    The function of a predator within a community is greatly based on its trophic niche, that is the number and the strength of feeding links. In generalist predators, which feed on a wide range of prey, the size and position of the trophic niche is likely determined by traits such as hunting mode, the stratum they occur in, their body size and age. We used stable isotope analyses ((13)C and (15)N) to measure the trophic niche size of nine spider species within a forest hedge community and tested for species traits and individual traits that influence stable isotope enrichment, niche size and resource use. The spiders Enoplognatha, Philodromus, Floronia, and Heliophanus had large isotopic niches, which correspond to a more generalistic feeding behaviour. In contrast, Araneus, Metellina and Agelena, as top predators in the system, had rather narrow niches. We found a negative correlation between trophic position and niche size. Differences in trophic position in spiders were explained by body size, hunting modes and stratum, while niche size was influenced by hunting mode. In Philodromus, the size of the trophic niche increased significantly with age. Fitting spiders to functional groups according to their mean body size, hunting mode and their habitat domain resulted in largely separated niches, which indicates that these traits are meaningful for separating functional entities in spiders. Functional groups based on habitat domain (stratum) caught the essential functional differences between the species with species higher up in the vegetation feeding on flying insects and herb and ground species also preying on forest floor decomposers. Interestingly, we found a gradient from large species using a higher habitat domain and having a smaller niche to smaller species foraging closer to the ground and having a larger niche. This shows that even within generalist predators, such as spiders, there is a gradient of specialism that can be predicted by functional traits.

  9. Convergent and divergent learning in photovoltaic pilot projects and subsequent niche development

    NARCIS (Netherlands)

    Mierlo, van B.

    2012-01-01

    A proposed strategy to facilitate the use and development of radical new sustainable technologies is the creation of niches. Learning in these niches and the social embedding of learning experiences can stimulate changes in existing sociotechnological regimes. Pilot projects in which new

  10. Niche construction through phenological plasticity: life history dynamics and ecological consequences.

    Science.gov (United States)

    Donohue, Kathleen

    2005-04-01

    The ability of an organism to alter the environment that it experiences has been termed 'niche construction'. Plants have several ways whereby they can determine the environment to which they are exposed at different life stages. This paper discusses three of these: plasticity in dispersal, flowering timing and germination timing. It reviews pathways through which niche construction alters evolutionary and ecological trajectories by altering the selective environment to which organisms are exposed, the phenotypic expression of plastic characters, and the expression of genetic variation. It provides examples whereby niche construction creates positive or negative feedbacks between phenotypes and environments, which in turn cause novel evolutionary constraints and novel life-history expression. Copyright New Phytologist (2005).

  11. Fuel cells niche market applications and design studies

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-07-01

    Mainstream fuel cell markets such as stationary power and transport propulsion have already received considerable attention. However, the niche areas considered in this report also offer considerable markets that are considered potentially ready for exploitation. This report examines those markets and considers the broad issues for exploitation. This programme of work has been funded under the DTI's Advanced Fuel Cell Programme. The overall aim of this project was to identify and evaluate niche market applications that have the potential to provide early commercially competitive market opportunities for fuel cell systems. Battery replacement, portable, mobile auxiliary power and stationary applications for non-standard generation are covered. (author)

  12. Northern glacial refugia and altitudinal niche divergence shape genome-wide differentiation in the emerging plant model Arabidopsis arenosa

    Czech Academy of Sciences Publication Activity Database

    Kolář, Filip; Fuxová, G.; Záveská, E.; Nagano, A. J.; Hyklová, L.; Lučanová, Magdalena; Kudoh, H.; Marhold, K.

    2016-01-01

    Roč. 25, č. 16 (2016), s. 3929-3949 ISSN 0962-1083 Institutional support: RVO:67985939 Keywords : approximate Bayesian computatuion * niche differentiation * phytogeography * Arabidopsis Subject RIV: EF - Botanics Impact factor: 6.086, year: 2016

  13. Are neural crest stem cells the missing link between hematopoietic and neurogenic niches?

    Directory of Open Access Journals (Sweden)

    Cécile eCoste

    2015-06-01

    Full Text Available Hematopoietic niches are defined as cellular and molecular microenvironments that regulate hematopoietic stem cell (HSC function together with stem cell autonomous mechanisms. Many different cell types have been characterized as contributors to the formation of HSC niches, such as osteoblasts, endothelial cells, Schwann cells, and mesenchymal progenitors. These mesenchymal progenitors have themselves been classified as CXC chemokine ligand (CXCL12-abundant reticular (CAR cells, stem cell factor expressing cells, or nestin-positive mesenchymal stem cells (MSCs, which have been recently identified as neural crest-derived cells (NCSCs. Together, these cells are spatially associated with HSCs and believed to provide appropriate microenvironments for HSC self-renewal, differentiation, mobilization and hibernation both by cell-to-cell contact and soluble factors. Interestingly, it appears that regulatory pathways governing the hematopoietic niche homeostasis are operating in the neurogenic niche as well. Therefore, this review paper aims to compare both the regulation of hematopoietic and neurogenic niches, in order to highlight the role of NCSCs and nervous system components in the development and the regulation of the hematopoietic system.

  14. Are neural crest stem cells the missing link between hematopoietic and neurogenic niches?

    Science.gov (United States)

    Coste, Cécile; Neirinckx, Virginie; Gothot, André; Wislet, Sabine; Rogister, Bernard

    2015-01-01

    Hematopoietic niches are defined as cellular and molecular microenvironments that regulate hematopoietic stem cell (HSC) function together with stem cell autonomous mechanisms. Many different cell types have been characterized as contributors to the formation of HSC niches, such as osteoblasts, endothelial cells, Schwann cells, and mesenchymal progenitors. These mesenchymal progenitors have themselves been classified as CXC chemokine ligand (CXCL) 12-abundant reticular (CAR) cells, stem cell factor expressing cells, or nestin-positive mesenchymal stem cells (MSCs), which have been recently identified as neural crest-derived cells (NCSCs). Together, these cells are spatially associated with HSCs and believed to provide appropriate microenvironments for HSC self-renewal, differentiation, mobilization and hibernation both by cell-cell contact and soluble factors. Interestingly, it appears that regulatory pathways governing the hematopoietic niche homeostasis are operating in the neurogenic niche as well. Therefore, this review paper aims to compare both the regulation of hematopoietic and neurogenic niches, in order to highlight the role of NCSCs and nervous system components in the development and the regulation of the hematopoietic system.

  15. Ecological niche dimensionality and the evolutionary diversification of stick insects.

    Directory of Open Access Journals (Sweden)

    Patrik Nosil

    Full Text Available The degree of phenotypic divergence and reproductive isolation between taxon pairs can vary quantitatively, and often increases as evolutionary divergence proceeds through various stages, from polymorphism to population differentiation, ecotype and race formation, speciation, and post-speciational divergence. Although divergent natural selection promotes divergence, it does not always result in strong differentiation. For example, divergent selection can fail to complete speciation, and distinct species pairs sometimes collapse ('speciation in reverse'. Widely-discussed explanations for this variability concern genetic architecture, and the geographic arrangement of populations. A less-explored possibility is that the degree of phenotypic and reproductive divergence between taxon pairs is positively related to the number of ecological niche dimensions (i.e., traits subject to divergent selection. Some data supporting this idea stem from laboratory experimental evolution studies using Drosophila, but tests from nature are lacking. Here we report results from manipulative field experiments in natural populations of herbivorous Timema stick insects that are consistent with this 'niche dimensionality' hypothesis. In such insects, divergent selection between host plants might occur for cryptic colouration (camouflage to evade visual predation, physiology (to detoxify plant chemicals, or both of these niche dimensions. We show that divergent selection on the single niche dimension of cryptic colouration can result in ecotype formation and intermediate levels of phenotypic and reproductive divergence between populations feeding on different hosts. However, greater divergence between a species pair involved divergent selection on both niche dimensions. Although further replication of the trends reported here is required, the results suggest that dimensionality of selection may complement genetic and geographic explanations for the degree of

  16. Megakaryocytes promote murine osteoblastic HSC niche expansion and stem cell engraftment after radioablative conditioning.

    Science.gov (United States)

    Olson, Timothy S; Caselli, Anna; Otsuru, Satoru; Hofmann, Ted J; Williams, Richard; Paolucci, Paolo; Dominici, Massimo; Horwitz, Edwin M

    2013-06-27

    Successful hematopoietic stem cell (HSC) transplantation requires donor HSC engraftment within specialized bone marrow microenvironments known as HSC niches. We have previously reported a profound remodeling of the endosteal osteoblastic HSC niche after total body irradiation (TBI), defined as relocalization of surviving megakaryocytes to the niche site and marked expansion of endosteal osteoblasts. We now demonstrate that host megakaryocytes function critically in expansion of the endosteal niche after preparative radioablation and in the engraftment of donor HSC. We show that TBI-induced migration of megakaryocytes to the endosteal niche depends on thrombopoietin signaling through the c-MPL receptor on megakaryocytes, as well as CD41 integrin-mediated adhesion. Moreover, niche osteoblast proliferation post-TBI required megakaryocyte-secreted platelet-derived growth factor-BB. Furthermore, blockade of c-MPL-dependent megakaryocyte migration and function after TBI resulted in a significant decrease in donor HSC engraftment in primary and competitive secondary transplantation assays. Finally, we administered thrombopoietin to mice beginning 5 days before marrow radioablation and ending 24 hours before transplant to enhance megakaryocyte function post-TBI, and found that this strategy significantly enhanced donor HSC engraftment, providing a rationale for improving hematopoietic recovery and perhaps overall outcome after clinical HSC transplantation.

  17. Ecological divergence and conservatism: spatiotemporal patterns of niche evolution in a genus of livebearing fishes (Poeciliidae: Xiphophorus).

    Science.gov (United States)

    Culumber, Zachary W; Tobler, Michael

    2016-02-19

    Ecological factors often have a strong impact on spatiotemporal patterns of biodiversity. The integration of spatial ecology and phylogenetics allows for rigorous tests of whether speciation is associated with niche conservatism (constraints on ecological divergence) or niche divergence. We address this question in a genus of livebearing fishes for which the role of sexual selection in speciation has long been studied, but in which the potential role of ecological divergence during speciation has not been tested. By combining reconstruction of ancestral climate tolerances and disparity indices, we show that the earliest evolutionary split in Xiphophorus was associated with significant divergence for temperature variables. Niche evolution and present day niches were most closely associated with each species' geographic distribution relative to a biogeographic barrier, the Trans-Mexican Volcanic Belt. Tests for similarity of the environmental backgrounds of closely related species suggested that the relative importance of niche conservatism and divergence during speciation varied among the primary clades of Xiphophorus. Closely related species in the two swordtail clades exhibited higher levels of niche overlap than expected given environmental background similarity indicative of niche conservatism. In contrast, almost all species of platyfish had significantly divergent niches compared to environmental backgrounds, which is indicative of niche divergence. The results suggest that the relative importance of niche conservatism and divergence differed among the clades of Xiphophorus and that traits associated with niche evolution may be more evolutionarily labile in the platyfishes. Our results ultimately suggest that the taxonomic scale of tests for conservatism and divergence could greatly influence inferences of their relative importance in the speciation process.

  18. Intestinal Stem Cell Niche: The Extracellular Matrix and Cellular Components

    Directory of Open Access Journals (Sweden)

    Laween Meran

    2017-01-01

    Full Text Available The intestinal epithelium comprises a monolayer of polarised columnar cells organised along the crypt-villus axis. Intestinal stem cells reside at the base of crypts and are constantly nourished by their surrounding niche for maintenance, self-renewal, and differentiation. The cellular microenvironment including the adjacent Paneth cells, stromal cells, smooth muscle cells, and neural cells as well as the extracellular matrix together constitute the intestinal stem cell niche. A dynamic regulatory network exists among the epithelium, stromal cells, and the matrix via complex signal transduction to maintain tissue homeostasis. Dysregulation of these biological or mechanical signals could potentially lead to intestinal injury and disease. In this review, we discuss the role of different intestinal stem cell niche components and dissect the interaction between dynamic matrix factors and regulatory signalling during intestinal stem cell homeostasis.

  19. Development and aging of a brain neural stem cell niche.

    Science.gov (United States)

    Conover, Joanne C; Todd, Krysti L

    2017-08-01

    In the anterior forebrain, along the lateral wall of the lateral ventricles, a neurogenic stem cell niche is found in a region referred to as the ventricular-subventricular zone (V-SVZ). In rodents, robust V-SVZ neurogenesis provides new neurons to the olfactory bulb throughout adulthood; however, with increasing age stem cell numbers are reduced and neurogenic capacity is significantly diminished, but new olfactory bulb neurons continue to be produced even in old age. Humans, in contrast, show little to no new neurogenesis after two years of age and whether V-SVZ neural stem cells persist in the adult human brain remains unclear. Here, we review functional and organizational differences in the V-SVZ stem cell niche of mice and humans, and examine how aging affects the V-SVZ niche and its associated functions. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Niche differentiation and expansion of plant species are associated with mycorrhizal symbiosis

    NARCIS (Netherlands)

    Gerz, Maret; Guillermo Bueno, C.; Ozinga, Wim A.; Zobel, Martin; Moora, Mari

    2018-01-01

    Mycorrhizal symbiosis is a widespread association between plant roots and mycorrhizal fungi, which is thought to contribute to plant niche differentiation and expansion. However, this has so far not been explicitly tested. To address the effect of mycorrhizal symbiosis on plants’ realized niches, we

  1. Disjunct populations of European vascular plant species keep the same climatic niches

    DEFF Research Database (Denmark)

    Wasof, Safaa; Lenoir, Jonathan; Aarrestad, Per Arild

    2015-01-01

    separated for thousands of years. Location: European Alps and Fennoscandia. Methods: Of the studied pool of 888 terrestrial vascular plant species occurring in both the Alps and Fennoscandia, we used two complementary approaches to test and quantify climatic-niche shifts for 31 species having strictly......Aim: Previous research on how climatic niches vary across species ranges has focused on a limited number of species, mostly invasive, and has not, to date, been very conclusive. Here we assess the degree of niche conservatism between distant populations of native alpine plant species that have been...... to be largely valid for arctic-alpine plants....

  2. Doctoral education in a successful ecological niche

    DEFF Research Database (Denmark)

    Christensen, Mette Krogh; Lund, Ole

    2014-01-01

    Scholarly communities are dependent on and often measured by their ability to attract and develop doctoral students. Recent literature suggests that most scholarly communities entail ecological niches in which the doctoral students learn the codes and practices of research. In this article, we...... successful doctoral education because it: 1) fleshes out the professional attitude that is necessary for becoming a successful researcher in the department, 2) shapes and adapts the doctoral students’ desires to grasp and identify with the department’s practices, and 3) provides the doctoral students...... explore the microclimate in an ecological niche of doctoral education. Based on a theoretical definition of microclimate as the emotional atmosphere that ties group members together and affects their actions, we conducted a case study that aimed to describe the key features of the microclimate...

  3. Exploring climate niches of ponderosa pine (Pinus ponderosa Douglas ex Lawson) haplotypes in the western United States: Implications for evolutionary history and conservation

    Science.gov (United States)

    Shinneman, Douglas; Means, Robert E.; Potter, Kevin M.; Hipkins, Valerie D.

    2016-01-01

    Ponderosa pine (Pinus ponderosa Douglas ex Lawson) occupies montane environments throughout western North America, where it is both an ecologically and economically important tree species. A recent study using mitochondrial DNA analysis demonstrated substantial genetic variation among ponderosa pine populations in the western U.S., identifying 10 haplotypes with unique evolutionary lineages that generally correspond spatially with distributions of the Pacific (P. p. var. ponderosa) and Rocky Mountain (P. p. var. scopulorum) varieties. To elucidate the role of climate in shaping the phylogeographic history of ponderosa pine, we used nonparametric multiplicative regression to develop predictive climate niche models for two varieties and 10 haplotypes and to hindcast potential distribution of the varieties during the last glacial maximum (LGM), ~22,000 yr BP. Our climate niche models performed well for the varieties, but haplotype models were constrained in some cases by small datasets and unmeasured microclimate influences. The models suggest strong relationships between genetic lineages and climate. Particularly evident was the role of seasonal precipitation balance in most models, with winter- and summer-dominated precipitation regimes strongly associated with P. p. vars. ponderosa and scopulorum, respectively. Indeed, where present-day climate niches overlap between the varieties, introgression of two haplotypes also occurs along a steep clinal divide in western Montana. Reconstructed climate niches for the LGM suggest potentially suitable climate existed for the Pacific variety in the California Floristic province, the Great Basin, and Arizona highlands, while suitable climate for the Rocky Mountain variety may have existed across the southwestern interior highlands. These findings underscore potentially unique phylogeographic origins of modern ponderosa pine evolutionary lineages, including potential adaptations to Pleistocene climates associated with

  4. Transcriptional reprogramming and phenotypic switching associated with the adaptation of Lactobacillus plantarum C2 to plant niches

    Science.gov (United States)

    Filannino, Pasquale; Di Cagno, Raffaella; Crecchio, Carmine; De Virgilio, Caterina; De Angelis, Maria; Gobbetti, Marco

    2016-01-01

    Lactobacillus plantarum has been isolated from a large variety of ecological niches, thus highlighting its remarkable environmental adaptability as a generalist. Plant fermentation conditions markedly affect the functional features of L. plantarum strains. We investigated the plant niche-specific traits of L. plantarum through whole-transcriptome and phenotypic microarray profiles. Carrot (CJ) and pineapple (PJ) juices were chosen as model systems, and MRS broth was used as a control. A set of 3,122 genes was expressed, and 21 to 31% of genes were differentially expressed depending on the plant niche and cell physiological state. L. plantarum C2 seemed to specifically respond to plant media conditions. When L. plantarum was cultured in CJ, useful pathways were activated, which were aimed to sense the environment, save energy and adopt alternative routes for NAD+ regeneration. In PJ the acidic environment caused a transcriptional switching, which was network-linked to an acid tolerance response involving carbohydrate flow, amino acid and protein metabolism, pH homeostasis and membrane fluidity. The most prominent phenotypic dissimilarities observed in cells grown in CJ and PJ were related to carbon and nitrogen metabolism, respectively. Summarising, a snapshot of a carrot and pineapple sensing and adaptive regulation model for L. plantarum C2 was proposed. PMID:27273017

  5. Spatial patterns, ecological niches, and interspecific competition of avian brood parasites: inferring from a case study of Korea.

    Science.gov (United States)

    Lee, Jin-Won; Noh, Hee-Jin; Lee, Yunkyoung; Kwon, Young-Soo; Kim, Chang-Hoe; Yoo, Jeong-Chil

    2014-09-01

    Since obligate avian brood parasites depend completely on the effort of other host species for rearing their progeny, the availability of hosts will be a critical resource for their life history. Circumstantial evidence suggests that intense competition for host species may exist not only within but also between species. So far, however, few studies have demonstrated whether the interspecific competition really occurs in the system of avian brood parasitism and how the nature of brood parasitism is related to their niche evolution. Using the occurrence data of five avian brood parasites from two sources of nationwide bird surveys in South Korea and publically available environmental/climatic data, we identified their distribution patterns and ecological niches, and applied species distribution modeling to infer the effect of interspecific competition on their spatial distribution. We found that the distribution patterns of five avian brood parasites could be characterized by altitude and climatic conditions, but overall their spatial ranges and ecological niches extensively overlapped with each other. We also found that the predicted distribution areas of each species were generally comparable to the realized distribution areas, and the numbers of individuals in areas where multiple species were predicted to coexist showed positive relationships among species. In conclusion, despite following different coevolutionary trajectories to adapt to their respect host species, five species of avian brood parasites breeding in South Korea occupied broadly similar ecological niches, implying that they tend to conserve ancestral preferences for ecological conditions. Furthermore, our results indicated that contrary to expectation interspecific competition for host availability between avian brood parasites seemed to be trivial, and thus, play little role in shaping their spatial distributions and ecological niches. Future studies, including the complete ranges of avian brood

  6. bantam miRNA is important for Drosophila blood cell homeostasis and a regulator of proliferation in the hematopoietic progenitor niche

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Victoria; Tokusumi, Tsuyoshi; Tokusumi, Yumiko; Schulz, Robert A., E-mail: rschulz@nd.edu

    2014-10-24

    Highlights: • bantam miRNA is endogenously expressed in the hematopoietic progenitor niche. • bantam is necessary and sufficient to induce cellular proliferation in the PSC. • bantam is upstream of the Insulin Receptor signaling pathway. • A model for positive regulation of hematopoietic niche growth is proposed. - Abstract: The Drosophila hematopoietic system is utilized in this study to gain novel insights into the process of growth control of the hematopoietic progenitor niche in blood development. The niche microenvironment is an essential component controlling the balance between progenitor populations and differentiated, mature blood cells and has been shown to lead to hematopoietic malignancies in humans when misregulated. MicroRNAs are one class of regulators associated with blood malignancies; however, there remains a relative paucity of information about the role of miRNAs in the niche. Here we demonstrate that bantam miRNA is endogenously active in the Drosophila hematopoietic progenitor niche, the posterior signaling center (PSC), and functions in the primary hematopoietic organ, the lymph gland, as a positive regulator of growth. Loss of bantam leads to a significant reduction in the PSC and overall lymph gland size, as well as a loss of the progenitor population and correlative premature differentiation of mature hemocytes. Interestingly, in addition to being essential for proper lymph gland development, we have determined bantam to be a novel upstream component of the insulin signaling cascade in the PSC and have unveiled dMyc as one factor central to bantam activity. These important findings identify bantam as a new hematopoietic regulator, place it in an evolutionarily conserved signaling pathway, present one way in which it is regulated, and provide a mechanism through which it facilitates cellular proliferation in the hematopoietic niche.

  7. bantam miRNA is important for Drosophila blood cell homeostasis and a regulator of proliferation in the hematopoietic progenitor niche

    International Nuclear Information System (INIS)

    Lam, Victoria; Tokusumi, Tsuyoshi; Tokusumi, Yumiko; Schulz, Robert A.

    2014-01-01

    Highlights: • bantam miRNA is endogenously expressed in the hematopoietic progenitor niche. • bantam is necessary and sufficient to induce cellular proliferation in the PSC. • bantam is upstream of the Insulin Receptor signaling pathway. • A model for positive regulation of hematopoietic niche growth is proposed. - Abstract: The Drosophila hematopoietic system is utilized in this study to gain novel insights into the process of growth control of the hematopoietic progenitor niche in blood development. The niche microenvironment is an essential component controlling the balance between progenitor populations and differentiated, mature blood cells and has been shown to lead to hematopoietic malignancies in humans when misregulated. MicroRNAs are one class of regulators associated with blood malignancies; however, there remains a relative paucity of information about the role of miRNAs in the niche. Here we demonstrate that bantam miRNA is endogenously active in the Drosophila hematopoietic progenitor niche, the posterior signaling center (PSC), and functions in the primary hematopoietic organ, the lymph gland, as a positive regulator of growth. Loss of bantam leads to a significant reduction in the PSC and overall lymph gland size, as well as a loss of the progenitor population and correlative premature differentiation of mature hemocytes. Interestingly, in addition to being essential for proper lymph gland development, we have determined bantam to be a novel upstream component of the insulin signaling cascade in the PSC and have unveiled dMyc as one factor central to bantam activity. These important findings identify bantam as a new hematopoietic regulator, place it in an evolutionarily conserved signaling pathway, present one way in which it is regulated, and provide a mechanism through which it facilitates cellular proliferation in the hematopoietic niche

  8. Niche Extracellular Matrix Components and Their Influence on HSC.

    Science.gov (United States)

    Domingues, Mélanie J; Cao, Huimin; Heazlewood, Shen Y; Cao, Benjamin; Nilsson, Susan K

    2017-08-01

    Maintenance of hematopoietic stem cells (HSC) takes place in a highly specialized microenvironment within the bone marrow. Technological improvements, especially in the field of in vivo imaging, have helped unravel the complexity of the niche microenvironment and have completely changed the classical concept from what was previously believed to be a static supportive platform, to a dynamic microenvironment tightly regulating HSC homeostasis through the complex interplay between diverse cell types, secreted factors, extracellular matrix molecules, and the expression of different transmembrane receptors. To add to the complexity, non-protein based metabolites have also been recognized as a component of the bone marrow niche. The objective of this review is to discuss the current understanding on how the different extracellular matrix components of the niche regulate HSC fate, both during embryonic development and in adulthood. Special attention will be provided to the description of non-protein metabolites, such as lipids and metal ions, which contribute to the regulation of HSC behavior. J. Cell. Biochem. 118: 1984-1993, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  9. [Niche and interspecific association of the dominant fish in the south coastal waters of Wenzhou, China].

    Science.gov (United States)

    Dong, Jing Rui; Shui, Bo Nian; Hu, Cheng Ye; Shui, Yu Yue; DU, Xiao; Tian, Kuo

    2017-05-18

    The studies about the niche and interspecific association in China were mainly focused on the plants, birds and marine animals, and seldom on fish. Based on the fishery resources survey in spring (May) and autumn (September) in 2015, the associations among major fish species in south coastal waters of Wenzhou were investigated. The methods including niche breadth, niche overlap, variance ratio (VR), Χ 2 -test, association coefficient (AC), percentage of co-occurrence (PC) and point correlation coefficients (Ф) were used. The results showed that 47 fish species were identified, including 9 orders, 27 families and 41 genera. Four species were dominant species and 9 were important species, which together accounted for 17%. The niche breadth cluster analysis demonstrated two clearly identifiable ecological niches. The first one referred to wide niche that included Harpodon nehereus, Collichthys lucidus, Engraulis japonicas, Pampus echinogaster, Argyrosomus argentatus, Polynemus sextarius, Decapterus maruadsi and Trichiurus haumela, and the second one was narrow niche that included Muraenesox cinereus, Amblychaeturichthys hexanema, Cunoglossus robustus, Pseudosciaena polyactis and Ilisha elongate. The niche overlap value of the main fish was 0-0.90, indicating that there was difference in the resource utilization among the species. The ecological niche widths of C. robustus and M. cinereus were narrow, and the overlap values were high. This indicated that there was competition between these two species. The VR analysis revealed significant positive correlation among the main fish species. In view of the advantages of Ф value, which could reduce the impact of the analysis results of Χ 2 -test, AC and PC to the interspecific association, the Ф value method was selected in this study, and the association of 63 couples were positive. Both the interspecific association and ecological niche had different degrees of correlation with the stability of community structure

  10. Latitudinal diversity gradients in New World bats: are they a consequence of niche conservatism?

    Science.gov (United States)

    Ramos Pereira, Maria João; Palmeirim, Jorge M

    2013-01-01

    The increase in species diversity from the Poles to the Equator is a major biogeographic pattern, but the mechanisms underlying it remain obscure. Our aim is to contribute to their clarification by describing the latitudinal gradients in species richness and in evolutionary age of species of New World bats, and testing if those patterns may be explained by the niche conservatism hypothesis. Maps of species ranges were used to estimate species richness in a 100 x 100 km grid. Root distances in a molecular phylogeny were used as a proxy for the age of species, and the mean root distance of the species in each cell of the grid was estimated. Generalised additive models were used to relate latitude with both species richness and mean root distance. This was done for each of the three most specious bat families and for all Chiroptera combined. Species richness increases towards the Equator in the whole of the Chiroptera and in the Phyllostomidae and Molossidae, families that radiated in the tropics, but the opposite trend is observed in the Vespertilionidae, which has a presumed temperate origin. In the whole of the Chiroptera, and in the three main families, there were more basal species in the higher latitudes, and more derived species in tropical areas. In general, our results were not consistent with the predictions of niche conservatism. Tropical niche conservatism seems to keep bat clades of tropical origin from colonizing temperate zones, as they lack adaptations to survive cold winters, such as the capacity to hibernate. However, the lower diversity of Vespertilionidae in the Neotropics is better explained by competition with a diverse pre-existing community of bats than by niche conservatism.

  11. A hybrid niched-island genetic algorithm applied to a nuclear core optimization problem

    International Nuclear Information System (INIS)

    Pereira, Claudio M.N.A.

    2005-01-01

    Diversity maintenance is a key-feature in most genetic-based optimization processes. The quest for such characteristic, has been motivating improvements in the original genetic algorithm (GA). The use of multiple populations (called islands) has demonstrating to increase diversity, delaying the genetic drift. Island Genetic Algorithms (IGA) lead to better results, however, the drift is only delayed, but not avoided. An important advantage of this approach is the simplicity and efficiency for parallel processing. Diversity can also be improved by the use of niching techniques. Niched Genetic Algorithms (NGA) are able to avoid the genetic drift, by containing evolution in niches of a single-population GA, however computational cost is increased. In this work it is investigated the use of a hybrid Niched-Island Genetic Algorithm (NIGA) in a nuclear core optimization problem found in literature. Computational experiments demonstrate that it is possible to take advantage of both, performance enhancement due to the parallelism and drift avoidance due to the use of niches. Comparative results shown that the proposed NIGA demonstrated to be more efficient and robust than an IGA and a NGA for solving the proposed optimization problem. (author)

  12. Single-cell analyses identify bioengineered niches for enhanced maintenance of hematopoietic stem cells.

    Science.gov (United States)

    Roch, Aline; Giger, Sonja; Girotra, Mukul; Campos, Vasco; Vannini, Nicola; Naveiras, Olaia; Gobaa, Samy; Lutolf, Matthias P

    2017-08-09

    The in vitro expansion of long-term hematopoietic stem cells (HSCs) remains a substantial challenge, largely because of our limited understanding of the mechanisms that control HSC fate choices. Using single-cell multigene expression analysis and time-lapse microscopy, here we define gene expression signatures and cell cycle hallmarks of murine HSCs and the earliest multipotent progenitors (MPPs), and analyze systematically single HSC fate choices in culture. Our analysis revealed twelve differentially expressed genes marking the quiescent HSC state, including four genes encoding cell-cell interaction signals in the niche. Under basal culture conditions, most HSCs rapidly commit to become early MPPs. In contrast, when we present ligands of the identified niche components such as JamC or Esam within artificial niches, HSC cycling is reduced and long-term multipotency in vivo is maintained. Our approach to bioengineer artificial niches should be useful in other stem cell systems.Haematopoietic stem cell (HSC) self-renewal is not sufficiently understood to recapitulate in vitro. Here, the authors generate gene signature and cell cycle hallmarks of single murine HSCs, and use identified endothelial receptors Esam and JamC as substrates to enhance HSC growth in engineered niches.

  13. Urban niche dynamics of Kaifeng city%开封市的城市生态位变化分析

    Institute of Scientific and Technical Information of China (English)

    丁圣彦; 李志恒

    2007-01-01

    Niche theory is one of the most important ecological theories. It is widely applied to analyzing such phenomena as competition among, and evolution of, urban ecosystem functional modules. This paper describes a study concerningdifferent functional modules of Kaifeng city urban ecosystem. Niche theory and techniques were used to analyze the changes of these functional modules in the period 1994-2003. The results showed that, in the period 1994-2003: (1) Niche value of the atmospheric environment and urban virescence modules increased, while niche value of the water environment and sound environment modules decreased; (2) niche value of the tertiary industry module increased, niche value of the secondary industry module decreased, while niche value of the primary industry module showed little change; and (3) niche value of the infrastructure, resource distribution, and production & social security modules increased, while niche value of the population module decreased. This study may contribute to macroscopic planning of urban functional modules,economic development, and environmental protection.

  14. Socio-technical transition as a co-evolutionary process: Innovation and the role of niche markets in the transition to motor vehicles

    Science.gov (United States)

    Birky, Alicia K.

    2008-10-01

    Significant reductions in greenhouse emissions from personal transportation will require a transition to an alternative technology regime based on renewable energy sources. Two bodies of research, the quasi-evolutionary (QE) model and the multi-level perspective (MLP) assert that processes within niches play a fundamental role in such transitions. This research asks whether the description of transitions based on this niche hypothesis and its underlying assumptions is consistent with the historical U.S. transition to motor vehicles at the beginning of the 20th century. Unique to this dissertation is the combination of the perspective of the entrepreneur with co-evolutionary approaches to socio-technical transitions. This approach is augmented with concepts from the industry life-cycle model and with a taxonomy of mechanisms of learning. Using this analytic framework, I examine specifically the role of entrepreneurial behavior and processes within and among firms in the co-evolution of technologies and institutions during the transition to motor vehicles. I find that niche markets played an important role in the development of the technology, institutions, and the industry. However, I also find that the diffusion of the automobile is not consistent with the niche hypothesis in the following ways: (1) product improvements and cost reductions were not realized in niche markets, but were achieved simultaneously with diffusion into mass markets; (2) in addition to learning-by-doing and learning-by-interacting with users, knowledge spillovers and interacting with suppliers were critical in this process; (3) cost reductions were not automatic results of expanding markets, but rather arose from the strategies of entrepreneurs based on personal perspectives and values. This finding supports the use of a behavioral approach with a micro-focus in the analysis of socio-technical change. I also find that the emergence and diffusion of the motor vehicle can only be understood by

  15. Bridging the Service Divide: Dual Labor Niches and Embedded Opportunities in Restaurant Work

    Directory of Open Access Journals (Sweden)

    Eli R. Wilson

    2018-01-01

    Full Text Available Restaurants and other interactive service workplaces in the United States serve as labor niches for two very different kinds of workers doing different tasks. Immigrant Latinos primarily work “back-of-the-house” jobs doing manual tasks, while class-privileged whites work “front-of-the-house” jobs performing customer-facing tasks. How do these social and structural cleavages between dual labor niches affect the workplace dynamic? Drawing on ethnographic research in upscale Los Angeles restaurants, I describe the closed boundaries between these distinct labor niches and the valuable bridging between them performed by certain workers who are able to ease social tensions and buffer the service labor process. I discuss the implications of these findings for the study of contemporary immigrant labor niches and the nature of the opportunities within them and between them.

  16. Ecological allometries and niche use dynamics across Komodo dragon ontogeny

    Science.gov (United States)

    Purwandana, Deni; Ariefiandy, Achmad; Imansyah, M. Jeri; Seno, Aganto; Ciofi, Claudio; Letnic, Mike; Jessop, Tim S.

    2016-04-01

    Ontogenetic allometries in ecological habits and niche use are key responses by which individuals maximize lifetime fitness. Moreover, such allometries have significant implications for how individuals influence population and community dynamics. Here, we examined how body size variation in Komodo dragons ( Varanus komodoensis) influenced ecological allometries in their: (1) prey size preference, (2) daily movement rates, (3) home range area, and (4) subsequent niche use across ontogeny. With increased body mass, Komodo dragons increased prey size with a dramatic switch from small (≤10 kg) to large prey (≥50 kg) in lizards heavier than 20 kg. Rates of foraging movement were described by a non-linear concave down response with lizard increasing hourly movement rates up until ˜20 kg body mass before decreasing daily movement suggesting reduced foraging effort in larger lizards. In contrast, home range area exhibited a sigmoid response with increased body mass. Intrapopulation ecological niche use and overlap were also strongly structured by body size. Thus, ontogenetic allometries suggest Komodo dragon's transition from a highly active foraging mode exploiting small prey through to a less active sit and wait feeding strategy focused on killing large ungulates. Further, our results suggest that as body size increases across ontogeny, the Komodo dragon exhibited marked ontogenetic niche shifts that enabled it to function as an entire vertebrate predator guild by exploiting prey across multiple trophic levels.

  17. Secreted protein Del-1 regulates myelopoiesis in the hematopoietic stem cell niche.

    Science.gov (United States)

    Mitroulis, Ioannis; Chen, Lan-Sun; Singh, Rashim Pal; Kourtzelis, Ioannis; Economopoulou, Matina; Kajikawa, Tetsuhiro; Troullinaki, Maria; Ziogas, Athanasios; Ruppova, Klara; Hosur, Kavita; Maekawa, Tomoki; Wang, Baomei; Subramanian, Pallavi; Tonn, Torsten; Verginis, Panayotis; von Bonin, Malte; Wobus, Manja; Bornhäuser, Martin; Grinenko, Tatyana; Di Scala, Marianna; Hidalgo, Andres; Wielockx, Ben; Hajishengallis, George; Chavakis, Triantafyllos

    2017-10-02

    Hematopoietic stem cells (HSCs) remain mostly quiescent under steady-state conditions but switch to a proliferative state following hematopoietic stress, e.g., bone marrow (BM) injury, transplantation, or systemic infection and inflammation. The homeostatic balance between quiescence, self-renewal, and differentiation of HSCs is strongly dependent on their interactions with cells that constitute a specialized microanatomical environment in the BM known as the HSC niche. Here, we identified the secreted extracellular matrix protein Del-1 as a component and regulator of the HSC niche. Specifically, we found that Del-1 was expressed by several cellular components of the HSC niche, including arteriolar endothelial cells, CXCL12-abundant reticular (CAR) cells, and cells of the osteoblastic lineage. Del-1 promoted critical functions of the HSC niche, as it regulated long-term HSC (LT-HSC) proliferation and differentiation toward the myeloid lineage. Del-1 deficiency in mice resulted in reduced LT-HSC proliferation and infringed preferentially upon myelopoiesis under both steady-state and stressful conditions, such as hematopoietic cell transplantation and G-CSF- or inflammation-induced stress myelopoiesis. Del-1-induced HSC proliferation and myeloid lineage commitment were mediated by β3 integrin on hematopoietic progenitors. This hitherto unknown Del-1 function in the HSC niche represents a juxtacrine homeostatic adaptation of the hematopoietic system in stress myelopoiesis.

  18. Niche conservatism and dispersal limitation cause large-scale phylogenetic structure in the New World palm flora

    DEFF Research Database (Denmark)

    Eiserhardt, Wolf L.; Svenning, J.-C.; Baker, William J.

    similarity decays after speciation depends on the rates of niche evolution and dispersal. If dispersal is slow compared to the tempo of lineage diversification, distributions change little during clade diversification. Phylogenetic niche conservatism precludes distributional shifts in environmental space......, and to the degree that distributions are limited by the niche, also in geographic space. Using phylogenetic turnover methods, we simultaneously analysed the distributions of all New World palms (n=547) and inferred to which degree phylogenetic niche conservatism and dispersal limitation, respectively, caused...

  19. A GRFa2/Prop1/stem (GPS) cell niche in the pituitary.

    Science.gov (United States)

    Garcia-Lavandeira, Montse; Quereda, Víctor; Flores, Ignacio; Saez, Carmen; Diaz-Rodriguez, Esther; Japon, Miguel A; Ryan, Aymee K; Blasco, Maria A; Dieguez, Carlos; Malumbres, Marcos; Alvarez, Clara V

    2009-01-01

    The adult endocrine pituitary is known to host several hormone-producing cells regulating major physiological processes during life. Some candidates to progenitor/stem cells have been proposed. However, not much is known about pituitary cell renewal throughout life and its homeostatic regulation during specific physiological changes, such as puberty or pregnancy, or in pathological conditions such as tumor development. We have identified in rodents and humans a niche of non-endocrine cells characterized by the expression of GFRa2, a Ret co-receptor for Neurturin. These cells also express b-Catenin and E-cadherin in an oriented manner suggesting a planar polarity organization for the niche. In addition, cells in the niche uniquely express the pituitary-specific transcription factor Prop1, as well as known progenitor/stem markers such as Sox2, Sox9 and Oct4. Half of these GPS (GFRa2/Prop1/Stem) cells express S-100 whereas surrounding elongated cells in contact with GPS cells express Vimentin. GFRa2+-cells form non-endocrine spheroids in culture. These spheroids can be differentiated to hormone-producing cells or neurons outlining the neuroectoderm potential of these progenitors. In vivo, GPSs cells display slow proliferation after birth, retain BrdU label and show long telomeres in its nuclei, indicating progenitor/stem cell properties in vivo. Our results suggest the presence in the adult pituitary of a specific niche of cells characterized by the expression of GFRa2, the pituitary-specific protein Prop1 and stem cell markers. These GPS cells are able to produce different hormone-producing and neuron-like cells and they may therefore contribute to postnatal pituitary homeostasis. Indeed, the relative abundance of GPS numbers is altered in Cdk4-deficient mice, a model of hypopituitarism induced by the lack of this cyclin-dependent kinase. Thus, GPS cells may display functional relevance in the physiological expansion of the pituitary gland throughout life as well as

  20. Endothelial progenitors encapsulated in bioartificial niches are insulated from systemic cytotoxicity and are angiogenesis competent.

    Science.gov (United States)

    Ratliff, B B; Ghaly, T; Brudnicki, P; Yasuda, K; Rajdev, M; Bank, M; Mares, J; Hatzopoulos, A K; Goligorsky, M S

    2010-07-01

    Intrinsic stem cells (SC) participate in tissue remodeling and regeneration in various diseases and following toxic insults. Failure of tissue regeneration is in part attributed to lack of SC protection from toxic stress of noxious stimuli, thus prompting intense research efforts to develop strategies for SC protection and functional preservation for in vivo delivery. One strategy is creation of artificial SC niches in an attempt to mimic the requirements of endogenous SC niches by generating scaffolds with properties of extracellular matrix. Here, we investigated the use of hyaluronic acid (HA) hydrogels as an artificial SC niche and examined regenerative capabilities of encapsulated embryonic endothelial progenitor cells (eEPC) in three different in vivo models. Hydrogel-encapsulated eEPC demonstrated improved resistance to toxic insult (adriamycin) in vitro, thus prompting in vivo studies. Implantation of HA hydrogels containing eEPC to mice with adriamycin nephropathy or renal ischemia resulted in eEPC mobilization to injured kidneys (and to a lesser extent to the spleen) and improvement of renal function, which was equal or superior to adoptively transferred EPC by intravenous infusion. In mice with hindlimb ischemia, EPC encapsulated in HA hydrogels dramatically accelerated the recovery of collateral circulation with the efficacy superior to intravenous infusion of EPC. In conclusion, HA hydrogels protect eEPC against adriamycin cytotoxicity and implantation of eEPC encapsulated in HA hydrogels supports renal regeneration in ischemic and cytotoxic (adriamycin) nephropathy and neovascularization of ischemic hindlimb, thus establishing their functional competence and superior capabilities to deliver stem cells stored in and released from this bioartificial niche.

  1. Niche modeling predictions of the potential distribution of Marmota himalayana, the host animal of plague in Yushu County of Qinghai

    Directory of Open Access Journals (Sweden)

    Liang Lu

    2016-02-01

    Full Text Available Abstract Background After the earthquake on 14, April 2010 at Yushu in China, a plague epidemic hosted by Himalayan marmot (Marmota himalayana became a major public health concern during the reconstruction period. A rapid assessment of the distribution of Himalayan marmot in the area was urgent. The aims of this study were to analyze the relationship between environmental factors and the distribution of burrow systems of the marmot and to predict the distribution of marmots. Methods Two types of marmot burrows (hibernation and temporary in Yushu County were investigated from June to September in 2011. The location of every burrow was recorded with a global positioning system receiver. An ecological niche model was used to determine the relationship between the burrow occurrence data and environmental variables, such as land surface temperature (LST in winter and summer, normalized difference vegetation index (NDVI in winter and summer, elevation, and soil type. The predictive accuracies of the models were assessed by the area under the curve of the receiving operator curve. Results The models for hibernation and temporary burrows both performed well. The contribution orders of the variables were LST in winter and soil type, NDVI in winter and elevation for the hibernation burrow model, and LST in summer, NDVI in summer, soil type and elevation in the temporary burrow model. There were non-linear relationships between the probability of burrow presence and LST, NDVI and elevation. LST of 14 and 23 °C, NDVI of 0.22 and 0.60, and 4100 m were inflection points. A substantially higher probability of burrow presence was observed in swamp soil and dark felty soil than in other soil types. The potential area for hibernation burrows was 5696 km2 (37.7 % of Yushu County, and the area for temporary burrows was 7711 km2 (51.0 % of Yushu County. Conclusions The results suggested that marmots preferred warm areas with relatively low altitudes and good

  2. Strategic niche management and sustainable innovation journeys : theory, findings, research agenda, and policy

    NARCIS (Netherlands)

    Schot, J.W.; Geels, F.W.

    2008-01-01

    This article discusses empirical findings and conceptual elaborations of the last 10 years in strategic niche management research (SNM). The SNM approach suggests that sustainable innovation journeys can be facilitated by creating technological niches, i.e. protected spaces that allow the

  3. Intersexual Trophic Niche Partitioning in an Ant-Eating spider (Araneae: Zodariidae)

    DEFF Research Database (Denmark)

    Pekár, Stanislav; Martisová, Martina; Bilde, T.

    2011-01-01

    lead to higher energy demands in females driven by fecundity selection, while males invest in mate searching. We tested predictions of the two hypotheses underlying intersexual trophic niche partitioning in a natural population of spiders. Zodarion jozefienae spiders specialize on Messor barbarus ants...... that are polymorphic in body size and hence comprise potential trophic niches for the spider, making this system well-suited to study intersexual trophic niche partitioning. Methodology/Principal Findings Comparative analysis of trophic morphology (the chelicerae) and body size of males, females and juveniles...... demonstrated highly female biased SSD (Sexual Size Dimorphism) in body size, body weight, and in the size of chelicerae, the latter arising from sex-specific growth patterns in trophic morphology. In the field, female spiders actively selected ant sub-castes that were larger than the average prey size...

  4. Macrophages Contribute to the Spermatogonial Niche in the Adult Testis

    Directory of Open Access Journals (Sweden)

    Tony DeFalco

    2015-08-01

    Full Text Available The testis produces sperm throughout the male reproductive lifespan by balancing self-renewal and differentiation of spermatogonial stem cells (SSCs. Part of the SSC niche is thought to lie outside the seminiferous tubules of the testis; however, specific interstitial components of the niche that regulate spermatogonial divisions and differentiation remain undefined. We identified distinct populations of testicular macrophages, one of which lies on the surface of seminiferous tubules, in close apposition to areas of tubules enriched for undifferentiated spermatogonia. These macrophages express spermatogonial proliferation- and differentiation-inducing factors, such as colony-stimulating factor 1 (CSF1 and enzymes involved in retinoic acid (RA biosynthesis. We show that transient depletion of macrophages leads to a disruption in spermatogonial differentiation. These findings reveal an unexpected role for macrophages in the spermatogonial niche in the testis and raise the possibility that macrophages play previously unappreciated roles in stem/progenitor cell regulation in other tissues.

  5. Niche versus neutrality: a dynamical analysis

    Science.gov (United States)

    Michael Kalyuzhny; Efrat Seri; Rachel Chocron; Curtis H. Flather; Ronen Kadmon; Nadav M. Shnerb

    2014-01-01

    Understanding the forces shaping ecological communities is of crucial importance for basic science and conservation. After 50 years in which ecological theory has focused on either stable communities driven by niche-based forces or nonstable “neutral” communities driven by demographic stochasticity, contemporary theories suggest that ecological communities are driven...

  6. The malignant niche: safe spaces for toxic stem cell marketing.

    Science.gov (United States)

    Sipp, Douglas

    2017-01-01

    Many tumors are sustained by microenvironments, or niches, that support and protect malignant cells, thus conferring a competitive advantage against both healthy cells and therapeutic interventions (for a brief review, see Yao and Link (Stem Cells 35: 3-8, 2017)). The global industry engaged in the commercial promotion of unproven and scientifically implausible cell-based "regenerative" therapies has developed a number of self-protective strategies that support its survival and growth in ways that are broadly analogous to the functions of the malignant niche.

  7. Niche construction and the evolution of leadership

    NARCIS (Netherlands)

    Spisak, B.R.; O'Brien, M.; Nicholson, N.; van Vugt, M.

    2015-01-01

    We use the concept of niche construction - the process whereby individuals, through their activities, interactions, and choices, modify their own and each other's environments - as an example of how biological evolution and cultural evolution interacted to form an integrative foundation of modern

  8. A classical model for the electron

    International Nuclear Information System (INIS)

    Visser, M.

    1989-01-01

    The construction of classical and semi-classical models for the electron has had a long and distinguished history. Such models are useful more for what they teach us about field theory than what they teach us about the electron. In this Letter I exhibit a classical model of the electron consisting of ordinary electromagnetism coupled with a self-interacting version of Newtonian gravity. The gravitational binding energy of the system balances the electrostatic energy in such a manner that the total rest mass of the electron is finite. (orig.)

  9. Cystic fibrosis-niche adaptation of Pseudomonas aeruginosa reduces virulence in multiple infection hosts.

    Directory of Open Access Journals (Sweden)

    Nicola Ivan Lorè

    Full Text Available The opportunistic pathogen Pseudomonas aeruginosa is able to thrive in diverse ecological niches and to cause serious human infection. P. aeruginosa environmental strains are producing various virulence factors that are required for establishing acute infections in several host organisms; however, the P. aeruginosa phenotypic variants favour long-term persistence in the cystic fibrosis (CF airways. Whether P. aeruginosa strains, which have adapted to the CF-niche, have lost their competitive fitness in the other environment remains to be investigated. In this paper, three P. aeruginosa clonal lineages, including early strains isolated at the onset of infection, and late strains, isolated after several years of chronic lung infection from patients with CF, were analysed in multi-host model systems of acute infection. P. aeruginosa early isolates caused lethality in the three non-mammalian hosts, namely Caenorhabditis elegans, Galleria mellonella, and Drosophila melanogaster, while late adapted clonal isolates were attenuated in acute virulence. When two different mouse genetic background strains, namely C57Bl/6NCrl and Balb/cAnNCrl, were used as acute infection models, early P. aeruginosa CF isolates were lethal, while late isolates exhibited reduced or abolished acute virulence. Severe histopathological lesions, including high leukocytes recruitment and bacterial load, were detected in the lungs of mice infected with P. aeruginosa CF early isolates, while late isolates were progressively cleared. In addition, systemic bacterial spread and invasion of epithelial cells, which were detected for P. aeruginosa CF early strains, were not observed with late strains. Our findings indicate that niche-specific selection in P. aeruginosa reduced its ability to cause acute infections across a broad range of hosts while maintaining the capacity for chronic infection in the CF host.

  10. Grateful parents raising grateful children: Niche selection and the socialization of child gratitude.

    Science.gov (United States)

    Rothenberg, William A; Hussong, Andrea M; Langley, Hillary A; Egerton, Gregory A; Halberstadt, Amy G; Coffman, Jennifer L; Mokrova, Irina; Costanzo, Philip R

    2017-01-01

    Given that children's exposure to gratitude-related activities may be one way that parents can socialize gratitude in their children, we examined whether parents' niche selection (i.e., tendency to choose perceived gratitude-inducing activities for their children) mediates the association between parents' reports of their own and their children's gratitude. Parent-child dyads ( N =101; children aged 6-9; 52% girls; 80% Caucasian; 85% mothers) participated in a laboratory visit and parents also completed a seven-day online diary regarding children's gratitude. Decomposing specific indirect effects within a structural equation model, we found that parents high in gratitude were more likely to set goals to use niche selection as a gratitude socialization strategy, and thereby more likely to place their children in gratitude-related activities. Placement in these activities, in turn, was associated with more frequent expression of gratitude in children. We describe future directions for research on parents' role in socializing gratitude in their children.

  11. Is 30 years enough time to niche segregation between a non-native and a native congeneric fish species? Evidences from stable isotopes

    Directory of Open Access Journals (Sweden)

    Gustavo Henrique Zaia Alves

    2015-12-01

    Full Text Available The invasion of non-native species that are phylogenetically similar to native species was observed in the Upper Paraná River following the construction of the Itaipu hydroelectric plant and subsequent removal of a natural geographic barrier (Sete Quedas Falls. Endemic fish species from the Lower Paraná River, such as the piranha Serrasalmus marginatus, successfully colonized the new environment. A few years later, S. marginatus had become the dominant species, while the prevalence of the congeneric species, Serrasalmus maculatus, had declined. Considering that the two piranha species naturally coexist in the Pantanal and that S. marginatus is a non-native species in the Upper Paraná River floodplain, we hypothesized that trophic niche overlap between Serrasalmus species only occurred in the Upper Paraná River floodplain due to short-term co-existence. The study area in which the isotopic niche overlap between S. maculatus and S. marginatus was evaluated consisted of two ponds located in different floodplains, the Pantanal and the Upper Paraná River. We used carbon and nitrogen stable isotope analysis to elucidate the differences in the energy intake by the native and non-native species. We used mixing models and calculated the isotopic niche area and niche overlap to infer the nature of the trophic interactions between the species in both habitats. According to the mixing model, the predominant source of carbon for both species was terrestrial. Nevertheless, in Upper Paraná River, the δ13C signature of the two species differed significantly and the non-native species had a greater niche width than the native species. In the Pantanal, there were no differences in δ13C, but the species differed with respect to δ 15N, and the niche widths were narrow for both species.Based on these results, it can be inferred that the species depend on different food sources. Piranhas obtain energy from distinct prey species, which probably consume

  12. Ecological allometries and niche use dynamics across Komodo dragon ontogeny.

    Science.gov (United States)

    Purwandana, Deni; Ariefiandy, Achmad; Imansyah, M Jeri; Seno, Aganto; Ciofi, Claudio; Letnic, Mike; Jessop, Tim S

    2016-04-01

    Ontogenetic allometries in ecological habits and niche use are key responses by which individuals maximize lifetime fitness. Moreover, such allometries have significant implications for how individuals influence population and community dynamics. Here, we examined how body size variation in Komodo dragons (Varanus komodoensis) influenced ecological allometries in their: (1) prey size preference, (2) daily movement rates, (3) home range area, and (4) subsequent niche use across ontogeny. With increased body mass, Komodo dragons increased prey size with a dramatic switch from small (≤10 kg) to large prey (≥50 kg) in lizards heavier than 20 kg. Rates of foraging movement were described by a non-linear concave down response with lizard increasing hourly movement rates up until ∼20 kg body mass before decreasing daily movement suggesting reduced foraging effort in larger lizards. In contrast, home range area exhibited a sigmoid response with increased body mass. Intrapopulation ecological niche use and overlap were also strongly structured by body size. Thus, ontogenetic allometries suggest Komodo dragon's transition from a highly active foraging mode exploiting small prey through to a less active sit and wait feeding strategy focused on killing large ungulates. Further, our results suggest that as body size increases across ontogeny, the Komodo dragon exhibited marked ontogenetic niche shifts that enabled it to function as an entire vertebrate predator guild by exploiting prey across multiple trophic levels.

  13. Mesenchymal stem cells in human placental chorionic villi reside in a vascular Niche

    NARCIS (Netherlands)

    Castrechini, N. M.; Murthi, P.; Gude, N. M.; Erwich, J. J. H. M.; Gronthos, S.; Zannettino, A.; Brennecke, S. R.; Kalionis, B.; Brennecke, S.P.

    The chorionic villi of human term placentae are a rich source of mesenchymal stem cells (PMSCs) The stem cell "niche" within the chorionic villi regulates how PMSCs participate in placental tissue generation, maintenance and repair, but the anatomic location of the niche has not been defined A

  14. Ecological Niche Modelling Predicts Southward Expansion of Lutzomyia (Nyssomyia flaviscutellata (Diptera: Psychodidae: Phlebotominae, Vector of Leishmania (Leishmania amazonensis in South America, under Climate Change.

    Directory of Open Access Journals (Sweden)

    Bruno M Carvalho

    Full Text Available Vector borne diseases are susceptible to climate change because distributions and densities of many vectors are climate driven. The Amazon region is endemic for cutaneous leishmaniasis and is predicted to be severely impacted by climate change. Recent records suggest that the distributions of Lutzomyia (Nyssomyia flaviscutellata and the parasite it transmits, Leishmania (Leishmania amazonensis, are expanding southward, possibly due to climate change, and sometimes associated with new human infection cases. We define the vector's climatic niche and explore future projections under climate change scenarios. Vector occurrence records were compiled from the literature, museum collections and Brazilian Health Departments. Six bioclimatic variables were used as predictors in six ecological niche model algorithms (BIOCLIM, DOMAIN, MaxEnt, GARP, logistic regression and Random Forest. Projections for 2050 used 17 general circulation models in two greenhouse gas representative concentration pathways: "stabilization" and "high increase". Ensemble models and consensus maps were produced by overlapping binary predictions. Final model outputs showed good performance and significance. The use of species absence data substantially improved model performance. Currently, L. flaviscutellata is widely distributed in the Amazon region, with records in the Atlantic Forest and savannah regions of Central Brazil. Future projections indicate expansion of the climatically suitable area for the vector in both scenarios, towards higher latitudes and elevations. L. flaviscutellata is likely to find increasingly suitable conditions for its expansion into areas where human population size and density are much larger than they are in its current locations. If environmental conditions change as predicted, the range of the vector is likely to expand to southeastern and central-southern Brazil, eastern Paraguay and further into the Amazonian areas of Bolivia, Peru, Ecuador

  15. Ecological Niche Modelling Predicts Southward Expansion of Lutzomyia (Nyssomyia) flaviscutellata (Diptera: Psychodidae: Phlebotominae), Vector of Leishmania (Leishmania) amazonensis in South America, under Climate Change.

    Science.gov (United States)

    Carvalho, Bruno M; Rangel, Elizabeth F; Ready, Paul D; Vale, Mariana M

    2015-01-01

    Vector borne diseases are susceptible to climate change because distributions and densities of many vectors are climate driven. The Amazon region is endemic for cutaneous leishmaniasis and is predicted to be severely impacted by climate change. Recent records suggest that the distributions of Lutzomyia (Nyssomyia) flaviscutellata and the parasite it transmits, Leishmania (Leishmania) amazonensis, are expanding southward, possibly due to climate change, and sometimes associated with new human infection cases. We define the vector's climatic niche and explore future projections under climate change scenarios. Vector occurrence records were compiled from the literature, museum collections and Brazilian Health Departments. Six bioclimatic variables were used as predictors in six ecological niche model algorithms (BIOCLIM, DOMAIN, MaxEnt, GARP, logistic regression and Random Forest). Projections for 2050 used 17 general circulation models in two greenhouse gas representative concentration pathways: "stabilization" and "high increase". Ensemble models and consensus maps were produced by overlapping binary predictions. Final model outputs showed good performance and significance. The use of species absence data substantially improved model performance. Currently, L. flaviscutellata is widely distributed in the Amazon region, with records in the Atlantic Forest and savannah regions of Central Brazil. Future projections indicate expansion of the climatically suitable area for the vector in both scenarios, towards higher latitudes and elevations. L. flaviscutellata is likely to find increasingly suitable conditions for its expansion into areas where human population size and density are much larger than they are in its current locations. If environmental conditions change as predicted, the range of the vector is likely to expand to southeastern and central-southern Brazil, eastern Paraguay and further into the Amazonian areas of Bolivia, Peru, Ecuador, Colombia and Venezuela

  16. Exploring the isotopic niche: isotopic variance, physiological incorporation, and the temporal dynamics of foraging

    Directory of Open Access Journals (Sweden)

    Justin Douglas Yeakel

    2016-01-01

    Full Text Available Consumer foraging behaviors are dynamic, changing in response to prey availability, seasonality, competition, and even the consumer's physiological state. The isotopic composition of a consumer is a product of these factors as well as the isotopic `landscape' of its prey, i.e. the isotopic mixing space. Stable isotope mixing models are used to back-calculate the most likely proportional contribution of a set of prey to a consumer's diet based on their respective isotopic distributions, however they are disconnected from ecological process. Here we build a mechanistic framework that links the ecological and physiological processes of an individual consumer to the isotopic distribution that describes its diet, and ultimately to the isotopic composition of its own tissues, defined as its `isotopic niche’. By coupling these processes, we systematically investigate under what conditions the isotopic niche of a consumer changes as a function of both the geometric properties of its mixing space and foraging strategies that may be static or dynamic over time. Results of our derivations reveal general insight into the conditions impacting isotopic niche width as a function of consumer specialization on prey, as well as the consumer's ability to transition between diets over time. We show analytically that moderate specialization on isotopically unique prey can serve to maximize a consumer's isotopic niche width, while temporally dynamic diets will tend to result in peak isotopic variance during dietary transitions. We demonstrate the relevance of our theoretical findings by examining a marine system composed of nine invertebrate species commonly consumed by sea otters. In general, our analytical framework highlights the complex interplay of mixing space geometry and consumer dietary behavior in driving expansion and contraction of the isotopic niche. Because this approach is established on ecological mechanism, it is well-suited for enhancing the

  17. β3-Adrenergic Regulation of EPC Features Through Manipulation of the Bone Marrow MSC Niche.

    Science.gov (United States)

    Vafaei, Rana; Nassiri, Seyed Mahdi; Siavashi, Vahid

    2017-12-01

    Mesenchymal stem cells (MSCs) reside in a specific niche in the bone marrow, however, biological features of this niche are still not fully understood. Given the interactions of MSCs with endothelial cells in different tissues, bone marrow MSC niche may influence the biological features of endothelial progenitor cells (EPCs). To understand the role of the sympathetic nervous system in regulation of the MSC niche, we examined whether the manipulation of the MSC niche via β3-adrenergic signals will affect EPC features. A selective β3 agonist (BRL37344) or a β3 antagonist (SR59230A) was administered in mice for 2 weeks to determine the potential effects of these regimens on the population of CD133 + stem cells in the bone marrow. Then, bone marrow-derived MSCs and EPCs were harvested and expanded from the mice to examine the effect of changes in the MSC niche on EPC features. Improved MSC colony forming potency with increased bone marrow stromal cell-derived factor 1 (SDF-1) (also known as C-X-C motif chemokine 12 [CXCL12]) expression was shown as a result of intensification of the bone marrow adrenergic signals through BRL37344 injection. On the other hand, the blockage of these signals limited the expression level of SDF-1 and resulted in bone marrow enrichment of CD133 + cells. Manipulation of the MSC niche and decreased SDF-1 expression via SR59230A injection also prompted EPCs to form more colonies with augmented proliferation and differentiation capacity. Overall, our results indicate that the β3-adrenergic signals regulate the MSC niche, thereby resulting in modulation of EPC biological features. J. Cell. Biochem. 118: 4753-4761, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  18. A Stromal Cell Niche for Human and Mouse Type 3 Innate Lymphoid Cells.

    Science.gov (United States)

    Hoorweg, Kerim; Narang, Priyanka; Li, Zhi; Thuery, Anne; Papazian, Natalie; Withers, David R; Coles, Mark C; Cupedo, Tom

    2015-11-01

    Adaptive immunity critically depends on the functional compartmentalization of secondary lymphoid organs. Mesenchymal stromal cells create and maintain specialized niches that support survival, activation, and expansion of T and B cells, and integrated analysis of lymphocytes and their niche has been instrumental in understanding adaptive immunity. Lymphoid organs are also home to type 3 innate lymphoid cells (ILC3), innate effector cells essential for barrier immunity. However, a specialized stromal niche for ILC3 has not been identified. A novel lineage-tracing approach now identifies a subset of murine fetal lymphoid tissue organizer cells that gives rise exclusively to adult marginal reticular cells. Moreover, both cell types are conserved from mice to humans and colocalize with ILC3 in secondary lymphoid tissues throughout life. In sum, we provide evidence that fetal stromal organizers give rise to adult marginal reticular cells and form a dedicated stromal niche for innate ILC3 in adaptive lymphoid organs. Copyright © 2015 by The American Association of Immunologists, Inc.

  19. Evolution of niche preference in Sphagnum peat mosses.

    Science.gov (United States)

    Johnson, Matthew G; Granath, Gustaf; Tahvanainen, Teemu; Pouliot, Remy; Stenøien, Hans K; Rochefort, Line; Rydin, Håkan; Shaw, A Jonathan

    2015-01-01

    Peat mosses (Sphagnum) are ecosystem engineers-species in boreal peatlands simultaneously create and inhabit narrow habitat preferences along two microhabitat gradients: an ionic gradient and a hydrological hummock-hollow gradient. In this article, we demonstrate the connections between microhabitat preference and phylogeny in Sphagnum. Using a dataset of 39 species of Sphagnum, with an 18-locus DNA alignment and an ecological dataset encompassing three large published studies, we tested for phylogenetic signal and within-genus changes in evolutionary rate of eight niche descriptors and two multivariate niche gradients. We find little to no evidence for phylogenetic signal in most component descriptors of the ionic gradient, but interspecific variation along the hummock-hollow gradient shows considerable phylogenetic signal. We find support for a change in the rate of niche evolution within the genus-the hummock-forming subgenus Acutifolia has evolved along the multivariate hummock-hollow gradient faster than the hollow-inhabiting subgenus Cuspidata. Because peat mosses themselves create some of the ecological gradients constituting their own habitats, the classic microtopography of Sphagnum-dominated peatlands is maintained by evolutionary constraints and the biological properties of related Sphagnum species. The patterns of phylogenetic signal observed here will instruct future study on the role of functional traits in peatland growth and reconstruction. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  20. Analytical local electron-electron interaction model potentials for atoms

    International Nuclear Information System (INIS)

    Neugebauer, Johannes; Reiher, Markus; Hinze, Juergen

    2002-01-01

    Analytical local potentials for modeling the electron-electron interaction in an atom reduce significantly the computational effort in electronic structure calculations. The development of such potentials has a long history, but some promising ideas have not yet been taken into account for further improvements. We determine a local electron-electron interaction potential akin to those suggested by Green et al. [Phys. Rev. 184, 1 (1969)], which are widely used in atom-ion scattering calculations, electron-capture processes, and electronic structure calculations. Generalized Yukawa-type model potentials are introduced. This leads, however, to shell-dependent local potentials, because the origin behavior of such potentials is different for different shells as has been explicated analytically [J. Neugebauer, M. Reiher, and J. Hinze, Phys. Rev. A 65, 032518 (2002)]. It is found that the parameters that characterize these local potentials can be interpolated and extrapolated reliably for different nuclear charges and different numbers of electrons. The analytical behavior of the corresponding localized Hartree-Fock potentials at the origin and at long distances is utilized in order to reduce the number of fit parameters. It turns out that the shell-dependent form of Green's potential, which we also derive, yields results of comparable accuracy using only one shell-dependent parameter

  1. Vlasov fluid model with electron pressure

    International Nuclear Information System (INIS)

    Gerwin, R.

    1975-11-01

    The Vlasov-ion, fluid-electron model of Freidberg for studying the linear stability of hot-ion pinch configurations is here extended to include electron pressure. Within the framework of an adiabatic electron-gas picture, it is shown that this model is still amenable to the numerical methods described by Lewis and Freidberg

  2. Analytic model of electron pulse propagation in ultrafast electron diffraction experiments

    International Nuclear Information System (INIS)

    Michalik, A.M.; Sipe, J.E.

    2006-01-01

    We present a mean-field analytic model to study the propagation of electron pulses used in ultrafast electron diffraction experiments (UED). We assume a Gaussian form to characterize the electron pulse, and derive a system of ordinary differential equations that are solved quickly and easily to give the pulse dynamics. We compare our model to an N-body numerical simulation and are able to show excellent agreement between the two result sets. This model is a convenient alternative to time consuming and computationally intense N-body simulations in exploring the dynamics of UED electron pulses, and as a tool for refining UED experimental designs

  3. Landscape heterogeneity drives intra-population niche variation and reproduction in an arctic top predator.

    Science.gov (United States)

    L'hérault, Vincent; Franke, Alastair; Lecomte, Nicolas; Alogut, Adam; Bêty, Joël

    2013-09-01

    While intra-population variability in resource use is ubiquitous, little is known of how this measure of niche diversity varies in space and its role in population dynamics. Here we examined how heterogeneous breeding environments can structure intra-population niche variation in both resource use and reproductive output. We investigated intra-population niche variation in the Arctic tundra ecosystem, studying peregrine falcon (Falco peregrinus tundrius, White) breeding within a terrestrial-marine gradient near Rankin Inlet, Nunavut, Canada. Using stable isotope analysis, we found that intra-population niches varied at the individual level; we examined within-nest and among-nest variation, though only the latter varied along the terrestrial-marine gradient (i.e., increased among-nest variability among birds nesting within the marine environment, indicating higher degree of specialization). Terrestrial prey species (small herbivores and insectivores) were consumed by virtually all falcons. Falcons nesting within the marine environment made use of marine prey (sea birds), but depended heavily on terrestrial prey (up to 90% of the diet). Using 28-years of peregrine falcon nesting data, we found a positive relationship between the proportion of terrestrial habitat surrounding nest sites and annual nestling production, but no relationship with the likelihood of successfully rearing at least one nestling reaching 25 days old. Annually, successful inland breeders raised 0.47 more young on average compared to offshore breeders, which yields potential fitness consequences for this long-living species. The analyses of niche and reproductive success suggest a potential breeding cost for accessing distant terrestrial prey, perhaps due to additional traveling costs, for those individuals with marine nest site locations. Our study indicates how landscape heterogeneity can generate proximate (niche variation) and ultimate (reproduction) consequences on a population of generalist

  4. Development of biomass power plant technologies in Malaysia: niche development and the formation of innovative capabilities

    DEFF Research Database (Denmark)

    Hansen, Ulrich Elmer

    The objective of this thesis is to contribute to advance further the emerging research agenda on the transfer and diffusion of low-carbon technologies in developing countries by adopting a study of the development of biomass power plant technologies in Malaysia. The main research question addresses...... successive periods of fieldwork in Malaysia. The thesis conceptualises the diffusion of biomass technologies in Malaysia as a niche development process and finds that the development of a palm oil biomass waste-to-energy niche in Malaysia has only made limited progress despite a period of twenty years...... of niche formation. The thesis identifies the reluctance to implement an efficient energy policy as the main limiting factor for niche development in this case. Although a number of donor programs have advocated the introduction of a stronger enabling framework for niche development, they have generally...

  5. Untangling the relationships among regional occupancy, species traits, and niche characteristics in stream invertebrates

    Science.gov (United States)

    Heino, Jani; Grönroos, Mira

    2014-01-01

    The regional occupancy and local abundance of species are affected by various species traits, but their relative effects are poorly understood. We studied the relationships between species traits and occupancy (i.e., proportion of sites occupied) or abundance (i.e., mean local abundance at occupied sites) of stream invertebrates using small-grained data (i.e., local stream sites) across a large spatial extent (i.e., three drainage basins). We found a significant, yet rather weak, linear relationship between occupancy and abundance. However, occupancy was strongly related to niche position (NP), but it showed a weaker relationship with niche breadth (NB). Abundance was at best weakly related to these explanatory niche-based variables. Biological traits, including feeding modes, habit traits, dispersal modes and body size classes, were generally less important in accounting for variation in occupancy and abundance. Our findings showed that the regional occupancy of stream invertebrate species is mostly related to niche characteristics, in particular, NP. However, the effects of NB on occupancy were affected by the measure itself. We conclude that niche characteristics determine the regional occupancy of species at relatively large spatial extents, suggesting that species distributions are determined by environmental variation among sites. PMID:24963387

  6. The hidden Niemann-Pick type C patient: clinical niches for a rare inherited metabolic disease.

    Science.gov (United States)

    Hendriksz, Christian J; Anheim, Mathieu; Bauer, Peter; Bonnot, Olivier; Chakrapani, Anupam; Corvol, Jean-Christophe; de Koning, Tom J; Degtyareva, Anna; Dionisi-Vici, Carlo; Doss, Sarah; Duning, Thomas; Giunti, Paola; Iodice, Rosa; Johnston, Tracy; Kelly, Dierdre; Klünemann, Hans-Hermann; Lorenzl, Stefan; Padovani, Alessandro; Pocovi, Miguel; Synofzik, Matthis; Terblanche, Alta; Then Bergh, Florian; Topçu, Meral; Tranchant, Christine; Walterfang, Mark; Velten, Christian; Kolb, Stefan A

    2017-05-01

    Niemann-Pick disease type C (NP-C) is a rare, inherited neurodegenerative disease of impaired intracellular lipid trafficking. Clinical symptoms are highly heterogeneous, including neurological, visceral, or psychiatric manifestations. The incidence of NP-C is under-estimated due to under-recognition or misdiagnosis across a wide range of medical fields. New screening and diagnostic methods provide an opportunity to improve detection of unrecognized cases in clinical sub-populations associated with a higher risk of NP-C. Patients in these at-risk groups ("clinical niches") have symptoms that are potentially related to NP-C, but go unrecognized due to other, more prevalent clinical features, and lack of awareness regarding underlying metabolic causes. Twelve potential clinical niches identified by clinical experts were evaluated based on a comprehensive, non-systematic review of literature published to date. Relevant publications were identified by targeted literature searches of EMBASE and PubMed using key search terms specific to each niche. Articles published in English or other European languages up to 2016 were included. Several niches were found to be relevant based on available data: movement disorders (early-onset ataxia and dystonia), organic psychosis, early-onset cholestasis/(hepato)splenomegaly, cases with relevant antenatal findings or fetal abnormalities, and patients affected by family history, consanguinity, and endogamy. Potentially relevant niches requiring further supportive data included: early-onset cognitive decline, frontotemporal dementia, parkinsonism, and chronic inflammatory CNS disease. There was relatively weak evidence to suggest amyotrophic lateral sclerosis or progressive supranuclear gaze palsy as potential niches. Several clinical niches have been identified that harbor patients at increased risk of NP-C.

  7. The nutritional nexus: linking niche, habitat variability and prey composition in a generalist marine predator.

    Science.gov (United States)

    Machovsky-Capuska, Gabriel E; Miller, Mark G R; Silva, Fabiola R O; Amiot, Christophe; Stockin, Karen A; Senior, Alistair M; Schuckard, Rob; Melville, David; Raubenheimer, David

    2018-06-05

    1.Our understanding of the niche concept will remain limited while the quantity and range of different food types eaten remains a dominant proxy for niche breadth, as this does not account for the broad ecological context that governs diet. Linking nutrition, physiology and behaviour are critical to predict the extent to which a species adjusts its nutritional niche breadth at the levels of prey ("prey composition niche", defined as the range of prey compositions eaten), and diet ("realized nutritional niche" is the range of diets composed through feeding on the prey). 2.Here we studied adult-chick rearing Australasian gannets (Morus serrator) to propose an integrative approach using sea surface temperature anomalies (SSTa), geographic location and bathymetry over different years, to explore their relationship with the nutritional composition of prey and diets (i.e., prey composition and nutritional niche breadth), habitat use and foraging behavior. 3.We found that gannets feed on prey that varied widely in their nutritional composition (have a broad prey composition niche), and composed diets from these prey that likewise varied in composition (have a broad realized nutritional niche), suggesting generalism at two levels of macronutrient selection. 4.Across seasons, we established "nutritional landscapes" (hereafter nutriscapes), linking the nutritional content of prey (wet mass protein to-lipid ratio -P:L-) to the most likely geographic area of capture and bathymetry. Nutriscapes varied in their P:L from 6.06 to 15.28, over time, space and bathymetry (0 to 150 m). 5.During warm water events (strong positive SSTa), gannets expanded their foraging habitat, increased their foraging trip duration and consumed prey and diets with low macronutrient content (wet mass proportions of P and L). They were also constrained to the smallest prey composition and realized nutritional niche breadths. 6.Our findings are consistent with previous suggestions that dietary generalism

  8. A practical guideline for examining a uterine niche using ultrasonography in non-pregnant women: a modified Delphi method amongst European experts.

    Science.gov (United States)

    Jordans, I P M; de Leeuw, R; Stegwee, S I; Amso, N N; Barri-Soldevila, P N; van den Bosch, T; Bourne, T; Brolmann, H A M; Donnez, O; Dueholm, M; Hehenkamp, W J K; Jastrow, N; Jurkovic, D; Mashiach, R; Naji, O; Streuli, I; Timmerman, D; Vd Voet, L F; Huirne, J A F

    2018-03-14

    To generate a uniform, internationally recognized guideline for detailed uterine niche evaluation by ultrasonography in non-pregnant women using a modified Delphi method amongst international experts. Fifteen international gynecological experts were recruited by their membership of the European niche taskforce group. All experts were physicians with extensive experience in niche evaluation in clinical practice and/or authors of niche studies. Relevant items for niche measurement were determined based on the results of a literature search and recommendations of a focus group. Two online questionnaires were sent to the expert panel and one group meeting was organized. Consensus was predefined as a consensus rate of at least 70%. In total 15 experts participated in this study. Consensus was reached for a total of 42 items on niche evaluation, including definitions, relevance, method of measurement and tips for visualization of the niche. All experts agreed on the proposed guideline for niche evaluation in non-pregnant women as presented in this paper. Consensus between niche experts was achieved on all items regarding ultrasonographic niche measurement. This article is protected by copyright. All rights reserved.

  9. Engineering Hydrogel Microenvironments to Recapitulate the Stem Cell Niche.

    Science.gov (United States)

    Madl, Christopher M; Heilshorn, Sarah C

    2018-06-04

    Stem cells are a powerful resource for many applications including regenerative medicine, patient-specific disease modeling, and toxicology screening. However, eliciting the desired behavior from stem cells, such as expansion in a naïve state or differentiation into a particular mature lineage, remains challenging. Drawing inspiration from the native stem cell niche, hydrogel platforms have been developed to regulate stem cell fate by controlling microenvironmental parameters including matrix mechanics, degradability, cell-adhesive ligand presentation, local microstructure, and cell-cell interactions. We survey techniques for modulating hydrogel properties and review the effects of microenvironmental parameters on maintaining stemness and controlling differentiation for a variety of stem cell types. Looking forward, we envision future hydrogel designs spanning a spectrum of complexity, ranging from simple, fully defined materials for industrial expansion of stem cells to complex, biomimetic systems for organotypic cell culture models.

  10. Co-niche construction between hosts and symbionts

    Indian Academy of Sciences (India)

    Symbiosis is a process that can generate evolutionary novelties and can extend the phenotypic niche space of organisms. Symbionts can act together with their hosts to co-construct host organs, within which symbionts are housed. Once established within hosts, symbionts can also influence various aspects of host ...

  11. Platelets prime hematopoietic and vascular niche to drive angiocrine-mediated liver regeneration.

    Science.gov (United States)

    Shido, Koji; Chavez, Deebly; Cao, Zhongwei; Ko, Jane; Rafii, Shahin; Ding, Bi-Sen

    2017-01-01

    In mammals, the livers regenerate after chemical injury or resection of hepatic lobe by hepatectomy. How liver regeneration is initiated after mass loss remains to be defined. Here, we report that following liver injury, activated platelets deploy SDF-1 and VEGF-A to stimulate CXCR7 + liver sinusoidal endothelial cell (LSEC) and VEGFR1 + myeloid cell, orchestrating hepatic regeneration. After carbon tetrachloride (CCl 4 ) injection or hepatectomy, platelets and CD11b + VEGFR1 + myeloid cells were recruited LSEC, and liver regeneration in both models was impaired in thrombopoietin-deficient ( Thpo -/- ) mice lacking circulating platelets. This impeded regeneration phenotype was recapitulated in mice with either conditional ablation of Cxcr7 in LSEC ( Cxcr7 iΔ/iΔ ) or Vegfr1 in myeloid cell ( Vegfr1 lysM/lysM ). Both Vegfr1 lysM/lysM and Cxcr7 iΔ/iΔ mice exhibited suppressed expression of hepatocyte growth factor and Wnt2, two crucial trophogenic angiocrine factors instigating hepatocyte propagation. Of note, administration of recombinant thrombopoietin restored the prohibited liver regeneration in the tested genetic models. As such, our data suggest that platelets and myeloid cells jointly activate the vascular niche to produce pro-regenerative endothelial paracrine/angiocrine factors. Modulating this "hematopoietic-vascular niche" might help to develop regenerative therapy strategy for hepatic disorders.

  12. Bifurcation into functional niches in adaptation.

    Science.gov (United States)

    White, Justin S; Adami, Christoph

    2004-01-01

    One of the central questions in evolutionary biology concerns the dynamics of adaptation and diversification. This issue can be addressed experimentally if replicate populations adapting to identical environments can be investigated in detail. We have studied 501 such replicas using digital organisms adapting to at least two fundamentally different functional niches (survival strategies) present in the same environment: one in which fast replication is the way to live, and another where exploitation of the environment's complexity leads to complex organisms with longer life spans and smaller replication rates. While these two modes of survival are closely analogous to those expected to emerge in so-called r and K selection scenarios respectively, the bifurcation of evolutionary histories according to these functional niches occurs in identical environments, under identical selective pressures. We find that the branching occurs early, and leads to drastic phenotypic differences (in fitness, sequence length, and gestation time) that are permanent and irreversible. This study confirms an earlier experimental effort using microorganisms, in that diversification can be understood at least in part in terms of bifurcations on saddle points leading to peak shifts, as in the picture drawn by Sewall Wright.

  13. The exploitation of the niche market through innovation and marketing : the case of Japanese small businesses

    OpenAIRE

    Sato, Yoshio

    1992-01-01

    Japan's economic growth brought many business oportunities and niche markets for small business, where new entrepreneurs entered. Competition and self-revolutionalizing efforts made the level of their technology and management highly specialized. Various examples of niche marketing strategies in Japan by several types of smaller businesses are followed. Recent new ventures' strategies, typical "venture businesses" activities, niche marketing by diversification strategies and self revolutional...

  14. Distribution and Conservation of Davilla (Dilleniaceae in Brazilian Atlantic Forest Using Ecological Niche Modeling

    Directory of Open Access Journals (Sweden)

    Ismael Martins Pereira

    2014-01-01

    Full Text Available We have modeled the ecological niche for 12 plant species belonging to the genus Davilla (Dilleniaceae which occur in the Atlantic Forest of Brazil. This group includes endemic species lianas threatened by extinction and is therefore a useful indicator for forest areas requiring conservation. The aims are to compare the distribution and richness of species within the protected areas, assessing the degree of protection and gap analysis of reserves for this group. We used the Maxent algorithm with environmental and occurrence data, and produced geographic distribution maps. The results show that high species richness occurs in forest and coastal forest of Espírito Santo to Bahia states. The endemic species comprise D. flexuosa, D. macrocarpa, D. flexuosa, D. grandifolia, and D. sessilifolia. In the Atlantic Forest of southeastern Brazil, the following endemic species occur: D. tintinnabulata and D. glaziovii, with this latter species being included in the “red list” due habitat loss and predatory extractivism. The indicators of species richness in the coastal region of Bahia correspond with floristic inventories that point to this area having a high biodiversity. Although this region has several protected areas, there are gaps in reserves, which, combined with anthropogenic threats and fragmentation, have caused several problems for biodiversity.

  15. Social intelligence, human intelligence and niche construction.

    Science.gov (United States)

    Sterelny, Kim

    2007-04-29

    This paper is about the evolution of hominin intelligence. I agree with defenders of the social intelligence hypothesis in thinking that externalist models of hominin intelligence are not plausible: such models cannot explain the unique cognition and cooperation explosion in our lineage, for changes in the external environment (e.g. increasing environmental unpredictability) affect many lineages. Both the social intelligence hypothesis and the social intelligence-ecological complexity hybrid I outline here are niche construction models. Hominin evolution is hominin response to selective environments that earlier hominins have made. In contrast to social intelligence models, I argue that hominins have both created and responded to a unique foraging mode; a mode that is both social in itself and which has further effects on hominin social environments. In contrast to some social intelligence models, on this view, hominin encounters with their ecological environments continue to have profound selective effects. However, though the ecological environment selects, it does not select on its own. Accidents and their consequences, differential success and failure, result from the combination of the ecological environment an agent faces and the social features that enhance some opportunities and suppress others and that exacerbate some dangers and lessen others. Individuals do not face the ecological filters on their environment alone, but with others, and with the technology, information and misinformation that their social world provides.

  16. Using environmental niche modeling to find suitable habitats for the Hard-ground Barasingha in Madhya Pradesh, India

    Directory of Open Access Journals (Sweden)

    C. P. Singh

    2015-09-01

    Full Text Available The subspecies of Swamp Deer, the Hard-ground Barasingha (Rucervus duvaucelii branderi Pocock, is presently found only in Kanha Tiger Reserve (KTR in Madhya Pradesh, India. This subspecies is highly vulnerable to extinction, and reintroduction in suitable sites is the need of the hour.  Environmental niche models (GARP, SVM, ED, CSM aimed at providing a detailed prediction of species distribution by relating presence of species to 19 bioclimatic indices were developed, using swamp deer occurrence records in KTR. The predictions were appropriately weighted with the prevailing LU/LC classes to identify suitable habitats in Madhya Pradesh, India. The result shows that the southern region of Madhya Pradesh is suitable for the sustenance of Barasingha with varying degrees of habitability. Vicarious validation shows that most of these forest areas were the same as that of historical records dating back to 50 years. However, land use maps can help identify areas where this subspecies can be reintroduced. 

  17. The human socio-cognitive niche and its evolutionary origins

    Science.gov (United States)

    Whiten, Andrew; Erdal, David

    2012-01-01

    Hominin evolution took a remarkable pathway, as the foraging strategy extended to large mammalian prey already hunted by a guild of specialist carnivores. How was this possible for a moderately sized ape lacking the formidable anatomical adaptations of these competing ‘professional hunters’? The long-standing answer that this was achieved through the elaboration of a new ‘cognitive niche’ reliant on intelligence and technology is compelling, yet insufficient. Here we present evidence from a diversity of sources supporting the hypothesis that a fuller answer lies in the evolution of a new socio-cognitive niche, the principal components of which include forms of cooperation, egalitarianism, mindreading (also known as ‘theory of mind’), language and cultural transmission, that go far beyond the most comparable phenomena in other primates. This cognitive and behavioural complex allows a human hunter–gatherer band to function as a unique and highly competitive predatory organism. Each of these core components of the socio-cognitive niche is distinctive to humans, but primate research has increasingly identified related capacities that permit inferences about significant ancestral cognitive foundations to the five pillars of the human social cognitive niche listed earlier. The principal focus of the present study was to review and integrate this range of recent comparative discoveries. PMID:22734055

  18. Wnt ligand presentation and reception: from the stem cell niche to tissue engineering.

    Science.gov (United States)

    Mills, Kate M; Szczerkowski, James L A; Habib, Shukry J

    2017-08-01

    Stem cells reside in niches where spatially restricted signals maintain a delicate balance between stem cell self-renewal and differentiation. Wnt family proteins are particularly suited for this role as they are modified by lipids, which constrain and spatially regulate their signalling range. In recent years, Wnt/β-catenin signalling has been shown to be essential for the self-renewal of a variety of mammalian stem cells. In this review, we discuss Wnt-responsive stem cells in their niche, and mechanisms by which Wnt ligands are presented to responsive cells. We also highlight recent progress in molecular visualization that has allowed for the monitoring of Wnt signalling within the stem cell compartment and new approaches to recapitulate this niche signalling in vitro Indeed, new technologies that present Wnt in a localized manner and mimic the three-dimensional microenvironment of stem cells will advance our understanding of Wnt signalling in the stem cell niche. These advances will expand current horizons to exploit Wnt ligands in the rapidly evolving fields of tissue engineering and regenerative medicine. © 2017 The Authors.

  19. Climatic niche evolution is faster in sympatric than allopatric lineages of the butterfly genus Pyrgus.

    Science.gov (United States)

    Pitteloud, Camille; Arrigo, Nils; Suchan, Tomasz; Mastretta-Yanes, Alicia; Vila, Roger; Dincă, Vlad; Hernández-Roldán, Juan; Brockmann, Ernst; Chittaro, Yannick; Kleckova, Irena; Fumagalli, Luca; Buerki, Sven; Pellissier, Loïc; Alvarez, Nadir

    2017-04-12

    Understanding how speciation relates to ecological divergence has long fascinated biologists. It is assumed that ecological divergence is essential to sympatric speciation, as a mechanism to avoid competition and eventually lead to reproductive isolation, while divergence in allopatry is not necessarily associated with niche differentiation. The impact of the spatial context of divergence on the evolutionary rates of abiotic dimensions of the ecological niche has rarely been explored for an entire clade. Here, we compare the magnitude of climatic niche shifts between sympatric versus allopatric divergence of lineages in butterflies. By combining next-generation sequencing, parametric biogeography and ecological niche analyses applied to a genus-wide phylogeny of Palaearctic Pyrgus butterflies, we compare evolutionary rates along eight climatic dimensions across sister lineages that diverged in large-scale sympatry versus allopatry. In order to examine the possible effects of the spatial scale at which sympatry is defined, we considered three sets of biogeographic assignments, ranging from narrow to broad definition. Our findings suggest higher rates of niche evolution along all climatic dimensions for sister lineages that diverge in sympatry, when using a narrow delineation of biogeographic areas. This result contrasts with significantly lower rates of climatic niche evolution found in cases of allopatric speciation, despite the biogeographic regions defined here being characterized by significantly different climates. Higher rates in allopatry are retrieved when biogeographic areas are too widely defined-in such a case allopatric events may be recorded as sympatric. Our results reveal the macro-evolutionary significance of abiotic niche differentiation involved in speciation processes within biogeographic regions, and illustrate the importance of the spatial scale chosen to define areas when applying parametric biogeographic analyses. © 2017 The Author(s).

  20. Adopting Strategic Niche Management to Evaluate EV Demonstration Projects in China

    Directory of Open Access Journals (Sweden)

    Yixi Xue

    2016-02-01

    Full Text Available Electric Vehicles (EVs are considered to be a potential viable technology to address the persistent unsustainable problems in transport sector. In this paper, we focus on analyzing the transition processes of EVs in China because the sustainability of developing countries is essential for the worldwide sustainability. The two-round demonstration programs of EVs in China were analyzed by adopting the strategic niche management (SNM approach so as to find out what niche protection has been provided and which obstacles hamper the further development of EVs. The results show that the financial subsidy is the most important protective measure. However, the diffusion results of EVs in different pilot cities are greatly different. The main reason lies in the uneven geographical landscape. In addition, some obstacles were exposed during the niche internal processes including low quality of expectations and poor alignment within the network. Based on the analysis results, we develop a list of suggestions that are important to consider when developing EVs.

  1. Modeling the ecologic niche of plague in sylvan and domestic animal hosts to delineate sources of human exposure in the western United States

    Directory of Open Access Journals (Sweden)

    Michael Walsh

    2015-12-01

    Full Text Available Plague has been established in the western United States (US since 1900 following the West Coast introduction of commensal rodents infected with Yersinia pestis via early industrial shipping. Over the last century, plague ecology has transitioned through cycles of widespread human transmission, urban domestic transmission among commensal rodents, and ultimately settled into the predominantly sylvan foci that remain today where it is maintained alternatively by enzootic and epizootic transmission. While zoonotic transmission to humans is much less common in modern times, significant plague risk remains in parts of the western US. Moreover, risk to some threatened species that are part of the epizootic cycle can be quite substantive. This investigation attempted to predict the risk of plague across the western US by modeling the ecologic niche of plague in sylvan and domestic animals identified between 2000 and 2015. A Maxent machine learning algorithm was used to predict this niche based on climate, altitude, land cover, and the presence of an important enzootic species, Peromyscus maniculatus. This model demonstrated good predictive ability (AUC = 86% and identified areas of high risk in central Colorado, north-central New Mexico, and southwestern and northeastern California. The presence of P. maniculatus, altitude, precipitation during the driest and wettest quarters, and distance to artificial surfaces, all contributed substantively to maximizing the gain function. These findings add to the known landscape epidemiology and infection ecology of plague in the western US and may suggest locations of particular risk to be targeted for wild and domestic animal intervention.

  2. Green Power Marketing - from Niches to Mass Markets

    International Nuclear Information System (INIS)

    Wuestenhagen, Rolf

    2000-01-01

    In the process of liberalization of the electricity market the customers are now in a position to participate in the decision on how their electricity is produced. In particular, many consumers have a preference for renewable energies. For the producers, marketing of 'eco-power' is an opportunity to achieve sustainable competitive advantage. However, the market share of these products is still quite small today, and 'eco-power' is usually marketed as an expensive niche product. From the perspective of sustainable development these niches are a necessary but not sufficient step. In this book, ways are discussed which could lead to a mass-market penetration of eco-power products. A theoretical analysis is combined with empirical evidence derived from the eco-power market in Germany, Switzerland, Great Britain and the U.S. as well as with a comparison with other market segments [de

  3. Role of the Stem Cell Niche in Hormone-induced Tumorigenesis in Fetal Mouse Mammary Epithelium

    National Research Council Canada - National Science Library

    Chepko, Gloria; Hilakivi-Clarke, Leena

    2006-01-01

    Develop an immunohistochemical method for identifying stem cells and stem cell niches, and to use this to determine if in utero estrogenic overstimulation causes changes in the number of stem cells or their niches...

  4. Axonal Control of the Adult Neural Stem Cell Niche

    Science.gov (United States)

    Tong, Cheuk Ka; Chen, Jiadong; Cebrián-Silla, Arantxa; Mirzadeh, Zaman; Obernier, Kirsten; Guinto, Cristina D.; Tecott, Laurence H.; García-Verdugo, Jose Manuel; Kriegstein, Arnold; Alvarez-Buylla, Arturo

    2014-01-01

    SUMMARY The ventricular-subventricular zone (V-SVZ) is an extensive germinal niche containing neural stem cells (NSC) in the walls of the lateral ventricles of the adult brain. How the adult brain’s neural activity influences the behavior of adult NSCs remains largely unknown. We show that serotonergic (5HT) axons originating from a small group of neurons in the raphe form an extensive plexus on most of the ventricular walls. Electron microscopy revealed intimate contacts between 5HT axons and NSCs (B1) or ependymal cells (E1) and these cells were labeled by a transsynaptic viral tracer injected into the raphe. B1 cells express the 5HT receptors 2C and 5A. Electrophysiology showed that activation of these receptors in B1 cells induced small inward currents. Intraventricular infusion of 5HT2C agonist or antagonist increased or decreased V-SVZ proliferation, respectively. These results indicate that supraependymal 5HT axons directly interact with NSCs to regulate neurogenesis via 5HT2C. PMID:24561083

  5. Ecology: a niche for cyanobacteria containing chlorophyll d

    DEFF Research Database (Denmark)

    Kühl, Michael; Chen, Min; Ralph, Peter J

    2005-01-01

    we demonstrate photosynthetic activity in Acaryochloris-like phototrophs that live underneath minute coral-reef invertebrates (didemnid ascidians) in a shaded niche enriched in near-infrared light. This discovery clarifies how these cyanobacteria are able to thrive as free-living organisms...

  6. Affordances and Landscapes: Overcoming the Nature-Culture Dichotomy through Niche Construction Theory.

    Science.gov (United States)

    Heras-Escribano, Manuel; De Pinedo-García, Manuel

    2017-01-01

    In this paper we reject the nature-culture dichotomy by means of the idea of affordance or possibility for action, which has important implications for landscape theory. Our hypothesis is that, just as the idea of affordance can serve to overcome the subjective-objective dichotomy, the ideas of landscape and ecological niche, properly defined, would allow us to also transcend the nature-culture dichotomy. First, we introduce an overview of landscape theory, emphasizing processual landscape theory as the most suitable approach for satisfying both cultural and naturalist approaches. After that, we introduce the idea of affordance and we analyze a tension between sociocultural and transcultural affordances (affordances that depend on cultural conventions and affordances that depend on lawful information and bodily aspects of agents). This tension has various implications for landscape theory and ecological niches. Our proposal is that sociocultural and transcultural aspects of affordances could be systematically accommodated if we apply niche construction theory (the theory that explains the process by which organisms modify their selective environments) as a methodological framework for explaining the emergence of ecological niches. This approach will lead us to an integrative account of landscapes as the products of the interaction between human and environmental elements, making it a clear example of a concept that transcends the nature-culture dichotomy.

  7. Cellular players of hematopoietic stem cell mobilization in the bone marrow niche.

    Science.gov (United States)

    Tay, Joshua; Levesque, Jean-Pierre; Winkler, Ingrid G

    2017-02-01

    Hematopoietic stem cells (HSC) reside in perivascular regions of the bone marrow (BM) embedded within a complex regulatory unit called the niche. Cellular components of HSC niches include vascular endothelial cells, mesenchymal stromal progenitor cells and a variety of mature hematopoietic cells such as macrophages, neutrophils, and megakaryocytes-further regulated by sympathetic nerves and complement components as described in this review. Three decades ago the discovery that cytokines induce a large number of HSC to mobilize from the BM into the blood where they are easily harvested, revolutionised the field of HSC transplantation-curative for immune-deficiencies and some malignancies. However, despite now routine use of granulocyte-colony stimulating factor (G-CSF) to mobilise HSC for transplant, only in last 15 years has research on the mechanisms behind why and how HSC can be induced to move into the blood began. These studies have revealed the complexity of the niche that retains HSC in the BM. This review describes how BM niches and HSC themselves change during administration of G-CSF-or in the recovery phase of chemotherapy-to facilitate movement of HSC into the blood, and research now leading to development of novel therapeutics to further boost HSC mobilization and transplant success.

  8. Cryptococcus gattii: Emergence in Western North America: Exploitation of a Novel Ecological Niche

    Directory of Open Access Journals (Sweden)

    Kausik Datta

    2009-01-01

    Full Text Available The relatively uncommon fungal pathogen Cryptococcus gattii recently emerged as a significant cause of cryptococcal disease in human and animals in the Pacific Northwest of North America. Although genetic studies indicated its possible presence in the Pacific Northwest for more than 30 years, C. gattii as an etiological agent was largely unknown in this region prior to 1999. The recent emergence may have been encouraged by changing conditions of climate or land use and/or host susceptibility, and predictive ecological niche modeling indicates a potentially wider spread. C. gattii can survive wide climatic variations and colonize the environment in tropical, subtropical, temperate, and dry climates. Long-term climate changes, such as the significantly elevated global temperature in the last 100 years, influence patterns of disease among plants and animals and create niche microclimates habitable by emerging pathogens. C. gattii may have exploited such a hitherto unrecognized but clement environment in the Pacific Northwest to provide a wider exposure and risk of infection to human and animal populations.

  9. Multifaceted Roles of Connexin 43 in Stem Cell Niches.

    Science.gov (United States)

    Genet, Nafiisha; Bhatt, Neha; Bourdieu, Antonin; Hirschi, Karen K

    2018-01-01

    Considerable progress has been made in the field of stem cell research; nonetheless, the use of stem cells for regenerative medicine therapies, for either endogenous tissue repair or cellular grafts post injury, remains a challenge. To better understand how to maintain stem cell potential in vivo and promote differentiation ex vivo, it is fundamentally important to elucidate the interactions between stem cells and their surrounding partners within their distinct niches. Among the vast array of proteins depicted as mediators for cell-to-cell interactions, connexin-comprised gap junctions play pivotal roles in the regulation of stem cell fate both in vivo and in vitro. This review summarizes and illustrates the current knowledge regarding the multifaceted roles of Cx43, specifically, in various stem cell niches.

  10. The impact of niche green developments in transforming the building sector: The case study of Lochiel Park

    International Nuclear Information System (INIS)

    Berry, Stephen; Davidson, Kathryn; Saman, Wasim

    2013-01-01

    Energy use in residential buildings is a significant contributor to global carbon emissions. The South Australian Government responded to concern for anthropogenic greenhouse gas emissions by creating a model development of near zero energy homes in a near zero carbon impact estate. The creation of the Lochiel Park Green Village challenged a collective of industry experts and policy makers to set objectives, performance targets and regulatory guidelines outside existing institutional and professional norms. Literature suggests that the creation of niche events can help the transition away from dominant technologies, practices and beliefs, and lead to organisations embracing new tools, construction practices, technologies, standards and policies. By applying a multi-level socio-technical framework, and utilising evidence collected from a series of interviews with key government and industry leaders, this paper examines how, under the influence of landscape pressures, structural change at the regime level can come from the incubation of ideas and experiences at the niche level. The available evidence finds that the creation of the Lochiel Park Green Village has allowed many individuals and organisations to gain a more detailed and practical understanding of sustainable housing, and has given organisations the confidence to change industry practices, government policies, and regulatory standards. -- Highlights: •We examined the impact of creating a net zero carbon residential development. •Structural change can come from incubation of experiences at the niche level. •Significant barriers to sustainability can be overcome through leadership. •Performance targets were set outside existing institutional and professional norms. •Niche events help transition from dominant technologies, practices and beliefs

  11. The impact of failure: unsuccessful bacterial invasions steer the soil microbial community away from the invader's niche.

    Science.gov (United States)

    Mallon, C A; Le Roux, X; van Doorn, G S; Dini-Andreote, F; Poly, F; Salles, J F

    2018-03-01

    Although many environments like soils are constantly subjected to invasion by alien microbes, invaders usually fail to succeed, succumbing to the robust diversity often found in nature. So far, only successful invasions have been explored, and it remains unknown to what extent an unsuccessful invasion can impact resident communities. Here we hypothesized that unsuccessful invasions can cause impacts to soil functioning by decreasing the diversity and niche breadth of resident bacterial communities, which could cause shifts to community composition and niche structure-an effect that is likely exacerbated when diversity is compromised. To examine this question, diversity gradients of soil microbial communities were subjected to invasion by the frequent, yet oft-unsuccessful soil invader, Escherichia coli, and evaluated for changes to diversity, bacterial community composition, niche breadth, and niche structure. Contrary to expectations, diversity and niche breadth increased across treatments upon invasion. Community composition and niche structure were also altered, with shifts of niche structure revealing an escape by the resident community away from the invader's resources. Importantly, the extent of the escape varied in response to the community's diversity, where less diverse communities experienced larger shifts. Thus, although transient and unsuccessful, the invader competed for resources with resident species and caused tangible impacts that modified both the diversity and functioning of resident communities, which can likely generate a legacy effect that influences future invasion attempts.

  12. Regulation of the hematopoietic stem cell lifecycle by the endothelial niche.

    Science.gov (United States)

    Ramalingam, Pradeep; Poulos, Michael G; Butler, Jason M

    2017-07-01

    Hematopoietic stem cells (HSCs) predominantly reside either in direct contact or in close proximity to the vascular endothelium throughout their lifespan. From the moment of HSC embryonic specification from hemogenic endothelium, endothelial cells (ECs) act as a critical cellular-hub that regulates a vast repertoire of biological processes crucial for HSC maintenance throughout its lifespan. In this review, we will discuss recent findings in endothelial niche-mediated regulation of HSC function during development, aging and regenerative conditions. Studies employing genetic vascular models have unequivocally confirmed that ECs provide the essential instructive cues for HSC emergence during embryonic development as well as adult HSC maintenance during homeostasis and regeneration. Aging of ECs may impair their ability to maintain HSC function contributing to the development of aging-associated hematopoietic deficiencies. These findings have opened up new avenues to explore the therapeutic application of ECs. ECs can be adapted to serve as an instructive platform to expand bona fide HSCs and also utilized as a cellular therapy to promote regeneration of the hematopoietic system following myelosuppressive and myeloablative injuries. ECs provide a fertile niche for maintenance of functional HSCs throughout their lifecycle. An improved understanding of the EC-HSC cross-talk will pave the way for development of EC-directed strategies for improving HSC function during aging.

  13. The electronic-commerce-oriented virtual merchandise model

    Science.gov (United States)

    Fang, Xiaocui; Lu, Dongming

    2004-03-01

    Electronic commerce has been the trend of commerce activities. Providing with Virtual Reality interface, electronic commerce has better expressing capacity and interaction means. But most of the applications of virtual reality technology in EC, 3D model is only the appearance description of merchandises. There is almost no information concerned with commerce information and interaction information. This resulted in disjunction of virtual model and commerce information. So we present Electronic Commerce oriented Virtual Merchandise Model (ECVMM), which combined a model with commerce information, interaction information and figure information of virtual merchandise. ECVMM with abundant information provides better support to information obtainment and communication in electronic commerce.

  14. Ontogenetic niche shifts in three Vaccinium species on a sub-alpine mountain side

    DEFF Research Database (Denmark)

    Auffret, Alistair G.; Meineri, Eric; Bruun, Hans Henrik

    2010-01-01

    Background: Climate warming in arctic and alpine regions is expected to result in the altitudinal migration of plant species, but current predictions neglect differences between species' regeneration niche and established niche. Aims: To examine potential recruitment of Vaccinium myrtillus, V. ul...

  15. A closer look at the main actors of Neotropical floodplain food webs: functional classification and niche overlap of dominant benthic invertebrates in a floodplain lake of Paraná River

    Directory of Open Access Journals (Sweden)

    Miguel Saigo

    2016-01-01

    Full Text Available ABSTRACT Functional classification of animals is necessary to enhance the predictive power of food web models. However, while there is a large database for functional classification of benthic invertebrates (Functional Feeding Groups, FFG in the temperate zone, the attribution of individual species of riverine invertebrates is still in its infancies in the Neotropical Region. Different authors hypothesized that diet breadth was larger in the Tropics, however detailed analysis are scarce. In the present study we aimed at classifying dominant benthic taxa of the Middle Paraná River floodplain (Argentina into trophic guilds by diet and niche overlap analyses. We sampled twelve taxa of benthic invertebrates from a floodplain lake during low water season and performed a gut content analysis as a baseline for FFG classification. We also used available diet information of other common taxa for statistical analysis. Then, we compared the variance of niche overlap, using Pianka's index, with that of simulated null model. After that we grouped taxa using Morisita similarity index with a threshold of 0.6 and compared niche overlap with null models within and between FFGs. Observed variance of niche overlap was greater than expected by chance, confirming the presence of FFGs among analyzed taxa. Considering trophic similarity of species, we identified four FFGs: collectors, omnivores, herbivores and predators. Niche overlap was greater than expected by stochastic null models within FFGs, and smaller between FFGs. Nearly one third of analyzed taxa were classified in a different FFG than their congeners of the Holarctic region. This result indicates that classifications performed in the Holarctic region should be used with care in the Neotropical region, even in subtropical systems

  16. Foraging niche segregation in Malaysian babblers (Family: Timaliidae.

    Directory of Open Access Journals (Sweden)

    Mohammad Saiful Mansor

    Full Text Available Tropical rainforests are considered as hotspots for bird diversity, yet little is known about the system that upholds the coexistence of species. Differences in body size that are associated with foraging strategies and spatial distribution are believed to promote the coexistence of closely related species by reducing competition. However, the fact that many babbler species do not differ significantly in their morphology has challenged this view. We studied the foraging ecology of nine sympatric babbler species (i.e., Pellorneum capistratum, P. bicolor, P. malaccense, Malacopteron cinereum, M. magnum, Stachyris nigriceps, S. nigricollis, S. maculata, and Cyanoderma erythropterum in the Krau Wildlife Reserve in Peninsular Malaysia. We investigated; i how these babblers forage in the wild and use vegetation to obtain food, and ii how these trophically similar species differ in spatial distribution and foraging tactics. Results indicated that most babblers foraged predominantly on aerial leaf litter and used gleaning manoeuvre in intermediate-density foliage but exhibited wide ranges of vertical strata usage, thus reducing interspecific competition. The principal component analysis indicated that two components, i.e., foraging height and substrate are important as mechanisms to allow the coexistence of sympatric babblers. The present findings revealed that these bird species have unique foraging niches that are distinct from each other, and this may apply to other insectivorous birds inhabiting tropical forests. This suggests that niche separation does occur among coexisting birds, thus following Gause' law of competitive exclusion, which states two species occupying the same niche will not stably coexist.

  17. Foraging niche segregation in Malaysian babblers (Family: Timaliidae).

    Science.gov (United States)

    Mansor, Mohammad Saiful; Ramli, Rosli

    2017-01-01

    Tropical rainforests are considered as hotspots for bird diversity, yet little is known about the system that upholds the coexistence of species. Differences in body size that are associated with foraging strategies and spatial distribution are believed to promote the coexistence of closely related species by reducing competition. However, the fact that many babbler species do not differ significantly in their morphology has challenged this view. We studied the foraging ecology of nine sympatric babbler species (i.e., Pellorneum capistratum, P. bicolor, P. malaccense, Malacopteron cinereum, M. magnum, Stachyris nigriceps, S. nigricollis, S. maculata, and Cyanoderma erythropterum) in the Krau Wildlife Reserve in Peninsular Malaysia. We investigated; i) how these babblers forage in the wild and use vegetation to obtain food, and ii) how these trophically similar species differ in spatial distribution and foraging tactics. Results indicated that most babblers foraged predominantly on aerial leaf litter and used gleaning manoeuvre in intermediate-density foliage but exhibited wide ranges of vertical strata usage, thus reducing interspecific competition. The principal component analysis indicated that two components, i.e., foraging height and substrate are important as mechanisms to allow the coexistence of sympatric babblers. The present findings revealed that these bird species have unique foraging niches that are distinct from each other, and this may apply to other insectivorous birds inhabiting tropical forests. This suggests that niche separation does occur among coexisting birds, thus following Gause' law of competitive exclusion, which states two species occupying the same niche will not stably coexist.

  18. Spermatogonial stem cell markers and niche in equids.

    Directory of Open Access Journals (Sweden)

    Guilherme M J Costa

    Full Text Available Spermatogonial stem cells (SSCs are the foundation of spermatogenesis and are located in a highly dynamic microenvironment called "niche" that influences all aspects of stem cell function, including homing, self-renewal and differentiation. Several studies have recently identified specific proteins that regulate the fate of SSCs. These studies also aimed at identifying surface markers that would facilitate the isolation of these cells in different vertebrate species. The present study is the first to investigate SSC physiology and niche in stallions and to offer a comparative evaluation of undifferentiated type A spermatogonia (Aund markers (GFRA1, PLZF and CSF1R in three different domestic equid species (stallions, donkeys, and mules. Aund were first characterized according to their morphology and expression of the GFRA1 receptor. Our findings strongly suggest that in stallions these cells were preferentially located in the areas facing the interstitium, particularly those nearby blood vessels. This distribution is similar to what has been observed in other vertebrate species. In addition, all three Aund markers were expressed in the equid species evaluated in this study. These markers have been well characterized in other mammalian species, which suggests that the molecular mechanisms that maintain the niche and Aund/SSCs physiology are conserved among mammals. We hope that our findings will help future studies needing isolation and cryopreservation of equids SSCs. In addition, our data will be very useful for studies that aim at preserving the germplasm of valuable animals, and involve germ cell transplantation or xenografts of equids testis fragments/germ cells suspensions.

  19. Foraging niche segregation in Malaysian babblers (Family: Timaliidae)

    Science.gov (United States)

    Mansor, Mohammad Saiful; Ramli, Rosli

    2017-01-01

    Tropical rainforests are considered as hotspots for bird diversity, yet little is known about the system that upholds the coexistence of species. Differences in body size that are associated with foraging strategies and spatial distribution are believed to promote the coexistence of closely related species by reducing competition. However, the fact that many babbler species do not differ significantly in their morphology has challenged this view. We studied the foraging ecology of nine sympatric babbler species (i.e., Pellorneum capistratum, P. bicolor, P. malaccense, Malacopteron cinereum, M. magnum, Stachyris nigriceps, S. nigricollis, S. maculata, and Cyanoderma erythropterum) in the Krau Wildlife Reserve in Peninsular Malaysia. We investigated; i) how these babblers forage in the wild and use vegetation to obtain food, and ii) how these trophically similar species differ in spatial distribution and foraging tactics. Results indicated that most babblers foraged predominantly on aerial leaf litter and used gleaning manoeuvre in intermediate-density foliage but exhibited wide ranges of vertical strata usage, thus reducing interspecific competition. The principal component analysis indicated that two components, i.e., foraging height and substrate are important as mechanisms to allow the coexistence of sympatric babblers. The present findings revealed that these bird species have unique foraging niches that are distinct from each other, and this may apply to other insectivorous birds inhabiting tropical forests. This suggests that niche separation does occur among coexisting birds, thus following Gause’ law of competitive exclusion, which states two species occupying the same niche will not stably coexist. PMID:28253284

  20. ECRB ALCOVE AND NICHE GROUND SUPPORT ANALYSIS

    International Nuclear Information System (INIS)

    J.W. Keifer

    1999-01-01

    The purpose of the analysis is to provide design bases for Enhanced Characterization of the Repository Block (ECRB) alcove and niche ground support drawings. The objective is to evaluate the ESF Alcove Ground Support Analysis (Ref 5.1) to determine if the calculations technically bound the ECRB alcoves and to address specific differences in the conditions and constraints

  1. Isotopic niche partitioning between two apex predators over time.

    Science.gov (United States)

    Drago, Massimiliano; Cardona, Luis; Franco-Trecu, Valentina; Crespo, Enrique A; Vales, Damián G; Borella, Florencia; Zenteno, Lisette; Gonzáles, Enrique M; Inchausti, Pablo

    2017-07-01

    Stable isotope analyses have become an important tool in reconstructing diets, analysing resource use patterns, elucidating trophic relations among predators and understanding the structure of food webs. Here, we use stable carbon and nitrogen isotope ratios in bone collagen to reconstruct and compare the isotopic niches of adult South American fur seals (Arctocephalus australis; n = 86) and sea lions (Otaria flavescens; n = 49) - two otariid species with marked morphological differences - in the Río de la Plata estuary (Argentina - Uruguay) and the adjacent Atlantic Ocean during the second half of the 20th century and the beginning of the 21st century. Samples from the middle Holocene (n = 7 fur seals and n = 5 sea lions) are also included in order to provide a reference point for characterizing resource partitioning before major anthropogenic modifications of the environment. We found that the South American fur seals and South American sea lions had distinct isotopic niches during the middle Holocene. Isotopic niche segregation was similar at the beginning of the second half of the 20th century, but has diminished over time. The progressive convergence of the isotopic niches of these two otariids during the second half of the 20th century and the beginning of the 21st century is most likely due to the increased reliance of South American fur seals on demersal prey. This recent dietary change in South American fur seals can be explained by at least two non-mutually exclusive mechanisms: (i) the decrease in the abundance of sympatric South American sea lions as a consequence of small colony size and high pup mortality resulting from commercial sealing; and (ii) the decrease in the average size of demersal fishes due to intense fishing of the larger class sizes, which may have increased their accessibility to those eared seals with a smaller mouth gape, that is, South American fur seals of both sexes and female South American sea lions. © 2017 The Authors

  2. Combgap Promotes Ovarian Niche Development and Chromatin Association of EcR-Binding Regions in BR-C.

    Science.gov (United States)

    Hitrik, Anna; Popliker, Malka; Gancz, Dana; Mukamel, Zohar; Lifshitz, Aviezer; Schwartzman, Omer; Tanay, Amos; Gilboa, Lilach

    2016-11-01

    The development of niches for tissue-specific stem cells is an important aspect of stem cell biology. Determination of niche size and niche numbers during organogenesis involves precise control of gene expression. How this is achieved in the context of a complex chromatin landscape is largely unknown. Here we show that the nuclear protein Combgap (Cg) supports correct ovarian niche formation in Drosophila by controlling ecdysone-Receptor (EcR)- mediated transcription and long-range chromatin contacts in the broad locus (BR-C). Both cg and BR-C promote ovarian growth and the development of niches for germ line stem cells. BR-C levels were lower when Combgap was either reduced or over-expressed, indicating an intricate regulation of the BR-C locus by Combgap. Polytene chromosome stains showed that Cg co-localizes with EcR, the major regulator of BR-C, at the BR-C locus and that EcR binding to chromatin was sensitive to changes in Cg levels. Proximity ligation assay indicated that the two proteins could reside in the same complex. Finally, chromatin conformation analysis revealed that EcR-bound regions within BR-C, which span ~30 KBs, contacted each other. Significantly, these contacts were stabilized in an ecdysone- and Combgap-dependent manner. Together, these results highlight Combgap as a novel regulator of chromatin structure that promotes transcription of ecdysone target genes and ovarian niche formation.

  3. Replacement of harmful animal use in life science education: the approach and activities of InterNICHE.

    Science.gov (United States)

    Jukes, Nick

    2004-06-01

    Harmful animal use in undergraduate education is increasingly being replaced by alternatives, such as computer software, manikins and simulators, ethically sourced animal cadavers, apprentice work with animal patients, and student self-experimentation. Combinations of such alternatives can better meet teaching objectives, reduce costs and avoid the negative pedagogical and social impact of animal experimentation. Since 1988, the International Network for Humane Education (InterNICHE, formerly EuroNICHE) has been working with teachers to replace harmful animal use and has been supporting students' right to conscientious objection. This paper presents the approach, history and current activities of InterNICHE. With a vision of 100% replacement, the network aims for empowerment by networking information and providing support. It works with the belief that most teachers want investment in the best quality and most humane education possible. The forthcoming second edition of the InterNICHE book, from Guinea Pig to Computer Mouse,1 includes practical details of progressive teaching aids and approaches, as well as case studies from teachers who employ such alternatives. In 1999, InterNICHE produced the film Alternatives in Education, now available in 20 languages. Such resources are complemented by outreach trips and conferences and an Alternatives Loan System, which offers products for familiarisation and assessment. The InterNICHE website (www.interniche.org) was launched in 2001.

  4. Invasion of Old World Phragmites australis in the New World: precipitation and temperature patterns combined with human influences redesign the invasive niche.

    Science.gov (United States)

    Guo, Wen-Yong; Lambertini, Carla; Li, Xiu-Zhen; Meyerson, Laura A; Brix, Hans

    2013-11-01

    After its introduction into North America, Euro-Asian Phragmites australis became an aggressive invasive wetland grass along the Atlantic coast of North America. Its distribution range has since expanded to the middle, south and southwest of North America, where invasive P. australis has replaced millions of hectares of native plants in inland and tidal wetlands. Another P. australis invasion from the Mediterranean region is simultaneously occurring in the Gulf region of the United States and some countries in South America. Here, we analysed the occurrence records of the two Old World invasive lineages of P. australis (Haplotype M and Med) in both their native and introduced ranges using environmental niche models (ENMs) to assess (i) whether a niche shift accompanied the invasions in the New World; (ii) the role of biologically relevant climatic variables and human influence in the process of invasion; and (iii) the current potential distribution of these two lineages. We detected local niche shifts along the East Coast of North America and the Gulf Coast of the United States for Haplotype M and around the Mississippi Delta and Florida of the United States for Med. The new niche of the introduced Haplotype M accounts for temperature fluctuations and increased precipitation. The introduced Med lineage has enlarged its original subtropical niche to the tropics-subtropics, invading regions with a high annual mean temperature (> ca. 10 °C) and high precipitation in the driest period. Human influence is an important factor for both niches. We suggest that an increase in precipitation in the 20th century, global warming and human-made habitats have shaped the invasive niches of the two lineages in the New World. However, as the invasions are ongoing and human and natural disturbances occur concomitantly, the future distribution ranges of the two lineages may diverge from the potential distribution ranges detected in this study. © 2013 John Wiley & Sons Ltd.

  5. Geographic distribution and ecological niche of plague in sub-Saharan Africa

    DEFF Research Database (Denmark)

    Neerinckx, Simon B; Peterson, Andrew T; Gulinck, Hubert

    2008-01-01

    Background Plague is a rapidly progressing, serious illness in humans that is likely to be fatal if not treated. It remains a public health threat, especially in sub-Saharan Africa. In spite of plague's highly focal nature, a thorough ecological understanding of the general distribution pattern...... of plague across sub-Saharan Africa has not been established to date. In this study, we used human plague data from sub-Saharan Africa for 1970-2007 in an ecological niche modeling framework to explore the potential geographic distribution of plague and its ecological requirements across Africa. Results We...... predict a broad potential distributional area of plague occurrences across sub-Saharan Africa. General tests of model's transferability suggest that our model can anticipate the potential distribution of plague occurrences in Madagascar and northern Africa. However, generality and predictive ability tests...

  6. Affordances and Landscapes: Overcoming the Nature–Culture Dichotomy through Niche Construction Theory

    Science.gov (United States)

    Heras-Escribano, Manuel; De Pinedo-García, Manuel

    2018-01-01

    In this paper we reject the nature–culture dichotomy by means of the idea of affordance or possibility for action, which has important implications for landscape theory. Our hypothesis is that, just as the idea of affordance can serve to overcome the subjective–objective dichotomy, the ideas of landscape and ecological niche, properly defined, would allow us to also transcend the nature–culture dichotomy. First, we introduce an overview of landscape theory, emphasizing processual landscape theory as the most suitable approach for satisfying both cultural and naturalist approaches. After that, we introduce the idea of affordance and we analyze a tension between sociocultural and transcultural affordances (affordances that depend on cultural conventions and affordances that depend on lawful information and bodily aspects of agents). This tension has various implications for landscape theory and ecological niches. Our proposal is that sociocultural and transcultural aspects of affordances could be systematically accommodated if we apply niche construction theory (the theory that explains the process by which organisms modify their selective environments) as a methodological framework for explaining the emergence of ecological niches. This approach will lead us to an integrative account of landscapes as the products of the interaction between human and environmental elements, making it a clear example of a concept that transcends the nature–culture dichotomy. PMID:29375426

  7. Weak Evidence of Regeneration Habitat but Strong Evidence of Regeneration Niche for a Leguminous Shrub

    Science.gov (United States)

    Delerue, Florian; Gonzalez, Maya; Michalet, Richard; Pellerin, Sylvain; Augusto, Laurent

    2015-01-01

    The identification of an ecological niche specific to the regeneration phase has mobilised significant attention. However, the importance of the regeneration niche concept remains unclear. Our main objective was to study the existence of such a regeneration niche for a leguminous shrub, Ulex europaeus. This study was carried out in southwest France in the context of water and nutrient stresses (mainly phosphorus limitation) due to the presence of nutrient-poor sandy soils. We analysed the regeneration of the species from the germination of seeds and emergence of new seedlings until the seedlings reached young shrub size. Our design included a P fertilisation treatment. We also investigated microsite characteristics (micro-topography and vegetation development) as they can interact with meteorological conditions and determine water availability for seeds and seedlings. We found that P availability controlled seedling growth and the time necessary to reach young shrub size. Water availability appeared to impact the species germination and seedlings survival. We also found that P and water availability depended on the interactions between microsite characteristics and climatic variations. Finally we found evidence that P and water availability are important ecological factors shaping the regeneration niche of the species, but we found weak evidence that any microsite would be appropriate for the regeneration of the species in the long term. Future studies regarding regeneration niches need to distinguish more clearly the ecological factors important for regeneration (the regeneration niche per se) and the physical world where the seedlings appear and develop (the regeneration habitat). PMID:26098877

  8. Weak Evidence of Regeneration Habitat but Strong Evidence of Regeneration Niche for a Leguminous Shrub.

    Directory of Open Access Journals (Sweden)

    Florian Delerue

    Full Text Available The identification of an ecological niche specific to the regeneration phase has mobilised significant attention. However, the importance of the regeneration niche concept remains unclear. Our main objective was to study the existence of such a regeneration niche for a leguminous shrub, Ulex europaeus. This study was carried out in southwest France in the context of water and nutrient stresses (mainly phosphorus limitation due to the presence of nutrient-poor sandy soils. We analysed the regeneration of the species from the germination of seeds and emergence of new seedlings until the seedlings reached young shrub size. Our design included a P fertilisation treatment. We also investigated microsite characteristics (micro-topography and vegetation development as they can interact with meteorological conditions and determine water availability for seeds and seedlings. We found that P availability controlled seedling growth and the time necessary to reach young shrub size. Water availability appeared to impact the species germination and seedlings survival. We also found that P and water availability depended on the interactions between microsite characteristics and climatic variations. Finally we found evidence that P and water availability are important ecological factors shaping the regeneration niche of the species, but we found weak evidence that any microsite would be appropriate for the regeneration of the species in the long term. Future studies regarding regeneration niches need to distinguish more clearly the ecological factors important for regeneration (the regeneration niche per se and the physical world where the seedlings appear and develop (the regeneration habitat.

  9. Pleiotrophin Regulates the Retention and Self-Renewal of Hematopoietic Stem Cells in the Bone Marrow Vascular Niche

    Directory of Open Access Journals (Sweden)

    Heather A. Himburg

    2012-10-01

    Full Text Available The mechanisms through which the bone marrow (BM microenvironment regulates hematopoietic stem cell (HSC fate remain incompletely understood. We examined the role of the heparin-binding growth factor pleiotrophin (PTN in regulating HSC function in the niche. PTN−/− mice displayed significantly decreased BM HSC content and impaired hematopoietic regeneration following myelosuppression. Conversely, mice lacking protein tyrosine phosphatase receptor zeta, which is inactivated by PTN, displayed significantly increased BM HSC content. Transplant studies revealed that PTN action was not HSC autonomous, but rather was mediated by the BM microenvironment. Interestingly, PTN was differentially expressed and secreted by BM sinusoidal endothelial cells within the vascular niche. Furthermore, systemic administration of anti-PTN antibody in mice substantially impaired both the homing of hematopoietic progenitor cells to the niche and the retention of BM HSCs in the niche. PTN is a secreted component of the BM vascular niche that regulates HSC self-renewal and retention in vivo.

  10. Impacts of CO2 taxes in an Economy with Niche Markets and Learning-by-doing

    International Nuclear Information System (INIS)

    Van der Zwaan, B.C.C.; Gerlagh, R.; Hofkes, M.W.; Klaassen, G.

    2003-09-01

    In this paper, we analyse the impact of carbon taxes on emission levels, when niche markets exist for new carbon-free technologies, and when these technologies experience 'learning-by-doing' effects. For this purpose, a general equilibrium model has been developed, DEMETER, which specifies two energy technologies: one based on fossil fuels and one on a composite of carbon-free energy technologies. Initially, the carbon-free technology has relatively high production costs, but niche markets ensure positive demand. Learning-by-doing decreases production costs, which increases the market share, which in turn accelerates learning-by-doing, and so forth. This mechanism allows a relatively modest carbon tax, of about 50 US$/tC, to almost stabilise carbon emissions at their 2000 levels throughout the entire 21st century. Sensitivity analysis shows that the required carbon tax for emission stabilisation crucially depends on the elasticity of substitution between the fossil fuel and carbon-free technology

  11. Multi-user cognitive radio network resource allocation based on the adaptive niche immune genetic algorithm

    International Nuclear Information System (INIS)

    Zu Yun-Xiao; Zhou Jie

    2012-01-01

    Multi-user cognitive radio network resource allocation based on the adaptive niche immune genetic algorithm is proposed, and a fitness function is provided. Simulations are conducted using the adaptive niche immune genetic algorithm, the simulated annealing algorithm, the quantum genetic algorithm and the simple genetic algorithm, respectively. The results show that the adaptive niche immune genetic algorithm performs better than the other three algorithms in terms of the multi-user cognitive radio network resource allocation, and has quick convergence speed and strong global searching capability, which effectively reduces the system power consumption and bit error rate. (geophysics, astronomy, and astrophysics)

  12. Climatic niche conservatism and ecological opportunity in the explosive radiation of arvicoline rodents (Arvicolinae, Cricetidae).

    Science.gov (United States)

    Lv, Xue; Xia, Lin; Ge, Deyan; Wu, Yongjie; Yang, Qisen

    2016-05-01

    Climatic niche conservatism shapes patterns of diversity in many taxonomic groups, while ecological opportunity (EO) can trigger rapid speciation that is less constrained by the amount of time a lineage has occupied a given habitat. These two processes are well studied, but limited research has considered their joint and relative roles in shaping diversity patterns. We characterized climatic and biogeographic variables for 102 species of arvicoline rodents (Arvicolinae, Cricetidae), testing the effects of climatic niche conservatism and EO on arvicoline diversification as lineages transitioned between biogeographic regions. We found that the amount of time a lineage has occupied a precipitation niche is positively correlated with diversity along a precipitation gradient, suggesting climatic niche conservatism. In contrast, shift in diversification rate explained diversity patterns along a temperature gradient. Our results suggest that an indirect relationship exists between temperature and diversification that is associated with EO as arvicoline rodents colonized warm Palearctic environments. Climatic niche conservatism alone did not fully explain diversity patterns under density-dependence, highlighting the additional importance of EO-related processes in promoting the explosive radiation in arvicoline rodents and shaping diversity pattern among biogeographic regions and along climatic gradients. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

  13. Beware batch culture: Seasonality and niche construction predicted to favor bacterial adaptive diversification.

    Directory of Open Access Journals (Sweden)

    Charles Rocabert

    2017-03-01

    Full Text Available Metabolic cross-feeding interactions between microbial strains are common in nature, and emerge during evolution experiments in the laboratory, even in homogeneous environments providing a single carbon source. In sympatry, when the environment is well-mixed, the reasons why emerging cross-feeding interactions may sometimes become stable and lead to monophyletic genotypic clusters occupying specific niches, named ecotypes, remain unclear. As an alternative to evolution experiments in the laboratory, we developed Evo2Sim, a multi-scale model of in silico experimental evolution, equipped with the whole tool case of experimental setups, competition assays, phylogenetic analysis, and, most importantly, allowing for evolvable ecological interactions. Digital organisms with an evolvable genome structure encoding an evolvable metabolic network evolved for tens of thousands of generations in environments mimicking the dynamics of real controlled environments, including chemostat or batch culture providing a single limiting resource. We show here that the evolution of stable cross-feeding interactions requires seasonal batch conditions. In this case, adaptive diversification events result in two stably co-existing ecotypes, with one feeding on the primary resource and the other on by-products. We show that the regularity of serial transfers is essential for the maintenance of the polymorphism, as it allows for at least two stable seasons and thus two temporal niches. A first season is externally generated by the transfer into fresh medium, while a second one is internally generated by niche construction as the provided nutrient is replaced by secreted by-products derived from bacterial growth. In chemostat conditions, even if cross-feeding interactions emerge, they are not stable on the long-term because fitter mutants eventually invade the whole population. We also show that the long-term evolution of the two stable ecotypes leads to character

  14. Ecological niche model of Phlebotomus perniciosus, the main vector of canine leishmaniasis in north-eastern Italy

    Directory of Open Access Journals (Sweden)

    Manuela Signorini

    2014-11-01

    Full Text Available With respect to the epidemiology of leishmaniasis, it is crucial to take into account the ecoclimatic and environ- mental characteristics that influence the distribution patterns of the vector sand fly species. It is also important to consider the possible impact of on-going climate changes on the emergence of this disease. In order to map the potential distribu- tion of Phlebotomus perniciosus, the main vector species of canine leishmaniasis in north-eastern Italy, geographical information systems tools, ecological niche models (ENM and remotely sensed environmental data were applied for a retrospective analysis of an entomological survey conducted in north-eastern Italy over 12 years. Sand fly trapping was conducted from 2001 to 2012 in 175 sites in the provinces of Veneto, Friuli-Venezia Giulia and Trentino-Alto Adige. We developed a predictive model of potential distribution of P. perniciosus using the maximum entropy algorithm software, based on seasonal normalized difference vegetation index, day and night land surface temperature, the Corine land cover 2006, a digital elevation model (GTOPO30 and climate layers obtained from the WorldClim database. The MaxEnt pre- diction found the more suitable habitat for P. perniciosus to be hilly areas (100-300 m above the mean sea level charac- terised by temperate climate during the winter and summer seasons, high winter vegetation cover and moderate rainfall during the activity season of vector sand fly. ENM provided a greater understanding of the geographical distribution and ecological requirements of P. perniciosus in the study area, which can be applied for the development of future surveil- lance strategies.

  15. RAMAN LIGHT SCATTERING IN PSEUDOSPIN-ELECTRON MODEL AT STRONG PSEUDOSPIN-ELECTRON INTERACTION

    Directory of Open Access Journals (Sweden)

    T.S.Mysakovych

    2004-01-01

    Full Text Available Anharmonic phonon contributions to Raman scattering in locally anharmonic crystal systems in the framework of the pseudospin-electron model with tunneling splitting of levels are investigated. The case of strong pseudospin-electron coupling is considered. Pseudospin and electron contributions to scattering are taken into account. Frequency dependences of Raman scattering intensity for different values of model parameters and for different polarization of scattering and incident light are investigated.

  16. Teaching Chemistry with Electron Density Models

    Science.gov (United States)

    Shusterman, Gwendolyn P.; Shusterman, Alan J.

    1997-07-01

    Linus Pauling once said that a topic must satisfy two criteria before it can be taught to students. First, students must be able to assimilate the topic within a reasonable amount of time. Second, the topic must be relevant to the educational needs and interests of the students. Unfortunately, the standard general chemistry textbook presentation of "electronic structure theory", set as it is in the language of molecular orbitals, has a difficult time satisfying either criterion. Many of the quantum mechanical aspects of molecular orbitals are too difficult for most beginning students to appreciate, much less master, and the few applications that are presented in the typical textbook are too limited in scope to excite much student interest. This article describes a powerful new method for teaching students about electronic structure and its relevance to chemical phenomena. This method, which we have developed and used for several years in general chemistry (G.P.S.) and organic chemistry (A.J.S.) courses, relies on computer-generated three-dimensional models of electron density distributions, and largely satisfies Pauling's two criteria. Students find electron density models easy to understand and use, and because these models are easily applied to a broad range of topics, they successfully convey to students the importance of electronic structure. In addition, when students finally learn about orbital concepts they are better prepared because they already have a well-developed three-dimensional picture of electronic structure to fall back on. We note in this regard that the types of models we use have found widespread, rigorous application in chemical research (1, 2), so students who understand and use electron density models do not need to "unlearn" anything before progressing to more advanced theories.

  17. Assessing the Global Risk of Establishment of Cydia pomonella (Lepidoptera: Tortricidae) using CLIMEX and MaxEnt Niche Models.

    Science.gov (United States)

    Kumar, Sunil; Neven, Lisa G; Zhu, Hongyu; Zhang, Runzhi

    2015-08-01

    Accurate assessment of insect pest establishment risk is needed by national plant protection organizations to negotiate international trade of horticultural commodities that can potentially carry the pests and result in inadvertent introductions in the importing countries. We used mechanistic and correlative niche models to quantify and map the global patterns of the potential for establishment of codling moth (Cydia pomonella L.), a major pest of apples, peaches, pears, and other pome and stone fruits, and a quarantine pest in countries where it currently does not occur. The mechanistic model CLIMEX was calibrated using species-specific physiological tolerance thresholds, whereas the correlative model MaxEnt used species occurrences and climatic spatial data. Projected potential distribution from both models conformed well to the current known distribution of codling moth. None of the models predicted suitable environmental conditions in countries located between 20°N and 20°S potentially because of shorter photoperiod, and lack of chilling requirement (Japan where codling moth currently does not occur but where its preferred host species (i.e., apple) is present. Average annual temperature and latitude were the main environmental variables associated with codling moth distribution at global level. The predictive models developed in this study present the global risk of establishment of codling moth, and can be used for monitoring potential introductions of codling moth in different countries and by policy makers and trade negotiators in making science-based decisions. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  18. Prospects for Jatropha biofuels in Tanzania: An analysis with Strategic Niche Management

    International Nuclear Information System (INIS)

    Eijck, Janske van; Romijn, Henny

    2008-01-01

    The paper reports on research in Tanzania about the scope for developing biofuels from an oil-seed bearing plant called Jatropha curcas Linnaeus. The plant is widely seen to have potential to help combat the greenhouse effect, help to stop local soil erosion, create additional income for the rural poor, and provide a major source of energy both locally and internationally. The principal analytic tool is Strategic Niche Management (SNM), an approach rooted in evolutionary innovation theory. We analyse how the scope for an energy transition is influenced by factors at three societal levels: the overarching 'landscape'; the sectoral setting or 'regime'; and the 'niche' level where the innovation develops and diffuses. Valuable niche processes were found in a few areas, especially in cultivation, but we conclude that there are still many obstacles in Tanzania's prevailing energy regime. The development of Jatropha biofuels is still in an early phase. We list policy recommendations and discuss some methodological issues arising from the use of SNM

  19. Proximity-based differential single cell analysis of the niche to identify stem/progenitor cell regulators

    Science.gov (United States)

    Silberstein, Lev; Goncalves, Kevin A; Kharchenko, Peter V; Turcotte, Raphael; Kfoury, Youmna; Mercier, Francois; Baryawno, Ninib; Severe, Nicolas; Bachand, Jacqueline; Spencer, Joel; Papazian, Ani; Lee, Dongjun; Chitteti, Brahmananda Reddy; Srour, Edward F; Hoggatt, Jonathan; Tate, Tiffany; Celso, Cristina Lo; Ono, Noriaki; Nutt, Stephen; Heino, Jyrki; Sipilä, Kalle; Shioda, Toshihiro; Osawa, Masatake; Lin, Charles P; Hu, Guo-fu; Scadden, David T

    2016-01-01

    SUMMARY Physiological stem cell function is regulated by secreted factors produced by niche cells. In this study, we describe an unbiased approach based on differential single-cell gene expression analysis of mesenchymal osteolineage cells close to and further removed from hematopoietic stem/progenitor cells to identify candidate niche factors. Mesenchymal cells displayed distinct molecular profiles based on their relative location. Amongst the genes which were preferentially expressed in proximal cells, we functionally examined three secreted or cell surface molecules not previously connected to HSPC biology: the secreted RNase Angiogenin, the cytokine IL18 and the adhesion molecule Embigin and discovered that all of these factors are HSPC quiescence regulators. Our proximity-based differential single cell approach therefore reveals molecular heterogeneity within niche cells and can be used to identify novel extrinsic stem/progenitor cell regulators. Similar approaches could also be applied to other stem cell/niche pairs to advance understanding of microenvironmental regulation of stem cell function. PMID:27524439

  20. Endothelial Progenitor Cell Dysfunction in Myelodysplastic Syndromes: Possible Contribution of a Defective Vascular Niche to Myelodysplasia

    Directory of Open Access Journals (Sweden)

    Luciana Teofili

    2015-05-01

    Full Text Available We set a model to replicate the vascular bone marrow niche by using endothelial colony forming cells (ECFCs, and we used it to explore the vascular niche function in patients with low-risk myelodysplastic syndromes (MDS. Overall, we investigated 56 patients and we observed higher levels of ECFCs in MDS than in healthy controls; moreover, MDS ECFCs were found variably hypermethylated for p15INK4b DAPK1, CDH1, or SOCS1. MDS ECFCs exhibited a marked adhesive capacity to normal mononuclear cells. When normal CD34+ cells were co-cultured with MDS ECFCs, they generated significant lower amounts of CD11b+ and CD41+ cells than in co-culture with normal ECFCs. At gene expression profile, several genes involved in cell adhesion were upregulated in MDS ECFCs, while several members of the Wingless and int (Wnt pathways were underexpressed. Furthermore, at miRNA expression profile, MDS ECFCs hypo-expressed various miRNAs involved in Wnt pathway regulation. The addition of Wnt3A reduced the expression of intercellular cell adhesion molecule-1 on MDS ECFCs and restored the defective expression of markers of differentiation. Overall, our data demonstrate that in low-risk MDS, ECFCs exhibit various primary abnormalities, including putative MDS signatures, and suggest the possible contribution of the vascular niche dysfunction to myelodysplasia.

  1. Climate, niche evolution, and diversification of the "bird-cage" evening primroses (Oenothera, sections Anogra and Kleinia).

    Science.gov (United States)

    Evans, Margaret E K; Smith, Stephen A; Flynn, Rachel S; Donoghue, Michael J

    2009-02-01

    We integrate climatic niche models and dated phylogenies to characterize the evolution of climatic niches in Oenothera sections Anogra and Kleinia (Onagraceae), and from that we make inferences on diversification in relation to climate. The evolution of climatic tolerances in Anogra + Kleinia has been heterogeneous, across phylogenetic groups and across different dimensions of climate. All the extant taxa occur in semiarid to arid conditions (annual precipitation of 10.1-49.1 cm and high temperatures in the warmest month of 28.5 degrees-40.1 degrees C), but there is striking variation among taxa in their climatic tolerances, especially temperature (minimum temperatures in the coldest month of -14.0 degrees to 5.3 degrees C) and summer versus winter precipitation (precipitation in the warmest quarter of 0.6-19.4 cm). Climatic disparity is especially pronounced in two subclades (californica, deltoides) that radiated in the southwestern United States and California, apparently including both divergent and convergent evolution of climatic tolerances. This niche evolution is remarkable, given the probable timescale of the radiation (approximately 1 million years). We suggest that the spatiotemporal climatic heterogeneity of western North America has served as a driver of diversification. Our data are also consistent with Axelrod's hypothesis that the spread of arid conditions in western North America stimulated diversification of arid-adapted lineages.

  2. Evolutionary responses to a constructed niche: ancient Mesoamericans as a model of gene-culture coevolution.

    Directory of Open Access Journals (Sweden)

    Tábita Hünemeier

    Full Text Available Culture and genetics rely on two distinct but not isolated transmission systems. Cultural processes may change the human selective environment and thereby affect which individuals survive and reproduce. Here, we evaluated whether the modes of subsistence in Native American populations and the frequencies of the ABCA1*Arg230Cys polymorphism were correlated. Further, we examined whether the evolutionary consequences of the agriculturally constructed niche in Mesoamerica could be considered as a gene-culture coevolution model. For this purpose, we genotyped 229 individuals affiliated with 19 Native American populations and added data for 41 other Native American groups (n = 1905 to the analysis. In combination with the SNP cluster of a neutral region, this dataset was then used to unravel the scenario involved in 230Cys evolutionary history. The estimated age of 230Cys is compatible with its origin occurring in the American continent. The correlation of its frequencies with the archeological data on Zea pollen in Mesoamerica/Central America, the neutral coalescent simulations, and the F(ST-based natural selection analysis suggest that maize domestication was the driving force in the increase in the frequencies of 230Cys in this region. These results may represent the first example of a gene-culture coevolution involving an autochthonous American allele.

  3. Monoenergetic electron parameters in a spheroid bubble model

    Science.gov (United States)

    Sattarian, H.; Sh., Rahmatallahpur; Tohidi, T.

    2013-02-01

    A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived. The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately, especially at the relativistic region. The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model. The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons ΔE/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions. As a result, the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model.

  4. Keeping stem cells under control: new insights into the mechanisms that limit niche-stem cell signaling within the reproductive system

    OpenAIRE

    Inaba, Mayu; Yamashita, Yukiko M.; Buszczak, Michael

    2016-01-01

    Adult stem cells reside in specialized microenvironments called niches that maintain stem cells in an undifferentiated and self-renewing state. Despite extensive studies on the signaling pathways that operate within stem cells and their niches, the mechanisms that restrict niche signal exclusively to stem cells remained elusive: such a mechanism is crucially important to ensure that stem cells undergo self-renewal while their progeny, often located just one cell diameter away from the niche, ...

  5. Novel therapeutic strategies to target leukemic cells that hijack compartmentalized continuous hematopoietic stem cell niches

    NARCIS (Netherlands)

    Hira, Vashendriya V. V.; van Noorden, Cornelis J. F.; Carraway, Hetty E.; Maciejewski, Jaroslaw P.; Molenaar, Remco J.

    2017-01-01

    Acute myeloid leukemia and acute lymphoblastic leukemia cells hijack hematopoietic stem cell (HSC) niches in the bone marrow and become leukemic stem cells (LSCs) at the expense of normal HSCs. LSCs are quiescent and resistant to chemotherapy and can cause relapse of the disease. HSCs in niches are

  6. Ovarian Stem Cell Niche and Follicular Renewal in Mammals

    Czech Academy of Sciences Publication Activity Database

    Bukovský, Antonín

    2011-01-01

    Roč. 294, č. 8 (2011), s. 1284-1306 ISSN 1932-8486 Institutional research plan: CEZ:AV0Z50520701 Keywords : ovary * stem cell niche * neo-oogenesis Subject RIV: EA - Cell Biology Impact factor: 1.473, year: 2011

  7. Occupy the Financial Niche – Saturation and Crisis (discontinuous decisions

    Directory of Open Access Journals (Sweden)

    Ionut PURICA

    2014-09-01

    Full Text Available The model presented is proposing an approach that could verify the nonlinear behaviour during a crisis, such that to quantify and predict potential discontinuous behaviour. In this case, the crisis behaviour associated with financial funds reallocation among various credit instruments, described as memes with the sense of Dawkins, is shown to be of discontinuous nature stemming from a logistic penetration in the financial behaviour niche. Actually the logistic penetration is typical in creating cyclic behaviour of economic structures as shown by Marchetti and others from IIASA. A Fokker-Planck equation description results in a stationary solution having a bifurcation like solution with evolution trajectories on a ‘cusp’ type catastrophe that may describe discontinuous decision behaviour

  8. A Model for Electronic Good Governance in Electronic Learning Sector of Iran

    Directory of Open Access Journals (Sweden)

    Alireza Moghaddasi

    2016-10-01

    Full Text Available Despite the various models and frameworks on electronic good governance are introduced, the multiple dimensions model of electronic good governance in the field of e-Learning has not been reviewed this subject in a integrated, comprehensive, process-oriented and systematic model. In this article, in order to explain the process of electronic good governance, by a systematic review of the related literature and backgrounds, all factors were identified using meta-synthesis methodology. Then, based on grounded theory methodology and Strauss and Corbin paradigmatic approach, the open, axial and selective coding were conducted. In the following, by using survey method, we determined the importance and priority of all proposed factors. It was also indicated that this research was innovative in the fields of methodology, results and the proposed model which had not been considered in the previous researches. So that, the proposed model resolved the shortcomings of past researches and made it possible for the public sector, private and civil society organizations to consider the process of establishing electronic good governance in e-Learning sector in Iran as a dynamic process.

  9. Analysis of operating model of electronic invoice colombian Colombian electronic billing analysis of the operational model

    Directory of Open Access Journals (Sweden)

    Sérgio Roberto da Silva

    2016-06-01

    Full Text Available Colombia has been one of the first countries to introduce electronic billing process on a voluntary basis, from a traditional to a digital version. In this context, the article analyzes the electronic billing process implemented in Colombia and the advantages. Methodological research is applied, qualitative, descriptive and documentary; where the regulatory framework and the conceptualization of the model is identified; the process of adoption of electronic billing is analyzed, and finally the advantages and disadvantages of its implementation is analyzed. The findings indicate that the model applied in Colombia to issue an electronic billing in sending and receiving process, is not complex, but it requires a small adequate infrastructure and trained personnel to reach all sectors, especially the micro and business which is the largest business network in the country.

  10. Branding Prince Edward County as a Gastronomic Niche Tourism Destination: A Case Study

    OpenAIRE

    Geneviève Brisson; Rocci Luppicini

    2015-01-01

    Increasingly, gastronomy is playing a role in people's motivation for travel, and destinations are making food and beverages their main attraction. This study explored the growing field of gastronomic tourism, a type of niche tourism, through the theoretical framework of destination branding theory. Using a qualitative case study research design, this research examined the branding of the emergent region of Prince Edward County, Ontario, Canada as a gastronomic niche tourism destination from ...

  11. Monoenergetic electron parameters in a spheroid bubble model

    International Nuclear Information System (INIS)

    Sattarian, H.; Rahmatallahpur, Sh.; Tohidi, T.

    2013-01-01

    A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived. The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately, especially at the relativistic region. The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model. The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons ΔE/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions. As a result, the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model. (physics of gases, plasmas, and electric discharges)

  12. The neural crest is a source of mesenchymal stem cells with specialized hematopoietic stem cell niche function.

    Science.gov (United States)

    Isern, Joan; García-García, Andrés; Martín, Ana M; Arranz, Lorena; Martín-Pérez, Daniel; Torroja, Carlos; Sánchez-Cabo, Fátima; Méndez-Ferrer, Simón

    2014-09-25

    Mesenchymal stem cells (MSCs) and osteolineage cells contribute to the hematopoietic stem cell (HSC) niche in the bone marrow of long bones. However, their developmental relationships remain unclear. In this study, we demonstrate that different MSC populations in the developing marrow of long bones have distinct functions. Proliferative mesoderm-derived nestin(-) MSCs participate in fetal skeletogenesis and lose MSC activity soon after birth. In contrast, quiescent neural crest-derived nestin(+) cells preserve MSC activity, but do not generate fetal chondrocytes. Instead, they differentiate into HSC niche-forming MSCs, helping to establish the HSC niche by secreting Cxcl12. Perineural migration of these cells to the bone marrow requires the ErbB3 receptor. The neonatal Nestin-GFP(+) Pdgfrα(-) cell population also contains Schwann cell precursors, but does not comprise mature Schwann cells. Thus, in the developing bone marrow HSC niche-forming MSCs share a common origin with sympathetic peripheral neurons and glial cells, and ontogenically distinct MSCs have non-overlapping functions in endochondrogenesis and HSC niche formation.

  13. Plant diversification promotes biocontrol services in peach orchards by shaping the ecological niches of insect herbivores and their natural enemies

    DEFF Research Database (Denmark)

    Wan, Nian Feng; Ji, Xiang Yun; Deng, Jian Yu

    2018-01-01

    Ecological niche indicators have been scarcely adopted to assess the biological control of insect herbivores by their natural enemies. We hypothesize that plant diversification promotes the biocontrol services by narrowing the niches of herbivores and broadening the niches of natural enemies....... Our study reveals that plant diversification promotes the biocontrol services by shaping the niche of herbivores and natural enemies, and provides a new assessment method to understand the biodiversity-niche-ecosystem management interactions........ In a large-scale experiment, we found that the abundance of natural enemies was increased by 38.1%, and the abundance of insect herbivores was decreased by 16.9% in peach orchards with plant diversification (treatment) compared to ones with monoculture (control). Stratified sampling indicated...

  14. PTEN Signaling in the Postnatal Perivascular Progenitor Niche Drives Medulloblastoma Formation.

    Science.gov (United States)

    Zhu, Guo; Rankin, Sherri L; Larson, Jon D; Zhu, Xiaoyan; Chow, Lionel M L; Qu, Chunxu; Zhang, Jinghui; Ellison, David W; Baker, Suzanne J

    2017-01-01

    Loss of the tumor suppressor gene PTEN exerts diverse outcomes on cancer in different developmental contexts. To gain insight into the effect of its loss on outcomes in the brain, we conditionally inactivated the murine Pten gene in neonatal neural stem/progenitor cells. Pten inactivation created an abnormal perivascular proliferative niche in the cerebellum that persisted in adult animals but did not progress to malignancy. Proliferating cells showed undifferentiated morphology and expressed the progenitor marker Nestin but not Math1, a marker of committed granule neuron progenitors. Codeletion of Pten and Trp53 resulted in fully penetrant medulloblastoma originating from the perivascular niche, which exhibited abnormal blood vessel networks and advanced neuronal differentiation of tumor cells. EdU pulse-chase experiments demonstrated a perivascular cancer stem cell population in Pten/Trp53 double mutant medulloblastomas. Genetic analyses revealed recurrent somatic inactivations of the tumor suppressor gene Ptch1 and a recapitulation of the sonic hedgehog subgroup of human medulloblastomas. Overall, our results showed that PTEN acts to prevent the proliferation of a progenitor niche in postnatal cerebellum predisposed to oncogenic induction of medulloblastoma. Cancer Res; 77(1); 123-33. ©2016 AACR. ©2016 American Association for Cancer Research.

  15. Bone marrow macrophages maintain hematopoietic stem cell (HSC) niches and their depletion mobilizes HSCs.

    Science.gov (United States)

    Winkler, Ingrid G; Sims, Natalie A; Pettit, Allison R; Barbier, Valérie; Nowlan, Bianca; Helwani, Falak; Poulton, Ingrid J; van Rooijen, Nico; Alexander, Kylie A; Raggatt, Liza J; Lévesque, Jean-Pierre

    2010-12-02

    In the bone marrow, hematopoietic stem cells (HSCs) reside in specific niches near osteoblast-lineage cells at the endosteum. To investigate the regulation of these endosteal niches, we studied the mobilization of HSCs into the bloodstream in response to granulocyte colony-stimulating factor (G-CSF). We report that G-CSF mobilization rapidly depletes endosteal osteoblasts, leading to suppressed endosteal bone formation and decreased expression of factors required for HSC retention and self-renewal. Importantly, G-CSF administration also depleted a population of trophic endosteal macrophages (osteomacs) that support osteoblast function. Osteomac loss, osteoblast suppression, and HSC mobilization occurred concomitantly, suggesting that osteomac loss could disrupt endosteal niches. Indeed, in vivo depletion of macrophages, in either macrophage Fas-induced apoptosis (Mafia) transgenic mice or by administration of clodronate-loaded liposomes to wild-type mice, recapitulated the: (1) loss of endosteal osteoblasts and (2) marked reduction of HSC-trophic cytokines at the endosteum, with (3) HSC mobilization into the blood, as observed during G-CSF administration. Together, these results establish that bone marrow macrophages are pivotal to maintain the endosteal HSC niche and that the loss of such macrophages leads to the egress of HSCs into the blood.

  16. Chick embryo xenograft model reveals a novel perineural niche for human adipose-derived stromal cells

    Directory of Open Access Journals (Sweden)

    Ingrid R. Cordeiro

    2015-09-01

    Full Text Available Human adipose-derived stromal cells (hADSC are a heterogeneous cell population that contains adult multipotent stem cells. Although it is well established that hADSC have skeletal potential in vivo in adult organisms, in vitro assays suggest further differentiation capacity, such as into glia. Thus, we propose that grafting hADSC into the embryo can provide them with a much more instructive microenvironment, allowing the human cells to adopt diverse fates or niches. Here, hADSC spheroids were grafted into either the presumptive presomitic mesoderm or the first branchial arch (BA1 regions of chick embryos. Cells were identified without previous manipulations via human-specific Alu probes, which allows efficient long-term tracing of heterogeneous primary cultures. When grafted into the trunk, in contrast to previous studies, hADSC were not found in chondrogenic or osteogenic territories up to E8. Surprisingly, 82.5% of the hADSC were associated with HNK1+ tissues, such as peripheral nerves. Human skin fibroblasts showed a smaller tropism for nerves. In line with other studies, hADSC also adopted perivascular locations. When grafted into the presumptive BA1, 74.6% of the cells were in the outflow tract, the final goal of cardiac neural crest cells, and were also associated with peripheral nerves. This is the first study showing that hADSC could adopt a perineural niche in vivo and were able to recognize cues for neural crest cell migration of the host. Therefore, we propose that xenografts of human cells into chick embryos can reveal novel behaviors of heterogeneous cell populations, such as response to migration cues.

  17. Feeding niches of four large herbivores in the Hluhluwe Game ...

    African Journals Online (AJOL)

    Feeding niches of four large herbivores in the Hluhluwe Game Reserve, Natal. ... equus burchelli burchelli; feeding; grass; grasses; habitat; herbivores; hluhluwe game reserve; kwazulu-natal; large herbivores; ... AJOL African Journals Online.

  18. Ecological niche shifts and environmental space anisotropy: a cautionary note Desplazamientos en el nicho y la anisotropía del espacio ambiental: una nota precautoria

    Directory of Open Access Journals (Sweden)

    Jorge Soberón

    2011-12-01

    Full Text Available The anisotropic structure of climatic space may cause significant (and to a large extent unappreciated non-evolutionary niche shifts. This can be seen mostly in the context of spatial transferability of ecological niche models. We explore this effect using a virtual species in the United States. We created a simple virtual species by postulating its fundamental niche as an ellipse in a two-dimensional realistic climatic space. The climatic combinations defined by the ellipse were projected in the geography of the United States and 2 regions of equal area were selected. The structure of niche in the 2 areas is compared. It is shown that the 2 regions have differently positioned subsets of the environmental space, which creates "shifts" in the realized niches despite the fact that no evolution and no biotic interactions are present. The most parsimonious hypothesis when ecological niche modeling reveals shifts in the realized niche is that environmental space is heterogeneous. Without considering differences in the structure of environmental space no speculation about niche evolution or the role of competitors should be attempted.La estructura anisotrópica del espacio climático puede causar desplazamientos significativos no evolutivos en los nichos de las especies. Este efecto poco apreciado en la literatura se manifiesta con gran claridad cuando se realizan transferencias espaciales de modelos de nicho ecológico. Se explora este efecto utilizando una especie virtual en los Estados Unidos. Se creó una especie virtual simplificada postulando su nicho fundamental en forma de una elipse en un espacio realista de 2 dimensiones. Las combinaciones climáticas definidas por la elipse se proyectaron en la geografía de los Estados Unidos y se seleccionaron 2 regiones de igual superficie espacial. Se compara la estructura del nicho en las 2 regiones, mostrando que estas 2 regiones espaciales presentan subconjuntos distintos del espacio de variables

  19. Niches for the Long-Term Maintenance of Tissue-Resident Memory T Cells

    Science.gov (United States)

    Takamura, Shiki

    2018-01-01

    Tissue-resident memory T cells (TRM cells) are a population of immune cells that reside in the lymphoid and non-lymphoid organs without recirculation through the blood. These important cells occupy and utilize unique anatomical and physiological niches that are distinct from those for other memory T cell populations, such as central memory T cells in the secondary lymphoid organs and effector memory T cells that circulate through the tissues. CD8+ TRM cells typically localize in the epithelial layers of barrier tissues where they are optimally positioned to act as sentinels to trigger antigen-specific protection against reinfection. CD4+ TRM cells typically localize below the epithelial layers, such as below the basement membrane, and cluster in lymphoid structures designed to optimize interactions with antigen-presenting cells upon reinfection. A key feature of TRM populations is their ability to be maintained in barrier tissues for prolonged periods of time. For example, skin CD8+ TRM cells displace epidermal niches originally occupied by γδ T cells, thereby enabling their stable persistence for years. It is also clear that the long-term maintenance of TRM cells in different microenvironments is dependent on multiple tissue-specific survival cues, although the specific details are poorly understood. However, not all TRM persist over the long term. Recently, we identified a new spatial niche for the maintenance of CD8+ TRM cells in the lung, which is created at the site of tissue regeneration after injury [termed repair-associated memory depots (RAMD)]. The short-lived nature of RAMD potentially explains the short lifespans of CD8+ TRM cells in this particular tissue. Clearly, a better understanding of the niche-dependent maintenance of TRM cells will be important for the development of vaccines designed to promote barrier immunity. In this review, we discuss recent advances in our understanding of the properties and nature of tissue-specific niches that

  20. Rates of change in climatic niches in plant and animal populations are much slower than projected climate change

    Science.gov (United States)

    Jezkova, Tereza

    2016-01-01

    Climate change may soon threaten much of global biodiversity. A critical question is: can species undergo niche shifts of sufficient speed and magnitude to persist within their current geographic ranges? Here, we analyse niche shifts among populations within 56 plant and animal species using time-calibrated trees from phylogeographic studies. Across 266 phylogeographic groups analysed, rates of niche change were much slower than rates of projected climate change (mean difference > 200 000-fold for temperature variables). Furthermore, the absolute niche divergence among populations was typically lower than the magnitude of projected climate change over the next approximately 55 years for relevant variables, suggesting the amount of change needed to persist may often be too great, even if these niche shifts were instantaneous. Rates were broadly similar between plants and animals, but especially rapid in some arthropods, birds and mammals. Rates for temperature variables were lower at lower latitudes, further suggesting that tropical species may be especially vulnerable to climate change. PMID:27881748

  1. Cell organisation in the colonic crypt: a theoretical comparison of the pedigree and niche concepts.

    Directory of Open Access Journals (Sweden)

    Richard C van der Wath

    Full Text Available The intestinal mucosa is a monolayer of rapidly self-renewing epithelial cells which is not only responsible for absorption of water and nutrients into the bloodstream but also acts as a protective barrier against harmful microbes entering the body. New functional epithelial cells are produced from stem cells, and their proliferating progeny. These stem cells are found within millions of crypts (tubular pits spaced along the intestinal tract. The entire intestinal epithelium is replaced every 2-3 days in mice (3-5 days in humans and hence cell production, differentiation, migration and turnover need to be tightly regulated. Malfunctions in this regulation are strongly linked to inflammatory bowel diseases and to the formation of adenomas and ultimately cancerous tumours. Despite a great deal of biological experimentation and observation, precisely how colonic crypts are regulated to produce mature colonocytes remains unclear. To assist in understanding how cell organisation in crypts is achieved, two very different conceptual models of cell behaviour are developed here, referred to as the 'pedigree' and the 'niche' models. The pedigree model proposes that crypt cells are largely preprogrammed and receive minimal prompting from the environment as they move through a routine of cell differentiation and proliferation to become mature colonocytes. The niche model proposes that crypt cells are primarily influenced by the local microenvironments along the crypt, and that predetermined cell behaviour plays a negligible role in their development. In this paper we present a computational model of colonic crypts in the mouse, which enables a comparison of the quality and controllability of mature coloncyte production by crypts operating under these two contrasting conceptual models of crypt regulation.

  2. Reproductive niche conservatism in the isolated New Zealand flora over 23 million years.

    Science.gov (United States)

    Conran, John G; Lee, William G; Lee, Daphne E; Bannister, Jennifer M; Kaulfuss, Uwe

    2014-10-01

    The temporal stability of plant reproductive features on islands has rarely been tested. Using flowers, fruits/cones and seeds from a well-dated (23 Ma) Miocene Lagerstätte in New Zealand, we show that across 23 families and 30 genera of forest angiosperms and conifers, reproductive features have remained constant for more than 20 Myr. Insect-, wind- and bird-pollinated flowers and wind- and bird-dispersed diaspores all indicate remarkable reproductive niche conservatism, despite widespread environmental and biotic change. In the past 10 Myr, declining temperatures and the absence of low-latitude refugia caused regional extinction of thermophiles, while orogenic processes steepened temperature, precipitation and nutrient gradients, limiting forest niches. Despite these changes, the palaeontological record provides empirical support for evidence from phylogeographical studies of strong niche conservatism within lineages and biomes. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  3. Umbilical cord mesenchyme stem cell local intramuscular injection for treatment of uterine niche

    Science.gov (United States)

    Fan, Dazhi; Wu, Shuzhen; Ye, Shaoxin; Wang, Wen; Guo, Xiaoling; Liu, Zhengping

    2017-01-01

    Abstract Background: Uterine niche is defined as a triangular anechoic structure at the site of the scar or a gap in the myometrium at the site of a previous caesarean section. The main clinical manifestations are postmenstrual spotting and intrauterine infection, which may seriously affect the daily life of nonpregnant women. Trials have shown an excellent safety and efficacy for the potential of mesenchymal stem cells (MSCs) as a therapeutic option for scar reconstruction. Therefore, this study is designed to investigate the safety and efficacy of using MSCs in the treatment for the uterine niche. Methods/design: This phase II clinical trial is a single-center, prospective, randomized, double-blind, placebo-controlled with 2 arms. One hundred twenty primiparous participants will be randomly (1:1 ratio) assigned to receive direct intramuscular injection of MSCs (a dose of 1∗107 cells in 1 mL of 0.9% saline) (MSCs group) or an identical-appearing 1 mL of 0.9% saline (placebo-controlled group) near the uterine incision. The primary outcome of this trial is to evaluate the proportion of participants at 6 months who is found uterine niche in the uterus by transvaginal utrasonography. Adverse events will be documented in a case report form. The study will be conducted at the Department of Obstetric of Southern Medical University Affiliated Maternal & Child Health Hospital of Foshan. Discussion: This trial is the first investigation of the potential for therapeutic use of MSCs for the management of uterine niche after cesarean delivery. Conclusion: This protocol will help to determine the efficacy and safety of MSCs treatment in uterine niche and bridge the gap with regards to the current preclinical and clinical evidence. Trial registration number: NCT02968459 (Clinical Trials.gov: http://clinicaltrials.gov/). PMID:29095305

  4. [Allelopathic effects of Artemisia sacrorum population in typical steppe based on niche theory].

    Science.gov (United States)

    Wang, Hui; Xie, Yong-Sheng; Cheng, Ji-Min; She, Xiao-Yan

    2012-03-01

    By using modified Levins niche width index and Pianka niche overlap index, this paper analyzed the ecological competition between constructive and dominant species in a typical steppe. The stem- and leaf extracts from the constructive species (Artemisia sacrorum) were utilized to study their allelopathic potential on the seed germination and plant growth of the dominant species (Stipa bungeana, Thymus mongolicus, S. grandis, and Leymus secalinus), and the ecological position of A. sacrorum in the steppe succession. In the steppe, S. bungeana had the widest niche width (0.99), followed by T. mongolicus (0.94), A. sacrorum (0.82), S. grandis (0.76), and L. secalinus (0.73). The niche overlap value between A. sacrorum and S. bungeana, S. bungeana and T. mongolicus, T. mongolicus and S. grandis, and A. sacrorum and T. mongolicus was 0.90, 0.95, 0.94, and 0.86, respectively. The allelopathic effects of A. sacrorum extracts varied with their concentration. For the seed germination, root growth, and shoot growth of the dominant species, A. sacrorum extracts showed a trend of promoting at low concentrations and inhibiting at high concentrations. The extracts of A. sacrorum had a stronger promotion effect on the root growth of S. bungeana than on that of T. mongolicus, but a stronger inhibition effect on the shoot growth of T. mongolicus than on that of S. bungeana. Methanol extracts had stronger allelopathic effects than aqueous extracts. The high niche overlap between A. sacrorum and S. bungeana, and T. mongolicus and S. grandis indicated that the steppe community would continue succession to S. bungeana, while A. sacrorum population was only an important transitional stage during the succession. The allelopathic effect of A. sacrorum played a driving role in the succession process.

  5. Within-population isotopic niche variability in savanna mammals: disparity between carnivores and herbivores

    Directory of Open Access Journals (Sweden)

    Daryl eCodron

    2016-02-01

    Full Text Available Large mammal ecosystems have relatively simple food webs, usually comprising three – and sometimes only two – trophic links. Since many syntopic species from the same trophic level therefore share resources, dietary niche partitioning features prominently within these systems. In African and other subtropical savannas, stable carbon isotopes readily distinguish between herbivore species for which foliage and other parts of dicot plants (13C-depleted C3 vegetation are the primary resource (browsers and those for which grasses (13C-enriched C4 vegetation are staples (grazers. Similarly, carbon isotopes distinguish between carnivore diets that may be richer in either browser, grazer, or intermediate-feeding prey. Here, we investigate levels of carbon and nitrogen isotopic niche variation and niche partitioning within populations (or species of carnivores and herbivores from South African savannas. We emphasize predictable differences in within-population trends across trophic levels: we expect that herbivore populations, which require more foraging effort due to higher intake requirements, are far less likely to display within-population resource partitioning than carnivore populations. Our results reveal generally narrower isotopic niche breadths in herbivore than carnivore populations, but more importantly we find lower levels of isotopic differentiation across individuals within herbivore species. While these results offer some support for our general hypothesis, the current paucity of isotopic data for African carnivores limits our ability to test the complete set of predictions arising from our hypothesis. Nevertheless, given the different ecological and ecophysiological constraints to foraging behaviour within each trophic level, comparisons across carnivores and herbivores, which are possible within such simplified foodwebs, make these systems ideal for developing a process-based understanding of conditions underlying the evolution of

  6. Stem Cell Interaction with Somatic Niche May Hold the Key to Fertility Restoration in Cancer Patients

    Directory of Open Access Journals (Sweden)

    Deepa Bhartiya

    2012-01-01

    Full Text Available The spontaneous return of fertility after bone marrow transplantation or heterotopic grafting of cryopreserved ovarian cortical tissue has surprised many, and a possible link with stem cells has been proposed. We have reviewed the available literature on ovarian stem cells in adult mammalian ovaries and presented a model that proposes that the ovary harbors two distinct populations of stem cells, namely, pluripotent, quiescent, very small embryonic-like stem cells (VSELs, and slightly larger “progenitor” ovarian germ stem cells (OGSCs. Besides compromising the somatic niche, oncotherapy destroys OGSCs since, like tumor cells, they are actively dividing; however VSELs persist since they are relatively quiescent. BMT or transplanted ovarian cortical tissue may help rejuvenate the ovarian niche, which possibly supports differentiation of persisting VSELs resulting in neo-oogenesis and follicular development responsible for successful pregnancies. Postnatal oogenesis in mammalian ovary from VSELs may be exploited for fertility restoration in cancer survivors including those who were earlier deprived of gametes and/or gonadal tissue cryopreservation options.

  7. Hematopoietic stem and progenitor cells regulate the regeneration of their niche by secreting Angiopoietin-1

    Science.gov (United States)

    Zhou, Bo O; Ding, Lei; Morrison, Sean J

    2015-01-01

    Hematopoietic stem cells (HSCs) are maintained by a perivascular niche in bone marrow but it is unclear whether the niche is reciprocally regulated by HSCs. Here, we systematically assessed the expression and function of Angiopoietin-1 (Angpt1) in bone marrow. Angpt1 was not expressed by osteoblasts. Angpt1 was most highly expressed by HSCs, and at lower levels by c-kit+ hematopoietic progenitors, megakaryocytes, and Leptin Receptor+ (LepR+) stromal cells. Global conditional deletion of Angpt1, or deletion from osteoblasts, LepR+ cells, Nes-cre-expressing cells, megakaryocytes, endothelial cells or hematopoietic cells in normal mice did not affect hematopoiesis, HSC maintenance, or HSC quiescence. Deletion of Angpt1 from hematopoietic cells and LepR+ cells had little effect on vasculature or HSC frequency under steady-state conditions but accelerated vascular and hematopoietic recovery after irradiation while increasing vascular leakiness. Hematopoietic stem/progenitor cells and LepR+ stromal cells regulate niche regeneration by secreting Angpt1, reducing vascular leakiness but slowing niche recovery. DOI: http://dx.doi.org/10.7554/eLife.05521.001 PMID:25821987

  8. Proximity-Based Differential Single-Cell Analysis of the Niche to Identify Stem/Progenitor Cell Regulators.

    Science.gov (United States)

    Silberstein, Lev; Goncalves, Kevin A; Kharchenko, Peter V; Turcotte, Raphael; Kfoury, Youmna; Mercier, Francois; Baryawno, Ninib; Severe, Nicolas; Bachand, Jacqueline; Spencer, Joel A; Papazian, Ani; Lee, Dongjun; Chitteti, Brahmananda Reddy; Srour, Edward F; Hoggatt, Jonathan; Tate, Tiffany; Lo Celso, Cristina; Ono, Noriaki; Nutt, Stephen; Heino, Jyrki; Sipilä, Kalle; Shioda, Toshihiro; Osawa, Masatake; Lin, Charles P; Hu, Guo-Fu; Scadden, David T

    2016-10-06

    Physiological stem cell function is regulated by secreted factors produced by niche cells. In this study, we describe an unbiased approach based on the differential single-cell gene expression analysis of mesenchymal osteolineage cells close to, and further removed from, hematopoietic stem/progenitor cells (HSPCs) to identify candidate niche factors. Mesenchymal cells displayed distinct molecular profiles based on their relative location. We functionally examined, among the genes that were preferentially expressed in proximal cells, three secreted or cell-surface molecules not previously connected to HSPC biology-the secreted RNase angiogenin, the cytokine IL18, and the adhesion molecule Embigin-and discovered that all of these factors are HSPC quiescence regulators. Therefore, our proximity-based differential single-cell approach reveals molecular heterogeneity within niche cells and can be used to identify novel extrinsic stem/progenitor cell regulators. Similar approaches could also be applied to other stem cell/niche pairs to advance the understanding of microenvironmental regulation of stem cell function. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. When do plant radiations influence community assembly? The importance of historical contingency in the race for niche space.

    Science.gov (United States)

    Tanentzap, Andrew J; Brandt, Angela J; Smissen, Rob D; Heenan, Peter B; Fukami, Tadashi; Lee, William G

    2015-07-01

    Plant radiations are widespread but their influence on community assembly has rarely been investigated. Theory and some evidence suggest that radiations can allow lineages to monopolize niche space when founding species arrive early into new bioclimatic regions and exploit ecological opportunities. These early radiations may subsequently reduce niche availability and dampen diversification of later arrivals. We tested this hypothesis of time-dependent lineage diversification and community dominance using the alpine flora of New Zealand. We estimated ages of 16 genera from published phylogenies and determined their relative occurrence across climatic and physical gradients in the alpine zone. We used these data to reconstruct occupancy of environmental space through time, integrating palaeoclimatic and palaeogeological changes. Our analysis suggested that earlier-colonizing lineages encountered a greater availability of environmental space, which promoted greater species diversity and occupancy of niche space. Genera that occupied broader niches were subsequently more dominant in local communities. An earlier time of arrival also contributed to greater diversity independently of its influence in accessing niche space. We suggest that plant radiations influence community assembly when they arise early in the occupancy of environmental space, allowing them to exclude later-arriving colonists from ecological communities by niche preemption. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  10. Modeling microwave/electron-cloud interaction

    International Nuclear Information System (INIS)

    Mattes, M; Sorolla, E; Zimmermann, F

    2013-01-01

    Starting from the separate codes BI-RME and ECLOUD or PyECLOUD, we are developing a novel joint simulation tool, which models the combined effect of a charged particle beam and of microwaves on an electron cloud. Possible applications include the degradation of microwave transmission in telecommunication satellites by electron clouds; the microwave-transmission techniques being used in particle accelerators for the purpose of electroncloud diagnostics; the microwave emission by the electron cloud itself in the presence of a magnetic field; and the possible suppression of electron-cloud formation in an accelerator by injecting microwaves of suitable amplitude and frequency. A few early simulation results are presented. (author)

  11. Phase-Space Models of Solitary Electron Hoies

    DEFF Research Database (Denmark)

    Lynov, Jens-Peter; Michelsen, Poul; Pécseli, Hans

    1985-01-01

    Two different phase-space models of solitary electron holes are investigated and compared with results from computer simulations of an actual laboratory experiment, carried out in a strongly magnetized, cylindrical plasma column. In the two models, the velocity distribution of the electrons...

  12. Stem Cell Niches in Glioblastoma: A Neuropathological View

    Directory of Open Access Journals (Sweden)

    Davide Schiffer

    2014-01-01

    Full Text Available Glioblastoma (GBM stem cells (GSCs, responsible for tumor growth, recurrence, and resistance to therapies, are considered the real therapeutic target, if they had no molecular mechanisms of resistance, in comparison with the mass of more differentiated cells which are insensitive to therapies just because of being differentiated and nonproliferating. GSCs occur in tumor niches where both stemness status and angiogenesis are conditioned by the microenvironment. In both perivascular and perinecrotic niches, hypoxia plays a fundamental role. Fifteen glioblastomas have been studied by immunohistochemistry and immunofluorescence for stemness and differentiation antigens. It has been found that circumscribed necroses develop inside hyperproliferating areas that are characterized by high expression of stemness antigens. Necrosis developed inside them because of the imbalance between the proliferation of tumor cells and endothelial cells; it reduces the number of GSCs to a thin ring around the former hyperproliferating area. The perinecrotic GSCs are nothing else that the survivors remnants of those populating hyperproliferating areas. In the tumor, GSCs coincide with malignant areas so that the need to detect where they are located is not so urgent.

  13. Satellite Cells and the Muscle Stem Cell Niche

    Science.gov (United States)

    Yin, Hang; Price, Feodor

    2013-01-01

    Adult skeletal muscle in mammals is a stable tissue under normal circumstances but has remarkable ability to repair after injury. Skeletal muscle regeneration is a highly orchestrated process involving the activation of various cellular and molecular responses. As skeletal muscle stem cells, satellite cells play an indispensible role in this process. The self-renewing proliferation of satellite cells not only maintains the stem cell population but also provides numerous myogenic cells, which proliferate, differentiate, fuse, and lead to new myofiber formation and reconstitution of a functional contractile apparatus. The complex behavior of satellite cells during skeletal muscle regeneration is tightly regulated through the dynamic interplay between intrinsic factors within satellite cells and extrinsic factors constituting the muscle stem cell niche/microenvironment. For the last half century, the advance of molecular biology, cell biology, and genetics has greatly improved our understanding of skeletal muscle biology. Here, we review some recent advances, with focuses on functions of satellite cells and their niche during the process of skeletal muscle regeneration. PMID:23303905

  14. Modeling Incoherent Electron Cloud Effects

    International Nuclear Information System (INIS)

    Vay, Jean-Luc; Benedetto, E.; Fischer, W.; Franchetti, G.; Ohmi, K.; Schulte, D.; Sonnad, K.; Tomas, R.; Vay, J.-L.; Zimmermann, F.; Rumolo, G.; Pivi, M.; Raubenheimer, T.

    2007-01-01

    Incoherent electron effects could seriously limit the beam lifetime in proton or ion storage rings, such as LHC, SPS, or RHIC, or blow up the vertical emittance of positron beams, e.g., at the B factories or in linear-collider damping rings. Different approaches to modeling these effects each have their own merits and drawbacks. We describe several simulation codes which simplify the descriptions of the beam-electron interaction and of the accelerator structure in various different ways, and present results for a toy model of the SPS. In addition, we present evidence that for positron beams the interplay of incoherent electron-cloud effects and synchrotron radiation can lead to a significant increase in vertical equilibrium emittance. The magnitude of a few incoherent e+e- scattering processes is also estimated. Options for future code development are reviewed

  15. Spatial Heterogeneity of Habitat Suitability for Rift Valley Fever Occurrence in Tanzania: An Ecological Niche Modelling Approach

    Science.gov (United States)

    Sindato, Calvin; Stevens, Kim B.; Karimuribo, Esron D.; Mboera, Leonard E. G.; Paweska, Janusz T.; Pfeiffer, Dirk U.

    2016-01-01

    Background Despite the long history of Rift Valley fever (RVF) in Tanzania, extent of its suitable habitat in the country remains unclear. In this study we investigated potential effects of temperature, precipitation, elevation, soil type, livestock density, rainfall pattern, proximity to wild animals, protected areas and forest on the habitat suitability for RVF occurrence in Tanzania. Materials and Methods Presence-only records of 193 RVF outbreak locations from 1930 to 2007 together with potential predictor variables were used to model and map the suitable habitats for RVF occurrence using ecological niche modelling. Ground-truthing of the model outputs was conducted by comparing the levels of RVF virus specific antibodies in cattle, sheep and goats sampled from locations in Tanzania that presented different predicted habitat suitability values. Principal Findings Habitat suitability values for RVF occurrence were higher in the northern and central-eastern regions of Tanzania than the rest of the regions in the country. Soil type and precipitation of the wettest quarter contributed equally to habitat suitability (32.4% each), followed by livestock density (25.9%) and rainfall pattern (9.3%). Ground-truthing of model outputs revealed that the odds of an animal being seropositive for RVFV when sampled from areas predicted to be most suitable for RVF occurrence were twice the odds of an animal sampled from areas least suitable for RVF occurrence (95% CI: 1.43, 2.76, p < 0.001). Conclusion/Significance The regions in the northern and central-eastern Tanzania were more suitable for RVF occurrence than the rest of the regions in the country. The modelled suitable habitat is characterised by impermeable soils, moderate precipitation in the wettest quarter, high livestock density and a bimodal rainfall pattern. The findings of this study should provide guidance for the design of appropriate RVF surveillance, prevention and control strategies which target areas with

  16. Realized niches explain spatial gradients in seasonal abundance of phytoplankton groups in the South China Sea

    Science.gov (United States)

    Xiao, Wupeng; Wang, Lei; Laws, Edward; Xie, Yuyuan; Chen, Jixin; Liu, Xin; Chen, Bingzhang; Huang, Bangqin

    2018-03-01

    A basic albeit elusive goal of ocean science is to predict the structure of biological communities from the multitude of environmental conditions they experience. Estimates of the realized niche-based traits (realized traits) of phytoplankton species or functional groups in temperate seas have shown that response traits can help reveal the mechanisms responsible for structuring phytoplankton communities, but such approaches have not been tested in tropical and subtropical marginal seas. Here, we used decadal-scale studies of pigment-based phytoplankton groups and environmental conditions in the South China Sea to test whether realized traits could explain the biogeographic patterns of phytoplankton variability. We estimated the mean and breadth of the phytoplankton realized niches based on responses of the group-specific phytoplankton composition to key environmental factors, and we showed that variations of major phytoplankton groups in this system can be explained by different adaptive trade-offs to constraints imposed by temperature, irradiance, and nutrient concentrations. Differences in the patterns of trade-offs clearly separated the dominant groups from one another and generated four sets of realized traits that mirrored the observed biogeographic distribution patterns. The phytoplankton realized niches and their associated traits that we characterized in the present study could help to predict responses of phytoplankton to changes in environmental conditions in the South China Sea and could be incorporated into global biogeochemical models to anticipate shifts in community structure under future climate scenarios.

  17. Niche partitioning of feeding microhabitats produces a unique function for herbivorous rabbitfishes (Perciformes, Siganidae) on coral reefs

    Science.gov (United States)

    Fox, R. J.; Bellwood, D. R.

    2013-03-01

    Niche theory predicts that coexisting species minimise competition by evolving morphological or behavioural specialisations that allow them to spread out along resource axes such as space, diet and temporal activity. These specialisations define how a species interacts with its environment and, by extension, determine its functional role. Here, we examine the feeding niche of three species of coral reef-dwelling rabbitfishes (Siganidae, Siganus). By comparing aspects of their feeding behaviour (bite location, bite rate, foraging distance) with that of representative species from two other abundant herbivorous fish families, the parrotfishes (Labridae, Scarus) and surgeonfishes (Acanthuridae, Acanthurus), we examine whether rabbitfishes have a feeding niche distinct from other members of the herbivore guild. Measurements of the penetration of the fishes' snouts and bodies into reef concavities when feeding revealed that rabbitfish fed to a greater degree from reef crevices and interstices than other herbivores. There was just a 40 % overlap in the penetration-depth niche between rabbitfish and surgeonfish and a 45 % overlap between rabbitfish and parrotfish, compared with the almost complete niche overlap (95 %) recorded for parrotfish and surgeonfish along this spatial niche axis. Aspects of the morphology of rabbitfish which may contribute to this niche segregation include a comparatively longer, narrower snout and narrower head. Our results suggest that sympatric coexistence of rabbitfish and other reef herbivores is facilitated by segregation along a spatial (and potentially dietary) axis. This segregation results in a unique functional role for rabbitfishes among roving herbivores that of "crevice-browser": a group that specifically feeds on crevice-dwelling algal or benthic organisms. This functional trait may have implications for reef ecosystem processes in terms of controlling the successional development of crevice-based algal communities, reducing their

  18. FTL Quantum Models of the Photon and the Electron

    International Nuclear Information System (INIS)

    Gauthier, Richard F.

    2007-01-01

    A photon is modeled by an uncharged superluminal quantum moving at 1.414c along an open 45-degree helical trajectory with radius R = λ/2π (where λ is the helical pitch or wavelength). A mostly superluminal spatial model of an electron is composed of a charged pointlike quantum circulating at an extremely high frequency ( 2.5 x 1020 hz) in a closed, double-looped hehcal trajectory whose helical pitch is one Compton wavelength h/mc. The quantum has energy and momentum but not rest mass, so its speed is not limited by c. sThe quantum's speed is superluminal 57% of the time and subluminal 43% of the time, passing through c twice in each trajectory cycle. The quantum's maximum speed in the electron's rest frame is 2.515c and its minimum speed is .707c. The electron model's helical trajectory parameters are selected to produce the electron's spin (ℎ/2π)/2 and approximate (without small QED corrections) magnetic moment e(ℎ/2π)/2m (the Bohr magneton μB) as well as its Dirac equation-related 'jittery motion' angular frequency 2mc2/(ℎ/2π), amplitude (ℎ/2π)/2mc and internal speed c. The two possible helicities of the electron model correspond to the electron and the positron. With these models, an electron is like a closed circulating photon. The electron's inertia is proposed to be related to the electron model's circulating internal Compton momentum mc. The internal superluminalily of the photon model, the internal superluminahty/subluminality of the electron model, and the proposed approach to the electron's inertia as ''momentum at rest'' within the electron, could be relevant to possible mechanisms of superluminal communication and transportation

  19. Peculiarities of designing Holistic Electronic Government Services Integration Model

    Directory of Open Access Journals (Sweden)

    Tadas Limba

    2011-12-01

    Full Text Available Purpos– the aim ok this paper is to develop a Holistic Electronic Government Services Integration Model which could ensure the efficient integration of electronic government services in the local self-government level.Methodolog– the following analyses have been carried out in thirkpaper: theoretical-systematic; normative and conceptual comparative analysis of the researcha A method of modeling has also been applied.Finding– the scientific work analyzes the improvement opportunities of the models of electronic government services and their application alternatives in Lithuanian municipalities. The newly developed model of electronic government services that has been designed basng on the principle of integrating online expert consultation is primarily targeted at improvement of inside processes’ changes of an organization. Practicing the application of that model in the local self-government level starting with improvement of inside processes of an organization should help adapt more accurately and efficiently to the changing needs of the society while providing electronic government services, thus establishing a higher public value.Practical implication– the practical novelty of work is reflected not only through the integration opportunities’ assessment of the principle of online expert consultation services into the theoretical models of electronic government services that have already been developed by the scientists, but also on the basis of this principle there has been created a “Holistic Electronic Government Services Integration Model” in accordance with “E-Diamond” model basis and its practical application realization with the design of “The project of implementing the principle of online expert consultation on the model of electronic government services” for the future investigations.Originalit– the systematic, comparative analysis of the models of electronic government services carried out in the scientific

  20. Inter-specific and seasonal comparison of the niches occupied by small cetaceans off north-west Iberia

    DEFF Research Database (Denmark)

    Fernandez Garcia, Rut; MacLeod, C. D.; Pierce, G. J.

    2013-01-01

    Knowledge of species' ecological niches can be used to assess ecological interactions between different taxa. Sixteen species of cetaceans have been recorded in Galician waters and niche partitioning is expected to occur among these species in order to allow them to co-exist. In this study, the n...

  1. Place prioritization for biodiversity content using species ecological niche modeling

    Directory of Open Access Journals (Sweden)

    Víctor Sánchez-Cordero

    2005-01-01

    Full Text Available Place prioritization for biodiversity representation is essential for conservation planning, particularly in megadiverse countries where high deforestation threatens biodiversity. Given the collecting biases and uneven sampling of biological inventories, there is a need to develop robust models of species’ distributions. By modeling species’ ecological niches using point occurrence data and digitized environmental feature maps, we can predict potential and extant distributions of species in untransformed landscapes, as well as in those transformed by vegetation change (including deforestation. Such distributional predictions provide a framework for use of species as biodiversity surrogates in place prioritization procedures such as those based on rarity and complementarity. Beyond biodiversity conservation, these predictions can also be used for place prioritization for ecological restoration under current conditions and under future scenarios of habitat change (e.g., deforestation scenarios. To illustrate these points, we (1 predict distributions under current and future deforestation scenarios for the Mexican endemic mammal Dipodomys phillipsii, and show how areas for restoration may be selected; and (2 propose conservation areas by combining nonvolant mammal distributional predictions as biodiversity surrogates with place prioritization procedures, to connect decreed natural protected areas in a region holding exceptional biodiversity: the Transvolcanic Belt in central Mexico. La selección de áreas prioritarias de conservación es fundamental en la planeación sistemática de la conservación, particularmente en países de mega-diversidad, en donde la alta deforestación es una de las amenazas a la biodiversidad. Debido a los sesgos taxonómicos y geográficos de colecta de los inventarios biológicos, es indispensable generar modelos robustos de distribución de especies. Al modelar el nicho ecológico de especies usando localidades de

  2. Model Comparison for Electron Thermal Transport

    Science.gov (United States)

    Moses, Gregory; Chenhall, Jeffrey; Cao, Duc; Delettrez, Jacques

    2015-11-01

    Four electron thermal transport models are compared for their ability to accurately and efficiently model non-local behavior in ICF simulations. Goncharov's transport model has accurately predicted shock timing in implosion simulations but is computationally slow and limited to 1D. The iSNB (implicit Schurtz Nicolai Busquet electron thermal transport method of Cao et al. uses multigroup diffusion to speed up the calculation. Chenhall has expanded upon the iSNB diffusion model to a higher order simplified P3 approximation and a Monte Carlo transport model, to bridge the gap between the iSNB and Goncharov models while maintaining computational efficiency. Comparisons of the above models for several test problems will be presented. This work was supported by Sandia National Laboratory - Albuquerque and the University of Rochester Laboratory for Laser Energetics.

  3. Model of electron capture in low-temperature glasses

    International Nuclear Information System (INIS)

    Bartczak, W.M.; Swiatla, D.; Kroh, J.

    1983-01-01

    The new model of electron capture by a statistical variety of traps in glassy matrices is proposed. The electron capture is interpreted as the radiationless transition (assisted by multiphonon emission) of the mobile electron to the localized state in the trap. The conception of 'unfair' and 'fair' traps is introduced. The 'unfair' trap captures the mobile electron by the shallow excited state. In contrast, the 'fair' trap captures the electron by the ground state. The model calculations of the statistical distributions of the occupied electron traps are presented and discussed with respect to experimental results. (author)

  4. Co-niche construction between hosts and symbionts: ideas and ...

    Indian Academy of Sciences (India)

    RENEE M. BORGES

    2017-07-05

    Jul 5, 2017 ... Centre for Ecological Sciences, Indian Institute of Science, Bengaluru 560 012, India ... Symbiosis is a process that can generate evolutionary novelties and can extend the phenotypic niche ..... order to facilitate interactions with ants, plants provide ... of mutualistic pollinators develops within the pollinated ...

  5. USign--a security enhanced electronic consent model.

    Science.gov (United States)

    Li, Yanyan; Xie, Mengjun; Bian, Jiang

    2014-01-01

    Electronic consent becomes increasingly popular in the healthcare sector given the many benefits it provides. However, security concerns, e.g., how to verify the identity of a person who is remotely accessing the electronic consent system in a secure and user-friendly manner, also arise along with the popularity of electronic consent. Unfortunately, existing electronic consent systems do not pay sufficient attention to those issues. They mainly rely on conventional password based authentication to verify the identity of an electronic consent user, which is far from being sufficient given that identity theft threat is real and significant in reality. In this paper, we present a security enhanced electronic consent model called USign. USign enhances the identity protection and authentication for electronic consent systems by leveraging handwritten signatures everyone is familiar with and mobile computing technologies that are becoming ubiquitous. We developed a prototype of USign and conducted preliminary evaluation on accuracy and usability of signature verification. Our experimental results show the feasibility of the proposed model.

  6. Lessons on electronic decoherence in molecules from exact modeling

    Science.gov (United States)

    Hu, Wenxiang; Gu, Bing; Franco, Ignacio

    2018-04-01

    Electronic decoherence processes in molecules and materials are usually thought and modeled via schemes for the system-bath evolution in which the bath is treated either implicitly or approximately. Here we present computations of the electronic decoherence dynamics of a model many-body molecular system described by the Su-Schrieffer-Heeger Hamiltonian with Hubbard electron-electron interactions using an exact method in which both electronic and nuclear degrees of freedom are taken into account explicitly and fully quantum mechanically. To represent the electron-nuclear Hamiltonian in matrix form and propagate the dynamics, the computations employ the Jordan-Wigner transformation for the fermionic creation/annihilation operators and the discrete variable representation for the nuclear operators. The simulations offer a standard for electronic decoherence that can be used to test approximations. They also provide a useful platform to answer fundamental questions about electronic decoherence that cannot be addressed through approximate or implicit schemes. Specifically, through simulations, we isolate basic mechanisms for electronic coherence loss and demonstrate that electronic decoherence is possible even for one-dimensional nuclear bath. Furthermore, we show that (i) decreasing the mass of the bath generally leads to faster electronic decoherence; (ii) electron-electron interactions strongly affect the electronic decoherence when the electron-nuclear dynamics is not pure-dephasing; (iii) classical bath models with initial conditions sampled from the Wigner distribution accurately capture the short-time electronic decoherence dynamics; (iv) model separable initial superpositions often used to understand decoherence after photoexcitation are only relevant in experiments that employ delta-like laser pulses to initiate the dynamics. These insights can be employed to interpret and properly model coherence phenomena in molecules.

  7. Rac1 GTPase Promotes Interaction of Hematopoietic Stem/Progenitor Cell with Niche and Participates in Leukemia Initiation and Maintenance in Mouse.

    Science.gov (United States)

    Chen, Shuying; Li, Huan; Li, Shouyun; Yu, Jing; Wang, Min; Xing, Haiyan; Tang, Kejing; Tian, Zheng; Rao, Qing; Wang, Jianxiang

    2016-07-01

    Interaction between hematopoietic stem/progenitor cells (HSPCs) with their niche is critical for HSPC function. The interaction also plays an important role in the multistep process of leukemogenesis. Rac1 GTPase has been found to be highly expressed and activated in leukemia patients. Here, by forced expression of constitutively active form of Rac1 (Rac1-V12) in HSPCs, we demonstrate that active Rac1 promotes interaction of HSPC with niche. We then established an active Rac1 associated acute myeloid leukemia (AML) model by expression of Rac1-V12 cooperated with AML1-ETO9a (AE9a) in mouse HSPCs. Compared with AE9a alone, Rac1-V12 cooperated with AE9a (AER) drives an AML with a short latency, demonstrating that activation of Rac1 GTPase in mice promotes AML development. The mechanism of this AML promotion is by a better homing and lodging of leukemia cells in niche, which further enhancing their colony formation, quiescence and preventing leukemia cells from apoptosis. Further study showed that an inhibitor targeting activated Rac1 can increase the efficacy of chemotherapeutic agents to leukemia cells. This study provides evidence that activation of Rac1 promotes leukemia development through enhancing leukemia cells' homing and retention in niche, and suggests that inhibition of Rac1 GTPase could be an effective way of eliminating AML cells. Stem Cells 2016;34:1730-1741. © 2016 AlphaMed Press.

  8. Prediction Model for Relativistic Electrons at Geostationary Orbit

    Science.gov (United States)

    Khazanov, George V.; Lyatsky, Wladislaw

    2008-01-01

    We developed a new prediction model for forecasting relativistic (greater than 2MeV) electrons, which provides a VERY HIGH correlation between predicted and actually measured electron fluxes at geostationary orbit. This model implies the multi-step particle acceleration and is based on numerical integrating two linked continuity equations for primarily accelerated particles and relativistic electrons. The model includes a source and losses, and used solar wind data as only input parameters. We used the coupling function which is a best-fit combination of solar wind/interplanetary magnetic field parameters, responsible for the generation of geomagnetic activity, as a source. The loss function was derived from experimental data. We tested the model for four year period 2004-2007. The correlation coefficient between predicted and actual values of the electron fluxes for whole four year period as well as for each of these years is stable and incredibly high (about 0.9). The high and stable correlation between the computed and actual electron fluxes shows that the reliable forecasting these electrons at geostationary orbit is possible.

  9. Discovery of fungus-mite mutualism in a unique niche

    NARCIS (Netherlands)

    Roets, F; Wingfield, M J; Crous, P W; Dreyer, L L

    2007-01-01

    The floral heads (infructescences) of South African Protea L. represent a most unusual niche for fungi of the economically important genus Ophiostoma Syd. and P. Syd. emend. Z.W. de Beer et al. Current consensus holds that most members of Ophiostoma are vectored by tree-infesting bark beetles.

  10. Human cultures as niche constructions within the solar system

    NARCIS (Netherlands)

    Van de Vliert, Evert

    This commentary seeks to refine Kashima’s (2016) timely and topical but too-general call for embedding culture within the planetary ecosystem. My starting point is that cultures are to an underestimated extent ongoing niche constructions within the merry-go-round of the Sun’s radiation, the Earth’s

  11. S100 chemokines mediate bookmarking of premetastatic niches

    Science.gov (United States)

    Rafii, Shahin; Lyden, David

    2010-01-01

    Primary tumours release soluble factors, including VEGF-A, TGFβ and TNFα, which induce expression of the chemokines S100A8 and S100A9 in the myeloid and endothelial cells within the lung before tumour metastasis. These chemokine-activated premetastatic niches support adhesion and invasion of disseminating malignant cells, thereby establishing a fertile habitat for metastatic tumours. PMID:17139281

  12. Surfaces and spaces: troubleshooting the study of dietary niche space overlap between North American stem primates and rodents

    Science.gov (United States)

    Prufrock, Kristen A.; López-Torres, Sergi; Silcox, Mary T.; Boyer, Doug M.

    2016-06-01

    Dental topographic metrics provide quantitative, biologically meaningful data on the three-dimensional (3D) form of teeth. In this study, three dental topographic metrics (Dirichlet normal energy (DNE), relief index (RFI), and orientation patch count rotated (OPCR)) are used to evaluate the presence of dietary niche overlap between North American plesiadapoid primates (Plesiadapidae, Carpolestidae, and Saxonellidae) and early rodents. Calculation of these metrics requires researchers to modify the 3D surface models of the teeth by cropping them to a region of interest and/or orienting them. The current study therefore also examines the error introduced by cropping and orientation, and evaluates the contribution of these metrics to the niche overlap hypothesis. Our results indicate that cropping creates significantly more variation in RFI than DNE. Furthermore, orientation is an even larger source of variation in the calculation of RFI than cropping. Orientation does not strongly influence OPCR values. However, none of these sources of error are significant enough to undermine the extent to which these metrics can speak to the niche overlap hypothesis. The DNE and RFI results suggest that carpolestids and saxonellids had very different molar morphologies from early rodents, and thus these groups were not adapted to consume the same resources. Some plesiadapids show similar levels of occlusal curvature, relief, and complexity to early rodents. The plesiadapid Chiromyoides, which has distinctively low cusps and weak shearing crest development, has molars that are the most rodent-like of all taxa compared. This suggests that Chiromyoides had a dietary niche that overlapped with early rodents and would have been the most likely to be competing over food resources. Results from the plesiadapoid-rodent dental topographic analysis highlight the utility of DNE for detecting more fine-scaled differences in occlusal surface morphology than OPCR, whereas RFI provided valuable

  13. Niche separation in flycatcher-like species in the lowland rainforests of Malaysia.

    Science.gov (United States)

    Mansor, Mohammad Saiful; Ramli, Rosli

    2017-07-01

    Niche theory suggests that sympatric species reduce interspecific competition through segregation of shared resources by adopting different attack manoeuvres. However, the fact that flycatcher-like bird species exclusively use the sally manoeuvre may thus challenge this view. We studied the foraging ecology of three flycatcher-like species (i.e. Paradise-flycatcher Terpsiphone sp., Black-naped Monarch Hypothymis azurea, and Rufous-winged Philentoma Philentoma pyrhoptera) in the Krau Wildlife Reserve in central Peninsular Malaysia. We investigated foraging preferences of each bird species and the potential niche partitioning via spatial or behavioural segregation. Foraging substrate was important parameter that effectively divided paradise-flycatcher from Black-naped Monarch and Rufous-winged Philentoma, where monarch and philentoma foraged mainly on live green leaves, while paradise-flycatcher foraged on the air. They also exhibited different foraging height preferences. Paradise-flycatcher, for instance, preferred the highest studied strata, while Black-naped Monarch foraged mostly in lower strata, and Rufous-winged Philentoma made use of the lowest strata. This study indicates that niche segregation occurs among sympatric species through foraging substrate and attack manoeuvres selection. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Stochastic model of the spinning electron

    International Nuclear Information System (INIS)

    Simaciu, I.; Borsos, Z.

    2002-01-01

    In Stochastic Electrodynamics (SED) it is demonstrated that electrostatic interaction is the result of the scattering of the Classical Zero-Point Field (CZPF) background by the charged particles. In such models, the electron is modelled as a two-dimensional oscillator, which interacts with the electric component of the CZPF background. The electron with spin is not only an electric monopole but also a magnetic dipole. The interaction of the spin electron with the CZPF background is not only electric but also magnetic. We calculate the scattering cross-section of magnetic dipole in the situation when a magnetic field, variable in time B arrow = B 0 arrow sin ωt, acts over the rigid magnetic dipole given by the symmetry of the model. The cross-section of a magnetic dipole σ m must be equal to the cross-section of an electric monopole σ e . This equality between σ m and σ e cross-sections is motivated, too, by the fact that, in the model of the two-dimensional oscillator, the electric charge q e has the motion speed c. (authors)

  15. Cytoarchitecture and ultrastructure of neural stem cell niches and neurogenic complexes maintaining adult neurogenesis in the olfactory midbrain of spiny lobsters, Panulirus argus.

    Science.gov (United States)

    Schmidt, Manfred; Derby, Charles D

    2011-08-15

    New interneurons are continuously generated in small proliferation zones within neuronal somata clusters in the olfactory deutocerebrum of adult decapod crustaceans. Each proliferation zone is connected to a clump of cells containing one neural stem cell (i.e., adult neuroblast), thus forming a "neurogenic complex." Here we provide a detailed analysis of the cytoarchitecture of neurogenic complexes in adult spiny lobsters, Panulirus argus, based on transmission electron microscopy and labeling with cell-type-selective markers. The clump of cells is composed of unique bipolar clump-forming cells that collectively completely envelop the adult neuroblast and are themselves ensheathed by a layer of processes of multipolar cell body glia. An arteriole is attached to the clump of cells, but dye perfusion experiments show that hemolymph has no access to the interior of the clump of cells. Thus, the clump of cells fulfills morphological criteria of a protective stem cell niche, with clump-forming cells constituting the adult neuroblast's microenvironment together with the cell body glia processes separating it from other tissue components. Bromodeoxyuridine pulse-chase experiments with short survival times suggest that adult neuroblasts are not quiescent but rather cycle actively during daytime. We propose a cell lineage model in which an asymmetrically dividing adult neuroblast repopulates the pool of neuronal progenitor cells in the associated proliferation zone. In conclusion, as in mammalian brains, adult neurogenesis in crustacean brains is fueled by neural stem cells that are maintained by stem cell niches that preserve elements of the embryonic microenvironment and contain glial and vascular elements. Copyright © 2011 Wiley-Liss, Inc.

  16. Wnt6 maintains anterior escort cells as an integral component of the germline stem cell niche.

    Science.gov (United States)

    Wang, Xiaoxi; Page-McCaw, Andrea

    2018-02-07

    Stem cells reside in a niche, a local environment whose cellular and molecular complexity is still being elucidated. In Drosophila ovaries, germline stem cells depend on cap cells for self-renewing signals and physical attachment. Germline stem cells also contact the anterior escort cells, and here we report that anterior escort cells are absolutely required for germline stem cell maintenance. When escort cells die from impaired Wnt signaling or hid expression, the loss of anterior escort cells causes loss of germline stem cells. Anterior escort cells function as an integral niche component by promoting DE-cadherin anchorage and by transiently expressing the Dpp ligand to promote full-strength BMP signaling in germline stem cells. Anterior escort cells are maintained by Wnt6 ligands produced by cap cells; without Wnt6 signaling, anterior escort cells die leaving vacancies in the niche, leading to loss of germline stem cells. Our data identify anterior escort cells as constituents of the germline stem cell niche, maintained by a cap cell-produced Wnt6 survival signal. © 2018. Published by The Company of Biologists Ltd.

  17. A life cycle assessment of biodiesel derived from the “niche filling” energy crop camelina in the USA

    International Nuclear Information System (INIS)

    Krohn, Brian J.; Fripp, Matthias

    2012-01-01

    Highlights: ► We conducted a life cycle analysis of biodiesel derived from Camelina sativa. ► Camelina biodiesel reduced GHG emissions and fossil fuel use by 40–60%. ► As a “niche filling” crop camelina can avoid land use change emissions. ► Low fertilizer use and yields >800 kg/ha are necessary for environmental viability. -- Abstract: Camelina sativa (L.) is a promising crop for biodiesel production that avoids many of the potential pitfalls of traditional biofuel crops, such as land use change (LUC) and food versus fuel. In this study the environmental viability of camelina biodiesel was assessed using life cycle analysis (LCA) methodology. The LCA was conducted using the spreadsheet model dubbed KABAM. KABAM found that camelina grown as a niche filling crop (in rotation with wheat or as a double crop) reduces greenhouse gas (GHG) emissions and fossil fuel use by 40–60% when compared to petroleum diesel. Furthermore, by avoiding LUC emissions, camelina biodiesel emits fewer GHGs than traditional soybean and canola biodiesel. Finally, a sensitivity analysis concluded that in order to maintain and increase the environmental viability of camelina and other niche filling biofuel crops, researchers and policy makers should focus their efforts on achieving satisfactory yields (1000–2000 kg/ha) while reducing nitrogen fertilizer inputs.

  18. Mouse Incisor Stem Cell Niche and Myb Transcription Factors

    Czech Academy of Sciences Publication Activity Database

    Švandová, Eva; Veselá, Barbora; Šmarda, J.; Hampl, A.; Radlanski, R.J.; Matalová, Eva

    2015-01-01

    Roč. 44, č. 5 (2015), s. 338-344 ISSN 0340-2096 R&D Projects: GA ČR GAP304/11/1418; GA ČR GCP302/12/J059 Institutional support: RVO:67985904 Keywords : c-Myb * stem cell niches Subject RIV: EA - Cell Biology Impact factor: 0.615, year: 2015

  19. Habitat suitability and ecological niches of different plankton functional types in the global ocean

    Science.gov (United States)

    Vogt, Meike; Brun, Philipp; Payne, Mark R.; O'Brien, Colleen J.; Bednaršek, Nina; Buitenhuis, Erik T.; Doney, Scott C.; Leblanc, Karine; Le Quéré, Corinne; Luo, Yawei; Moriarty, Róisín; O'Brien, Todd D.; Schiebel, Ralf; Swan, Chantal

    2013-04-01

    Marine plankton play a central role in the biogeochemical cycling of important elements such as carbon, nitrogen, and sulphur. While our knowledge about marine ecosystem structure and functioning is still scarce and episodic, several recent observational studies confirm that marine ecosystems have been changing due to recent climate change, overfishing, and coastal eutrophication. In order to better understand marine ecosystem dynamics, the MAREDAT initiative has recently collected abundance and biomass data for 5 autotrophic (diatoms, Phaeocystis, coccolithophores, nitrogen fixers, picophytoplankton), and 6 heterotrophic plankton functional types (PFTs; bacteri