WorldWideScience

Sample records for underlie functional diversification

  1. Functional neural circuits that underlie developmental stuttering.

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    Jianping Qiao

    Full Text Available The aim of this study was to identify differences in functional and effective brain connectivity between persons who stutter (PWS and typically developing (TD fluent speakers, and to assess whether those differences can serve as biomarkers to distinguish PWS from TD controls. We acquired resting-state functional magnetic resonance imaging data in 44 PWS and 50 TD controls. We then used Independent Component Analysis (ICA together with Hierarchical Partner Matching (HPM to identify networks of robust, functionally connected brain regions that were highly reproducible across participants, and we assessed whether connectivity differed significantly across diagnostic groups. We then used Granger Causality (GC to study the causal interactions (effective connectivity between the regions that ICA and HPM identified. Finally, we used a kernel support vector machine to assess how well these measures of functional connectivity and granger causality discriminate PWS from TD controls. Functional connectivity was stronger in PWS compared with TD controls in the supplementary motor area (SMA and primary motor cortices, but weaker in inferior frontal cortex (IFG, Broca's area, caudate, putamen, and thalamus. Additionally, causal influences were significantly weaker in PWS from the IFG to SMA, and from the basal ganglia to IFG through the thalamus, compared to TD controls. ICA and GC indices together yielded an accuracy of 92.7% in classifying PWS from TD controls. Our findings suggest the presence of dysfunctional circuits that support speech planning and timing cues for the initiation and execution of motor sequences in PWS. Our high accuracy of classification further suggests that these aberrant brain features may serve as robust biomarkers for PWS.

  2. Functional neural circuits that underlie developmental stuttering.

    Science.gov (United States)

    Qiao, Jianping; Wang, Zhishun; Zhao, Guihu; Huo, Yuankai; Herder, Carl L; Sikora, Chamonix O; Peterson, Bradley S

    2017-01-01

    The aim of this study was to identify differences in functional and effective brain connectivity between persons who stutter (PWS) and typically developing (TD) fluent speakers, and to assess whether those differences can serve as biomarkers to distinguish PWS from TD controls. We acquired resting-state functional magnetic resonance imaging data in 44 PWS and 50 TD controls. We then used Independent Component Analysis (ICA) together with Hierarchical Partner Matching (HPM) to identify networks of robust, functionally connected brain regions that were highly reproducible across participants, and we assessed whether connectivity differed significantly across diagnostic groups. We then used Granger Causality (GC) to study the causal interactions (effective connectivity) between the regions that ICA and HPM identified. Finally, we used a kernel support vector machine to assess how well these measures of functional connectivity and granger causality discriminate PWS from TD controls. Functional connectivity was stronger in PWS compared with TD controls in the supplementary motor area (SMA) and primary motor cortices, but weaker in inferior frontal cortex (IFG, Broca's area), caudate, putamen, and thalamus. Additionally, causal influences were significantly weaker in PWS from the IFG to SMA, and from the basal ganglia to IFG through the thalamus, compared to TD controls. ICA and GC indices together yielded an accuracy of 92.7% in classifying PWS from TD controls. Our findings suggest the presence of dysfunctional circuits that support speech planning and timing cues for the initiation and execution of motor sequences in PWS. Our high accuracy of classification further suggests that these aberrant brain features may serve as robust biomarkers for PWS.

  3. Functional neural circuits that underlie developmental stuttering

    Science.gov (United States)

    Zhao, Guihu; Huo, Yuankai; Herder, Carl L.; Sikora, Chamonix O.; Peterson, Bradley S.

    2017-01-01

    The aim of this study was to identify differences in functional and effective brain connectivity between persons who stutter (PWS) and typically developing (TD) fluent speakers, and to assess whether those differences can serve as biomarkers to distinguish PWS from TD controls. We acquired resting-state functional magnetic resonance imaging data in 44 PWS and 50 TD controls. We then used Independent Component Analysis (ICA) together with Hierarchical Partner Matching (HPM) to identify networks of robust, functionally connected brain regions that were highly reproducible across participants, and we assessed whether connectivity differed significantly across diagnostic groups. We then used Granger Causality (GC) to study the causal interactions (effective connectivity) between the regions that ICA and HPM identified. Finally, we used a kernel support vector machine to assess how well these measures of functional connectivity and granger causality discriminate PWS from TD controls. Functional connectivity was stronger in PWS compared with TD controls in the supplementary motor area (SMA) and primary motor cortices, but weaker in inferior frontal cortex (IFG, Broca’s area), caudate, putamen, and thalamus. Additionally, causal influences were significantly weaker in PWS from the IFG to SMA, and from the basal ganglia to IFG through the thalamus, compared to TD controls. ICA and GC indices together yielded an accuracy of 92.7% in classifying PWS from TD controls. Our findings suggest the presence of dysfunctional circuits that support speech planning and timing cues for the initiation and execution of motor sequences in PWS. Our high accuracy of classification further suggests that these aberrant brain features may serve as robust biomarkers for PWS. PMID:28759567

  4. Neural Tuning Functions Underlie Both Generalization and Interference.

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    Ian S Howard

    Full Text Available In sports, the role of backswing is considered critical for generating a good shot, even though it plays no direct role in hitting the ball. We recently demonstrated the scientific basis of this phenomenon by showing that immediate past movement affects the learning and recall of motor memories. This effect occurred regardless of whether the past contextual movement was performed actively, passively, or shown visually. In force field studies, it has been shown that motor memories generalize locally and that the level of compensation decays as a function of movement angle away from the trained movement. Here we examine if the contextual effect of past movement exhibits similar patterns of generalization and whether it can explain behavior seen in interference studies. Using a single force-field learning task, the directional tuning curves of both the prior contextual movement and the subsequent force field adaptive movements were measured. The adaptation movement direction showed strong directional tuning, decaying to zero by 90° relative to the training direction. The contextual movement direction exhibited a similar directional tuning, although the effect was always above 60%. We then investigated the directional tuning of the passive contextual movement using interference tasks, where the contextual movements that uniquely specified the force field direction were separated by ±15° or ±45°. Both groups showed a pronounced tuning effect, which could be well explained by the directional tuning functions for single force fields. Our results show that contextual effect of past movement influences predictive force compensation, even when adaptation does not require contextual information. However, when such past movement contextual information is crucial to the task, such as in an interference study, it plays a strong role in motor memory learning and recall. This work demonstrates that similar tuning responses underlie both generalization of

  5. The Impact of Organismal Innovation on Functional and Ecological Diversification.

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    Wainwright, Peter C; Price, Samantha A

    2016-09-01

    Innovations in organismal functional morphology are thought to be a major force in shaping evolutionary patterns, with the potential to drive adaptive radiation and influence the evolutionary prospects for lineages. But the evolutionary consequences of innovation are diverse and usually do not result in adaptive radiation. What factors shape the macroevolutionary impact of innovations? We assert that little is known in general about the macroevolutionary outcomes associated with functional innovations and we discuss a framework for studying biological innovations in an evolutionary context. Innovations are novel functional mechanisms that enhance organismal performance. The ubiquity of trade-offs in functional systems means that enhanced performance on one axis often occurs at the expense of performance on another axis, such that many innovations result in an exchange of performance capabilities, rather than an expansion. Innovations may open up new resources for exploitation but their consequences for functional and ecological diversification depend heavily on the adaptive landscape around these novel resources. As an example of a broader program that we imagine, we survey five feeding innovations in labrid fishes, an exceptionally successful and ecologically diverse group of reef fishes, and explore their impact on the rate of evolution of jaw functional morphology. All of the innovations provide performance enhancements and result in changes in patterns of resource use, but most are not associated with subsequent functional diversification or substantial ecological diversification. Because selection acts on a specific performance enhancement and not on the evolutionary potential of an innovation, the enhancement of diversity may be highly serendipitous. The macroevolutionary potential of innovations depends critically on the interaction between the performance enhancement and the ecological opportunity that is exposed. © The Author 2016. Published by Oxford

  6. Disconnection and hyper-connectivity underlie reorganization after TBI: A rodent functional connectomic analysis.

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    Harris, N G; Verley, D R; Gutman, B A; Thompson, P M; Yeh, H J; Brown, J A

    2016-03-01

    predicted by the structural deficits, not only within the primary sensorimotor injury site and pericontused regions, but the normally connected homotopic cortex, as well as subcortical regions, all of which persisted chronically. Especially novel in this study is the unanticipated finding of widespread increases in connection strength that dwarf both the degree and extent of the functional disconnections, and which persist chronically in some sensorimotor and subcortically connected regions. Exploratory global network analysis showed changes in network parameters indicative of possible acutely increased random connectivity and temporary reductions in modularity that were matched by local increases in connectedness and increased efficiency among more weakly connected regions. The global network parameters: shortest path-length, clustering coefficient and modularity that were most affected by trauma also scaled with the severity of injury, so that the corresponding regional measures were correlated to the injury severity most notably at 7 and 14 days and especially within, but not limited to, the contralateral cortex. These changes in functional network parameters are discussed in relation to the known time-course of physiologic and anatomic data that underlie structural and functional reorganization in this experiment model of TBI. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Towards understanding the evolution and functional diversification of DNA-containing plant organelles

    DEFF Research Database (Denmark)

    Leister, Dario Michael

    2016-01-01

    direct way to reconstruct the evolutionary history of plastids and mitochondria is to sequence and analyze their relatively small genomes. However, understanding the functional diversification of these organelles requires the identification of their complete protein repertoires - which is the ultimate...

  8. Late-stage diversification of biologically active pyridazinones via a direct C-H functionalization strategy.

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    Li, Wei; Fan, Zhoulong; Geng, Kaijun; Xu, Youjun; Zhang, Ao

    2015-01-14

    Divergent C-H functionalization reactions (arylation, carboxylation, olefination, thiolation, acetoxylation, halogenation, naphthylation) using a pyridazinone moiety as an internal directing group were successfully established. This approach offers a late-stage, ortho-selective diversification of a biologically active pyridazinone scaffold. Seven series of novel pyridazinone analogues were synthesized conveniently as the synthetic precursors of potential sortase A (SrtA) inhibitors.

  9. Heterozygous STAT1 gain-of-function mutations underlie an unexpectedly broad clinical phenotype

    NARCIS (Netherlands)

    Toubiana, Julie; Okada, Satoshi; Hiller, Julia; Oleastro, Matias; Lagos Gomez, Macarena; Aldave Becerra, Juan Carlos; Ouachée-Chardin, Marie; Fouyssac, Fanny; Girisha, Katta Mohan; Etzioni, Amos; van Montfrans, Joris M.; Camcioglu, Yildiz; Kerns, Leigh Ann; Belohradsky, Bernd; Blanche, Stéphane; Bousfiha, Aziz; Rodriguez-Gallego, Carlos; Meyts, Isabelle; Kisand, Kai; Reichenbach, Janine; Renner, Ellen D; Rosenzweig, Sergio; Grimbacher, Bodo; van de Veerdonk, Frank L; Traidl-Hoffmann, Claudia; Picard, Capucine; Marodi, Laszlo; Morio, Tomohiro; Kobayashi, Masao; Lilic, Desa; Milner, Joshua D; Holland, Steven; Casanova, Jean-Laurent; Puel, Anne

    2016-01-01

    Since their discovery in patients with autosomal dominant (AD) chronic mucocutaneous candidiasis (CMC) in 2011, heterozygous STAT1 gain-of-function (GOF) mutations have increasingly been identified worldwide. The clinical spectrum associated with them needed to be delineated. We enrolled 274

  10. Enantioselective functionalization of allylic C-H bonds following a strategy of functionalization and diversification.

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    Sharma, Ankit; Hartwig, John F

    2013-11-27

    We report the enantioselective functionalization of allylic C-H bonds in terminal alkenes by a strategy involving the installation of a temporary functional group at the terminal carbon atom by C-H bond functionalization, followed by the catalytic diversification of this intermediate with a broad scope of reagents. The method consists of a one-pot sequence of palladium-catalyzed allylic C-H bond oxidation under neutral conditions to form linear allyl benzoates, followed by iridium-catalyzed allylic substitution. This overall transformation forms a variety of chiral products containing a new C-N, C-O, C-S, or C-C bond at the allylic position in good yield with a high branched-to-linear selectivity and excellent enantioselectivity (ee ≤97%). The broad scope of the overall process results from separating the oxidation and functionalization steps; by doing so, the scope of nucleophile encompasses those sensitive to direct oxidative functionalization. The high enantioselectivity of the overall process is achieved by developing an allylic oxidation that occurs without acid to form the linear isomer with high selectivity. These allylic functionalization processes are amenable to an iterative sequence leading to (1,n)-functionalized products with catalyst-controlled diastereo- and enantioselectivity. The utility of the method in the synthesis of biologically active molecules has been demonstrated.

  11. The concomitant apoptosis and EMT underlie the fundamental functions of TGF-β.

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    Song, Jianguo; Shi, Weiwei

    2018-01-01

    TGF-β's multipotent cellular effects and their relations are critical for TGF-β's pathophysiological functions. However, these effects may appear to be paradoxical in understanding TGF-β's functions. Apoptosis and epithelial-mesenchymal transition (EMT) are two fundamental events that are deeply linked to various physiological and disease-related processes. These two major cellular fates are subtly regulated and can be potently stimulated by TGF-β, which profoundly contribute to the biological roles of TGF-β. Moreover, these two events are also indirectly and directly correlated with TGF-β-mediated growth inhibition and are relevant to the current understanding of the roles of TGF-β in tumorigenesis and cancer progression. Although TGF-β-induced apoptosis and EMT can be singly independent cellular events, they can also be mutually exclusive but interrelated concomitant events in various cases. Thus, the modulation of apoptosis and EMT is essential for the seemingly paradoxical functions of TGF-β. However, the concomitant effect of TGF-β on apoptosis and EMT, the balance and regulated alterations of them are still been ignored or underestimated. This review focuses on the TGF-β-induced concomitant apoptosis and EMT. We aim to provide an insight in understanding their significance, balance, and modulation in TGF-β-mediated biological functions. © The Author 2017. Published by Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  12. Functional and structural changes in internal pudendal arteries underlie erectile dysfunction induced by androgen deprivation

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    Rhéure Alves-Lopes

    2017-01-01

    Full Text Available Androgen deficiency is strongly associated with erectile dysfunction (ED. Inadequate penile arterial blood flow is one of the major causes of ED. The blood flow to the corpus cavernosum is mainly derived from the internal pudendal arteries (IPAs; however, no study has evaluated the effects of androgen deprivation on IPA′s function. We hypothesized that castration impairs IPAs reactivity and structure, contributing to ED. In our study, Wistar male rats, 8-week-old, were castrated and studied 30 days after orchiectomy. Functional and structural properties of rat IPAs were determined using wire and pressure myograph systems, respectively. Protein expression was determined by Western blot and immunohistochemistry. Plasma testosterone levels were determined using the IMMULITE 1000 Immunoassay System. Castrated rats exhibited impaired erectile function, represented by decreased intracavernosal pressure/mean arterial pressure ratio. IPAs from castrated rats exhibited decreased phenylephrine- and electrical field stimulation (EFS-induced contraction and decreased acetylcholine- and EFS-induced vasodilatation. IPAs from castrated rats exhibited decreased internal diameter, external diameter, thickness of the arterial wall, and cross-sectional area. Castration decreased nNOS and α-actin expression and increased collagen expression, p38 (Thr180/Tyr182 phosphorylation, as well as caspase 3 cleavage. In conclusion, androgen deficiency is associated with impairment of IPA reactivity and structure and increased apoptosis signaling markers. Our findings suggest that androgen deficiency-induced vascular dysfunction is an event involving hypotrophic vascular remodeling of IPAs.

  13. Functional diversification of Argonautes in nematodes: an expanding universe.

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    Buck, Amy H; Blaxter, Mark

    2013-08-01

    In the last decade, many diverse RNAi (RNA interference) pathways have been discovered that mediate gene silencing at epigenetic, transcriptional and post-transcriptional levels. The diversity of RNAi pathways is inherently linked to the evolution of Ago (Argonaute) proteins, the central protein component of RISCs (RNA-induced silencing complexes). An increasing number of diverse Agos have been identified in different species. The functions of most of these proteins are not yet known, but they are generally assumed to play roles in development, genome stability and/or protection against viruses. Recent research in the nematode Caenorhabditis elegans has expanded the breadth of RNAi functions to include transgenerational epigenetic memory and, possibly, environmental sensing. These functions are inherently linked to the production of secondary siRNAs (small interfering RNAs) that bind to members of a clade of WAGOs (worm-specific Agos). In the present article, we review briefly what is known about the evolution and function of Ago proteins in eukaryotes, including the expansion of WAGOs in nematodes. We postulate that the rapid evolution of WAGOs enables the exceptional functional plasticity of nematodes, including their capacity for parasitism.

  14. Functional diversification of structurally alike NLR proteins in plants.

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    Chakraborty, Joydeep; Jain, Akansha; Mukherjee, Dibya; Ghosh, Suchismita; Das, Sampa

    2018-04-01

    In due course of evolution many pathogens alter their effector molecules to modulate the host plants' metabolism and immune responses triggered upon proper recognition by the intracellular nucleotide-binding oligomerization domain containing leucine-rich repeat (NLR) proteins. Likewise, host plants have also evolved with diversified NLR proteins as a survival strategy to win the battle against pathogen invasion. NLR protein indeed detects pathogen derived effector proteins leading to the activation of defense responses associated with programmed cell death (PCD). In this interactive process, genome structure and plasticity play pivotal role in the development of innate immunity. Despite being quite conserved with similar biological functions in all eukaryotes, the intracellular NLR immune receptor proteins happen to be structurally distinct. Recent studies have made progress in identifying transcriptional regulatory complexes activated by NLR proteins. In this review, we attempt to decipher the intracellular NLR proteins mediated surveillance across the evolutionarily diverse taxa, highlighting some of the recent updates on NLR protein compartmentalization, molecular interactions before and after activation along with insights into the finer role of these receptor proteins to combat invading pathogens upon their recognition. Latest information on NLR sensors, helpers and NLR proteins with integrated domains in the context of plant pathogen interactions are also discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

  15. Early stages of functional diversification in the Rab GTPase gene family revealed by genomic and localization studies in Paramecium species.

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    Bright, Lydia J; Gout, Jean-Francois; Lynch, Michael

    2017-04-15

    New gene functions arise within existing gene families as a result of gene duplication and subsequent diversification. To gain insight into the steps that led to the functional diversification of paralogues, we tracked duplicate retention patterns, expression-level divergence, and subcellular markers of functional diversification in the Rab GTPase gene family in three Paramecium aurelia species. After whole-genome duplication, Rab GTPase duplicates are more highly retained than other genes in the genome but appear to be diverging more rapidly in expression levels, consistent with early steps in functional diversification. However, by localizing specific Rab proteins in Paramecium cells, we found that paralogues from the two most recent whole-genome duplications had virtually identical localization patterns, and that less closely related paralogues showed evidence of both conservation and diversification. The functionally conserved paralogues appear to target to compartments associated with both endocytic and phagocytic recycling functions, confirming evolutionary and functional links between the two pathways in a divergent eukaryotic lineage. Because the functionally diversifying paralogues are still closely related to and derived from a clade of functionally conserved Rab11 genes, we were able to pinpoint three specific amino acid residues that may be driving the change in the localization and thus the function in these proteins. © 2017 Bright et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  16. Identification of a new genomic hot spot of evolutionary diversification of protein function.

    Directory of Open Access Journals (Sweden)

    Aline Winkelmann

    Full Text Available Establishment of phylogenetic relationships remains a challenging task because it is based on computational analysis of genomic hot spots that display species-specific sequence variations. Here, we identify a species-specific thymine-to-guanine sequence variation in the Glrb gene which gives rise to species-specific splice donor sites in the Glrb genes of mouse and bushbaby. The resulting splice insert in the receptor for the inhibitory neurotransmitter glycine (GlyR conveys synaptic receptor clustering and specific association with a particular synaptic plasticity-related splice variant of the postsynaptic scaffold protein gephyrin. This study identifies a new genomic hot spot which contributes to phylogenetic diversification of protein function and advances our understanding of phylogenetic relationships.

  17. Functional diversification of sea urchin ABCC1 (MRP1) by alternative splicing.

    Science.gov (United States)

    Gökirmak, Tufan; Campanale, Joseph P; Reitzel, Adam M; Shipp, Lauren E; Moy, Gary W; Hamdoun, Amro

    2016-06-01

    The multidrug resistance protein (MRP) family encodes a diverse repertoire of ATP-binding cassette (ABC) transporters with multiple roles in development, disease, and homeostasis. Understanding MRP evolution is central to unraveling their roles in these diverse processes. Sea urchins occupy an important phylogenetic position for understanding the evolution of vertebrate proteins and have been an important invertebrate model system for study of ABC transporters. We used phylogenetic analyses to examine the evolution of MRP transporters and functional approaches to identify functional forms of sea urchin MRP1 (also known as SpABCC1). SpABCC1, the only MRP homolog in sea urchins, is co-orthologous to human MRP1, MRP3, and MRP6 (ABCC1, ABCC3, and ABCC6) transporters. However, efflux assays revealed that alternative splicing of exon 22, a region critical for substrate interactions, could diversify functions of sea urchin MRP1. Phylogenetic comparisons also indicate that while MRP1, MRP3, and MRP6 transporters potentially arose from a single transporter in basal deuterostomes, alternative splicing appears to have been the major mode of functional diversification in invertebrates, while duplication may have served a more important role in vertebrates. These results provide a deeper understanding of the evolutionary origins of MRP transporters and the potential mechanisms used to diversify their functions in different groups of animals. Copyright © 2016 the American Physiological Society.

  18. Decoupled diversification dynamics of feeding morphology following a major functional innovation in marine butterflyfishes.

    Science.gov (United States)

    Konow, Nicolai; Price, Samantha; Abom, Richard; Bellwood, David; Wainwright, Peter

    2017-08-16

    The diversity of fishes on coral reefs is influenced by the evolution of feeding innovations. For instance, the evolution of an intramandibular jaw joint has aided shifts to corallivory in Chaetodon butterflyfishes following their Miocene colonization of coral reefs. Today, over half of all Chaetodon species consume coral, easily the largest concentration of corallivores in any reef fish family. In contrast with Chaetodon , other chaetodontids, including the long-jawed bannerfishes, remain less intimately associated with coral and mainly consume other invertebrate prey. Here, we test (i) if intramandibular joint (IMJ) evolution in Chaetodon has accelerated feeding morphological diversification, and (ii) if cranial and post-cranial traits were affected similarly. We measured 19 cranial functional morphological traits, gut length and body elongation for 33 Indo-Pacific species. Comparisons of Brownian motion rate parameters revealed that cranial diversification was about four times slower in Chaetodon butterflyfishes with the IMJ than in other chaetodontids. However, the rate of gut length evolution was significantly faster in Chaetodon , with no group-differences for body elongation. The contrasting patterns of cranial and post-cranial morphological evolution stress the importance of comprehensive datasets in ecomorphology. The IMJ appears to enhance coral feeding ability in Chaetodon and represents a design breakthrough that facilitates this trophic strategy. Meanwhile, variation in gut anatomy probably reflects diversity in how coral tissues are procured and assimilated. Bannerfishes, by contrast, retain a relatively unspecialized gut for processing invertebrate prey, but have evolved some of the most extreme cranial mechanical innovations among bony fishes for procuring elusive prey. © 2017 The Author(s).

  19. Quantitative traits and diversification.

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    FitzJohn, Richard G

    2010-12-01

    Quantitative traits have long been hypothesized to affect speciation and extinction rates. For example, smaller body size or increased specialization may be associated with increased rates of diversification. Here, I present a phylogenetic likelihood-based method (quantitative state speciation and extinction [QuaSSE]) that can be used to test such hypotheses using extant character distributions. This approach assumes that diversification follows a birth-death process where speciation and extinction rates may vary with one or more traits that evolve under a diffusion model. Speciation and extinction rates may be arbitrary functions of the character state, allowing much flexibility in testing models of trait-dependent diversification. I test the approach using simulated phylogenies and show that a known relationship between speciation and a quantitative character could be recovered in up to 80% of the cases on large trees (500 species). Consistent with other approaches, detecting shifts in diversification due to differences in extinction rates was harder than when due to differences in speciation rates. Finally, I demonstrate the application of QuaSSE to investigate the correlation between body size and diversification in primates, concluding that clade-specific differences in diversification may be more important than size-dependent diversification in shaping the patterns of diversity within this group.

  20. Diversification of non-visual photopigment parapinopsin in spectral sensitivity for diverse pineal functions.

    Science.gov (United States)

    Koyanagi, Mitsumasa; Wada, Seiji; Kawano-Yamashita, Emi; Hara, Yuichiro; Kuraku, Shigehiro; Kosaka, Shigeaki; Kawakami, Koichi; Tamotsu, Satoshi; Tsukamoto, Hisao; Shichida, Yoshinori; Terakita, Akihisa

    2015-09-15

    Recent genome projects of various animals have uncovered an unexpectedly large number of opsin genes, which encode protein moieties of photoreceptor molecules, in most animals. In visual systems, the biological meanings of this diversification are clear; multiple types of visual opsins with different spectral sensitivities are responsible for color vision. However, the significance of the diversification of non-visual opsins remains uncertain, in spite of the importance of understanding the molecular mechanism and evolution of varied non-visual photoreceptions. Here, we investigated the diversification of the pineal photopigment parapinopsin, which serves as the UV-sensitive photopigment for the pineal wavelength discrimination in the lamprey, linking it with other pineal photoreception. Spectroscopic analyses of the recombinant pigments of the two teleost parapinopsins PP1 and PP2 revealed that PP1 is a UV-sensitive pigment, similar to lamprey parapinopsin, but PP2 is a blue-sensitive pigment, with an absorption maximum at 460-480 nm, showing the diversification of non-visual pigment with respect to spectral sensitivity. We also found that PP1 and PP2 exhibit mutually exclusive expressions in the pineal organs of three teleost species. By using transgenic zebrafish in which these parapinopsin-expressing cells are labeled, we found that PP1-expressing cells basically possess neuronal processes, which is consistent with their involvement in wavelength discrimination. Interestingly, however, PP2-expressing cells rarely possess neuronal processes, raising the possibility that PP2 could be involved in non-neural responses rather than neural responses. Furthermore, we found that PP2-expressing cells contain serotonin and aanat2, the key enzyme involved in melatonin synthesis from serotonin, whereas PP1-expressing cells do not contain either, suggesting that blue-sensitive PP2 is instead involved in light-regulation of melatonin secretion. In this paper, we have clearly

  1. Evolution of an arsenal: structural and functional diversification of the venom system in the advanced snakes (Caenophidia).

    Science.gov (United States)

    Fry, Bryan G; Scheib, Holger; van der Weerd, Louise; Young, Bruce; McNaughtan, Judith; Ramjan, S F Ryan; Vidal, Nicolas; Poelmann, Robert E; Norman, Janette A

    2008-02-01

    Venom is a key innovation underlying the evolution of advanced snakes (Caenophidia). Despite this, very little is known about venom system structural diversification, toxin recruitment event timings, or toxin molecular evolution. A multidisciplinary approach was used to examine the diversification of the venom system and associated toxins across the full range of the approximately 100 million-year-old advanced snake clade with a particular emphasis upon families that have not secondarily evolved a front-fanged venom system ( approximately 80% of the 2500 species). Analysis of cDNA libraries revealed complex venom transcriptomes containing multiple toxin types including three finger toxins, cobra venom factor, cysteine-rich secretory protein, hyaluronidase, kallikrein, kunitz, lectin, matrix metalloprotease, phospholipase A(2), snake venom metalloprotease/a disintegrin and metalloprotease, and waprin. High levels of sequence diversity were observed, including mutations in structural and functional residues, changes in cysteine spacing, and major deletions/truncations. Morphological analysis comprising gross dissection, histology, and magnetic resonance imaging also demonstrated extensive modification of the venom system architecture in non-front-fanged snakes in contrast to the conserved structure of the venom system within the independently evolved front-fanged elapid or viperid snakes. Further, a reduction in the size and complexity of the venom system was observed in species in which constriction has been secondarily evolved as the preferred method of prey capture or dietary preference has switched from live prey to eggs or to slugs/snails. Investigation of the timing of toxin recruitment events across the entire advanced snake radiation indicates that the evolution of advanced venom systems in three front-fanged lineages is associated with recruitment of new toxin types or explosive diversification of existing toxin types. These results support the role of venom

  2. Dissection of structural and functional requirements that underlie the interaction of ERdj3 protein with substrates in the endoplasmic reticulum.

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    Otero, Joel H; Lizák, Beata; Feige, Matthias J; Hendershot, Linda M

    2014-10-03

    ERdj3, a mammalian endoplasmic reticulum (ER) Hsp40/DnaJ family member, binds unfolded proteins, transfers them to BiP, and concomitantly stimulates BiP ATPase activity. However, the requirements for ERdj3 binding to and release from substrates in cells are not well understood. We found that ERdj3 homodimers that cannot stimulate the ATPase activity of BiP (QPD mutants) bound to unfolded ER proteins under steady state conditions in much greater amounts than wild-type ERdj3. This was due to reduced release from these substrates as opposed to enhanced binding, although in both cases dimerization was strictly required for substrate binding. Conversely, heterodimers consisting of one wild-type and one mutant ERdj3 subunit bound substrates at levels comparable with wild-type ERdj3 homodimers, demonstrating that release requires only one protomer to be functional in stimulating BiP ATPase activity. Co-expressing wild-type ERdj3 and a QPD mutant, which each exclusively formed homodimers, revealed that the release rate of wild-type ERdj3 varied according to the relative half-lives of substrates, suggesting that ERdj3 release is an important step in degradation of unfolded client proteins in the ER. Furthermore, pulse-chase experiments revealed that the binding of QPD mutant homodimers remained constant as opposed to increasing, suggesting that ERdj3 does not normally undergo reiterative binding cycles with substrates. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  3. What Factors Underlie Vertical and Horizontal Export Diversification

    African Journals Online (AJOL)

    Ritsumeikan Asia Pacific University

    progress in initiating process of economic and social development. .... Source: UNCTAD Hand Book of Statistics, UNCTAD database. Though many ...... Development and Harvard Institute for International Development: Harvard University,.

  4. What Factors Underlie Vertical and Horizontal Export Diversification

    African Journals Online (AJOL)

    Ritsumeikan Asia Pacific University

    effects by introducing renewable energy source, supplying modern cooking fuels, and substituting cleaner fuels for dirty ones and increasing energy efficiency. ..... A common practice in adoption studies is to divide the adoption population in to.

  5. What Factors Underlie Vertical and Horizontal Export Diversification

    African Journals Online (AJOL)

    Ritsumeikan Asia Pacific University

    zero-inflated negative binomial model was used to explain farmer frequency of ... 2 Ethiopian Economic Association/Ethiopian Economic Policy Research Institute, ... small coffee farmers to deal with income risk ex ante or address adverse income ..... of the self-reported data is subject to the usual caveats that apply when.

  6. Top-down and bottom-up attention-to-memory: mapping functional connectivity in two distinct networks that underlie cued and uncued recognition memory.

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    Burianová, Hana; Ciaramelli, Elisa; Grady, Cheryl L; Moscovitch, Morris

    2012-11-15

    The objective of this study was to examine the functional connectivity of brain regions active during cued and uncued recognition memory to test the idea that distinct networks would underlie these memory processes, as predicted by the attention-to-memory (AtoM) hypothesis. The AtoM hypothesis suggests that dorsal parietal cortex (DPC) allocates effortful top-down attention to memory retrieval during cued retrieval, whereas ventral parietal cortex (VPC) mediates spontaneous bottom-up capture of attention by memory during uncued retrieval. To identify networks associated with these two processes, we conducted a functional connectivity analysis of a left DPC and a left VPC region, both identified by a previous analysis of task-related regional activations. We hypothesized that the two parietal regions would be functionally connected with distinct neural networks, reflecting their engagement in the differential mnemonic processes. We found two spatially dissociated networks that overlapped only in the precuneus. During cued trials, DPC was functionally connected with dorsal attention areas, including the superior parietal lobules, right precuneus, and premotor cortex, as well as relevant memory areas, such as the left hippocampus and the middle frontal gyri. During uncued trials, VPC was functionally connected with ventral attention areas, including the supramarginal gyrus, cuneus, and right fusiform gyrus, as well as the parahippocampal gyrus. In addition, activity in the DPC network was associated with faster response times for cued retrieval. This is the first study to show a dissociation of the functional connectivity of posterior parietal regions during episodic memory retrieval, characterized by a top-down AtoM network involving DPC and a bottom-up AtoM network involving VPC. Copyright © 2012 Elsevier Inc. All rights reserved.

  7. Molecular evolution and the role of oxidative stress in the expansion and functional diversification of cytosolic glutathione transferases

    Directory of Open Access Journals (Sweden)

    Vasconcelos Vítor

    2010-09-01

    Full Text Available Abstract Background Cytosolic glutathione transferases (cGST are a large group of ubiquitous enzymes involved in detoxification and are well known for their undesired side effects during chemotherapy. In this work we have performed thorough phylogenetic analyses to understand the various aspects of the evolution and functional diversification of cGSTs. Furthermore, we assessed plausible correlations between gene duplication and substrate specificity of gene paralogs in humans and selected species, notably in mammalian enzymes and their natural substrates. Results We present a molecular phylogeny of cytosolic GSTs that shows that several classes of cGSTs are more ubiquitous and thus have an older ancestry than previously thought. Furthermore, we found that positive selection is implicated in the diversification of cGSTs. The number of duplicate genes per class is generally higher for groups of enzymes that metabolize products of oxidative damage. Conclusions 1 Protection against oxidative stress seems to be the major driver of positive selection in mammalian cGSTs, explaining the overall expansion pattern of this subfamily; 2 Given the functional redundancy of GSTs that metabolize xenobiotic chemicals, we would expect the loss of gene duplicates, but by contrast we observed a gene expansion of this family, which likely has been favored by: i the diversification of endogenous substrates; ii differential tissue expression; and iii increased specificity for a particular molecule; 3 The increased availability of sequence data from diversified taxa is likely to continue to improve our understanding of the early origin of the different cGST classes.

  8. Functional diversification of duplicated CYC2 clade genes in regulation of inflorescence development in Gerbera hybrida (Asteraceae).

    Science.gov (United States)

    Juntheikki-Palovaara, Inka; Tähtiharju, Sari; Lan, Tianying; Broholm, Suvi K; Rijpkema, Anneke S; Ruonala, Raili; Kale, Liga; Albert, Victor A; Teeri, Teemu H; Elomaa, Paula

    2014-09-01

    The complex inflorescences (capitula) of Asteraceae consist of different types of flowers. In Gerbera hybrida (gerbera), the peripheral ray flowers are bilaterally symmetrical and lack functional stamens while the central disc flowers are more radially symmetrical and hermaphroditic. Proteins of the CYC2 subclade of the CYC/TB1-like TCP domain transcription factors have been recruited several times independently for parallel evolution of bilaterally symmetrical flowers in various angiosperm plant lineages, and have also been shown to regulate flower-type identity in Asteraceae. The CYC2 subclade genes in gerbera show largely overlapping gene expression patterns. At the level of single flowers, their expression domain in petals shows a spatial shift from the dorsal pattern known so far in species with bilaterally symmetrical flowers, suggesting that this change in expression may have evolved after the origin of Asteraceae. Functional analysis indicates that GhCYC2, GhCYC3 and GhCYC4 mediate positional information at the proximal-distal axis of the inflorescence, leading to differentiation of ray flowers, but that they also regulate ray flower petal growth by affecting cell proliferation until the final size and shape of the petals is reached. Moreover, our data show functional diversification for the GhCYC5 gene. Ectopic activation of GhCYC5 increases flower density in the inflorescence, suggesting that GhCYC5 may promote the flower initiation rate during expansion of the capitulum. Our data thus indicate that modification of the ancestral network of TCP factors has, through gene duplications, led to the establishment of new expression domains and to functional diversification. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

  9. Comparative functional analyses of ultrabithorax reveal multiple steps and paths to diversification of legs in the adaptive radiation of semi-aquatic insects.

    Science.gov (United States)

    Khila, Abderrahman; Abouheif, Ehab; Rowe, Locke

    2014-08-01

    Invasion of new ecological habitats is often associated with lineage diversification, yet the genetic changes underlying invasions and radiations are poorly understood. Over 200 million years ago, the semi-aquatic insects invaded water surface from a common terrestrial ancestor and diversified to exploit a wide array of niches. Here, we uncover the changes in regulation and function of the gene Ultrabithorax associated with both the invasion of water surface and the subsequent diversification of the group. In the common ancestor of the semi-aquatic insects, a novel deployment of Ubx protein in the mid-legs increased their length, thereby enhancing their role in water surface walking. In derived lineages that specialize in rowing on the open water, additional changes in the timing of Ubx expression further elongated the mid-legs thereby facilitating their function as oars. In addition, Ubx protein function was selectively reversed to shorten specific rear-leg segments, thereby enabling their function as rudders. These changes in Ubx have generated distinct niche-specialized morphologies that account for the remarkable diversification of the semi-aquatic insects. Therefore, changes in the regulation and function of a key developmental gene may facilitate both the morphological change necessary to transition to novel habitats and fuel subsequent morphological diversification. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  10. Function-oriented synthesis: biological evaluation of laulimalide analogues derived from a last step cross metathesis diversification strategy.

    Science.gov (United States)

    Mooberry, Susan L; Hilinski, Michael K; Clark, Erin A; Wender, Paul A

    2008-01-01

    Laulimalide is a potent microtubule stabilizing agent and a promising anticancer therapeutic lead. The identification of stable, efficacious and accessible analogues is critical to clinically exploiting this novel lead. To determine which structural features of laulimalide are required for beneficial function and thus for accessing superior clinical candidates, a series of side chain analogues were prepared through a last step cross metathesis diversification strategy and their biological activities were evaluated. Five analogues, differing in potency from 233 nM to 7.9 muM, effectively inhibit cancer cell proliferation. Like laulimalide, they retain activity against multidrug resistant cells, stabilize microtubules and cause the formation of aberrant mitotic spindles, mitotic accumulation, Bcl-2 phosphorylation and initiation of apoptosis. Structural modifications in the C 23-C 27 dihydropyran side chain can be made without changing the overall mechanism of action, but it is clear that this subunit has more than a bystander role.

  11. Deciphering functional diversification within the lichen microbiota by meta-omics.

    Science.gov (United States)

    Cernava, Tomislav; Erlacher, Armin; Aschenbrenner, Ines Aline; Krug, Lisa; Lassek, Christian; Riedel, Katharina; Grube, Martin; Berg, Gabriele

    2017-07-19

    Recent evidence of specific bacterial communities extended the traditional concept of fungal-algal lichen symbioses by a further organismal kingdom. Although functional roles were already assigned to dominant members of the highly diversified microbiota, a substantial fraction of the ubiquitous colonizers remained unexplored. We employed a multi-omics approach to further characterize functional guilds in an unconventional model system. The general community structure of the lichen-associated microbiota was shown to be highly similar irrespective of the employed omics approach. Five highly abundant bacterial orders-Sphingomonadales, Rhodospirillales, Myxococcales, Chthoniobacterales, and Sphingobacteriales-harbor functions that are of substantial importance for the holobiome. Identified functions range from the provision of vitamins and cofactors to the degradation of phenolic compounds like phenylpropanoid, xylenols, and cresols. Functions that facilitate the persistence of Lobaria pulmonaria under unfavorable conditions were present in previously overlooked fractions of the microbiota. So far, unrecognized groups like Chthoniobacterales (Verrucomicrobia) emerged as functional protectors in the lichen microbiome. By combining multi-omics and imaging techniques, we highlight previously overlooked participants in the complex microenvironment of the lichens.

  12. Diversification: Far term (2000 - )

    Science.gov (United States)

    1975-01-01

    Diversification, intended to underly the far term of the energy conservation program, was defined to imply conservation through substitution for scarce energy resources by maximizing the total number of viable energy system types in every sector. The following requirements or aspects of diversification that must be studied were given: fuel mix and end use patterns for various alternative diversification plans, current status of diversification, advantages and disadvantages of diversification, constraints and criteria, diversification actions and their controls, and means for implementing the chosen diversification strategy. The following advantages resulting from diversification were described: competition, crisis-related situations, local energy production, decentralized plant locations, long range energy policy, and environmental overloads. The major criteria by which a diversification program should be judged, the major constraints affecting the approaches, and the road to diversification, were elaborated.

  13. Molecular Evolution and Functional Diversification of Replication Protein A1 in Plants

    Science.gov (United States)

    Aklilu, Behailu B.; Culligan, Kevin M.

    2016-01-01

    Replication protein A (RPA) is a heterotrimeric, single-stranded DNA binding complex required for eukaryotic DNA replication, repair, and recombination. RPA is composed of three subunits, RPA1, RPA2, and RPA3. In contrast to single RPA subunit genes generally found in animals and yeast, plants encode multiple paralogs of RPA subunits, suggesting subfunctionalization. Genetic analysis demonstrates that five Arabidopsis thaliana RPA1 paralogs (RPA1A to RPA1E) have unique and overlapping functions in DNA replication, repair, and meiosis. We hypothesize here that RPA1 subfunctionalities will be reflected in major structural and sequence differences among the paralogs. To address this, we analyzed amino acid and nucleotide sequences of RPA1 paralogs from 25 complete genomes representing a wide spectrum of plants and unicellular green algae. We find here that the plant RPA1 gene family is divided into three general groups termed RPA1A, RPA1B, and RPA1C, which likely arose from two progenitor groups in unicellular green algae. In the family Brassicaceae the RPA1B and RPA1C groups have further expanded to include two unique sub-functional paralogs RPA1D and RPA1E, respectively. In addition, RPA1 groups have unique domains, motifs, cis-elements, gene expression profiles, and pattern of conservation that are consistent with proposed functions in monocot and dicot species, including a novel C-terminal zinc-finger domain found only in plant RPA1C-like sequences. These results allow for improved prediction of RPA1 subunit functions in newly sequenced plant genomes, and potentially provide a unique molecular tool to improve classification of Brassicaceae species. PMID:26858742

  14. Evolution and Functional Diversification of the GLI Family of Transcription Factors in Vertebrates

    Directory of Open Access Journals (Sweden)

    Amir Ali Abbasi

    2009-05-01

    Full Text Available Background: In vertebrates the “SONIC HEDGEHOG” signalling pathway has been implicated in cell-fate determination, proliferation and the patterning of many different cell types and organs. As the GLI family members (GLI1, GLI2 and GLI3 are key mediators of hedgehog morphogenetic signals, over the past couple of decades they have been extensively scrutinized by genetic, molecular and biochemical means. Thus, a great deal of information is currently available about the functional aspects of GLI proteins in various vertebrate species. To address the roles of GLI genes in diversifying the repertoire of the Hh signalling and deploying them for the vertebrate specifications, in this study we have examined the evolutionary patterns of vertebrate GLI sequences within and between species. Results: Phylogenetic tree analysis suggests that the vertebrate GLI1, GLI2 and GLI3 genes diverged after the separation of urochordates from vertebrates and before the tetrapods-bony fishes split. Lineage specific duplication events were also detected. Estimation of mode and strength of selection acting on GLI orthologs demonstrated that all members of the GLI gene family experienced more relaxed selection in teleost fish than in the mammalian lineage. Furthermore, the GLI1 gene appeared to have been exposed to different functional constraints in fish and tetrapod lineages, whilst a similar level of functional constraints on GLI2 and GLI3 was suggested by comparable average non-synonymous (Ka substitutions across the lineages. A relative rate test suggested that the majority of the paralogous copies of the GLI family analyzed evolved with similar evolutionary rates except GLI1 which evolved at a significantly faster rate than its paralogous counterparts in tetrapods. Conclusions: Our analysis shows that sequence evolutionary patterns of GLI family members are largely correlated with the reported similarities and differences in the functionality of GLI proteins

  15. Structural and functional diversification in the teleost S100 family of calcium-binding proteins

    Directory of Open Access Journals (Sweden)

    Korsching Sigrun I

    2008-02-01

    Full Text Available Abstract Background Among the EF-Hand calcium-binding proteins the subgroup of S100 proteins constitute a large family with numerous and diverse functions in calcium-mediated signaling. The evolutionary origin of this family is still uncertain and most studies have examined mammalian family members. Results We have performed an extensive search in several teleost genomes to establish the s100 gene family in fish. We report that the teleost S100 repertoire comprises fourteen different subfamilies which show remarkable similarity across six divergent teleost species. Individual species feature distinctive subsets of thirteen to fourteen genes that result from local gene duplications and gene losses. Eight of the fourteen S100 subfamilies are unique for teleosts, while six are shared with mammalian species and three of those even with cartilaginous fish. Several S100 family members are found in jawless fish already, but none of them are clear orthologs of cartilaginous or bony fish s100 genes. All teleost s100 genes show the expected structural features and are subject to strong negative selection. Many aspects of the genomic arrangement and location of mammalian s100 genes are retained in the teleost s100 gene family, including a completely conserved intron/exon border between the two EF hands. Zebrafish s100 genes exhibit highly specific and characteristic expression patterns, showing both redundancy and divergence in their cellular expression. In larval tissue expression is often restricted to specific cell types like keratinocytes, hair cells, ionocytes and olfactory receptor neurons as demonstrated by in situ hybridization. Conclusion The origin of the S100 family predates at least the segregation of jawed from jawless fish and some extant family members predate the divergence of bony from cartilaginous fish. Despite a complex pattern of gene gains and losses the total repertoire size is remarkably constant between species. On the expression

  16. The evolution of pepsinogen C genes in vertebrates: duplication, loss and functional diversification.

    Directory of Open Access Journals (Sweden)

    Luís Filipe Costa Castro

    Full Text Available BACKGROUND: Aspartic proteases comprise a large group of enzymes involved in peptide proteolysis. This collection includes prominent enzymes globally categorized as pepsins, which are derived from pepsinogen precursors. Pepsins are involved in gastric digestion, a hallmark of vertebrate physiology. An important member among the pepsinogens is pepsinogen C (Pgc. A particular aspect of Pgc is its apparent single copy status, which contrasts with the numerous gene copies found for example in pepsinogen A (Pga. Although gene sequences with similarity to Pgc have been described in some vertebrate groups, no exhaustive evolutionary framework has been considered so far. METHODOLOGY/PRINCIPAL FINDINGS: By combining phylogenetics and genomic analysis, we find an unexpected Pgc diversity in the vertebrate sub-phylum. We were able to reconstruct gene duplication timings relative to the divergence of major vertebrate clades. Before tetrapod divergence, a single Pgc gene tandemly expanded to produce two gene lineages (Pgbc and Pgc2. These have been differentially retained in various classes. Accordingly, we find Pgc2 in sauropsids, amphibians and marsupials, but not in eutherian mammals. Pgbc was retained in amphibians, but duplicated in the ancestor of amniotes giving rise to Pgb and Pgc1. The latter was retained in mammals and probably in reptiles and marsupials but not in birds. Pgb was kept in all of the amniote clade with independent episodes of loss in some mammalian species. Lineage specific expansions of Pgc2 and Pgbc have also occurred in marsupials and amphibians respectively. We find that teleost and tetrapod Pgc genes reside in distinct genomic regions hinting at a possible translocation. CONCLUSIONS: We conclude that the repertoire of Pgc genes is larger than previously reported, and that tandem duplications have modelled the history of Pgc genes. We hypothesize that gene expansion lead to functional divergence in tetrapods, coincident with the

  17. Reduce, reuse, and recycle: developmental evolution of trait diversification.

    Science.gov (United States)

    Preston, Jill C; Hileman, Lena C; Cubas, Pilar

    2011-03-01

    A major focus of evolutionary developmental (evo-devo) studies is to determine the genetic basis of variation in organismal form and function, both of which are fundamental to biological diversification. Pioneering work on metazoan and flowering plant systems has revealed conserved sets of genes that underlie the bauplan of organisms derived from a common ancestor. However, the extent to which variation in the developmental genetic toolkit mirrors variation at the phenotypic level is an active area of research. Here we explore evidence from the angiosperm evo-devo literature supporting the frugal use of genes and genetic pathways in the evolution of developmental patterning. In particular, these examples highlight the importance of genetic pleiotropy in different developmental modules, thus reducing the number of genes required in growth and development, and the reuse of particular genes in the parallel evolution of ecologically important traits.

  18. Diversification and Corporate Governance

    NARCIS (Netherlands)

    G.W.J. Hendrikse (George); A.A.C.J. van Oijen

    2002-01-01

    textabstractThis article addresses the impact of governance structure on diversification behavior. Hypotheses are developed regarding the differences in diversification strategy of cooperatives and stock listed companies. The analysis shows that stock listed companies are more diversified than

  19. Diversification of energy sources

    Science.gov (United States)

    1975-01-01

    The concept of energy source diversification was introduced as a substitution conservation action. The current status and philosophy behind a diversification program is presented in the context of a national energy policy. Advantages, disadvantages (constraints), and methods of implementation for diversification are discussed. The energy source systems for diversification are listed and an example impact assessment is outlined which deals with the water requirements of the specific energy systems.

  20. Do Theory of Mind and Executive Function Deficits Underlie the Adverse Outcomes Associated with Profound Early Deprivation?: Findings from the English and Romanian Adoptees Study

    Science.gov (United States)

    Colvert, Emma; Rutter, Michael; Kreppner, Jana; Beckett, Celia; Castle, Jenny; Groothues, Christine; Hawkins, Amanda; Stevens, Suzanne; Sonuga-Barke, Edmund J. S.

    2008-01-01

    Theory of Mind (ToM) and Executive Function (EF) have been associated with autism and with attention-deficit hyperactivity disorder (ADHD), and hence might play a role in similar syndromes found following profound early institutional deprivation. In order to examine this possibility the current study included a group of 165 Romanian adoptees, of…

  1. Altered Intrinsic Pyramidal Neuron Properties and Pathway-Specific Synaptic Dysfunction Underlie Aberrant Hippocampal Network Function in a Mouse Model of Tauopathy.

    Science.gov (United States)

    Booth, Clair A; Witton, Jonathan; Nowacki, Jakub; Tsaneva-Atanasova, Krasimira; Jones, Matthew W; Randall, Andrew D; Brown, Jonathan T

    2016-01-13

    The formation and deposition of tau protein aggregates is proposed to contribute to cognitive impairments in dementia by disrupting neuronal function in brain regions, including the hippocampus. We used a battery of in vivo and in vitro electrophysiological recordings in the rTg4510 transgenic mouse model, which overexpresses a mutant form of human tau protein, to investigate the effects of tau pathology on hippocampal neuronal function in area CA1 of 7- to 8-month-old mice, an age point at which rTg4510 animals exhibit advanced tau pathology and progressive neurodegeneration. In vitro recordings revealed shifted theta-frequency resonance properties of CA1 pyramidal neurons, deficits in synaptic transmission at Schaffer collateral synapses, and blunted plasticity and imbalanced inhibition at temporoammonic synapses. These changes were associated with aberrant CA1 network oscillations, pyramidal neuron bursting, and spatial information coding in vivo. Our findings relate tauopathy-associated changes in cellular neurophysiology to altered behavior-dependent network function. Dementia is characterized by the loss of learning and memory ability. The deposition of tau protein aggregates in the brain is a pathological hallmark of dementia; and the hippocampus, a brain structure known to be critical in processing learning and memory, is one of the first and most heavily affected regions. Our results show that, in area CA1 of hippocampus, a region involved in spatial learning and memory, tau pathology is associated with specific disturbances in synaptic, cellular, and network-level function, culminating in the aberrant encoding of spatial information and spatial memory impairment. These studies identify several novel ways in which hippocampal information processing may be disrupted in dementia, which may provide targets for future therapeutic intervention. Copyright © 2016 Booth, Witton et al.

  2. Geographic diversification in banking

    NARCIS (Netherlands)

    Fang, Yiwei; van Lelyveld, Iman

    2014-01-01

    In the aftermath of the 2007-2009 crisis, banks claiming positive diversification benefits are being met with skepticism. Nevertheless, diversification might be important and sizable for some large internationally active banking groups. We use a universally applicable correlation matrix approach to

  3. Saccharomyces cerevisiae Differential Functionalization of Presumed ScALT1 and ScALT2 Alanine Transaminases Has Been Driven by Diversification of Pyridoxal Phosphate Interactions

    Directory of Open Access Journals (Sweden)

    Erendira Rojas-Ortega

    2018-05-01

    Full Text Available Saccharomyces cerevisiae arose from an interspecies hybridization (allopolyploidiza-tion, followed by Whole Genome Duplication. Diversification analysis of ScAlt1/ScAlt2 indicated that while ScAlt1 is an alanine transaminase, ScAlt2 lost this activity, constituting an example in which one of the members of the gene pair lacks the apparent ancestral physiological role. This paper analyzes structural organization and pyridoxal phosphate (PLP binding properties of ScAlt1 and ScAlt2 indicating functional diversification could have determined loss of ScAlt2 alanine transaminase activity and thus its role in alanine metabolism. It was found that ScAlt1 and ScAlt2 are dimeric enzymes harboring 67% identity and intact conservation of the catalytic residues, with very similar structures. However, tertiary structure analysis indicated that ScAlt2 has a more open conformation than that of ScAlt1 so that under physiological conditions, while PLP interaction with ScAlt1 allows the formation of two tautomeric PLP isomers (enolimine and ketoenamine ScAlt2 preferentially forms the ketoenamine PLP tautomer, indicating a modified polarity of the active sites which affect the interaction of PLP with these proteins, that could result in lack of alanine transaminase activity in ScAlt2. The fact that ScAlt2 forms a catalytically active Schiff base with PLP and its position in an independent clade in “sensu strictu” yeasts suggests this protein has a yet undiscovered physiological function.

  4. Saccharomyces cerevisiae Differential Functionalization of Presumed ScALT1 and ScALT2 Alanine Transaminases Has Been Driven by Diversification of Pyridoxal Phosphate Interactions

    Science.gov (United States)

    Rojas-Ortega, Erendira; Aguirre-López, Beatriz; Reyes-Vivas, Horacio; González-Andrade, Martín; Campero-Basaldúa, Jose C.; Pardo, Juan P.; González, Alicia

    2018-01-01

    Saccharomyces cerevisiae arose from an interspecies hybridization (allopolyploidiza-tion), followed by Whole Genome Duplication. Diversification analysis of ScAlt1/ScAlt2 indicated that while ScAlt1 is an alanine transaminase, ScAlt2 lost this activity, constituting an example in which one of the members of the gene pair lacks the apparent ancestral physiological role. This paper analyzes structural organization and pyridoxal phosphate (PLP) binding properties of ScAlt1 and ScAlt2 indicating functional diversification could have determined loss of ScAlt2 alanine transaminase activity and thus its role in alanine metabolism. It was found that ScAlt1 and ScAlt2 are dimeric enzymes harboring 67% identity and intact conservation of the catalytic residues, with very similar structures. However, tertiary structure analysis indicated that ScAlt2 has a more open conformation than that of ScAlt1 so that under physiological conditions, while PLP interaction with ScAlt1 allows the formation of two tautomeric PLP isomers (enolimine and ketoenamine) ScAlt2 preferentially forms the ketoenamine PLP tautomer, indicating a modified polarity of the active sites which affect the interaction of PLP with these proteins, that could result in lack of alanine transaminase activity in ScAlt2. The fact that ScAlt2 forms a catalytically active Schiff base with PLP and its position in an independent clade in “sensu strictu” yeasts suggests this protein has a yet undiscovered physiological function. PMID:29867852

  5. The Expansion and Functional Diversification of the Mammalian Ribonuclease A Superfamily Epitomizes the Efficiency of Multigene Families at Generating Biological Novelty

    Science.gov (United States)

    Goo, Stephen M.; Cho, Soochin

    2013-01-01

    The ribonuclease (RNase) A superfamily is a vertebrate-specific gene family. Because of a massive expansion that occurred during the early mammalian evolution, extant mammals in general have much more RNase genes than nonmammalian vertebrates. Mammalian RNases have been associated with diverse physiological functions including digestion, cytotoxicity, angiogenesis, male reproduction, and host defense. However, it is still uncertain when their expansion occurred and how a wide array of functions arose during their evolution. To answer these questions, we generate a compendium of all RNase genes identified in 20 complete mammalian genomes including the platypus, Ornithorhynchus anatinus. Using this, we delineate 13 ancient RNase gene lineages that arose before the divergence between the monotreme and the other mammals (∼220 Ma). These 13 ancient gene lineages are differentially retained in the 20 mammals, and the rate of protein sequence evolution is highly variable among them, which suggest that they have undergone extensive functional diversification. In addition, we identify 22 episodes of recent expansion of RNase genes, many of which have signatures of adaptive functional differentiation. Exemplifying this, bursts of gene duplication occurred for the RNase1, RNase4, and RNase5 genes of the little brown bat (Myotis lucifugus), which might have contributed to the species’ effective defense against heavier pathogen loads caused by its communal roosting behavior. Our study illustrates how host-defense systems can generate new functions efficiently by employing a multigene family, which is crucial for a host organism to adapt to its ever-changing pathogen environment. PMID:24162010

  6. International diversification and Microfinance

    NARCIS (Netherlands)

    Galema, R.; Lensink, B.W.; Spierdijk, L.

    2011-01-01

    International commercial banks, institutional investors, and private investors have become increasingly interested in financing microfinance institutions (MFIs). This paper investigates whether adding microfinance funds to a portfolio of risky international assets yields diversification gains. By

  7. International diversification and Microfinance

    NARCIS (Netherlands)

    Galema, Rients; Lensink, Robert; Spierdijk, Laura

    International commercial banks, institutional investors, and private investors have become increasingly interested in financing microfinance institutions (MFIs). This paper investigates whether adding microfinance funds to a portfolio of risky international assets yields diversification gains. By

  8. Pathways to diversification

    OpenAIRE

    Al Hashemi, Hamed

    2016-01-01

    A fundamental research question in regional economic development, is why some regions are able to diversify into new products and industries, while others continue to face challenges in diversification? This doctorate research explores the different pathways to diversification. It follows the three-stage modular structure of DBA for Cranfield School of Management. This thesis consists of a systematic literature review, a single qualitative case study on UAE, and a research synthesis of publis...

  9. Risk, ambiguity, and diversification

    OpenAIRE

    Sautua, Santiago-Ignacio

    2016-01-01

    Attitudes toward risk influence the decision to diversify among uncertain options. Yet, because in most situations the options are ambiguous, attitudes toward ambiguity may also play an important role. I conduct a laboratory experiment to investigate the effect of ambiguity on the decision to diversify. I find that diversification is more prevalent and more persistent under ambiguity than under risk. Moreover, excess diversification under ambiguity is driven by participants who stick with a s...

  10. Hospital diversification strategy.

    Science.gov (United States)

    Eastaugh, Steven R

    2014-01-01

    To determine the impact of health system restructuring on the levels of hospital diversification and operating ratio this article analyzed 94 teaching hospitals and 94 community hospitals during the period 2008-2013. The 47 teaching hospitals are matched with 47 other teaching hospitals experiencing the same financial market position in 2008, but with different levels of preference for risk and diversification in their strategic plan. Covariates in the analysis included levels of hospital competition and the degree of local government planning (for example, highly regulated in New York, in contrast to Texas). Moreover, 47 nonteaching community hospitals are matched with 47 other community hospitals in 2008, having varying manager preferences for service-line diversification and risk. Diversification and operating ratio are modeled in a two-stage least squares (TSLS) framework as jointly dependent. Institutional diversification is found to yield better financial position, and the better operating profits provide the firm the wherewithal to diversify. Some services are in a growth phase, like bariatric weight-loss surgery and sleep disorder clinics. Hospital managers' preferences for risk/return potential were considered. An institution life cycle hypothesis is advanced to explain hospital behavior: boom and bust, diversification, and divestiture, occasionally leading to closure or merger.

  11. Blood flow patterns underlie developmental heart defects.

    Science.gov (United States)

    Midgett, Madeline; Thornburg, Kent; Rugonyi, Sandra

    2017-03-01

    Although cardiac malformations at birth are typically associated with genetic anomalies, blood flow dynamics also play a crucial role in heart formation. However, the relationship between blood flow patterns in the early embryo and later cardiovascular malformation has not been determined. We used the chicken embryo model to quantify the extent to which anomalous blood flow patterns predict cardiac defects that resemble those in humans and found that restricting either the inflow to the heart or the outflow led to reproducible abnormalities with a dose-response type relationship between blood flow stimuli and the expression of cardiac phenotypes. Constricting the outflow tract by 10-35% led predominantly to ventricular septal defects, whereas constricting by 35-60% most often led to double outlet right ventricle. Ligation of the vitelline vein caused mostly pharyngeal arch artery malformations. We show that both cardiac inflow reduction and graded outflow constriction strongly influence the development of specific and persistent abnormal cardiac structure and function. Moreover, the hemodynamic-associated cardiac defects recapitulate those caused by genetic disorders. Thus our data demonstrate the importance of investigating embryonic blood flow conditions to understand the root causes of congenital heart disease as a prerequisite to future prevention and treatment. NEW & NOTEWORTHY Congenital heart defects result from genetic anomalies, teratogen exposure, and altered blood flow during embryonic development. We show here a novel "dose-response" type relationship between the level of blood flow alteration and manifestation of specific cardiac phenotypes. We speculate that abnormal blood flow may frequently underlie congenital heart defects. Copyright © 2017 the American Physiological Society.

  12. On portfolio risk diversification

    Science.gov (United States)

    Takada, Hellinton H.; Stern, Julio M.

    2017-06-01

    The first portfolio risk diversification strategy was put into practice by the All Weather fund in 1996. The idea of risk diversification is related to the risk contribution of each available asset class or investment factor to the total portfolio risk. The maximum diversification or the risk parity allocation is achieved when the set of risk contributions is given by a uniform distribution. Meucci (2009) introduced the maximization of the Rényi entropy as part of a leverage constrained optimization problem to achieve such diversified risk contributions when dealing with uncorrelated investment factors. A generalization of the risk parity is the risk budgeting when there is a prior for the distribution of the risk contributions. Our contribution is the generalization of the existent optimization frameworks to be able to solve the risk budgeting problem. In addition, our framework does not possess any leverage constraint.

  13. Rotational diversification and intensification

    Science.gov (United States)

    Diversification and intensification of inland Pacific Northwest (PNW) dryland cereal cropping systems can present win-win scenarios that deliver short and long-term benefits for producers and the environment, stabilizing profit and increasing adaptability to and mitigation of climate change. Improvi...

  14. Fusion helps diversification

    NARCIS (Netherlands)

    Liang, S.; Ren, Z.; de Rijke, M.

    2014-01-01

    A popular strategy for search result diversification is to first retrieve a set of documents utilizing a standard retrieval method and then rerank the results. We adopt a different perspective on the problem, based on data fusion. Starting from the hypothesis that data fusion can improve performance

  15. Why Revenue Diversification Matters

    Science.gov (United States)

    Leuhusen, Fredrik Carl Axel Peter

    2017-01-01

    Revenue diversification is a term that becomes more relevant as higher education institutions are confronted with increased regulation, competition, declining enrollments, and strained finances. A challenge that many institutions face is that expenditures are higher than revenues and increase faster than them. The term Revenue diversification…

  16. Tol2 transposon-mediated transgenesis in the Midas cichlid (Amphilophus citrinellus) - towards understanding gene function and regulatory evolution in an ecological model system for rapid phenotypic diversification.

    Science.gov (United States)

    Kratochwil, Claudius F; Sefton, Maggie M; Liang, Yipeng; Meyer, Axel

    2017-11-23

    The Midas cichlid species complex (Amphilophus spp.) is widely known among evolutionary biologists as a model system for sympatric speciation and adaptive phenotypic divergence within extremely short periods of time (a few hundred generations). The repeated parallel evolution of adaptive phenotypes in this radiation, combined with their near genetic identity, makes them an excellent model for studying phenotypic diversification. While many ecological and evolutionary studies have been performed on Midas cichlids, the molecular basis of specific phenotypes, particularly adaptations, and their underlying coding and cis-regulatory changes have not yet been studied thoroughly. For the first time in any New World cichlid, we use Tol2 transposon-mediated transgenesis in the Midas cichlid (Amphilophus citrinellus). By adapting existing microinjection protocols, we established an effective protocol for transgenesis in Midas cichlids. Embryos were injected with a Tol2 plasmid construct that drives enhanced green fluorescent protein (eGFP) expression under the control of the ubiquitin promoter. The transgene was successfully integrated into the germline, driving strong ubiquitous expression of eGFP in the first transgenic Midas cichlid line. Additionally, we show transient expression of two further transgenic constructs, ubiquitin::tdTomato and mitfa::eGFP. Transgenesis in Midas cichlids will facilitate further investigation of the genetic basis of species-specific traits, many of which are adaptations. Transgenesis is a versatile tool not only for studying regulatory elements such as promoters and enhancers, but also for testing gene function through overexpression of allelic gene variants. As such, it is an important first step in establishing the Midas cichlid as a powerful model for studying adaptive coding and non-coding changes in an ecological and evolutionary context.

  17. Genomic diversification of giant enteric symbionts reflects host dietary lifestyles

    KAUST Repository

    Ngugi, David; Miyake, Sou; Cahill, Matthew; Vinu, Manikandan; Hackmann, Timothy J.; Blom, Jochen; Tietbohl, Matthew; Berumen, Michael L.; Stingl, Ulrich

    2017-01-01

    of metabolic diversification of enteric microbiota involved in the degradation of algal biomass in these fishes. The enteric microbiota is also phylogenetically and functionally simple relative to the complex lignocellulose-degrading microbiota of terrestrial

  18. Natural Constraints to Species Diversification.

    Directory of Open Access Journals (Sweden)

    Eric Lewitus

    2016-08-01

    Full Text Available Identifying modes of species diversification is fundamental to our understanding of how biodiversity changes over evolutionary time. Diversification modes are captured in species phylogenies, but characterizing the landscape of diversification has been limited by the analytical tools available for directly comparing phylogenetic trees of groups of organisms. Here, we use a novel, non-parametric approach and 214 family-level phylogenies of vertebrates representing over 500 million years of evolution to identify major diversification modes, to characterize phylogenetic space, and to evaluate the bounds and central tendencies of species diversification. We identify five principal patterns of diversification to which all vertebrate families hold. These patterns, mapped onto multidimensional space, constitute a phylogenetic space with distinct properties. Firstly, phylogenetic space occupies only a portion of all possible tree space, showing family-level phylogenies to be constrained to a limited range of diversification patterns. Secondly, the geometry of phylogenetic space is delimited by quantifiable trade-offs in tree size and the heterogeneity and stem-to-tip distribution of branching events. These trade-offs are indicative of the instability of certain diversification patterns and effectively bound speciation rates (for successful clades within upper and lower limits. Finally, both the constrained range and geometry of phylogenetic space are established by the differential effects of macroevolutionary processes on patterns of diversification. Given these properties, we show that the average path through phylogenetic space over evolutionary time traverses several diversification stages, each of which is defined by a different principal pattern of diversification and directed by a different macroevolutionary process. The identification of universal patterns and natural constraints to diversification provides a foundation for understanding the

  19. Natural Constraints to Species Diversification.

    Science.gov (United States)

    Lewitus, Eric; Morlon, Hélène

    2016-08-01

    Identifying modes of species diversification is fundamental to our understanding of how biodiversity changes over evolutionary time. Diversification modes are captured in species phylogenies, but characterizing the landscape of diversification has been limited by the analytical tools available for directly comparing phylogenetic trees of groups of organisms. Here, we use a novel, non-parametric approach and 214 family-level phylogenies of vertebrates representing over 500 million years of evolution to identify major diversification modes, to characterize phylogenetic space, and to evaluate the bounds and central tendencies of species diversification. We identify five principal patterns of diversification to which all vertebrate families hold. These patterns, mapped onto multidimensional space, constitute a phylogenetic space with distinct properties. Firstly, phylogenetic space occupies only a portion of all possible tree space, showing family-level phylogenies to be constrained to a limited range of diversification patterns. Secondly, the geometry of phylogenetic space is delimited by quantifiable trade-offs in tree size and the heterogeneity and stem-to-tip distribution of branching events. These trade-offs are indicative of the instability of certain diversification patterns and effectively bound speciation rates (for successful clades) within upper and lower limits. Finally, both the constrained range and geometry of phylogenetic space are established by the differential effects of macroevolutionary processes on patterns of diversification. Given these properties, we show that the average path through phylogenetic space over evolutionary time traverses several diversification stages, each of which is defined by a different principal pattern of diversification and directed by a different macroevolutionary process. The identification of universal patterns and natural constraints to diversification provides a foundation for understanding the deep-time evolution of

  20. Natural Constraints to Species Diversification

    Science.gov (United States)

    Lewitus, Eric; Morlon, Hélène

    2016-01-01

    Identifying modes of species diversification is fundamental to our understanding of how biodiversity changes over evolutionary time. Diversification modes are captured in species phylogenies, but characterizing the landscape of diversification has been limited by the analytical tools available for directly comparing phylogenetic trees of groups of organisms. Here, we use a novel, non-parametric approach and 214 family-level phylogenies of vertebrates representing over 500 million years of evolution to identify major diversification modes, to characterize phylogenetic space, and to evaluate the bounds and central tendencies of species diversification. We identify five principal patterns of diversification to which all vertebrate families hold. These patterns, mapped onto multidimensional space, constitute a phylogenetic space with distinct properties. Firstly, phylogenetic space occupies only a portion of all possible tree space, showing family-level phylogenies to be constrained to a limited range of diversification patterns. Secondly, the geometry of phylogenetic space is delimited by quantifiable trade-offs in tree size and the heterogeneity and stem-to-tip distribution of branching events. These trade-offs are indicative of the instability of certain diversification patterns and effectively bound speciation rates (for successful clades) within upper and lower limits. Finally, both the constrained range and geometry of phylogenetic space are established by the differential effects of macroevolutionary processes on patterns of diversification. Given these properties, we show that the average path through phylogenetic space over evolutionary time traverses several diversification stages, each of which is defined by a different principal pattern of diversification and directed by a different macroevolutionary process. The identification of universal patterns and natural constraints to diversification provides a foundation for understanding the deep-time evolution of

  1. Determinants of farm diversification in the Netherlands

    NARCIS (Netherlands)

    Meraner, M.; Heijman, W.J.M.; Kuhlman, J.W.; Finger, R.

    2015-01-01

    Farm diversification has been prominently supported by agricultural policy makers aiming to support rural development. To increase the understanding of determinants influencing diversification and hence to increase the efficiency of policies aiming to support farm diversification this paper presents

  2. Functional diversification of hsp40: distinct j-protein functional requirements for two prions allow for chaperone-dependent prion selection.

    Science.gov (United States)

    Harris, Julia M; Nguyen, Phil P; Patel, Milan J; Sporn, Zachary A; Hines, Justin K

    2014-07-01

    Yeast prions are heritable amyloid aggregates of functional yeast proteins; their propagation to subsequent cell generations is dependent upon fragmentation of prion protein aggregates by molecular chaperone proteins. Mounting evidence indicates the J-protein Sis1 may act as an amyloid specificity factor, recognizing prion and other amyloid aggregates and enabling Ssa and Hsp104 to act in prion fragmentation. Chaperone interactions with prions, however, can be affected by variations in amyloid-core structure resulting in distinct prion variants or 'strains'. Our genetic analysis revealed that Sis1 domain requirements by distinct variants of [PSI+] are strongly dependent upon overall variant stability. Notably, multiple strong [PSI+] variants can be maintained by a minimal construct of Sis1 consisting of only the J-domain and glycine/phenylalanine-rich (G/F) region that was previously shown to be sufficient for cell viability and [RNQ+] prion propagation. In contrast, weak [PSI+] variants are lost under the same conditions but maintained by the expression of an Sis1 construct that lacks only the G/F region and cannot support [RNQ+] propagation, revealing mutually exclusive requirements for Sis1 function between these two prions. Prion loss is not due to [PSI+]-dependent toxicity or dependent upon a particular yeast genetic background. These observations necessitate that Sis1 must have at least two distinct functional roles that individual prions differentially require for propagation and which are localized to the glycine-rich domains of the Sis1. Based on these distinctions, Sis1 plasmid-shuffling in a [PSI+]/[RNQ+] strain permitted J-protein-dependent prion selection for either prion. We also found that, despite an initial report to the contrary, the human homolog of Sis1, Hdj1, is capable of [PSI+] prion propagation in place of Sis1. This conservation of function is also prion-variant dependent, indicating that only one of the two Sis1-prion functions may have

  3. Defense mutualisms enhance plant diversification.

    Science.gov (United States)

    Weber, Marjorie G; Agrawal, Anurag A

    2014-11-18

    The ability of plants to form mutualistic relationships with animal defenders has long been suspected to influence their evolutionary success, both by decreasing extinction risk and by increasing opportunity for speciation through an expanded realized niche. Nonetheless, the hypothesis that defense mutualisms consistently enhance plant diversification across lineages has not been well tested due to a lack of phenotypic and phylogenetic information. Using a global analysis, we show that the >100 vascular plant families in which species have evolved extrafloral nectaries (EFNs), sugar-secreting organs that recruit arthropod mutualists, have twofold higher diversification rates than families that lack species with EFNs. Zooming in on six distantly related plant clades, trait-dependent diversification models confirmed the tendency for lineages with EFNs to display increased rates of diversification. These results were consistent across methodological approaches. Inference using reversible-jump Markov chain Monte Carlo (MCMC) to model the placement and number of rate shifts revealed that high net diversification rates in EFN clades were driven by an increased number of positive rate shifts following EFN evolution compared with sister clades, suggesting that EFNs may be indirect facilitators of diversification. Our replicated analysis indicates that defense mutualisms put lineages on a path toward increased diversification rates within and between clades, and is concordant with the hypothesis that mutualistic interactions with animals can have an impact on deep macroevolutionary patterns and enhance plant diversity.

  4. Sources and sinks of diversification and conservation priorities for the Mexican tropical dry forest.

    Directory of Open Access Journals (Sweden)

    Judith X Becerra

    Full Text Available Elucidating the geographical history of diversification is critical for inferring where future diversification may occur and thus could be a valuable aid in determining conservation priorities. However, it has been difficult to recognize areas with a higher likelihood of promoting diversification. We reconstructed centres of origin of lineages and identified areas in the Mexican tropical dry forest that have been important centres of diversification (sources and areas where species are maintained but where diversification is less likely to occur (diversity sinks. We used a molecular phylogeny of the genus Bursera, a dominant member of the forest, along with information on current species distributions. Results indicate that vast areas of the forest have historically functioned as diversity sinks, generating few or no extant Bursera lineages. Only a few areas have functioned as major engines of diversification. Long-term preservation of biodiversity may be promoted by incorporation of such knowledge in decision-making.

  5. Does Intelligence Affect Economic Diversification?

    OpenAIRE

    Kodila-Tedika, Oasis; Asongu, Simplice A.

    2014-01-01

    This paper extends the growing literature on knowledge economy by investigating the effect of intelligence on economic diversification. Using a battery of estimation techniques that are robust to endogeneity, we find that human capital has positive effects on export diversification, manufactured added value and export manufactures. This empirical evidence is based on a world sample for the period 2010. The findings have significant implications for the fight against the Dutch disease. In esse...

  6. A role for Runx transcription factor signaling in dorsal root ganglion sensory neuron diversification.

    Science.gov (United States)

    Kramer, Ina; Sigrist, Markus; de Nooij, Joriene C; Taniuchi, Ichiro; Jessell, Thomas M; Arber, Silvia

    2006-02-02

    Subpopulations of sensory neurons in the dorsal root ganglion (DRG) can be characterized on the basis of sensory modalities that convey distinct peripheral stimuli, but the molecular mechanisms that underlie sensory neuronal diversification remain unclear. Here, we have used genetic manipulations in the mouse embryo to examine how Runx transcription factor signaling controls the acquisition of distinct DRG neuronal subtype identities. Runx3 acts to diversify an Ngn1-independent neuronal cohort by promoting the differentiation of proprioceptive sensory neurons through erosion of TrkB expression in prospective TrkC+ sensory neurons. In contrast, Runx1 controls neuronal diversification within Ngn1-dependent TrkA+ neurons by repression of neuropeptide CGRP expression and controlling the fine pattern of laminar termination in the dorsal spinal cord. Together, our findings suggest that Runx transcription factor signaling plays a key role in sensory neuron diversification.

  7. Nonsense-mediated mRNA decay and loss-of-function of the protein underlie the X-linked epilepsy associated with the W356× mutation in synapsin I.

    Directory of Open Access Journals (Sweden)

    Maila Giannandrea

    Full Text Available Synapsins are a family of neuronal phosphoproteins associated with the cytosolic surface of synaptic vesicles. Experimental evidence suggests a role for synapsins in synaptic vesicle clustering and recycling at the presynaptic terminal, as well as in neuronal development and synaptogenesis. Synapsin knock-out (Syn1(-/- mice display an epileptic phenotype and mutations in the SYN1 gene have been identified in individuals affected by epilepsy and/or autism spectrum disorder. We investigated the impact of the c.1067G>A nonsense transition, the first mutation described in a family affected by X-linked syndromic epilepsy, on the expression and functional properties of the synapsin I protein. We found that the presence of a premature termination codon in the human SYN1 transcript renders it susceptible to nonsense-mediated mRNA decay (NMD. Given that the NMD efficiency is highly variable among individuals and cell types, we investigated also the effects of expression of the mutant protein and found that it is expressed at lower levels compared to wild-type synapsin I, forms perinuclear aggregates and is unable to reach presynaptic terminals in mature hippocampal neurons grown in culture. Taken together, these data indicate that in patients carrying the W356× mutation the function of synapsin I is markedly impaired, due to both the strongly decreased translation and the altered function of the NMD-escaped protein, and support the value of Syn1(-/- mice as an experimental model mimicking the human pathology.

  8. Herbivory increases diversification across insect clades.

    Science.gov (United States)

    Wiens, John J; Lapoint, Richard T; Whiteman, Noah K

    2015-09-24

    Insects contain more than half of all living species, but the causes of their remarkable diversity remain poorly understood. Many authors have suggested that herbivory has accelerated diversification in many insect clades. However, others have questioned the role of herbivory in insect diversification. Here, we test the relationships between herbivory and insect diversification across multiple scales. We find a strong, positive relationship between herbivory and diversification among insect orders. However, herbivory explains less variation in diversification within some orders (Diptera, Hemiptera) or shows no significant relationship with diversification in others (Coleoptera, Hymenoptera, Orthoptera). Thus, we support the overall importance of herbivory for insect diversification, but also show that its impacts can vary across scales and clades. In summary, our results illuminate the causes of species richness patterns in a group containing most living species, and show the importance of ecological impacts on diversification in explaining the diversity of life.

  9. Governance Structure, Product Diversification, and Performance

    NARCIS (Netherlands)

    A.A.C.J. van Oijen; G.W.J. Hendrikse (George)

    2002-01-01

    textabstractProduct diversification and its financial outcomes have been studied exhaustively. However, previous literature has focused on corporations, ignoring other important legal organizations or governance structures. In this paper, we study the diversification strategies of cooperatives and

  10. DIVERSIFICATION OF A SAFETY FOOTWEAR PRODUCT

    OpenAIRE

    HARNAGEA Marta Cătălina; SECAN Cristina

    2017-01-01

    Product diversification is a usual strategy of footwear producers. As a requirement related to competitiveness in this domain, diversification can be done by practical application of some criteria. Considering this aspect, the paper proposes a research on the diversification in the case of a safety footwear product by modifying its component patterns, while keeping the initial shape of the product. Thus, starting from a safety shoe model, diversification was performed by changing the configur...

  11. Diversification at Financial Institutions and Systemic Crises

    NARCIS (Netherlands)

    Wagner, W.B.

    2006-01-01

    We show that the diversification of risks at financial institutions has unwelcome effects by increasing the likelihood of systems crises.As a result, complete diversification is not warranted adn the optimal degree of diversification is arbitrarily low.We also identify externalities that cause

  12. Land fragmentation and production diversification

    NARCIS (Netherlands)

    Ciaian, Pavel; Guri, Fatmir; Rajcaniova, Miroslava; Drabik, Dusan; Paloma, Sergio Gomez Y.

    2018-01-01

    We analyze the impact of land fragmentation on production diversification in rural Albania. Albania represents a particularly interesting case for studying land fragmentation as the fragmentation is a direct outcome of land reforms. The results indicate that land fragmentation is an important driver

  13. Correlation order, merging and diversification

    NARCIS (Netherlands)

    Dhaene, J.; Denuit, M.; Vanduffel, S.

    2009-01-01

    We investigate the influence of the dependence between random losses on the shortfall and on the diversification benefit that arises from merging these losses. We prove that increasing the dependence between losses, expressed in terms of correlation order, has an increasing effect on the shortfall,

  14. Hummingbird pollination and the diversification of angiosperms: an old and successful association in Gesneriaceae.

    Science.gov (United States)

    Serrano-Serrano, Martha Liliana; Rolland, Jonathan; Clark, John L; Salamin, Nicolas; Perret, Mathieu

    2017-04-12

    The effects of specific functional groups of pollinators in the diversification of angiosperms are still to be elucidated. We investigated whether the pollination shifts or the specific association with hummingbirds affected the diversification of a highly diverse angiosperm lineage in the Neotropics. We reconstructed a phylogeny of 583 species from the Gesneriaceae family and detected diversification shifts through time, inferred the timing and amount of transitions among pollinator functional groups, and tested the association between hummingbird pollination and speciation and extinction rates. We identified a high frequency of pollinator transitions, including reversals to insect pollination. Diversification rates of the group increased through time since 25 Ma, coinciding with the evolution of hummingbird-adapted flowers and the arrival of hummingbirds in South America. We showed that plants pollinated by hummingbirds have a twofold higher speciation rate compared with plants pollinated by insects, and that transitions among functional groups of pollinators had little impact on the diversification process. We demonstrated that floral specialization on hummingbirds for pollination has triggered rapid diversification in the Gesneriaceae family since the Early Miocene, and that it represents one of the oldest identified plant-hummingbird associations. Biotic drivers of plant diversification in the Neotropics could be more related to this specific type of pollinator (hummingbirds) than to shifts among different functional groups of pollinators. © 2017 The Author(s).

  15. Diversification, evolution and sub-functionalization of 70kDa heat-shock proteins in two sister species of antarctic krill: differences in thermal habitats, responses and implications under climate change.

    Science.gov (United States)

    Cascella, Kévin; Jollivet, Didier; Papot, Claire; Léger, Nelly; Corre, Erwan; Ravaux, Juliette; Clark, Melody S; Toullec, Jean-Yves

    2015-01-01

    A comparative thermal tolerance study was undertaken on two sister species of Euphausiids (Antarctic krills) Euphausia superba and Euphausia crystallorophias. Both are essential components of the Southern Ocean ecosystem, but occupy distinct environmental geographical locations with slightly different temperature regimes. They therefore provide a useful model system for the investigation of adaptations to thermal tolerance. Initial CTmax studies showed that E. superba was slightly more thermotolerant than E. crystallorophias. Five Hsp70 mRNAs were characterized from the RNAseq data of both species and subsequent expression kinetics studies revealed notable differences in induction of each of the 5 orthologues between the two species, with E. crystallorophias reacting more rapidly than E. superba. Furthermore, analyses conducted to estimate the evolutionary rates and selection strengths acting on each gene tended to support the hypothesis that diversifying selection has contributed to the diversification of this gene family, and led to the selective relaxation on the inducible C form with its possible loss of function in the two krill species. The sensitivity of the epipelagic species E. crystallorophias to temperature variations and/or its adaptation to cold is enhanced when compared with its sister species, E. superba. These results indicate that ice krill could be the first of the two species to be impacted by the warming of coastal waters of the Austral ocean in the coming years due to climate change.

  16. Dynamic Diversification in Corporate Credit

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Jacobs, Kris; Jin, Xisong

    We characterize diversification in corporate credit using a new class of dynamic copula models which can capture dynamic dependence and asymmetry in large samples of firms. We also document important differences between credit spread and equity return dependence dynamics. Modeling a decade...... the crisis and remain high as well. The most important shocks to credit dependence occur in August of 2007 and in August of 2011, but interestingly these dates are not associated with significant changes to median credit spreads....

  17. Export diversification and structural changes in South Africa

    Directory of Open Access Journals (Sweden)

    Ireen Choga

    2015-07-01

    Full Text Available What is the nature and extent of export diversification in South Africa? The primary purpose of this paper is to seek empirical answers to this question. In an attempt to derive empirical measures of the extent of export diversification and the structural changes taking place in South Africa, this paper uses a sample of a group of 28 selected commodities for the period 1980-2012 for which the most recent data is available. The following methods were used to measure the extent of export diversification and the structural changes in export diversification: Commodity-specific cumulative export Experience function, the Commodity-specific traditional index (CSTI, variance of CSTI, concentration ratio and the aggregate specialisation index. The Commodity-Specific Cumulative Experience Function plots show that roughly, commodities such as scientific equipment, transport equipment, motor vehicles, furniture, machinery and electronic products were shifted to the right indicating that the commodities are non-traditional in nature whereas gold coal agricultural products and wood are traditional in nature. The CSTI rankings indicated that motor vehicle exports ranked first showing that motor vehicles are non-traditional exports. Findings of this paper corroborate findings of other scholars; we conclude that our results are complementary.

  18. Diversification patterns and survival as firms mature

    DEFF Research Database (Denmark)

    Coad, Alexander Jean-Luc; Guenther, C.

    2013-01-01

    We focus on the relationship between age and diversification patterns of German machine tool manufacturers in the post-war era. We distinguish between 'minor diversification' (adding a new product variation within a familiar submarket) and 'major diversification' (expanding the product portfolio...... lines). Second, we find that product portfolios of larger firms tend to be more diversified. Third, with respect to consecutive diversification activities, quantile autoregression plots show that firms experiencing diversification in one period are unlikely to repeat this behavior in the following year....... Fourth, survival estimations reveal that diversification activities reduce the risk of exit in general and to a varying degree at different ages. These results are interpreted using Penrosean growth theory....

  19. Diversity spurs diversification in ecological communities.

    Science.gov (United States)

    Calcagno, Vincent; Jarne, Philippe; Loreau, Michel; Mouquet, Nicolas; David, Patrice

    2017-06-09

    Diversity is a fundamental, yet threatened, property of ecological systems. The idea that diversity can itself favour diversification, in an autocatalytic process, is very appealing but remains controversial. Here, we study a generalized model of ecological communities and investigate how the level of initial diversity influences the possibility of evolutionary diversification. We show that even simple models of intra- and inter-specific ecological interactions can predict a positive effect of diversity on diversification: adaptive radiations may require a threshold number of species before kicking-off. We call this phenomenon DDAR (diversity-dependent adaptive radiations) and identify mathematically two distinct pathways connecting diversity to diversification, involving character displacement and the positive diversity-productivity relationship. Our results may explain observed delays in adaptive radiations at the macroscale and diversification patterns reported in experimental microbial communities, and shed new light on the dynamics of ecological diversity, the diversity-dependence of diversification rates, and the consequences of biodiversity loss.

  20. Diversity spurs diversification in ecological communities

    Science.gov (United States)

    Calcagno, Vincent; Jarne, Philippe; Loreau, Michel; Mouquet, Nicolas; David, Patrice

    2017-06-01

    Diversity is a fundamental, yet threatened, property of ecological systems. The idea that diversity can itself favour diversification, in an autocatalytic process, is very appealing but remains controversial. Here, we study a generalized model of ecological communities and investigate how the level of initial diversity influences the possibility of evolutionary diversification. We show that even simple models of intra- and inter-specific ecological interactions can predict a positive effect of diversity on diversification: adaptive radiations may require a threshold number of species before kicking-off. We call this phenomenon DDAR (diversity-dependent adaptive radiations) and identify mathematically two distinct pathways connecting diversity to diversification, involving character displacement and the positive diversity-productivity relationship. Our results may explain observed delays in adaptive radiations at the macroscale and diversification patterns reported in experimental microbial communities, and shed new light on the dynamics of ecological diversity, the diversity-dependence of diversification rates, and the consequences of biodiversity loss.

  1. Sectoral Diversification as Insurance against Economic Instability

    OpenAIRE

    Jan Kluge

    2015-01-01

    This paper examines the extent to which sectoral diversification can act as an insurance mechanism against fluctuations in regional gross value added growth rates. I apply portfolio theory to the growth-instability properties of German districts. Furthermore, I define a comprehensive diversification measure and use Stochastic Frontier Analysis in order to estimate whether diversification allows regions to achieve more efficient growth-instability combinations, i.e., greater stability at given...

  2. Correlations-Adjusted Export Market Diversification

    OpenAIRE

    Jung Joo La

    2011-01-01

    This paper introduces new export market diversification indices incorporated with correlations of business cycles among export partners to identify the actual effects of export market diversification on export instability. Three existing export market diversification indices reflect the dispersion level in terms of the number of export partners and their export shares, without a clear control for correlations among export earnings from export partners. In addition, they are underestimated or ...

  3. Functional diversification upon leader protease domain duplication in the Citrus tristeza virus genome: Role of RNA sequences and the encoded proteins.

    Science.gov (United States)

    Kang, Sung-Hwan; Atallah, Osama O; Sun, Yong-Duo; Folimonova, Svetlana Y

    2018-01-15

    Viruses from the family Closteroviridae show an example of intra-genome duplications of more than one gene. In addition to the hallmark coat protein gene duplication, several members possess a tandem duplication of papain-like leader proteases. In this study, we demonstrate that domains encoding the L1 and L2 proteases in the Citrus tristeza virus genome underwent a significant functional divergence at the RNA and protein levels. We show that the L1 protease is crucial for viral accumulation and establishment of initial infection, whereas its coding region is vital for virus transport. On the other hand, the second protease is indispensable for virus infection of its natural citrus host, suggesting that L2 has evolved an important adaptive function that mediates virus interaction with the woody host. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Farm multifunctional diversification and agricultural landscape trasformations

    Directory of Open Access Journals (Sweden)

    Emilio Chiodo

    Full Text Available The work aims to analyze changes in agricultural landscape linked to transformations in agricultural productive system. The territory for analysis is situated along the “internal Marche ridge” of the Apennines, in the province of Ancona (Marche region, partly included in the Regional Natural Park “Gola della Rossa e Frassassi”. The work aims at elaborating an investigative methodology which can highlight the transformation of territorial structures and the dynamics that influence management of the territory and landscape in order to provide operative instructions for an integrated elaboration of instruments for urban planning and economic programming, specially for agricultural policies. Multi-functionality and diversification in agriculture are the instruments that can help agriculture to improve the economic value of products and at the same time to improve the quality of territory and landscape.

  5. Functional diversification of grapevine MYB5a and MYB5b in the control of flavonoid biosynthesis in a petunia anthocyanin regulatory mutant.

    Science.gov (United States)

    Cavallini, Erika; Zenoni, Sara; Finezzo, Laura; Guzzo, Flavia; Zamboni, Anita; Avesani, Linda; Tornielli, Giovanni Battista

    2014-03-01

    Flavonoids play a key role in grapevine physiology and also contribute substantially to the quality of berries and wines. VvMYB5a and VvMYB5b are R2R3-MYB transcription factors previously proposed to control the spatiotemporal expression of flavonoid structural genes during berry development. We investigated the functions of these two proteins in detail by heterologous expression in a petunia an2 mutant, which has negligible anthocyanin levels in the petals because it lacks the MYB protein PhAN2. We also expressed VvMYBA1, the grapevine ortholog of petunia PhAN2, in the same genetic background. The anthocyanin profiles induced by expressing these transgenes in the petals revealed that VvMYBA1 is the functional ortholog of PhAN2 and that, unlike VvMYB5a, VvMYB5b can partially complement the an2 mutation. Transcriptomic analysis of petals by microarray hybridization and quantitative PCR confirmed that VvMYB5b up-regulates a subset of anthocyanin structural genes, whereas VvMYB5a has a more limited impact on the expression of genes related to anthocyanin biosynthesis. Furthermore, we identified additional specific and common targets of these two regulators, related to vacuolar acidification and membrane remodeling. Taken together, these data provide insight into the role of VvMYB5a and VvMYB5b in flavonoid biosynthesis and provide evidence for additional regulatory roles in distinct pathways.

  6. Diversification Strategies and Firm Performance: A Sample Selection Approach

    OpenAIRE

    Santarelli, Enrico; Tran, Hien Thu

    2013-01-01

    This paper is based upon the assumption that firm profitability is determined by its degree of diversification which in turn is strongly related to the antecedent decision to carry out diversification activities. This calls for an empirical approach that permits the joint analysis of the three interrelated and consecutive stages of the overall diversification process: diversification decision, degree of diversification, and outcome of diversification. We apply parametric and semiparametric ap...

  7. Scale effects and morphological diversification in hindlimb segment mass proportions in neognath birds.

    Science.gov (United States)

    Kilbourne, Brandon M

    2014-01-01

    In spite of considerable work on the linear proportions of limbs in amniotes, it remains unknown whether differences in scale effects between proximal and distal limb segments has the potential to influence locomotor costs in amniote lineages and how changes in the mass proportions of limbs have factored into amniote diversification. To broaden our understanding of how the mass proportions of limbs vary within amniote lineages, I collected data on hindlimb segment masses - thigh, shank, pes, tarsometatarsal segment, and digits - from 38 species of neognath birds, one of the most speciose amniote clades. I scaled each of these traits against measures of body size (body mass) and hindlimb size (hindlimb length) to test for departures from isometry. Additionally, I applied two parameters of trait evolution (Pagel's λ and δ) to understand patterns of diversification in hindlimb segment mass in neognaths. All segment masses are positively allometric with body mass. Segment masses are isometric with hindlimb length. When examining scale effects in the neognath subclade Land Birds, segment masses were again positively allometric with body mass; however, shank, pedal, and tarsometatarsal segment masses were also positively allometric with hindlimb length. Methods of branch length scaling to detect phylogenetic signal (i.e., Pagel's λ) and increasing or decreasing rates of trait change over time (i.e., Pagel's δ) suffer from wide confidence intervals, likely due to small sample size and deep divergence times. The scaling of segment masses appears to be more strongly related to the scaling of limb bone mass as opposed to length, and the scaling of hindlimb mass distribution is more a function of scale effects in limb posture than proximo-distal differences in the scaling of limb segment mass. Though negative allometry of segment masses appears to be precluded by the need for mechanically sound limbs, the positive allometry of segment masses relative to body mass may

  8. Industrial Diversification, Employment and Rural Poverty Reduction ...

    African Journals Online (AJOL)

    This study compares the impact of industrial diversification on employment and rural poverty reduction in China and Nigeria. The fact that both countries ... better success. Key Words: Agro-Allied Industry, Industrial Diversification, Rural Development, Poverty Reduction, Employment, Non-Farm Enterprise, Nigerian Economy.

  9. Personalized search result diversification via structured learning

    NARCIS (Netherlands)

    Liang, S.; Ren, Z.; de Rijke, M.

    2014-01-01

    This paper is concerned with the problem of personalized diversification of search results, with the goal of enhancing the performance of both plain diversification and plain personalization algorithms. In previous work, the problem has mainly been tackled by means of unsupervised learning. To

  10. Factors Influencing Livelihood Diversification among Rural Farmers ...

    African Journals Online (AJOL)

    This research study was set out to analyze factors influencing rural farmer's engagement in livelihood diversification in the study area. The specific objectives were; to identify the different levels of farmers' engagement in livelihood diversification, determine the socio-demographic factors or forces that influence farmers' ...

  11. Livelihood diversification and implications on poverty and ...

    African Journals Online (AJOL)

    This paper on livelihood diversification is based on an ongoing study under VicRes programme being undertaken in the Lake Victoria Basin, in Tanzania, Kenya and Uganda. We examine how changing socio-economic and environmental conditions contribute to livelihood diversification, land-use changes, poverty ...

  12. Evolutionary diversification of plant shikimate kinase gene duplicates.

    Directory of Open Access Journals (Sweden)

    Geoffrey Fucile

    2008-12-01

    Full Text Available Shikimate kinase (SK; EC 2.7.1.71 catalyzes the fifth reaction of the shikimate pathway, which directs carbon from the central metabolism pool to a broad range of secondary metabolites involved in plant development, growth, and stress responses. In this study, we demonstrate the role of plant SK gene duplicate evolution in the diversification of metabolic regulation and the acquisition of novel and physiologically essential function. Phylogenetic analysis of plant SK homologs resolves an orthologous cluster of plant SKs and two functionally distinct orthologous clusters. These previously undescribed genes, shikimate kinase-like 1 (SKL1 and -2 (SKL2, do not encode SK activity, are present in all major plant lineages, and apparently evolved under positive selection following SK gene duplication over 400 MYA. This is supported by functional assays using recombinant SK, SKL1, and SKL2 from Arabidopsis thaliana (At and evolutionary analyses of the diversification of SK-catalytic and -substrate binding sites based on theoretical structure models. AtSKL1 mutants yield albino and novel variegated phenotypes, which indicate SKL1 is required for chloroplast biogenesis. Extant SKL2 sequences show a strong genetic signature of positive selection, which is enriched in a protein-protein interaction module not found in other SK homologs. We also report the first kinetic characterization of plant SKs and show that gene expression diversification among the AtSK inparalogs is correlated with developmental processes and stress responses. This study examines the functional diversification of ancient and recent plant SK gene duplicates and highlights the utility of SKs as scaffolds for functional innovation.

  13. Diversification and Challenges of Software Engineering Standards

    Science.gov (United States)

    Poon, Peter T.

    1994-01-01

    The author poses certain questions in this paper: 'In the future, should there be just one software engineering standards set? If so, how can we work towards that goal? What are the challenges of internationalizing standards?' Based on the author's personal view, the statement of his position is as follows: 'There should NOT be just one set of software engineering standards in the future. At the same time, there should NOT be the proliferation of standards, and the number of sets of standards should be kept to a minimum.It is important to understand the diversification of the areas which are spanned by the software engineering standards.' The author goes on to describe the diversification of processes, the diversification in the national and international character of standards organizations, the diversification of the professional organizations producing standards, the diversification of the types of businesses and industries, and the challenges of internationalizing standards.

  14. Diversification Models of Sales Activity for Steady Development of an Enterprise

    OpenAIRE

    Nestor Shpak; Tamara Kyrylych; Jolita Greblikaitė

    2016-01-01

    The paper substantiates the importance of the optimal directionality choice of sales activity as one of the main lines of enterprise activity, the functioning of which should be complete, synchronous and complementary. Diversification is one of the powerful instruments to ensure the steady development of the sales activity of an enterprise. Three models of sales activity diversification of an enterprise are developed. The first model is based on unveiling the potential of sales channels and a...

  15. Portfolio diversification in energy markets

    International Nuclear Information System (INIS)

    Galvani, Valentina; Plourde, Andre

    2010-01-01

    This paper's results indicate that futures for crude oil, natural gas and unleaded gasoline fail to enhance the performance of representative energy stocks in terms of return to risk, but do decrease the overall level of risk exposure borne by passive equity investors. Our findings suggest that futures contracts on energy commodities are valuable to market participants with an interest in hedging against price fluctuations in energy markets by buy-and-hold strategies. However, this conclusion is reversed when one takes the perspective of traders whose core interests can be better approximated through the return to risk-bearing. In fact, this paper documents that return-to-risk maximizing agents are unlikely to profit from trading energy futures in addition to energy stocks. Moreover, futures for energy commodities fail to offer significant diversification gains with respect to energy stocks once investors adopt simple dynamic trading strategies that rely on readily available pricing information. (author)

  16. Portfolio diversification in energy markets

    Energy Technology Data Exchange (ETDEWEB)

    Galvani, Valentina; Plourde, Andre [Department of Economics at the University of Alberta, Edmonton, AB (Canada)

    2010-03-15

    This paper's results indicate that futures for crude oil, natural gas and unleaded gasoline fail to enhance the performance of representative energy stocks in terms of return to risk, but do decrease the overall level of risk exposure borne by passive equity investors. Our findings suggest that futures contracts on energy commodities are valuable to market participants with an interest in hedging against price fluctuations in energy markets by buy-and-hold strategies. However, this conclusion is reversed when one takes the perspective of traders whose core interests can be better approximated through the return to risk-bearing. In fact, this paper documents that return-to-risk maximizing agents are unlikely to profit from trading energy futures in addition to energy stocks. Moreover, futures for energy commodities fail to offer significant diversification gains with respect to energy stocks once investors adopt simple dynamic trading strategies that rely on readily available pricing information. (author)

  17. Temporal diversification of Central American cichlids

    Directory of Open Access Journals (Sweden)

    Hulsey C Darrin

    2010-09-01

    Full Text Available Abstract Background Cichlid fishes are classic examples of adaptive radiation because of their putative tendency to explosively diversify after invading novel environments. To examine whether ecological opportunity increased diversification (speciation minus extinction early in a species-rich cichlid radiation, we determined if Heroine cichlids experienced a burst of diversification following their invasion of Central America. Results We first reconstructed the Heroine phylogeny and determined the basal node to use as the root of Central American Heroine diversification. We then examined the influence of incomplete taxon sampling on this group's diversification patterns. First, we added missing species randomly to the phylogeny and assessed deviations from a constant rate of lineage accumulation. Using a range of species numbers, we failed to recover significant deviations from a pure-birth process and found little support for an early burst of diversification. Then, we examined patterns of lineage accumulation as nodes were increasingly truncated. We assumed that as we removed more recently diverged lineages that sampling would become more complete thereby increasing the power to detect deviations from a pure-birth model. However, truncation of nodes provided even less support for an early burst of diversification. Conclusions Contrary to expectations, our analyses suggest Heroine cichlids did not undergo a burst of diversification when they invaded from South America. Throughout their history in Central America, Heroine cichlids appear to have diversified at a constant rate.

  18. Sex-specific evolution during the diversification of live-bearing fishes.

    Science.gov (United States)

    Culumber, Zachary W; Tobler, Michael

    2017-08-01

    Natural selection is often assumed to drive parallel functional diversification of the sexes. But males and females exhibit fundamental differences in their biology, and it remains largely unknown how sex differences affect macroevolutionary patterns. On microevolutionary scales, we understand how natural and sexual selection interact to give rise to sex-specific evolution during phenotypic diversification and speciation. Here we show that ignoring sex-specific patterns of functional trait evolution misrepresents the macroevolutionary adaptive landscape and evolutionary rates for 112 species of live-bearing fishes (Poeciliidae). Males and females of the same species evolve in different adaptive landscapes. Major axes of female morphology were correlated with environmental variables but not reproductive investment, while male morphological variation was primarily associated with sexual selection. Despite the importance of both natural and sexual selection in shaping sex-specific phenotypic diversification, species diversification was overwhelmingly associated with ecological divergence. Hence, the inter-predictability of mechanisms of phenotypic and species diversification may be limited in many systems. These results underscore the importance of explicitly addressing sex-specific diversification in empirical and theoretical frameworks of evolutionary radiations to elucidate the roles of different sources of selection and constraint.

  19. Transformation and diversification in early mammal evolution.

    Science.gov (United States)

    Luo, Zhe-Xi

    2007-12-13

    Evolution of the earliest mammals shows successive episodes of diversification. Lineage-splitting in Mesozoic mammals is coupled with many independent evolutionary experiments and ecological specializations. Classic scenarios of mammalian morphological evolution tend to posit an orderly acquisition of key evolutionary innovations leading to adaptive diversification, but newly discovered fossils show that evolution of such key characters as the middle ear and the tribosphenic teeth is far more labile among Mesozoic mammals. Successive diversifications of Mesozoic mammal groups multiplied the opportunities for many dead-end lineages to iteratively evolve developmental homoplasies and convergent ecological specializations, parallel to those in modern mammal groups.

  20. Economic diversification: Explaining the pattern of diversification in the global economy and its implications for fostering diversification in poorer countries

    NARCIS (Netherlands)

    Freire Junior, Clovis

    2017-01-01

    Economic diversification is very relevant for poorer developing countries to create jobs and foster economic development. That need has been recognised in key internationally agreed development goals. The empirical economic literature has identified several stylised facts about the pattern of

  1. Piscivory limits diversification of feeding morphology in centrarchid fishes.

    Science.gov (United States)

    Collar, David C; O'Meara, Brian C; Wainwright, Peter C; Near, Thomas J

    2009-06-01

    Proximity to an adaptive peak influences a lineage's potential to diversify. We tested whether piscivory, a high quality but functionally demanding trophic strategy, represents an adaptive peak that limits morphological diversification in the teleost fish clade, Centrarchidae. We synthesized published diet data and applied a well-resolved, multilocus and time-calibrated phylogeny to reconstruct ancestral piscivory. We measured functional features of the skull and performed principal components analysis on species' values for these variables. To assess the role of piscivory on morphological diversification, we compared the fit of several models of evolution for each principal component (PC), where model parameters were allowed to vary between lineages that differed in degree of piscivory. According to the best-fitting model, two adaptive peaks influenced PC 1 evolution, one peak shared between highly and moderately piscivorous lineages and another for nonpiscivores. Brownian motion better fit PCs 2, 3, and 4, but the best Brownian models infer a slow rate of PC 2 evolution shared among all piscivores and a uniquely slow rate of PC 4 evolution in highly piscivorous lineages. These results suggest that piscivory limits feeding morphology diversification, but this effect is most severe in lineages that exhibit an extreme form of this diet.

  2. Diversification as the strategic direction of foreign economic activity

    Directory of Open Access Journals (Sweden)

    Yu.I. Dozorova

    2015-12-01

    Full Text Available The issue of diversification, diversification of exports and imports, diversification of foreign trade. Determined the importance of diversification strategy to improve economic performance and proved that diversification allows the flexibility to respond to changing market opportunities and reduce the risks that may occur during production specialization. With the diversification of the company reinforce its competitive position in the market. The concept of diversification is used in the formulation of portfolio strategy as one of the four components, namely a vector or direction of future growth areas of the company. The proposed provisions, by which we can achieve a positive result. Proved that by diversifying, the company improves its economic performance.

  3. Nested radiations and the pulse of angiosperm diversification: increased diversification rates often follow whole genome duplications.

    Science.gov (United States)

    Tank, David C; Eastman, Jonathan M; Pennell, Matthew W; Soltis, Pamela S; Soltis, Douglas E; Hinchliff, Cody E; Brown, Joseph W; Sessa, Emily B; Harmon, Luke J

    2015-07-01

    Our growing understanding of the plant tree of life provides a novel opportunity to uncover the major drivers of angiosperm diversity. Using a time-calibrated phylogeny, we characterized hot and cold spots of lineage diversification across the angiosperm tree of life by modeling evolutionary diversification using stepwise AIC (MEDUSA). We also tested the whole-genome duplication (WGD) radiation lag-time model, which postulates that increases in diversification tend to lag behind established WGD events. Diversification rates have been incredibly heterogeneous throughout the evolutionary history of angiosperms and reveal a pattern of 'nested radiations' - increases in net diversification nested within other radiations. This pattern in turn generates a negative relationship between clade age and diversity across both families and orders. We suggest that stochastically changing diversification rates across the phylogeny explain these patterns. Finally, we demonstrate significant statistical support for the WGD radiation lag-time model. Across angiosperms, nested shifts in diversification led to an overall increasing rate of net diversification and declining relative extinction rates through time. These diversification shifts are only rarely perfectly associated with WGD events, but commonly follow them after a lag period. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  4. Personalised Diversification Using Intent-Aware Portfolio

    OpenAIRE

    Wasilewski, Jacek; Hurley, Neil J.

    2017-01-01

    The intent-aware diversification framework considers a set of aspects associated with items to be recommended. A baseline recommendation is greedily re-ranked using an objective that promotes diversity across the aspects. In this paper the framework is analysed and a new intent-aware objective is derived that considers the minimum variance criterion, connecting the framework directly to portfolio diversification from finance. We derive an aspect model that supports the goal of minimum varianc...

  5. Putting all your eggs in one basket: life-history strategies, bet hedging, and diversification.

    Science.gov (United States)

    White, Andrew Edward; Li, Yexin Jessica; Griskevicius, Vladas; Neuberg, Steven L; Kenrick, Douglas T

    2013-05-01

    Diversification of resources is a strategy found everywhere from the level of microorganisms to that of giant Wall Street investment firms. We examine the functional nature of diversification using life-history theory-a framework for understanding how organisms navigate resource-allocation trade-offs. This framework suggests that diversification may be adaptive or maladaptive depending on one's life-history strategy and that these differences should be observed under conditions of threat. In three studies, we found that cues of mortality threat interact with one index of life-history strategy, childhood socioeconomic status (SES), to affect diversification. Among those from low-SES backgrounds, mortality threat increased preferences for diversification. However, among those from high-SES backgrounds, mortality threat had the opposite effect, inclining people to put all their eggs in one basket. The same interaction pattern emerged with a potential biomarker of life-history strategy, oxidative stress. These findings highlight when, and for whom, different diversification strategies can be advantageous.

  6. Dioecy does not consistently accelerate or slow lineage diversification across multiple genera of angiosperms.

    Science.gov (United States)

    Sabath, Niv; Goldberg, Emma E; Glick, Lior; Einhorn, Moshe; Ashman, Tia-Lynn; Ming, Ray; Otto, Sarah P; Vamosi, Jana C; Mayrose, Itay

    2016-02-01

    Dioecy, the sexual system in which male and female organs are found in separate individuals, allows greater specialization for sex-specific functions and can be advantageous under various ecological and environmental conditions. However, dioecy is rare among flowering plants. Previous studies identified contradictory trends regarding the relative diversification rates of dioecious lineages vs their nondioecious counterparts, depending on the methods and data used. We gathered detailed species-level data for dozens of genera that contain both dioecious and nondioecious species. We then applied a probabilistic approach that accounts for differential speciation, extinction, and transition rates between states to examine whether there is an association between dioecy and lineage diversification. We found a bimodal distribution, whereby dioecious lineages exhibited higher diversification in certain genera but lower diversification in others. Additional analyses did not uncover an ecological or life history trait that could explain a context-dependent effect of dioecy on diversification. Furthermore, in-depth simulations of neutral characters demonstrated that such bimodality is also found when simulating neutral characters across the observed trees. Our analyses suggest that - at least for these genera with the currently available data - dioecy neither consistently places a strong brake on diversification nor is a strong driver. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  7. Regional Diversity and Diversification in Mammals.

    Science.gov (United States)

    Machac, Antonin; Graham, Catherine H

    2017-01-01

    The effects of regional diversity on diversification remain controversial. The classic hypothesis that diversification decelerates as regional diversity increases has been recently revived. Yet, there is little geographic evidence for slower diversification across regions of high diversity, and diversity is often thought to promote diversification through its effects on ecological divergence and speciation. Here, we use the newest phylogeny for mammals (4,990 species) and two different methods to test the effects of regional diversity on diversification. We find that regions of high diversity are dominated by expanding clades that are far from their estimated carrying capacities. Regions of low diversity host clades that are small and mostly saturated. These results were supported across mammals and their six largest orders. They were corroborated by the two methods when controlling for clade relatedness, clade nestedness, and clade size. Together, these results reject the hypothesis that high geographic concentration of mammals effectively suppresses their further diversification. Instead, highly diverse regions (especially the tropics) seem to act as the engine of mammalian richness.

  8. Study of methodology diversification in diagnostics

    International Nuclear Information System (INIS)

    Suda, Kazunori; Yonekawa, Tsuyoshi; Yoshikawa, Shinji; Hasegawa, Makoto

    1999-03-01

    There are several research activities to enhance safety and reliability of nuclear power plant operation and maintenance. We are developing a concept of an autonomous operation system where the role of operators is replaced with artificial intelligence. The purpose of the study described in this report is to develop a operator support system in abnormal plant situations. Conventionally, diagnostic modules based on individual methodology such as expert system have been developed and verified. In this report, methodology diversification is considered to integrate diagnostic modules which performance are confirmed using information processing technique. Technical issues to be considered in diagnostic methodology diversification are; 1)reliability of input data, 2)diversification of knowledge models, algorithms and reasoning schemes, 3)mutual complement and robustness. The diagnostic module utilizing the different approaches defined along with strategy of diversification was evaluated using fast breeder plant simulator. As a result, we confirmed that any singular diagnostic module can not meet accuracy criteria for the entire set of anomaly events. In contrast with this, we confirmed that every abnormality could be precisely diagnosed by a mutual combination. In other words, legitimacy of approach selected by strategy of diversification was shown, and methodology diversification attained clear efficiency for abnormal diagnosis. It has been also confirmed that the diversified diagnostic system implemented in this study is able to maintain its accuracy even in case that encountered scale of abnormality is different from reference cases embedded in the knowledge base. (author)

  9. Primate diversification inferred from phylogenies and fossils.

    Science.gov (United States)

    Herrera, James P

    2017-12-01

    Biodiversity arises from the balance between speciation and extinction. Fossils record the origins and disappearance of organisms, and the branching patterns of molecular phylogenies allow estimation of speciation and extinction rates, but the patterns of diversification are frequently incongruent between these two data sources. I tested two hypotheses about the diversification of primates based on ∼600 fossil species and 90% complete phylogenies of living species: (1) diversification rates increased through time; (2) a significant extinction event occurred in the Oligocene. Consistent with the first hypothesis, analyses of phylogenies supported increasing speciation rates and negligible extinction rates. In contrast, fossils showed that while speciation rates increased, speciation and extinction rates tended to be nearly equal, resulting in zero net diversification. Partially supporting the second hypothesis, the fossil data recorded a clear pattern of diversity decline in the Oligocene, although diversification rates were near zero. The phylogeny supported increased extinction ∼34 Ma, but also elevated extinction ∼10 Ma, coinciding with diversity declines in some fossil clades. The results demonstrated that estimates of speciation and extinction ignoring fossils are insufficient to infer diversification and information on extinct lineages should be incorporated into phylogenetic analyses. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  10. Diversification criteria for power systems

    International Nuclear Information System (INIS)

    Kharbach, Mohammed

    2016-01-01

    Growing power demand, fuel availability and prices, technology changes, the environmental impacts of energy consumption, the changing regulatory environments and the uncertainties around such elements make the planning for optimal power mix a challenging task. The diversity approach is advocated as a most appropriate planning methodology for the optimal energy mix (Hickey et al., 2010). Shannon Wiener Index (SWI), which is the most cited diversity metric has been used to assess power systems diversity mainly from an energy perspective. To our best knowledge, there is no rigorous justification why energy has been the main variable used in diversification exercises rather than other variables such as capacity. We use a stylized power generation framework to show that diversity based on energy or capacity could lead to different outcomes in terms of vulnerability to fuel exposure, among others. We also introduce a Shannon Wiener Index ratio (SWIR) that we believe captures better the diversity of a power system compared to the standard SWI. - Highlights: • Ranking power systems, from a diversity perspective, based on one criteria has many shortcomings. • Diversity based on energy or capacity could lead to different outcomes in terms of vulnerability to fuel exposure, among others. • A Shannon Wiener Index ratio (SWIR) captures better the diversity of a power system compared to the standard SWI.

  11. The influence of an innovative locomotor strategy on the phenotypic diversification of triggerfish (family: Balistidae).

    Science.gov (United States)

    Dornburg, Alex; Sidlauskas, Brian; Santini, Francesco; Sorenson, Laurie; Near, Thomas J; Alfaro, Michael E

    2011-07-01

    Innovations in locomotor morphology have been invoked as important drivers of vertebrate diversification, although the influence of novel locomotion strategies on marine fish diversification remains largely unexplored. Using triggerfish as a case study, we determine whether the evolution of the distinctive synchronization of enlarged dorsal and anal fins that triggerfish use to swim may have catalyzed the ecological diversification of the group. By adopting a comparative phylogenetic approach to quantify median fin and body shape integration and to assess the tempo of functional and morphological evolution in locomotor traits, we find that: (1) functional and morphological components of the locomotive system exhibit a strong signal of correlated evolution; (2) triggerfish partitioned locomotor morphological and functional spaces early in their history; and (3) there is no strong evidence that a pulse of lineage diversification accompanied the major episode of phenotypic diversification. Together these findings suggest that the acquisition of a distinctive mode of locomotion drove an early radiation of shape and function in triggerfish, but not an early radiation of species. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

  12. Rapid and recent diversification patterns in Anseriformes birds: Inferred from molecular phylogeny and diversification analyses.

    Directory of Open Access Journals (Sweden)

    Zhonglou Sun

    Full Text Available The Anseriformes is a well-known and widely distributed bird order, with more than 150 species in the world. This paper aims to revise the classification, determine the phylogenetic relationships and diversification patterns in Anseriformes by exploring the Cyt b, ND2, COI genes and the complete mitochondrial genomes (mito-genomes. Molecular phylogeny and genetic distance analyses suggest that the Dendrocygna species should be considered as an independent family, Dendrocygnidae, rather than a member of Anatidae. Molecular timescale analyses suggests that the ancestral diversification occurred during the Early Eocene Climatic Optimum (58 ~ 50 Ma. Furthermore, diversification analyses showed that, after a long period of constant diversification, the median initial speciation rate was accelerated three times, and finally increased to approximately 0.3 sp/My. In the present study, both molecular phylogeny and diversification analyses results support that Anseriformes birds underwent rapid and recent diversification in their evolutionary history, especially in modern ducks, which show extreme diversification during the Plio-Pleistocene (~ 5.3 Ma. Therefore, our study support that the Plio-Pleistocene climate fluctuations are likely to have played a significant role in promoting the recent diversification for Anseriformes.

  13. Rapid and recent diversification patterns in Anseriformes birds: Inferred from molecular phylogeny and diversification analyses.

    Science.gov (United States)

    Sun, Zhonglou; Pan, Tao; Hu, Chaochao; Sun, Lu; Ding, Hengwu; Wang, Hui; Zhang, Chenling; Jin, Hong; Chang, Qing; Kan, Xianzhao; Zhang, Baowei

    2017-01-01

    The Anseriformes is a well-known and widely distributed bird order, with more than 150 species in the world. This paper aims to revise the classification, determine the phylogenetic relationships and diversification patterns in Anseriformes by exploring the Cyt b, ND2, COI genes and the complete mitochondrial genomes (mito-genomes). Molecular phylogeny and genetic distance analyses suggest that the Dendrocygna species should be considered as an independent family, Dendrocygnidae, rather than a member of Anatidae. Molecular timescale analyses suggests that the ancestral diversification occurred during the Early Eocene Climatic Optimum (58 ~ 50 Ma). Furthermore, diversification analyses showed that, after a long period of constant diversification, the median initial speciation rate was accelerated three times, and finally increased to approximately 0.3 sp/My. In the present study, both molecular phylogeny and diversification analyses results support that Anseriformes birds underwent rapid and recent diversification in their evolutionary history, especially in modern ducks, which show extreme diversification during the Plio-Pleistocene (~ 5.3 Ma). Therefore, our study support that the Plio-Pleistocene climate fluctuations are likely to have played a significant role in promoting the recent diversification for Anseriformes.

  14. How Well Can We Detect Lineage-Specific Diversification-Rate Shifts? A Simulation Study of Sequential AIC Methods.

    Science.gov (United States)

    May, Michael R; Moore, Brian R

    2016-11-01

    Evolutionary biologists have long been fascinated by the extreme differences in species numbers across branches of the Tree of Life. This has motivated the development of statistical methods for detecting shifts in the rate of lineage diversification across the branches of phylogenic trees. One of the most frequently used methods, MEDUSA, explores a set of diversification-rate models, where each model assigns branches of the phylogeny to a set of diversification-rate categories. Each model is first fit to the data, and the Akaike information criterion (AIC) is then used to identify the optimal diversification model. Surprisingly, the statistical behavior of this popular method is uncharacterized, which is a concern in light of: (1) the poor performance of the AIC as a means of choosing among models in other phylogenetic contexts; (2) the ad hoc algorithm used to visit diversification models, and; (3) errors that we reveal in the likelihood function used to fit diversification models to the phylogenetic data. Here, we perform an extensive simulation study demonstrating that MEDUSA (1) has a high false-discovery rate (on average, spurious diversification-rate shifts are identified [Formula: see text] of the time), and (2) provides biased estimates of diversification-rate parameters. Understanding the statistical behavior of MEDUSA is critical both to empirical researchers-in order to clarify whether these methods can make reliable inferences from empirical datasets-and to theoretical biologists-in order to clarify the specific problems that need to be solved in order to develop more reliable approaches for detecting shifts in the rate of lineage diversification. [Akaike information criterion; extinction; lineage-specific diversification rates; phylogenetic model selection; speciation.]. © The Author(s) 2016. Published by Oxford University Press, on behalf of the Society of Systematic Biologists.

  15. Molecular phylogenetics and the diversification of hummingbirds.

    Science.gov (United States)

    McGuire, Jimmy A; Witt, Christopher C; Remsen, J V; Corl, Ammon; Rabosky, Daniel L; Altshuler, Douglas L; Dudley, Robert

    2014-04-14

    The tempo of species diversification in large clades can reveal fundamental evolutionary mechanisms that operate on large temporal and spatial scales. Hummingbirds have radiated into a diverse assemblage of specialized nectarivores comprising 338 species, but their evolutionary history has not, until now, been comprehensively explored. We studied hummingbird diversification by estimating a time-calibrated phylogeny for 284 hummingbird species, demonstrating that hummingbirds invaded South America by ∼22 million years ago, and subsequently diversified into nine principal clades (see [5-7]). Using ancestral state reconstruction and diversification analyses, we (1) estimate the age of the crown-group hummingbird assemblage, (2) investigate the timing and patterns of lineage accumulation for hummingbirds overall and regionally, and (3) evaluate the role of Andean uplift in hummingbird speciation. Detailed analyses reveal disparate clade-specific processes that allowed for ongoing species diversification. One factor was significant variation among clades in diversification rates. For example, the nine principal clades of hummingbirds exhibit ∼15-fold variation in net diversification rates, with evidence for accelerated speciation of a clade that includes the Bee, Emerald, and Mountain Gem groups of hummingbirds. A second factor was colonization of key geographic regions, which opened up new ecological niches. For example, some clades diversified in the context of the uplift of the Andes Mountains, whereas others were affected by the formation of the Panamanian land bridge. Finally, although species accumulation is slowing in all groups of hummingbirds, several major clades maintain rapid rates of diversification on par with classical examples of rapid adaptive radiation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Diagnosis of Diversification Processes at an Enterprise

    Directory of Open Access Journals (Sweden)

    Skrynkovskyy Ruslan M.

    2017-06-01

    Full Text Available The aim of the article is formation and development of theoretical and methodological basis for diagnosing diversification processes at an enterprise in the context and on the basis of theory and practice of economics and enterprise management. It is found that: 1 one of the most common ways of development of an enterprise is diversification, which contributes to effective implementation of its development strategy and formation of its prospects; 2 diagnosis of diversification processes at an enterprise is a targeted evaluation of its state, trends and development prospects associated with identification of new spheres (branches of activities and penetration into them, development of new production technologies and markets, expansion of the range of products (goods, which is most conducive to effective realization of competitive advantages of an enterprise with the purpose of maximization of its incomes received from all directions of its activity and minimization of expected risks. It is determined that the key business indicators of the diagnostic system are indicators that reflect the level of diversification of an enterprise’s activities: the absolute level of diversification; the transformed concentration index; the Berry index / the Herfindahl-Hirschman index; the concentration ratio of the sphere of activity (branch according to the descending (or increasing principle; the entropy index; the Atton index; the index of diversification; the level of risk. The prospect for further scientific and practical research in this area is development of a multi-criteria system for diagnosing the activities of enterprises, taking into account diagnosis of diversification processes at an enterprise as a partial diagnostic purpose of the system of partial diagnostic purposes of the multi-criteria system of economic diagnosis of an enterprise.

  17. Antipredator defenses predict diversification rates

    Science.gov (United States)

    Arbuckle, Kevin; Speed, Michael P.

    2015-01-01

    The “escape-and-radiate” hypothesis predicts that antipredator defenses facilitate adaptive radiations by enabling escape from constraints of predation, diversified habitat use, and subsequently speciation. Animals have evolved diverse strategies to reduce the direct costs of predation, including cryptic coloration and behavior, chemical defenses, mimicry, and advertisement of unprofitability (conspicuous warning coloration). Whereas the survival consequences of these alternative defenses for individuals are well-studied, little attention has been given to the macroevolutionary consequences of alternative forms of defense. Here we show, using amphibians as the first, to our knowledge, large-scale empirical test in animals, that there are important macroevolutionary consequences of alternative defenses. However, the escape-and-radiate hypothesis does not adequately describe them, due to its exclusive focus on speciation. We examined how rates of speciation and extinction vary across defensive traits throughout amphibians. Lineages that use chemical defenses show higher rates of speciation as predicted by escape-and-radiate but also show higher rates of extinction compared with those without chemical defense. The effect of chemical defense is a net reduction in diversification compared with lineages without chemical defense. In contrast, acquisition of conspicuous coloration (often used as warning signals or in mimicry) is associated with heightened speciation rates but unchanged extinction rates. We conclude that predictions based on the escape-and-radiate hypothesis must incorporate the effect of traits on both speciation and extinction, which is rarely considered in such studies. Our results also suggest that knowledge of defensive traits could have a bearing on the predictability of extinction, perhaps especially important in globally threatened taxa such as amphibians. PMID:26483488

  18. Income diversification and risk for fishermen.

    Science.gov (United States)

    Kasperski, Stephen; Holland, Daniel S

    2013-02-05

    Catches and prices from many fisheries exhibit high interannual variability, leading to variability in the income derived by fishery participants. The economic risk posed by this may be mitigated in some cases if individuals participate in several different fisheries, particularly if revenues from those fisheries are uncorrelated or vary asynchronously. We construct indices of gross income diversification from fisheries at the level of individual vessels and find that the income of the current fleet of vessels on the US West Coast and in Alaska is less diverse than at any point in the past 30 y. We also find a dome-shaped relationship between the variability of individuals' income and income diversification, which implies that a small amount of diversification does not reduce income risk but that higher levels of diversification can substantially reduce the variability of income from fishing. Moving from a single fishery strategy to a 50-25-25 split in revenues reduces the expected coefficient of variation of gross revenues between 24% and 65% for the vessels included in this study. The increasing access restrictions in many marine fisheries through license reductions and moratoriums have the potential to limit fishermen's ability to diversify their income risk across multiple fisheries. Catch share programs often result in consolidation initially and may reduce diversification. However, catch share programs also make it feasible for fishermen to build a portfolio of harvest privileges and potentially reduce their income risk. Therefore, catch share programs create both threats and opportunities for fishermen wishing to maintain diversified fishing strategies.

  19. Explosive ice age diversification of kiwi.

    Science.gov (United States)

    Weir, Jason T; Haddrath, Oliver; Robertson, Hugh A; Colbourne, Rogan M; Baker, Allan J

    2016-09-20

    Molecular dating largely overturned the paradigm that global cooling during recent Pleistocene glacial cycles resulted in a burst of species diversification although some evidence exists that speciation was commonly promoted in habitats near the expanding and retracting ice sheets. Here, we used a genome-wide dataset of more than half a million base pairs of DNA to test for a glacially induced burst of diversification in kiwi, an avian family distributed within several hundred kilometers of the expanding and retracting glaciers of the Southern Alps of New Zealand. By sampling across the geographic range of the five kiwi species, we discovered many cryptic lineages, bringing the total number of kiwi taxa that currently exist to 11 and the number that existed just before human arrival to 16 or 17. We found that 80% of kiwi diversification events date to the major glacial advances of the Middle and Late Pleistocene. During this period, New Zealand was repeatedly fragmented by glaciers into a series of refugia, with the tiny geographic ranges of many kiwi lineages currently distributed in areas adjacent to these refugia. Estimates of effective population size through time show a dramatic bottleneck during the last glacial cycle in all but one kiwi lineage, as expected if kiwi were isolated in glacially induced refugia. Our results support a fivefold increase in diversification rates during key glacial periods, comparable with levels observed in classic adaptive radiations, and confirm that at least some lineages distributed near glaciated regions underwent rapid ice age diversification.

  20. Hospital diversification: how to involve the pharmacy.

    Science.gov (United States)

    Smith, J E; Black, B L

    1987-05-01

    Participation by hospital pharmacy departments in planning and development of diversified services is described. Diversification requires market planning. Seven basic marketing steps are identification of mission, goals, and objectives; identification of growth strategies (market penetration, market development, product development, and diversification); market analysis of external factors (size, growth, and logistics; reimbursement and financial considerations; competition; regulatory issues; and legal issues); market analysis of internal factors (departmental organization and reporting lines, demographics of the institution, and costs and productivity associated with the new service); program development and design; implementation; and evaluation. Hospitals can diversify by expanding acute-care services through management contracts and mergers; developing new services to include long-term-care, ambulatory-care, occupational-health, and wellness programs; starting other health-care ventures, such as consulting, continuing medical education, and continuing education for nurses; and expanding into non-health-care businesses. Vertical diversification is finding new markets for existing services; horizontal diversification is development of new services for new markets. To diversify, an institution may need to change its corporate structure; it may form a family of corporations that includes a university, nonprofit hospitals, holding companies, for-profit corporations, joint ventures, and service organizations. Through diversification, institutions and pharmacy departments can create alternative sources of funding and offer more comprehensive services to patients.

  1. Is the potential for international diversification disappearing?

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Errunza, Vihang; Jacobs, Kris

    2012-01-01

    International equity markets are characterized by nonlinear dependence and asymmetries. We propose a new dynamic asymmetric copula model to capture long-run and short-run dependence, multivariate nonnormality, and asymmetries in large cross-sections. We find that correlations have increased...... markedly in both developed markets (DMs) and emerging markets (EMs), but they are much lower in EMs than in DMs. Tail dependence has also increased, but its level is still relatively low in EMs. We propose new measures of dynamic diversification benefits that take into account higher-order moments...... and nonlinear dependence. The benefits from international diversification have reduced over time, drastically so for DMs. EMs still offer significant diversification benefits, especially during large market downturns....

  2. The challenge of technology diversification and markets

    International Nuclear Information System (INIS)

    Bollini, G.

    2002-01-01

    Tecnatom is developing since several years ago the diversification of technologies and markets given its enterprise vocation of technological leadership in the services and products supplied in both the national and international nuclear market. In this paper, a description of the historical development of these technologies is made, and how the diversification is initiated in the global market, as well as the identification of the segments of the industrial market where services and products of high technology can be provided. A description of the diversification strategy is included and several results of this policy are presented for the aircraft and space market, the transport market, the industrial processes market, etc. Finally, examples of developments of new technologies of virtual reality and augmented reality are explained and how these new capabilities feedback in the nuclear market. (Author)

  3. Correlation dynamics and international diversification benefits

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Errunza, Vihang; Jacobs, Kris

    2014-01-01

    that it is possible to model co-movements for many countries simultaneously using BEKK, DCC, and DECO models. Empirically, we find that correlations have trended upward significantly for both DMs and EMs. Based on a time-varying measure of diversification benefits, we find that it is not possible to circumvent...... the increasing correlations in a long-only portfolio by adjusting the portfolio weights over time. However, we do find some evidence that adding EMs to a DM-only portfolio increases diversification benefits....

  4. Correlation Dynamics and International Diversification Benefits

    DEFF Research Database (Denmark)

    Christoffersen, Peter; Errunza, Vihang R.; Jacobs, Kris

    that it is possible to model co-movements for many countries simultaneously using BEKK, DCC, and DECO models. Empirically, we find that correlations have significantly trended upward for both DMs and EMs. Based on a time-varying measure of diversification benefit, we find that it is not possible in a long......-only portfolio to circumvent the increasing correlations by adjusting the portfolio weights over time. However, we do find some evidence that adding EMs to a DM-only portfolio increases diversification benefits....

  5. Origin and diversification of TRIM ubiquitin ligases.

    Directory of Open Access Journals (Sweden)

    Ignacio Marín

    Full Text Available Most proteins of the TRIM family (also known as RBCC family are ubiquitin ligases that share a peculiar protein structure, characterized by including an N-terminal RING finger domain closely followed by one or two B-boxes. Additional protein domains found at their C termini have been used to classify TRIM proteins into classes. TRIMs are involved in multiple cellular processes and many of them are essential components of the innate immunity system of animal species. In humans, it has been shown that mutations in several TRIM-encoding genes lead to diverse genetic diseases and contribute to several types of cancer. They had been hitherto detected only in animals. In this work, by comprehensively analyzing the available diversity of TRIM and TRIM-like protein sequences and evaluating their evolutionary patterns, an improved classification of the TRIM family is obtained. Members of one of the TRIM subfamilies defined, called Subfamily A, turn to be present not only in animals, but also in many other eukaryotes, such as fungi, apusozoans, alveolates, excavates and plants. The rest of subfamilies are animal-specific and several of them originated only recently. Subfamily A proteins are characterized by containing a MATH domain, suggesting a potential evolutionary connection between TRIM proteins and a different type of ubiquitin ligases, known as TRAFs, which contain quite similar MATH domains. These results indicate that the TRIM family emerged much earlier than so far thought and contribute to our understanding of its origin and diversification. The structural and evolutionary links with the TRAF family of ubiquitin ligases can be experimentally explored to determine whether functional connections also exist.

  6. Result diversification based on query-specific cluster ranking

    NARCIS (Netherlands)

    He, J.; Meij, E.; de Rijke, M.

    2011-01-01

    Result diversification is a retrieval strategy for dealing with ambiguous or multi-faceted queries by providing documents that cover as many facets of the query as possible. We propose a result diversification framework based on query-specific clustering and cluster ranking, in which diversification

  7. International Diversification Versus Domestic Diversification: Mean-Variance Portfolio Optimization and Stochastic Dominance Approaches

    Directory of Open Access Journals (Sweden)

    Fathi Abid

    2014-05-01

    Full Text Available This paper applies the mean-variance portfolio optimization (PO approach and the stochastic dominance (SD test to examine preferences for international diversification versus domestic diversification from American investors’ viewpoints. Our PO results imply that the domestic diversification strategy dominates the international diversification strategy at a lower risk level and the reverse is true at a higher risk level. Our SD analysis shows that there is no arbitrage opportunity between international and domestic stock markets; domestically diversified portfolios with smaller risk dominate internationally diversified portfolios with larger risk and vice versa; and at the same risk level, there is no difference between the domestically and internationally diversified portfolios. Nonetheless, we cannot find any domestically diversified portfolios that stochastically dominate all internationally diversified portfolios, but we find some internationally diversified portfolios with small risk that dominate all the domestically diversified portfolios.

  8. Opponent appetitive-aversive neural processes underlie predictive learning of pain relief.

    Science.gov (United States)

    Seymour, Ben; O'Doherty, John P; Koltzenburg, Martin; Wiech, Katja; Frackowiak, Richard; Friston, Karl; Dolan, Raymond

    2005-09-01

    Termination of a painful or unpleasant event can be rewarding. However, whether the brain treats relief in a similar way as it treats natural reward is unclear, and the neural processes that underlie its representation as a motivational goal remain poorly understood. We used fMRI (functional magnetic resonance imaging) to investigate how humans learn to generate expectations of pain relief. Using a pavlovian conditioning procedure, we show that subjects experiencing prolonged experimentally induced pain can be conditioned to predict pain relief. This proceeds in a manner consistent with contemporary reward-learning theory (average reward/loss reinforcement learning), reflected by neural activity in the amygdala and midbrain. Furthermore, these reward-like learning signals are mirrored by opposite aversion-like signals in lateral orbitofrontal cortex and anterior cingulate cortex. This dual coding has parallels to 'opponent process' theories in psychology and promotes a formal account of prediction and expectation during pain.

  9. Fusion and diversification in information retrieval

    NARCIS (Netherlands)

    Liang, S.

    2014-01-01

    Data fusion and search result diversification are two critical research topics in information retrieval. Data fusion approaches combine search result lists in order to produce a new and hopefully better ranking. We propose two data fusion models for microblog search that exploit temporal information

  10. Global loss diversification in the insurance sector

    NARCIS (Netherlands)

    Sheremet, O.; Lucas, A.

    2009-01-01

    We study the possibility for international diversification of catastrophe risk by the insurance sector. Adopting the argument that large insurance losses may be a 'globalizing factor' for the industry, we study the dependence of geographically distant insurance markets via equity returns. In

  11. Global elevational diversity and diversification of birds.

    Science.gov (United States)

    Quintero, Ignacio; Jetz, Walter

    2018-03-08

    Mountain ranges harbour exceptionally high biodiversity, which is now under threat from rapid environmental change. However, despite decades of effort, the limited availability of data and analytical tools has prevented a robust and truly global characterization of elevational biodiversity gradients and their evolutionary origins. This has hampered a general understanding of the processes involved in the assembly and maintenance of montane communities. Here we show that a worldwide mid-elevation peak in bird richness is driven by wide-ranging species and disappears when we use a subsampling procedure that ensures even species representation in space and facilitates evolutionary interpretation. Instead, richness corrected for range size declines linearly with increasing elevation. We find that the more depauperate assemblages at higher elevations are characterized by higher rates of diversification across all mountain regions, rejecting the idea that lower recent diversification rates are the general cause of less diverse biota. Across all elevations, assemblages on mountains with high rates of past temperature change exhibit more rapid diversification, highlighting the importance of climatic fluctuations in driving the evolutionary dynamics of mountain biodiversity. While different geomorphological and climatic attributes of mountain regions have been pivotal in determining the remarkable richness gradients observed today, our results underscore the role of ongoing and often very recent diversification processes in maintaining the unique and highly adapted biodiversity of higher elevations.

  12. Determinants of Related and Unrelated Export Diversification

    Directory of Open Access Journals (Sweden)

    Muhammad Ali

    2017-12-01

    Full Text Available This paper contributes to the literature on determinants of the export diversification by introducing related variety (RV and unrelated variety (UV in the analysis in addition to the traditional entropy based measure at three-digit Standard International Trade Classification (SITC level, overall variety (OV. RV measures variety in cognitively related industries, while UV measures variety in industries that are unrelated to each other. Studies on RV and UV have shown that the dynamics of their relationship with economic growth and innovation may differ and one would expect that the determinants of RV and UV may also be different. Therefore, using data on manufacturing sector exports for 130 countries from 1996 to 2011, this paper identifies the determinants of export diversification with primary focus on foreign direct investment as an external source of knowledge and a stimulus to entrepreneurship and human capital as a measure of productive capabilities. Considering the concern of endogeneity bias, estimations of the econometric models were performed using generalized method of moments. Findings show that some of the determinants of diversification affect RV, UV and OV differently. For instance, foreign direct investment (FDI negatively affects RV while it has no significant relationship with OV and UV. Moreover, interaction of human capital with FDI appears to be positive and significant for UV and RV while interaction of human capital with trade openness is significant and positive for RV only, showing the importance of knowledge through external sources in the process of related diversification.

  13. Determinants Of Vertical And Horizontal Export Diversification ...

    African Journals Online (AJOL)

    The study also reveals domestic investment plays an important role to enhance vertical as well as horizontal export diversification for East Asia, while it only ... resource-based industries and gradually shift production and exports from customary products to more dynamic ones by developing competitive advantage in the ...

  14. Development Strategy 0f Local Food Diversification

    Directory of Open Access Journals (Sweden)

    Imelda Imelda

    2017-03-01

    Full Text Available The purpose of this research is to develop strategies that can be applied in the development of local food diversification in West Kalimantan. The data used are primary data and secondary data. Variables examined included internal factors (strengths and weaknesses and external factors (opportunities and threats in the development of local food diversification in West Kalimantan. Data analysis were conducted in qualitative descriptive to describe the pattern of food consumption in West Kalimantan and continued with a SWOT analysis to carry out the development strategy of the local food diversification in West Kalimantan. The analysis result showed that the strategy for the development of local food diversification in West Kalimantan is SO strategy (Strengths - Opportunities those are: 1 the increase in synergy between the government and the micro, small and medium enterprises for the development of local food products, 2 the utilization of communications and market information system in improving the marketing of local food products on micro, small and medium enterprises, and 3 the utilization of unutilized agricultural land to improve the quality and quantity of local food products.

  15. Unparalleled rates of species diversification in Europe

    Science.gov (United States)

    Valente, Luis M.; Savolainen, Vincent; Vargas, Pablo

    2010-01-01

    The most rapid species radiations have been reported from ‘evolutionary laboratories’, such as the Andes and the Cape of South Africa, leading to the prevailing view that diversification elsewhere has not been as dramatic. However, few studies have explicitly assessed rates of diversification in northern regions such as Europe. Here, we show that carnations (Dianthus, Caryophyllaceae), a well-known group of plants from temperate Eurasia, have diversified at the most rapid rate ever reported in plants or terrestrial vertebrates. Using phylogenetic methods, we found that the majority of species of carnations belong to a lineage that is remarkably species-rich in Europe, and arose at the rate of 2.2–7.6 species per million years. Unlike most previous studies that have inferred rates of diversification in young diverse groups, we use a conservative approach throughout that explicitly incorporates the uncertainties associated with phylogenetic inference, molecular dating and incomplete taxon sampling. We detected a shift in diversification rates of carnations coinciding with a period of increase in climatic aridity in the Pleistocene, suggesting a link between climate and biodiversity. This explosive radiation suggests that Europe, the continent with the world's best-studied flora, has been underestimated as a cradle of recent and rapid speciation. PMID:20106850

  16. Evolutionary origins and diversification of proteobacterial mutualists.

    Science.gov (United States)

    Sachs, Joel L; Skophammer, Ryan G; Bansal, Nidhanjali; Stajich, Jason E

    2014-01-22

    Mutualistic bacteria infect most eukaryotic species in nearly every biome. Nonetheless, two dilemmas remain unresolved about bacterial-eukaryote mutualisms: how do mutualist phenotypes originate in bacterial lineages and to what degree do mutualists traits drive or hinder bacterial diversification? Here, we reconstructed the phylogeny of the hyperdiverse phylum Proteobacteria to investigate the origins and evolutionary diversification of mutualistic bacterial phenotypes. Our ancestral state reconstructions (ASRs) inferred a range of 34-39 independent origins of mutualist phenotypes in Proteobacteria, revealing the surprising frequency with which host-beneficial traits have evolved in this phylum. We found proteobacterial mutualists to be more often derived from parasitic than from free-living ancestors, consistent with the untested paradigm that bacterial mutualists most often evolve from pathogens. Strikingly, we inferred that mutualists exhibit a negative net diversification rate (speciation minus extinction), which suggests that mutualism evolves primarily via transitions from other states rather than diversification within mutualist taxa. Moreover, our ASRs infer that proteobacterial mutualist lineages exhibit a paucity of reversals to parasitism or to free-living status. This evolutionary conservatism of mutualism is contrary to long-standing theory, which predicts that selection should often favour mutants in microbial mutualist populations that exploit or abandon more slowly evolving eukaryotic hosts.

  17. Agricultural diversification strategies in small island states

    NARCIS (Netherlands)

    Drori, I.; Gayle, D. J.

    1991-01-01

    Across the small island states of the Caribbean, the need for greater agricultural diversification is a constant policy concern, as exemplified by the case of Barbados. Although the cane sugar industry in Barbados remains one of the more cost-efficient in the world, the structures of both the

  18. Technology diversification, coherence, and performance of firms

    NARCIS (Netherlands)

    Leten, B.; Belderbos, R.A.; Looy, van B.

    2007-01-01

    Technological diversification at the firm level (i.e., the expansion of a firm's technology base into a wide range of technology fields) is found to be a prevailing phenomenon in all three major industrialized regions,—the United States, Europe, and Japan—prompting the term multitechnology

  19. The impact of inefficiency on diversification

    NARCIS (Netherlands)

    Oude Lansink, A.G.J.M.; Stefanou, S.E.; Kapelko, M.

    2015-01-01

    Diversification is often seen as a risk management tool, but specialization allows operators to exploit scale economies in single outputs and offers specialized operators more opportunities to fine-tune their skills which can promote a greater degree of technical proficiency. Measuring economies of

  20. Portfolio Diversification Effects of Downside Risk

    NARCIS (Netherlands)

    N. Hyung (Namwon); C.G. de Vries (Casper)

    2004-01-01

    textabstractRisk managers use portfolios to diversify away the un-priced risk of individual securities. In this paper we compare the benefits of portfolio diversification for downside risk in case returns are normally distributed with the case fat tailed distributed returns. The downside risk of a

  1. Economic diversification and poverty in rural India

    NARCIS (Netherlands)

    Kijima, Yoko; Lanjouw, Peter

    This paper analyses National Sample Survey data for 1987-88, 1993-94 and 1999-00 to explore the relationship between rural diversification and poverty. While there is little consensus regarding the rate of poverty decline during the 1990s, the region-level estimates provided here suggest that

  2. Determinants of Crop Diversification in Ethiopia:

    African Journals Online (AJOL)

    Diversification of agriculture is central to economic transformation. It contributes to ... growth and poverty reduction strategies of Ethiopia place emphasized on broad ..... Similarly, (Bonham et al., 2012) found that positive relationship between on-farm diversity of pearl millet and income from agricultural production in India.

  3. Geographic Diversification, Competition and Bank Survival

    NARCIS (Netherlands)

    Jochem, T.

    2013-01-01

    This article analyzes the effects from portfolio diversification and banking competition on the stability of U.S. banks during the 2008-2011 banking crisis. To do so, it uses exogenous cross-sectional and time-series variation in states' branching restrictions between 1997-2005, the degree of local

  4. Plastome phylogeny and early diversification of Brassicaceae.

    Science.gov (United States)

    Guo, Xinyi; Liu, Jianquan; Hao, Guoqian; Zhang, Lei; Mao, Kangshan; Wang, Xiaojuan; Zhang, Dan; Ma, Tao; Hu, Quanjun; Al-Shehbaz, Ihsan A; Koch, Marcus A

    2017-02-16

    The family Brassicaceae encompasses diverse species, many of which have high scientific and economic importance. Early diversifications and phylogenetic relationships between major lineages or clades remain unclear. Here we re-investigate Brassicaceae phylogeny with complete plastomes from 51 species representing all four lineages or 5 of 6 major clades (A, B, C, E and F) as identified in earlier studies. Bayesian and maximum likelihood phylogenetic analyses using a partitioned supermatrix of 77 protein coding genes resulted in nearly identical tree topologies exemplified by highly supported relationships between clades. All four lineages were well identified and interrelationships between them were resolved. The previously defined Clade C was found to be paraphyletic (the genus Megadenia formed a separate lineage), while the remaining clades were monophyletic. Clade E (lineage III) was sister to clades B + C rather than to all core Brassicaceae (clades A + B + C or lineages I + II), as suggested by a previous transcriptome study. Molecular dating based on plastome phylogeny supported the origin of major lineages or clades between late Oligocene and early Miocene, and the following radiative diversification across the family took place within a short timescale. In addition, gene losses in the plastomes occurred multiple times during the evolutionary diversification of the family. Plastome phylogeny illustrates the early diversification of cruciferous species. This phylogeny will facilitate our further understanding of evolution and adaptation of numerous species in the model family Brassicaceae.

  5. DIVERSIFICATION OF A SAFETY FOOTWEAR PRODUCT

    Directory of Open Access Journals (Sweden)

    HARNAGEA Marta Cătălina

    2017-05-01

    Full Text Available Product diversification is a usual strategy of footwear producers. As a requirement related to competitiveness in this domain, diversification can be done by practical application of some criteria. Considering this aspect, the paper proposes a research on the diversification in the case of a safety footwear product by modifying its component patterns, while keeping the initial shape of the product. Thus, starting from a safety shoe model, diversification was performed by changing the configuration in the joining area of two patterns of the product. By joining the tongue with the bellows tongue, the upper with the quarter, the heel counter with the quarter and the collar and heel counter with quarter has resulted a family of models characterized by a reduction of the number of patterns in the product. The size of the set presents a significant influence on the theoretical nesting factor and implicitly on the size of the wastes. The analysis of the resulting new model types lead to highlighting the influence of the patterns number of the uppers and the area of the set on the usage index of the leather surface when cutting the parts and on the specific consumption.

  6. Efficient Diversification According to Stochastic Dominance Criteria

    NARCIS (Netherlands)

    Kuosmanen, T.K.

    2004-01-01

    This paper develops the first operational tests of portfolio efficiency based on the general stochastic dominance (SD) criteria that account for an infinite set of diversification strategies. The main insight is to preserve the cross-sectional dependence of asset returns when forming portfolios by

  7. Abnormal Brain Dynamics Underlie Speech Production in Children with Autism Spectrum Disorder.

    Science.gov (United States)

    Pang, Elizabeth W; Valica, Tatiana; MacDonald, Matt J; Taylor, Margot J; Brian, Jessica; Lerch, Jason P; Anagnostou, Evdokia

    2016-02-01

    A large proportion of children with autism spectrum disorder (ASD) have speech and/or language difficulties. While a number of structural and functional neuroimaging methods have been used to explore the brain differences in ASD with regards to speech and language comprehension and production, the neurobiology of basic speech function in ASD has not been examined. Magnetoencephalography (MEG) is a neuroimaging modality with high spatial and temporal resolution that can be applied to the examination of brain dynamics underlying speech as it can capture the fast responses fundamental to this function. We acquired MEG from 21 children with high-functioning autism (mean age: 11.43 years) and 21 age- and sex-matched controls as they performed a simple oromotor task, a phoneme production task and a phonemic sequencing task. Results showed significant differences in activation magnitude and peak latencies in primary motor cortex (Brodmann Area 4), motor planning areas (BA 6), temporal sequencing and sensorimotor integration areas (BA 22/13) and executive control areas (BA 9). Our findings of significant functional brain differences between these two groups on these simple oromotor and phonemic tasks suggest that these deficits may be foundational and could underlie the language deficits seen in ASD. © 2015 The Authors Autism Research published by Wiley Periodicals, Inc. on behalf of International Society for Autism Research.

  8. Neutral stability, drift, and the diversification of languages.

    Science.gov (United States)

    Pawlowitsch, Christina; Mertikopoulos, Panayotis; Ritt, Nikolaus

    2011-10-21

    The diversification of languages is one of the most interesting facts about language that seek explanation from an evolutionary point of view. Conceptually the question is related to explaining mechanisms of speciation. An argument that prominently figures in evolutionary accounts of language diversification is that it serves the formation of group markers which help to enhance in-group cooperation. In this paper we use the theory of evolutionary games to show that language diversification on the level of the meaning of lexical items can come about in a perfectly cooperative world solely as a result of the effects of frequency-dependent selection. Importantly, our argument does not rely on some stipulated function of language diversification in some co-evolutionary process, but comes about as an endogenous feature of the model. The model that we propose is an evolutionary language game in the style of Nowak et al. (1999) [The evolutionary language game. J. Theor. Biol. 200, 147-162], which has been used to explain the rise of a signaling system or protolanguage from a prelinguistic environment. Our analysis focuses on the existence of neutrally stable polymorphisms in this model, where, on the level of the population, a signal can be used for more than one concept or a concept can be inferred by more than one signal. Specifically, such states cannot be invaded by a mutation for bidirectionality, that is, a mutation that tries to resolve the existing ambiguity by linking each concept to exactly one signal in a bijective way. However, such states are not resistant against drift between the selectively neutral variants that are present in such a state. Neutral drift can be a pathway for a mutation for bidirectionality that was blocked before but that finally will take over the population. Different directions of neutral drift open the door for a mutation for bidirectionality to appear on different resident types. This mechanism-which can be seen as a form of shifting

  9. Boom and bust: ancient and recent diversification in bichirs (Polypteridae: Actinopterygii), a relictual lineage of ray-finned fishes.

    Science.gov (United States)

    Near, Thomas J; Dornburg, Alex; Tokita, Masayoshi; Suzuki, Dai; Brandley, Matthew C; Friedman, Matt

    2014-04-01

    Understanding the history that underlies patterns of species richness across the Tree of Life requires an investigation of the mechanisms that not only generate young species-rich clades, but also those that maintain species-poor lineages over long stretches of evolutionary time. However, diversification dynamics that underlie ancient species-poor lineages are often hidden due to a lack of fossil evidence. Using information from the fossil record and time calibrated molecular phylogenies, we investigate the history of lineage diversification in Polypteridae, which is the sister lineage of all other ray-finned fishes (Actinopterygii). Despite originating at least 390 million years (Myr) ago, molecular timetrees support a Neogene origin for the living polypterid species. Our analyses demonstrate polypterids are exceptionally species depauperate with a stem lineage duration that exceeds 380 million years (Ma) and is significantly longer than the stem lineage durations observed in other ray-finned fish lineages. Analyses of the fossil record show an early Late Cretaceous (100.5-83.6 Ma) peak in polypterid genus richness, followed by 60 Ma of low richness. The Neogene species radiation and evidence for high-diversity intervals in the geological past suggest a "boom and bust" pattern of diversification that contrasts with common perceptions of relative evolutionary stasis in so-called "living fossils." © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

  10. Allopatric distribution and diversification without niche shift in a bryophyte-feeding basal moth lineage (Lepidoptera: Micropterigidae).

    Science.gov (United States)

    Imada, Yume; Kawakita, Atsushi; Kato, Makoto

    2011-10-22

    The Lepidoptera represent one of the most successful radiations of plant-feeding insects, which predominantly took place within angiosperms beginning in the Cretaceous period. Angiosperm colonization is thought to underlie the evolutionary success of the Lepidoptera because angiosperms provide an enormous range of niches for ecological speciation to take place. By contrast, the basal lepidopteran lineage, Micropterigidae, remained unassociated with angiosperms since Jurassic times but nevertheless achieved a modest diversity in the Japanese Archipelago. We explored the causes and processes of diversification of the Japanese micropterigid moths by performing molecular phylogenetic analysis and extensive ecological surveying. Phylogenetic analysis recovered a monophyletic group of approximately 25 East Asian endemic species that feed exclusively on the liverwort Conocephalum conicum, suggesting that niche shifts hardly played a role in their diversification. Consistent with the low flying ability of micropterigid moths, the distributions of the Conocephalum specialists are each localized and allopatric, indicating that speciation by geographical isolation has been the major process shaping the diversity of Japanese Micropterigidae. To our knowledge, this is the largest radiation of herbivorous insects that does not accompany any apparent niche differentiation. We suggest that the significance of non-ecological speciation during the diversification of the Lepidoptera is commonly underestimated.

  11. Freshwater biodiversity and aquatic insect diversification.

    Science.gov (United States)

    Dijkstra, Klaas-Douwe B; Monaghan, Michael T; Pauls, Steffen U

    2014-01-01

    Inland waters cover less than 1% of Earth's surface but harbor more than 6% of all insect species: Nearly 100,000 species from 12 orders spend one or more life stages in freshwater. Little is known about how this remarkable diversity arose, although allopatric speciation and ecological adaptation are thought to be primary mechanisms. Freshwater habitats are highly susceptible to environmental change and exhibit marked ecological gradients. Standing waters appear to harbor more dispersive species than running waters, but there is little understanding of how this fundamental ecological difference has affected diversification. In contrast to the lack of evolutionary studies, the ecology and habitat preferences of aquatic insects have been intensively studied, in part because of their widespread use as bioindicators. The combination of phylogenetics with the extensive ecological data provides a promising avenue for future research, making aquatic insects highly suitable models for the study of ecological diversification.

  12. Optimising investment performance through international diversification

    Directory of Open Access Journals (Sweden)

    J. Swart

    2014-01-01

    Full Text Available International portfolio diversification is often advocated as a way of enhancing portfolio performance particularly through the reduction of portfolio risk. Portfolio managers in Europe have for decades routinely invested a substantial portion of their portfolios in securities that were issued in other countries. During the last decade US investors have held a significant amount of foreign securities with over a trillion dollars invested in foreign assets by 1994. South African institutions have been allowed some freedom to diversify internationally since mid 1995 and individual investors since July 1997. In this paper the potential diversification benefits for South African investors are considered. The stability over time of the correlation structure is investigated and simple ex-ante investment strategies are formulated and evaluated.

  13. Diversification versus specialization in complex ecosystems.

    Directory of Open Access Journals (Sweden)

    Riccardo Di Clemente

    Full Text Available By analyzing the distribution of revenues across the production sectors of quoted firms we suggest a novel dimension that drives the firms diversification process at country level. Data show a non trivial macro regional clustering of the diversification process, which underlines the relevance of geopolitical environments in determining the microscopic dynamics of economic entities. These findings demonstrate the possibility of singling out in complex ecosystems those micro-features that emerge at macro-levels, which could be of particular relevance for decision-makers in selecting the appropriate parameters to be acted upon in order to achieve desirable results. The understanding of this micro-macro information exchange is further deepened through the introduction of a simplified dynamic model.

  14. A behavioral analysis of investor diversification

    OpenAIRE

    Fuertes, A.; Muradoglu, G.; Ozturkkal, B.

    2014-01-01

    This paper studies the link between individual investors’ portfolio diversification levels and various personal traits that proxy informational advantages and overconfidence. The analysis is based on objective data from the largest Turkish brokerage house tracking 59,951 individual investors’ accounts with a total of 3,248,654 million transactions over the period 2008–2010. Wealthier, highly educated, older investors working in the finance sector and those trading relatively often show higher...

  15. Testing for coevolutionary diversification: linking pattern with process.

    Science.gov (United States)

    Althoff, David M; Segraves, Kari A; Johnson, Marc T J

    2014-02-01

    Coevolutionary diversification is cited as a major mechanism driving the evolution of diversity, particularly in plants and insects. However, tests of coevolutionary diversification have focused on elucidating macroevolutionary patterns rather than the processes giving rise to such patterns. Hence, there is weak evidence that coevolution promotes diversification. This is in part due to a lack of understanding about the mechanisms by which coevolution can cause speciation and the difficulty of integrating results across micro- and macroevolutionary scales. In this review, we highlight potential mechanisms of coevolutionary diversification, outline approaches to examine this process across temporal scales, and propose a set of minimal requirements for demonstrating coevolutionary diversification. Our aim is to stimulate research that tests more rigorously for coevolutionary diversification. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. The Impact of International Diversification on the Corporate Valuation

    OpenAIRE

    Jakubenko Alena Anatol'evna

    2014-01-01

    The article deals with the impact of international diversification strategy on the corporate valuation. It describes theory basis that can explain the sources for value added in companies that use diversification strategy. The article gives also the comprehensive view on the methodology of evaluation of international diversification influence on the corporate value and comparative analysis of inconsistent empirical results of different researches concerning the nature of key relationships’ be...

  17. Diversification and Corporate Performance: An Evaluation of Chinese Enterprises

    OpenAIRE

    Lou, Dannilou

    2013-01-01

    ABSTRACT This study conducts the relationship between diversification and corporate performance in the People’s Republic of China (PRC)’s business environment. Diversification continues to be an important strategy for corporate growth and better performance. Most of the previous studies on the same topic are reviewed in developed economies, they addresses a negative relationship between diversification and corporate performance. The objective of this study is to investigate the diversifi...

  18. DOES FIRM DIVERSIFICATION REPRESENT A VALUE ADDED FOR STOCKHOLDERS?

    OpenAIRE

    Juan Otero-Serrano

    2011-01-01

    This study empirically tests the effect of diversification on firm performance, controlling for factors influencing returns other than diversification. This study also investigates if the diversification effect has the same impact on firm performance at different points in time. The sample used consists of all firms with available data from Compustat Industry Segment Database and Research Files for the period between 1979 and 2006. Carhart (1997) four-factor model results suggest that diversi...

  19. Darwinism for the Genomic Age: Connecting Mutation to Diversification

    OpenAIRE

    Hua, Xia; Bromham, Lindell

    2017-01-01

    A growing body of evidence suggests that rates of diversification of biological lineages are correlated with differences in genome-wide mutation rate. Given that most research into differential patterns of diversification rate have focused on species traits or ecological parameters, a connection to the biochemical processes of genome change is an unexpected observation. While the empirical evidence for a significant association between mutation rate and diversification rate is mounting, there...

  20. Portfolio Diversification in the South-East European Equity Markets

    OpenAIRE

    Zaimovic Azra; Arnaut-Berilo Almira; Mustafic Arnela

    2017-01-01

    Diversification potential enables investors to manage their risk and decrease risk exposure. Good diversification policy is a safety net that prevents a portfolio from losing its value. A well-diversified portfolio consists of different categories of property with low correlations, while highly correlated markets have the feature of low possibilities for diversification. The biggest riddle in the world of investments is to find the optimal portfolio within a set of available assets with limit...

  1. Bats, clocks, and rocks: diversification patterns in Chiroptera.

    Science.gov (United States)

    Jones, Kate E; Bininda-Emonds, Olaf R P; Gittleman, John L

    2005-10-01

    Identifying nonrandom clade diversification is a critical first step toward understanding the evolutionary processes underlying any radiation and how best to preserve future phylogenetic diversity. However, differences in diversification rates have not been quantitatively assessed for the majority of groups because of the lack of necessary analytical tools (e.g., complete species-level phylogenies, estimates of divergence times, and robust statistics which incorporate phylogenetic uncertainty and test appropriate null models of clade growth). Here, for the first time, we investigate diversification rate heterogeneity in one of the largest groups studied thus far, the bats (Mammalia: Chiroptera). We use a recent, robust statistical approach (whole-tree likelihood-based relative rate tests) on complete dated species-level supertree phylogenies. As has been demonstrated previously for most other groups, among-lineage diversification rate within bats has not been constant. However, we show that bat diversification is more heterogeneous than in other mammalian clades thus far studied. The whole-tree likelihood-based relative rates tests suggest that clades within the families Phyllostomidae and Molossidae underwent a number of significant changes in relative diversification rate. There is also some evidence for rate shifts within Pteropodidae, Emballonuridae, Rhinolophidae, Hipposideridae, and Vespertilionidae, but the significance of these shifts depends on polytomy resolution within each family. Diversification rate in bats has also not been constant, with the largest diversification rate shifts occurring 30-50 million years ago, a time overlapping with the greatest number of shifts in flowering plant diversification rates.

  2. Corporate Diversification and Firm Performance: Evidence from Asian Hotel Industry

    Directory of Open Access Journals (Sweden)

    Ooi Chai-Aun

    2014-01-01

    Full Text Available The unstable environment of hotel industry which is driven by the fluctuation of tourism demand has motivated this study to look into the best diversification strategy for firm performance betterment. 42 hotel firms are investigated across 4 Asian economies, from year 2001 to 2012. Our results suggest that unrelated industrial diversification is the only alternative to improve hotel firm performance. Unrelated international diversification instead has a significant negative effect towards firm performance. Our results further show that board of directors implies a significant link to the relationship between diversification and firm performance, only in a crisis period.

  3. Motives and chances of firm diversification: theory and empirical evidence

    International Nuclear Information System (INIS)

    Briglauer, W.

    2001-11-01

    It is beyond controversy that the majority of the largest companies in the industrialized countries perform to a certain extent product diversification strategies. Tying up to this finding the underlying work firstly deals with alternative theoretical and empirical definitions of corporate diversification. Subsequently the theoretical part mainly elaborates an industrial economic framework for categorizing motives of firm diversification. Despite of some inevitable degree of arbitrariness, a relatively widespread and sufficient categorization can be presented. With regards to the relevant economic literature most explanations of product diversification can be classified appropriately. Observing diversification activities one would prima facie infer a positive relationship between product diversification and firm performance, but both, theory and empirical evidence, yield ambiguous results. The empirical part provides a list of existing studies, classified according to the theoretical categorization. In an overview some stylised facts are filtered and discussed consecutively. Most notably, it was found that related diversification strategies significantly outperform strategies of unrelated diversification. At the end of the empirical section econometric methods are applied to agricultural and industrial economic (relating to telecommunication markets) data sets. For the agricultural studies a significantly positive relationship between product diversification and firm performance was found. In contrast no significant results were obtained for the telecommunication markets. (author)

  4. Testing the Relationships between Diversification, Species Richness, and Trait Evolution.

    Science.gov (United States)

    Kozak, Kenneth H; Wiens, John J

    2016-11-01

    Understanding which traits drive species diversification is essential for macroevolutionary studies and to understand patterns of species richness among clades. An important tool for testing if traits influence diversification is to estimate rates of net diversification for each clade, and then test for a relationship between traits and diversification rates among clades. However, this general approach has become very controversial. Numerous papers have now stated that it is inappropriate to analyze net diversification rates in groups in which clade richness is not positively correlated with clade age. Similarly, some have stated that variation in net diversification rates does not explain variation in species richness patterns among clades across the Tree of Life. Some authors have also suggested that strong correlations between richness and diversification rates are a statistical artifact and effectively inevitable. If this latter point is true, then correlations between richness and diversification rates would be uninformative (or even misleading) for identifying how much variation in species richness among clades is explained by variation in net diversification rates. Here, we use simulations (based on empirical data for plethodontid salamanders) to address three main questions. First, how is variation in net diversification rates among clades related to the relationship between clade age and species richness? Second, how accurate are these net diversification rate estimators, and does the age-richness relationship have any relevance to their accuracy? Third, is a relationship between species richness and diversification rates an inevitable, statistical artifact? Our simulations show that strong, positive age-richness relationships arise when diversification rates are invariant among clades, whereas realistic variation in diversification rates among clades frequently disrupts this relationship. Thus, a significant age-richness relationship should not be a

  5. Genetic diversification of chemokine CXCL16 and its receptor CXCR6 in primates.

    Science.gov (United States)

    Xu, Feifei; He, Dan; Liu, Jiabin; Ni, Qingyong; Lyu, Yongqing; Xiong, Shiqiu; Li, Yan

    2018-08-01

    Chemokine CXCL16 and its receptor CXCR6 are associated with a series of physiological and pathological processes in cooperative and stand-alone fashions. To shed insight into their versatile nature, we studied genetic variations of CXCL16 and CXCR6 in primates. Evolutionary analyses revealed that these genes underwent a similar evolutionary fate. Both genes experienced adaptive diversification with the phylogenetic division of cercopithecoids (Old World monkeys) and hominoids (humans, great apes, and gibbons) from their common ancestor. In contrast, they were conserved in the periods preceding and following the dividing process. In terms of the adaptive diversification between cercopithecoids and hominoids, the adaptive genetic changes have occurred in the mucin-like and chemokine domains of CXCL16 and the N-terminus and transmembrane helixes of CXCR6. In combination with currently available structural and functional information for CXCL16 and CXCR6, the parallels between the evolutionary footprints and the co-occurrence of adaptive diversification at some evolutionary stage suggest that interplay could exist between the diversification-related amino acid sites, or between the domains on which the identified sites are located, in physiological processes such as chemotaxis and/or cell adhesion. Copyright © 2018 Elsevier Ltd. All rights reserved.

  6. Interspecific geographic range size-body size relationship and the diversification dynamics of Neotropical furnariid birds.

    Science.gov (United States)

    Inostroza-Michael, Oscar; Hernández, Cristián E; Rodríguez-Serrano, Enrique; Avaria-Llautureo, Jorge; Rivadeneira, Marcelo M

    2018-05-01

    Among the earliest macroecological patterns documented, is the range and body size relationship, characterized by a minimum geographic range size imposed by the species' body size. This boundary for the geographic range size increases linearly with body size and has been proposed to have implications in lineages evolution and conservation. Nevertheless, the macroevolutionary processes involved in the origin of this boundary and its consequences on lineage diversification have been poorly explored. We evaluate the macroevolutionary consequences of the difference (hereafter the distance) between the observed and the minimum range sizes required by the species' body size, to untangle its role on the diversification of a Neotropical species-rich bird clade using trait-dependent diversification models. We show that speciation rate is a positive hump-shaped function of the distance to the lower boundary. The species with highest and lowest distances to minimum range size had lower speciation rates, while species close to medium distances values had the highest speciation rates. Further, our results suggest that the distance to the minimum range size is a macroevolutionary constraint that affects the diversification process responsible for the origin of this macroecological pattern in a more complex way than previously envisioned. © 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.

  7. Diversification rates indicate an early role of adaptive radiations at the origin of modern echinoid fauna.

    Directory of Open Access Journals (Sweden)

    Simon Boivin

    Full Text Available Evolutionary radiations are fascinating phenomena corresponding to a dramatic diversification of taxa and a burst of cladogenesis over short periods of time. Most evolutionary radiations have long been regarded as adaptive but this has seldom been demonstrated with large-scale comparative datasets including fossil data. Originating in the Early Jurassic, irregular echinoids are emblematic of the spectacular diversification of mobile marine faunas during the Mesozoic Marine Revolution. They diversified as they colonized various habitats, and now constitute the main component of echinoid fauna in modern seas. The evolutionary radiation of irregular echinoids has long been considered as adaptive but this hypothesis has never been tested. In the present work we analyze the evolution of echinoid species richness and morphological disparity over 37 million years based on an extensive fossil dataset. Our results demonstrate that morphological and functional diversifications in certain clades of irregular echinoids were exceptionally high compared to other clades and that they were associated with the evolution of new modes of life and so can be defined as adaptive radiations. The role played by ecological opportunities in the diversification of these clades was critical, with the evolution of the infaunal mode of life promoting the adaptive radiation of irregular echinoids.

  8. Biogenetically inspired synthesis and skeletal diversification of indole alkaloids.

    Science.gov (United States)

    Mizoguchi, Haruki; Oikawa, Hideaki; Oguri, Hiroki

    2014-01-01

    To access architecturally complex natural products, chemists usually devise a customized synthetic strategy for constructing a single target skeleton. In contrast, biosynthetic assembly lines often employ divergent intramolecular cyclizations of a polyunsaturated common intermediate to produce diverse arrays of scaffolds. With the aim of integrating such biogenetic strategies, we show the development of an artificial divergent assembly line generating unprecedented numbers of scaffold variations of terpenoid indole alkaloids. This approach not only allows practical access to multipotent intermediates, but also enables systematic diversification of skeletal, stereochemical and functional group properties without structural simplification of naturally occurring alkaloids. Three distinct modes of [4+2] cyclizations and two types of redox-mediated annulations provided divergent access to five skeletally distinct scaffolds involving iboga-, aspidosperma-, andranginine- and ngouniensine-type skeletons and a non-natural variant within six to nine steps from tryptamine. The efficiency of our approach was demonstrated by successful total syntheses of (±)-vincadifformine, (±)-andranginine and (-)-catharanthine.

  9. Genomic diversification of giant enteric symbionts reflects host dietary lifestyles

    KAUST Repository

    Ngugi, David

    2017-08-24

    Herbivorous surgeonfishes are an ecologically successful group of reef fish that rely on marine algae as their principal food source. Here, we elucidated the significance of giant enteric symbionts colonizing these fishes regarding their roles in the digestive processes of hosts feeding predominantly on polysiphonous red algae and brown Turbinaria algae, which contain different polysaccharide constituents. Using metagenomics, single-cell genomics, and metatranscriptomic analyses, we provide evidence of metabolic diversification of enteric microbiota involved in the degradation of algal biomass in these fishes. The enteric microbiota is also phylogenetically and functionally simple relative to the complex lignocellulose-degrading microbiota of terrestrial herbivores. Over 90% of the enzymes for deconstructing algal polysaccharides emanate from members of a single bacterial lineage,

  10. Scale and technological factors in the diversification structure of business firms

    NARCIS (Netherlands)

    Castaldi, C; Milakovic, M; Secchi, A

    We present empirical evidence on diversification patterns in Italian manufacturing firms, where we observe a robust relationship between firm size and diversification levels. The overall findings support the 'resource-' and 'competence-based' theories of corporate diversification. In addition, we

  11. JAK/Stat signaling regulates heart precursor diversification in Drosophila

    Science.gov (United States)

    Johnson, Aaron N.; Mokalled, Mayssa H.; Haden, Tom N.; Olson, Eric N.

    2011-01-01

    Intercellular signal transduction pathways regulate the NK-2 family of transcription factors in a conserved gene regulatory network that directs cardiogenesis in both flies and mammals. The Drosophila NK-2 protein Tinman (Tin) was recently shown to regulate Stat92E, the Janus kinase (JAK) and Signal transducer and activator of transcription (Stat) pathway effector, in the developing mesoderm. To understand whether the JAK/Stat pathway also regulates cardiogenesis, we performed a systematic characterization of JAK/Stat signaling during mesoderm development. Drosophila embryos with mutations in the JAK/Stat ligand upd or in Stat92E have non-functional hearts with luminal defects and inappropriate cell aggregations. Using strong Stat92E loss-of-function alleles, we show that the JAK/Stat pathway regulates tin expression prior to heart precursor cell diversification. tin expression can be subdivided into four phases and, in Stat92E mutant embryos, the broad phase 2 expression pattern in the dorsal mesoderm does not restrict to the constrained phase 3 pattern. These embryos also have an expanded pericardial cell domain. We show the E(spl)-C gene HLHm5 is expressed in a pattern complementary to tin during phase 3 and that this expression is JAK/Stat dependent. In addition, E(spl)-C mutant embryos phenocopy the cardiac defects of Stat92E embryos. Mechanistically, JAK/Stat signals activate E(spl)-C genes to restrict Tin expression and the subsequent expression of the T-box transcription factor H15 to direct heart precursor diversification. This study is the first to characterize a role for the JAK/Stat pathway during cardiogenesis and identifies an autoregulatory circuit in which tin limits its own expression domain. PMID:21965617

  12. 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

  13. Recurrent, Robust and Scalable Patterns Underlie Human Approach and Avoidance

    Science.gov (United States)

    Kennedy, David N.; Lehár, Joseph; Lee, Myung Joo; Blood, Anne J.; Lee, Sang; Perlis, Roy H.; Smoller, Jordan W.; Morris, Robert; Fava, Maurizio

    2010-01-01

    Background Approach and avoidance behavior provide a means for assessing the rewarding or aversive value of stimuli, and can be quantified by a keypress procedure whereby subjects work to increase (approach), decrease (avoid), or do nothing about time of exposure to a rewarding/aversive stimulus. To investigate whether approach/avoidance behavior might be governed by quantitative principles that meet engineering criteria for lawfulness and that encode known features of reward/aversion function, we evaluated whether keypress responses toward pictures with potential motivational value produced any regular patterns, such as a trade-off between approach and avoidance, or recurrent lawful patterns as observed with prospect theory. Methodology/Principal Findings Three sets of experiments employed this task with beautiful face images, a standardized set of affective photographs, and pictures of food during controlled states of hunger and satiety. An iterative modeling approach to data identified multiple law-like patterns, based on variables grounded in the individual. These patterns were consistent across stimulus types, robust to noise, describable by a simple power law, and scalable between individuals and groups. Patterns included: (i) a preference trade-off counterbalancing approach and avoidance, (ii) a value function linking preference intensity to uncertainty about preference, and (iii) a saturation function linking preference intensity to its standard deviation, thereby setting limits to both. Conclusions/Significance These law-like patterns were compatible with critical features of prospect theory, the matching law, and alliesthesia. Furthermore, they appeared consistent with both mean-variance and expected utility approaches to the assessment of risk. Ordering of responses across categories of stimuli demonstrated three properties thought to be relevant for preference-based choice, suggesting these patterns might be grouped together as a relative preference

  14. Recurrent, robust and scalable patterns underlie human approach and avoidance.

    Directory of Open Access Journals (Sweden)

    Byoung Woo Kim

    2010-05-01

    Full Text Available Approach and avoidance behavior provide a means for assessing the rewarding or aversive value of stimuli, and can be quantified by a keypress procedure whereby subjects work to increase (approach, decrease (avoid, or do nothing about time of exposure to a rewarding/aversive stimulus. To investigate whether approach/avoidance behavior might be governed by quantitative principles that meet engineering criteria for lawfulness and that encode known features of reward/aversion function, we evaluated whether keypress responses toward pictures with potential motivational value produced any regular patterns, such as a trade-off between approach and avoidance, or recurrent lawful patterns as observed with prospect theory.Three sets of experiments employed this task with beautiful face images, a standardized set of affective photographs, and pictures of food during controlled states of hunger and satiety. An iterative modeling approach to data identified multiple law-like patterns, based on variables grounded in the individual. These patterns were consistent across stimulus types, robust to noise, describable by a simple power law, and scalable between individuals and groups. Patterns included: (i a preference trade-off counterbalancing approach and avoidance, (ii a value function linking preference intensity to uncertainty about preference, and (iii a saturation function linking preference intensity to its standard deviation, thereby setting limits to both.These law-like patterns were compatible with critical features of prospect theory, the matching law, and alliesthesia. Furthermore, they appeared consistent with both mean-variance and expected utility approaches to the assessment of risk. Ordering of responses across categories of stimuli demonstrated three properties thought to be relevant for preference-based choice, suggesting these patterns might be grouped together as a relative preference theory. Since variables in these patterns have been

  15. Eurisys: chemistry and petroleum as diversification centers

    International Nuclear Information System (INIS)

    Anon.

    1996-01-01

    The Eurisys Network has followed in 1995 its strategy of diversification and extended its engineering and servicing activities outside the nuclear domain towards other sectors such as the hydrocarbons sector. This development led to a 26% turnover increase (4.7 billions of French Francs (GF) in 1996 with respect to 3.8 GF in 1994) and a net result of 204 millions of Francs for the group. This short paper summarises the new servicing activities and contracts of the group in the petrochemistry, chemistry, petroleum and natural gas domain. (J.S.)

  16. Corporate Diversification, Firm Value and State Ownership in Chinese Publicly Listed Companies

    OpenAIRE

    Liu, Yang

    2015-01-01

    Corporate diversification has long been a focused and deeply developed field, defined as the process of a company expand its business into different areas. There are mainly three different types of corporate diversification: product diversification (related or unrelated) and geographic market diversification (home market or international market). Our research is concentrated on the first form of diversification. In addition, the relationship between corporate diversification and firm valu...

  17. Result Diversification Based on Query-Specific Cluster Ranking

    NARCIS (Netherlands)

    J. He (Jiyin); E. Meij; M. de Rijke (Maarten)

    2011-01-01

    htmlabstractResult diversification is a retrieval strategy for dealing with ambiguous or multi-faceted queries by providing documents that cover as many facets of the query as possible. We propose a result diversification framework based on query-specific clustering and cluster ranking,

  18. Factor decomposition and diversification in european corporate bond markets

    NARCIS (Netherlands)

    Pieterse-Bloem, M.; Mahieu, R.J.

    2013-01-01

    In this paper we present an analysis of diversification strategies on portfolios of European corporate bonds. From the perspective of a US-based investor we study whether mean–variance diversification strategies change as a result of the introduction of the European Economic and Monetary Union

  19. Investment characteristics, stock characteristics and portfolio diversification of finance professionals

    OpenAIRE

    Mohammad Tariqul Islam Khan; Siow-Hooi Tan; Lee-Lee Chong; Hway-Boon Ong

    2017-01-01

    This study estimates if Malaysian finance professionals' investment characteristics and stock characteristics' preferences affect their portfolio diversification, and whether the effects of these predictors vary across professionals' gender, income and experience. Employing a survey and ordinal regression models, the findings demonstrate that investment characteristics such as active trading, usage of internet and telephone, and saving for retirement objective are likely to improve diversific...

  20. Factor decomposition and diversification in European corporate bond markets

    NARCIS (Netherlands)

    Pieterse-Bloem, M.; Mahieu, R.J.

    2013-01-01

    In this paper we present an analysis of diversification strategies on portfolios of European corporate bonds. From the perspective of a US-based investor we study whether mean–variance diversification strategies change as a result of the introduction of the European Economic and Monetary Union

  1. Botswana: A Note on Economic Diversification | Sekwati | Botswana ...

    African Journals Online (AJOL)

    Despite a series of supportive policies over the years, economic diversification remains an obscurity for Botswana. The economy remains heavily dependent on diamond mining, while the private sector, considered pivotal in the strategy for diversification, continues to be shallow and narrow, with weak inter sectoral diversity ...

  2. Relatedness as driver of regional diversification : a research agenda

    NARCIS (Netherlands)

    Boschma, Ron

    2017-01-01

    Relatedness as driver of regional diversification: a research agenda. Regional Studies. The regional diversification literature claims that regions diversify in new activities related to their existing activities from which new activities draw on and combine local capabilities. The paper offers a

  3. Funding Reforms and Revenue Diversification--Patterns, Challenges and Rhetoric

    Science.gov (United States)

    Teixeira, Pedro; Koryakina, Tatyana

    2013-01-01

    In recent years, much has been written about the challenging financial context faced by many European higher education institutions, and the pressures towards funding diversification. However, the evidence available indicates that funding diversification has seldom lived up to the rhetorical expectations of marketization and privatization that…

  4. Diversification Management at Tertiary Education Level: A Review

    Science.gov (United States)

    Takwate, Kwaji Tizhe

    2016-01-01

    This paper examines the concept of management of diversification at tertiary education level in view of the growth of national secondary education system which vested high scramble for tertiary education was made in relation to question of access and expansion. This paper examines management of diversification at tertiary education level as a…

  5. Irrational Diversification; An Examination of Individual Portfolio Choice

    NARCIS (Netherlands)

    2011-01-01

    textabstractWe study individual portfolio choice in a laboratory experiment and find strong evidence for heuristic behavior. The subjects tend to focus on the marginal distribution of an asset, while largely ignoring its diversification benefits. They follow a conditional 1/n diversification

  6. Vertical integration and diversification of acute care hospitals: conceptual definitions.

    Science.gov (United States)

    Clement, J P

    1988-01-01

    The terms vertical integration and diversification, although used quite frequently, are ill-defined for use in the health care field. In this article, the concepts are defined--specifically for nonuniversity acute care hospitals. The resulting definitions are more useful than previous ones for predicting the effects of vertical integration and diversification.

  7. Effects of Diversification of Assets on Mean and Variance | Jayeola ...

    African Journals Online (AJOL)

    Diversification is a means of minimizing risk and maximizing returns by investing in a variety of assets of the portfolio. This paper is written to determine the effects of diversification of three types of Assets; uncorrelated, perfectly correlated and perfectly negatively correlated assets on mean and variance. To go about this, ...

  8. The Socioeconomic Basis of Farm Enterprise Diversification Decisions.

    Science.gov (United States)

    Anosike, Nnamdi; Coughenour, C. Milton

    1990-01-01

    Examines research relating farm size inversely to specialization and directly to farm-enterprise diversification. Develops model of farm management decision making. Tests model using survey examining land tenure, off-farm work, education, and environmental factors. Concludes diversification linked to farm size, human capital, and environmental…

  9. Place of Manufacture Diversification in Cyclical Development of the Enterprise

    Science.gov (United States)

    Erofeev, Alexander G.; Smolin, Georgy K.

    2016-01-01

    The relevance of the researched problem is caused by the fact that diversification is one of the best options for reforming enterprises. The aim of the research: to consider changes in production of outputs in development cycles of the enterprise. This will help to reveal the nature of manufacture diversification. The leading method to the…

  10. Antipredator behavior promotes diversification of feeding strategies.

    Science.gov (United States)

    Ledón-Rettig, Cris C; Pfennig, David W

    2012-07-01

    Animals often facultatively engage in less risky behavior when predators are present. Few studies, however, have investigated whether, or how, such predator-mediated behavior promotes diversification. Here, we ask whether tadpoles of the spadefoot toad Scaphiopus couchii have a diminished ability to utilize a potentially valuable resource--anostracan fairy shrimp--because of behavioral responses to predation risk imposed by carnivorous tadpoles of the genus Spea. Observations of a congener of Sc. couchii that occurs in allopatry with Spea, coupled with an ancestral character state reconstruction, revealed that Sc. couchii's ancestors likely consumed shrimp. By experimentally manipulating the presence of Spea carnivore-morph tadpoles in microcosms, we found that Sc. couchii reduce feeding and avoid areas where both Spea carnivores and shrimp occur. We hypothesize that the recurrent expression of such behaviors in sympatric populations of Sc. couchii led to the evolutionary fixation of a detritivorous feeding strategy, which is associated with a reduced risk of predation from Spea carnivores. Generally, predator-mediated behavior might play a key role in promoting diversification of feeding strategies.

  11. The Trend of International Risk Diversification

    Directory of Open Access Journals (Sweden)

    Oana Mionel

    2013-10-01

    Full Text Available The goal of this paper is to analyze the international diversification of risk through portfolio diversification based on investments abroad, particularly by investing in currencies of emerging countries. The starting point of the analysis is the work of Harry Markowitz, Portfolio selection, a reference work for the global financial environment in which the author states that a portfolio is efficient if it provides the highest possible expected return for a given level of risk and the lowest possible level of risk for any expected rate of earnings. The information used for this study comes from numerous sources and of great importance to international financial markets. The results based on the used data and information provide a comprehensive scan of how Federal Reserve proposed a clustered index of currencies, the current trend of exchange, the emerging BRIC countries scenario for 2050 and sources of the volatile emerging markets. Thus, following the completion of this work, we consider it necessary to pay attention to the course of emerging markets whose economic development and openness plays a significant role in their penetration of international investors’ investment plan.

  12. Diversification of the Economy: Institutional Aspects

    Directory of Open Access Journals (Sweden)

    Nataliya Al. Kravchenko

    2017-12-01

    Full Text Available Institutional conditions are significant factors influencing motivation, behavior and performance results of different economic agents, which, in turn, determine directions and dynamics of structural shifts in the economy. There is a wide range of research on influence of various formal and informal institutions on processes of structural dynamics and diversification of economic activity through innovations in particular. We have carried out in-depth analysis of scientific publications on institutional impact at the level of the country as a whole and regions within countries, comparisons of different countries on the impact of institutional factors on production and technological diversification and their connection to economic development. As the main conceptual approaches, we emphasize evolutionary economics, theory of agglomeration economics and new economic geography. Based on the analysis we draw a conclusion, important for Russian economy, about priority directions of changing spatial and product specialization concerning resource regions of Russia. In conclusion of the article perspective directions for the future research on mutual influence of institutions and changes of production and technological structure, which are vital for Russian economy and its regions, are formulated.

  13. Fruit evolution and diversification in campanulid angiosperms.

    Science.gov (United States)

    Beaulieu, Jeremy M; Donoghue, Michael J

    2013-11-01

    With increases in both the size and scope of phylogenetic trees, we are afforded a renewed opportunity to address long-standing comparative questions, such as whether particular fruit characters account for much of the variation in diversity among flowering plant clades. Studies to date have reported conflicting results, largely as a consequence of taxonomic scale and a reliance on potentially conservative statistical measures. Here we examine a larger and older angiosperm clade, the Campanulidae, and infer the rates of character transitions among the major fruit types, emphasizing the evolution of the achene fruits that are most frequently observed within the group. Our analyses imply that campanulids likely originated bearing capsules, and that all subsequent fruit diversity was derived from various modifications of this dry fruit type. We also found that the preponderance of lineages bearing achenes is a consequence of not only being a fruit type that is somewhat irreversible once it evolves, but one that also seems to have a positive association with diversification rates. Although these results imply the achene fruit type is a significant correlate of diversity patterns observed across campanulids, we conclude that it remains difficult to confidently and directly view this character state as the actual cause of increased diversification rates. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

  14. Plant feeding promotes diversification in the Crustacea.

    Science.gov (United States)

    Poore, Alistair G B; Ahyong, Shane T; Lowry, James K; Sotka, Erik E

    2017-08-15

    About half of the world's animal species are arthropods associated with plants, and the ability to consume plant material has been proposed to be an important trait associated with the spectacular diversification of terrestrial insects. We review the phylogenetic distribution of plant feeding in the Crustacea, the other major group of arthropods that commonly consume plants, to estimate how often plant feeding has arisen and to test whether this dietary transition is associated with higher species numbers in extant clades. We present evidence that at least 31 lineages of marine, freshwater, and terrestrial crustaceans (including 64 families and 185 genera) have independently overcome the challenges of consuming plant material. These plant-feeding clades are, on average, 21-fold more speciose than their sister taxa, indicating that a shift in diet is associated with increased net rates of diversification. In contrast to herbivorous insects, most crustaceans have very broad diets, and the increased richness of taxa that include plants in their diet likely results from access to a novel resource base rather than host-associated divergence.

  15. Rational temporal predictions can underlie apparent failures to delay gratification

    Science.gov (United States)

    McGuire, Joseph T.; Kable, Joseph W.

    2013-01-01

    An important category of seemingly maladaptive decisions involves failure to postpone gratification. A person pursuing a desirable long-run outcome may abandon it in favor of a short-run alternative that has been available all along. Here we present a theoretical framework in which this seemingly irrational behavior emerges from stable preferences and veridical judgments. Our account recognizes that decision makers generally face uncertainty regarding the time at which future outcomes will materialize. When timing is uncertain, the value of persistence depends crucially on the nature of a decision-maker’s prior temporal beliefs. Certain forms of temporal beliefs imply that a delay’s predicted remaining length increases as a function of time already waited. In this type of situation, the rational, utility-maximizing strategy is to persist for a limited amount of time and then give up. We show empirically that people’s explicit predictions of remaining delay lengths indeed increase as a function of elapsed time in several relevant domains, implying that temporal judgments offer a rational basis for limiting persistence. We then develop our framework into a simple working model and show how it accounts for individual differences in a laboratory task (the well-known “marshmallow test”). We conclude that delay-of-gratification failure, generally viewed as a manifestation of limited self-control capacity, can instead arise as an adaptive response to the perceived statistics of one’s environment. PMID:23458085

  16. Interregional synaptic maps among engram cells underlie memory formation.

    Science.gov (United States)

    Choi, Jun-Hyeok; Sim, Su-Eon; Kim, Ji-Il; Choi, Dong Il; Oh, Jihae; Ye, Sanghyun; Lee, Jaehyun; Kim, TaeHyun; Ko, Hyoung-Gon; Lim, Chae-Seok; Kaang, Bong-Kiun

    2018-04-27

    Memory resides in engram cells distributed across the brain. However, the site-specific substrate within these engram cells remains theoretical, even though it is generally accepted that synaptic plasticity encodes memories. We developed the dual-eGRASP (green fluorescent protein reconstitution across synaptic partners) technique to examine synapses between engram cells to identify the specific neuronal site for memory storage. We found an increased number and size of spines on CA1 engram cells receiving input from CA3 engram cells. In contextual fear conditioning, this enhanced connectivity between engram cells encoded memory strength. CA3 engram to CA1 engram projections strongly occluded long-term potentiation. These results indicate that enhanced structural and functional connectivity between engram cells across two directly connected brain regions forms the synaptic correlate for memory formation. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  17. Corporate Diversification and Firm Performance: an Empirical Study

    Directory of Open Access Journals (Sweden)

    Olu Ojo

    2009-05-01

    Full Text Available The importance of diversification and performance in then strategic management literature is widely accepted among academics and practitioners . However, the proxies for performance and diversification that have been employed in past strategy research has not been unanimously agreed upon. Given the current state of confusion that exists with regard to the impact of corporate diversification on firm performance in selected Nigerian companies. The reason for increased interest in diversification has always been on the possibility that diversification is related to corporate performance. However , while this topic is rich in studies, empirical evidence semerging from various studies about the effect of diversification on performance have so far yield mixed results that are inconclusive and contradictory. In addition , despite the existence of these studies, very litlle attention has been given to the companies in developing countries including Nigeria. This means that there is a major gap in the relevant literature on developing countries which has to be covered by research. This research attempts to fill this gap by studying the situation of the Nigeria companies and providing more empirical evidence on the effects of corporate diversification on firm performance based on individual company-level data. Survey research design was adopted in this study with the application of simple random sampling tehnique in selecting our case study companies as well as our respondents. Primary data were collected through questionnaire. Data were analysed through descriptive statistics and correlation and coefficient of determination were used to test our hypothese. It was discovered that diversification impacted performance of these companies posivitely and we recommend that these companies should engage in geographical diversification in addition to other forms of diversification they are currently involved in for maximum performance.

  18. Impaired Mitochondrial Dynamics Underlie Axonal Defects in Hereditary Spastic Paraplegias.

    Science.gov (United States)

    Denton, Kyle; Mou, Yongchao; Xu, Chong-Chong; Shah, Dhruvi; Chang, Jaerak; Blackstone, Craig; Li, Xue-Jun

    2018-05-02

    Mechanisms by which long corticospinal axons degenerate in hereditary spastic paraplegia (HSP) are largely unknown. Here, we have generated induced pluripotent stem cells (iPSCs) from patients with two autosomal recessive forms of HSP, SPG15 and SPG48, which are caused by mutations in the ZFYVE26 and AP5Z1 genes encoding proteins in the same complex, the spastizin and AP5Z1 proteins, respectively. In patient iPSC-derived telencephalic glutamatergic and midbrain dopaminergic neurons, neurite number, length and branching are significantly reduced, recapitulating disease-specific phenotypes. We analyzed mitochondrial morphology and noted a significant reduction in both mitochondrial length and their densities within axons of these HSP neurons. Mitochondrial membrane potential was also decreased, confirming functional mitochondrial defects. Notably, mdivi-1, an inhibitor of the mitochondrial fission GTPase DRP1, rescues mitochondrial morphology defects and suppresses the impairment in neurite outgrowth and late-onset apoptosis in HSP neurons. Furthermore, knockdown of these HSP genes causes similar axonal defects, also mitigated by treatment with mdivi-1. Finally, neurite outgrowth defects in SPG15 and SPG48 cortical neurons can be rescued by knocking down DRP1 directly. Thus, abnormal mitochondrial morphology caused by an imbalance of mitochondrial fission and fusion underlies specific axonal defects and serves as a potential therapeutic target for SPG15 and SPG48.

  19. Breakdown of local information processing may underlie isoflurane anesthesia effects.

    Science.gov (United States)

    Wollstadt, Patricia; Sellers, Kristin K; Rudelt, Lucas; Priesemann, Viola; Hutt, Axel; Fröhlich, Flavio; Wibral, Michael

    2017-06-01

    The disruption of coupling between brain areas has been suggested as the mechanism underlying loss of consciousness in anesthesia. This hypothesis has been tested previously by measuring the information transfer between brain areas, and by taking reduced information transfer as a proxy for decoupling. Yet, information transfer is a function of the amount of information available in the information source-such that transfer decreases even for unchanged coupling when less source information is available. Therefore, we reconsidered past interpretations of reduced information transfer as a sign of decoupling, and asked whether impaired local information processing leads to a loss of information transfer. An important prediction of this alternative hypothesis is that changes in locally available information (signal entropy) should be at least as pronounced as changes in information transfer. We tested this prediction by recording local field potentials in two ferrets after administration of isoflurane in concentrations of 0.0%, 0.5%, and 1.0%. We found strong decreases in the source entropy under isoflurane in area V1 and the prefrontal cortex (PFC)-as predicted by our alternative hypothesis. The decrease in source entropy was stronger in PFC compared to V1. Information transfer between V1 and PFC was reduced bidirectionally, but with a stronger decrease from PFC to V1. This links the stronger decrease in information transfer to the stronger decrease in source entropy-suggesting reduced source entropy reduces information transfer. This conclusion fits the observation that the synaptic targets of isoflurane are located in local cortical circuits rather than on the synapses formed by interareal axonal projections. Thus, changes in information transfer under isoflurane seem to be a consequence of changes in local processing more than of decoupling between brain areas. We suggest that source entropy changes must be considered whenever interpreting changes in information

  20. Different evolutionary pathways underlie the morphology of wrist bones in hominoids.

    Science.gov (United States)

    Kivell, Tracy L; Barros, Anna P; Smaers, Jeroen B

    2013-10-23

    The hominoid wrist has been a focus of numerous morphological analyses that aim to better understand long-standing questions about the evolution of human and hominoid hand use. However, these same analyses also suggest various scenarios of complex and mosaic patterns of morphological evolution within the wrist and potentially multiple instances of homoplasy that would benefit from require formal analysis within a phylogenetic context.We identify morphological features that principally characterize primate - and, in particular, hominoid (apes, including humans) - wrist evolution and reveal the rate, process and evolutionary timing of patterns of morphological change on individual branches of the primate tree of life. Linear morphological variables of five wrist bones - the scaphoid, lunate, triquetrum, capitate and hamate - are analyzed in a diverse sample of extant hominoids (12 species, 332 specimens), Old World (8 species, 43 specimens) and New World (4 species, 26 specimens) monkeys, fossil Miocene apes (8 species, 20 specimens) and Plio-Pleistocene hominins (8 species, 18 specimens). Results reveal a combination of parallel and synapomorphic morphology within haplorrhines, and especially within hominoids, across individual wrist bones. Similar morphology of some wrist bones reflects locomotor behaviour shared between clades (scaphoid, triquetrum and capitate) while others (lunate and hamate) indicate clade-specific synapomorphic morphology. Overall, hominoids show increased variation in wrist bone morphology compared with other primate clades, supporting previous analyses, and demonstrate several occurrences of parallel evolution, particularly between orangutans and hylobatids, and among hominines (extant African apes, humans and fossil hominins). Our analyses indicate that different evolutionary processes can underlie the evolution of a single anatomical unit (the wrist) to produce diversity in functional and morphological adaptations across individual wrist

  1. If diversification is good, why don't countries diversify more? The political economy of diversification in resource-rich countries

    International Nuclear Information System (INIS)

    Wiig, Arne; Kolstad, Ivar

    2012-01-01

    For resource-rich countries, diversification is claimed to represent a strategy for reducing resource curse problems. This, however, depends on whether diversification has a positive effect on the country's institutions. While there is a lot of evidence that exports of oil have a negative impact on institutions, we know much less about the extent to which diversification leads to better institutions. This article applies recent political economy theory to the phenomenon of diversification. Theoretical arguments suggest that it is the pattern of industrial activity rather than diversification per se, which affects institutions like democracy. In other words, not all forms of diversification lead to better institutions. Furthermore, where diversification has a positive impact on institutions, diversification may be difficult to attain when it threatens the power base of the ruling elite. A possible implication of these arguments is that policies for diversification should focus on international regulation affecting elite incentives, rather than domestic industrial policy. - Highlights: ► Diversification can be a strategy for reducing resource curse problems in oil-rich countries. ► But this requires that diversification has a positive effect on the institutions of a country. ► It is the pattern of industrial activity rather than diversification per se, which affects institutions like democracy. ► Diversification may be difficult to attain when it threatens the power basis of the ruling elite. ► Policies for diversification should focus on international ruling affect elite incentives, rather than home industrial policy.

  2. EDF and GDF diversification; La diversification d'EDF et de GDF

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-11-08

    In the last years Electricite de France (EDF) and Gaz de France (GDF) developed intervening strategies in a number of sectors opened to competition, the so-called strategies of diversification or complementary activities. These new strategies have multiple objectives as, for instance, prospective monopole evolution, increasing exigence of the consumers' demand, or else competence valuing. Ever since 1991, these strategic orientations developed with the support of public powers that worked out first measures of organization and monitoring. Although the frame was loose and rather tolerant, boosting EDF and GDF diversification was perceived by the concerned professionals as an aggression directed against them. Following a strong mobilization of professional organizations and a number of elected persons, in mid 1993, the minister of industry was impelled to tackle personally with the matter what resulted in an accurate system of framing. The GDF diversification is essentially characterized by a 'thermal pole' corresponding to the activities of heating operation. GDF controls, around the company Danto Rogeat and the old branches of Shell group, about 5% of a market of heating operation in France, i.e., represents the third place in a rather monopolized sector where the two main operators represent almost 75%. The EDF diversification is but more diffuse. Three main fields emerge distinctly: the waste processing, public lighting, and engineering. EDF is also present on more restraint markets as cartography, tele-surveillance, cable TV, aquaculture. The implementation of the system is presented where prerogatives of the Council of State on one hand and the Council of Competition on the other hand are stipulated. The disposition frame system is constituted of two measures stipulating the application of commendation from the two councils and provisions ensuring the transparency, respectively.

  3. Is BAMM Flawed? Theoretical and Practical Concerns in the Analysis of Multi-Rate Diversification Models.

    Science.gov (United States)

    Rabosky, Daniel L; Mitchell, Jonathan S; Chang, Jonathan

    2017-07-01

    Bayesian analysis of macroevolutionary mixtures (BAMM) is a statistical framework that uses reversible jump Markov chain Monte Carlo to infer complex macroevolutionary dynamics of diversification and phenotypic evolution on phylogenetic trees. A recent article by Moore et al. (MEA) reported a number of theoretical and practical concerns with BAMM. Major claims from MEA are that (i) BAMM's likelihood function is incorrect, because it does not account for unobserved rate shifts; (ii) the posterior distribution on the number of rate shifts is overly sensitive to the prior; and (iii) diversification rate estimates from BAMM are unreliable. Here, we show that these and other conclusions from MEA are generally incorrect or unjustified. We first demonstrate that MEA's numerical assessment of the BAMM likelihood is compromised by their use of an invalid likelihood function. We then show that "unobserved rate shifts" appear to be irrelevant for biologically plausible parameterizations of the diversification process. We find that the purportedly extreme prior sensitivity reported by MEA cannot be replicated with standard usage of BAMM v2.5, or with any other version when conventional Bayesian model selection is performed. Finally, we demonstrate that BAMM performs very well at estimating diversification rate variation across the ${\\sim}$20% of simulated trees in MEA's data set for which it is theoretically possible to infer rate shifts with confidence. Due to ascertainment bias, the remaining 80% of their purportedly variable-rate phylogenies are statistically indistinguishable from those produced by a constant-rate birth-death process and were thus poorly suited for the summary statistics used in their performance assessment. We demonstrate that inferences about diversification rates have been accurate and consistent across all major previous releases of the BAMM software. We recognize an acute need to address the theoretical foundations of rate-shift models for

  4. Germline V repertoires: Origin, maintenance, diversification.

    Science.gov (United States)

    Steele, E J; Lindley, R A

    2018-06-01

    In our view, Melvin Cohn (Scand J Immunol. 2018;87:e12640) has set out the logical guidelines towards a resolution of the very real enigma of the selectability of vertebrate germline Ig V repertoires under the current evolutionary paradigm…" A somatically derived repertoire scrambles this (germline VL + VH) substrate so that its specificities are lost, making it un-selectable in the germline. Consequently, evolution faced an incompatibility." It is argued here in Reply that a reverse transcriptase-based soma-to-germline process (S->G) targeting germline V segment arrays goes some considerable way to resolving fundamental contradictions on the origin, maintenance and then real-time adaptive diversification of these limited sets of V segments encoded within various V repertoire arrays. © 2018 The Foundation for the Scandinavian Journal of Immunology.

  5. Ants sow the seeds of global diversification in flowering plants.

    Science.gov (United States)

    Lengyel, Szabolcs; Gove, Aaron D; Latimer, Andrew M; Majer, Jonathan D; Dunn, Robert R

    2009-01-01

    The extraordinary diversification of angiosperm plants in the Cretaceous and Tertiary periods has produced an estimated 250,000-300,000 living angiosperm species and has fundamentally altered terrestrial ecosystems. Interactions with animals as pollinators or seed dispersers have long been suspected as drivers of angiosperm diversification, yet empirical examples remain sparse or inconclusive. Seed dispersal by ants (myrmecochory) may drive diversification as it can reduce extinction by providing selective advantages to plants and can increase speciation by enhancing geographical isolation by extremely limited dispersal distances. Using the most comprehensive sister-group comparison to date, we tested the hypothesis that myrmecochory leads to higher diversification rates in angiosperm plants. As predicted, diversification rates were substantially higher in ant-dispersed plants than in their non-myrmecochorous relatives. Data from 101 angiosperm lineages in 241 genera from all continents except Antarctica revealed that ant-dispersed lineages contained on average more than twice as many species as did their non-myrmecochorous sister groups. Contrasts in species diversity between sister groups demonstrated that diversification rates did not depend on seed dispersal mode in the sister group and were higher in myrmecochorous lineages in most biogeographic regions. Myrmecochory, which has evolved independently at least 100 times in angiosperms and is estimated to be present in at least 77 families and 11 000 species, is a key evolutionary innovation and a globally important driver of plant diversity. Myrmecochory provides the best example to date for a consistent effect of any mutualism on large-scale diversification.

  6. Biological factors contributing to bark and ambrosia beetle species diversification.

    Science.gov (United States)

    Gohli, Jostein; Kirkendall, Lawrence R; Smith, Sarah M; Cognato, Anthony I; Hulcr, Jiri; Jordal, Bjarte H

    2017-05-01

    The study of species diversification can identify the processes that shape patterns of species richness across the tree of life. Here, we perform comparative analyses of species diversification using a large dataset of bark beetles. Three examined covariates-permanent inbreeding (sibling mating), fungus farming, and major host type-represent a range of factors that may be important for speciation. We studied the association of these covariates with species diversification while controlling for evolutionary lag on adaptation. All three covariates were significantly associated with diversification, but fungus farming showed conflicting patterns between different analyses. Genera that exhibited interspecific variation in host type had higher rates of species diversification, which may suggest that host switching is a driver of species diversification or that certain host types or forest compositions facilitate colonization and thus allopatric speciation. Because permanent inbreeding is thought to facilitate dispersal, the positive association between permanent inbreeding and diversification rates suggests that dispersal ability may contribute to species richness. Bark beetles are ecologically unique; however, our results indicate that their impressive species diversity is largely driven by mechanisms shown to be important for many organism groups. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  7. Diversification rates and species richness across the Tree of Life.

    Science.gov (United States)

    Scholl, Joshua P; Wiens, John J

    2016-09-14

    Species richness varies dramatically among clades across the Tree of Life, by over a million-fold in some cases (e.g. placozoans versus arthropods). Two major explanations for differences in richness among clades are the clade-age hypothesis (i.e. species-rich clades are older) and the diversification-rate hypothesis (i.e. species-rich clades diversify more rapidly, where diversification rate is the net balance of speciation and extinction over time). Here, we examine patterns of variation in diversification rates across the Tree of Life. We address how rates vary across higher taxa, whether rates within higher taxa are related to the subclades within them, and how diversification rates of clades are related to their species richness. We find substantial variation in diversification rates, with rates in plants nearly twice as high as in animals, and rates in some eukaryotes approximately 10-fold faster than prokaryotes. Rates for each kingdom-level clade are then significantly related to the subclades within them. Although caution is needed when interpreting relationships between diversification rates and richness, a positive relationship between the two is not inevitable. We find that variation in diversification rates seems to explain most variation in richness among clades across the Tree of Life, in contrast to the conclusions of previous studies. © 2016 The Author(s).

  8. Courting disaster: How diversification rate affects fitness under risk

    Science.gov (United States)

    Ratcliff, William C; Hawthorne, Peter; Libby, Eric

    2015-01-01

    Life is full of risk. To deal with this uncertainty, many organisms have evolved bet-hedging strategies that spread risk through phenotypic diversification. These rates of diversification can vary by orders of magnitude in different species. Here we examine how key characteristics of risk and organismal ecology affect the fitness consequences of variation in diversification rate. We find that rapid diversification is strongly favored when the risk faced has a wide spatial extent, with a single disaster affecting a large fraction of the population. This advantage is especially great in small populations subject to frequent disaster. In contrast, when risk is correlated through time, slow diversification is favored because it allows adaptive tracking of disasters that tend to occur in series. Naturally evolved diversification mechanisms in diverse organisms facing a broad array of environmental risks largely support these results. The theory presented in this article provides a testable ecological hypothesis to explain the prevalence of slow stochastic switching among microbes and rapid, within-clutch diversification strategies among plants and animals. PMID:25410817

  9. Diversification rates have declined in the Malagasy herpetofauna.

    Science.gov (United States)

    Scantlebury, Daniel P

    2013-09-07

    The evolutionary origins of Madagascar's biodiversity remain mysterious despite the fact that relative to land area, there is no other place with consistently high levels of species richness and endemism across a range of taxonomic levels. Most efforts to explain diversification on the island have focused on geographical models of speciation, but recent studies have begun to address the island's accumulation of species through time, although with conflicting results. Prevailing hypotheses for diversification on the island involve either constant diversification rates or scenarios where rates decline through time. Using relative-time-calibrated phylogenies for seven endemic vertebrate clades and a model-fitting framework, I find evidence that diversification rates have declined through time on Madagascar. I show that diversification rates have clearly declined throughout the history of each clade, and models invoking diversity-dependent reductions to diversification rates best explain the diversification histories for each clade. These results are consistent with the ecological theory of adaptive radiation, and, coupled with ancillary observations about ecomorphological and life-history evolution, strongly suggest that adaptive radiation was an important formative process for one of the most species-rich regions on the Earth. These results cast the Malagasy biota in a new light and provide macroevolutionary justification for conservation initiatives.

  10. Courting disaster: How diversification rate affects fitness under risk.

    Science.gov (United States)

    Ratcliff, William C; Hawthorne, Peter; Libby, Eric

    2015-01-01

    Life is full of risk. To deal with this uncertainty, many organisms have evolved bet-hedging strategies that spread risk through phenotypic diversification. These rates of diversification can vary by orders of magnitude in different species. Here we examine how key characteristics of risk and organismal ecology affect the fitness consequences of variation in diversification rate. We find that rapid diversification is strongly favored when the risk faced has a wide spatial extent, with a single disaster affecting a large fraction of the population. This advantage is especially great in small populations subject to frequent disaster. In contrast, when risk is correlated through time, slow diversification is favored because it allows adaptive tracking of disasters that tend to occur in series. Naturally evolved diversification mechanisms in diverse organisms facing a broad array of environmental risks largely support these results. The theory presented in this article provides a testable ecological hypothesis to explain the prevalence of slow stochastic switching among microbes and rapid, within-clutch diversification strategies among plants and animals. © 2014 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

  11. Diversification in Private Equity Funds : On Knowledge-sharing, Risk-aversion and Limited-attention

    NARCIS (Netherlands)

    Humphery-Jenner, M.

    2011-01-01

    This paper examines diversification as a source of value creation and destruction in private equity. The literature has focused on the `diversification discount' in corporations. It has not analyzed diversification in PE-funds, where diversification might increase value by ameliorating managerial

  12. Diversification patterns in the growth of firms : evidence from Italian manufacturing

    NARCIS (Netherlands)

    Castaldi, C.; Milakovic, M.; Secchi, A.

    2003-01-01

    We present empirical evidence on diversification patterns in Italian manufacturing firms and detect a robust relationship between firm size and diversification levels, with an elasticity of diversification that does not depend on firm size and is well below unity. Diversification does not lead to

  13. Impending Doom: The Loss of Diversification before a Crisis

    Directory of Open Access Journals (Sweden)

    Libin Yang

    2017-11-01

    Full Text Available We present four methods of assessing the diversification potential within a stock market, and two of these are based on principal component analysis. They were applied to the Australian stock exchange for the years 2000 to 2014 and all show a consistent picture. The potential for diversification declined almost monotonically in the three years prior to the 2008 financial crisis, leaving investors poorly diversified at the onset of the Global Financial Crisis. On one of the four measures, the diversification potential declined even further in the 2011 European debt crisis and the American credit downgrade.

  14. An insight into the diversification policy of the utilities

    International Nuclear Information System (INIS)

    Verbeek, P.

    1989-01-01

    This paper focuses on that part of the utilities' procurement strategy dealing with geographical diversification of supplies of uranium and fuel cycle services. The prospects for the future development of nuclear power have moderated in recent years while uranium resources have remained plentiful. Consequently, it is appropriate to look again at the reasons for supply diversification. The principal issue is no longer that of ten or twenty services - conversion, enrichment and fuel fabrication. Reasons for diversification today are related to the economic and political feasibility of production and shipment at the right time, in the right quantities and at the right prices. (author)

  15. Triterpene Structural Diversification by Plant Cytochrome P450 Enzymes

    Directory of Open Access Journals (Sweden)

    Sumit Ghosh

    2017-11-01

    Full Text Available Cytochrome P450 monooxygenases (P450s represent the largest enzyme family of the plant metabolism. Plants typically devote about 1% of the protein-coding genes for the P450s to execute primary metabolism and also to perform species-specific specialized functions including metabolism of the triterpenes, isoprene-derived 30-carbon compounds. Triterpenes constitute a large and structurally diverse class of natural products with various industrial and pharmaceutical applications. P450-catalyzed structural modification is crucial for the diversification and functionalization of the triterpene scaffolds. In recent times, a remarkable progress has been made in understanding the function of the P450s in plant triterpene metabolism. So far, ∼80 P450s are assigned biochemical functions related to the plant triterpene metabolism. The members of the subfamilies CYP51G, CYP85A, CYP90B-D, CYP710A, CYP724B, and CYP734A are generally conserved across the plant kingdom to take part in plant primary metabolism related to the biosynthesis of essential sterols and steroid hormones. However, the members of the subfamilies CYP51H, CYP71A,D, CYP72A, CYP81Q, CYP87D, CYP88D,L, CYP93E, CYP705A, CYP708A, and CYP716A,C,E,S,U,Y are required for the metabolism of the specialized triterpenes that might perform species-specific functions including chemical defense toward specialized pathogens. Moreover, a recent advancement in high-throughput sequencing of the transcriptomes and genomes has resulted in identification of a large number of candidate P450s from diverse plant species. Assigning biochemical functions to these P450s will be of interest to extend our knowledge on triterpene metabolism in diverse plant species and also for the sustainable production of valuable phytochemicals.

  16. On the Diversification of the Translation Apparatus across Eukaryotes

    Directory of Open Access Journals (Sweden)

    Greco Hernández

    2012-01-01

    Full Text Available Diversity is one of the most remarkable features of living organisms. Current assessments of eukaryote biodiversity reaches 1.5 million species, but the true figure could be several times that number. Diversity is ingrained in all stages and echelons of life, namely, the occupancy of ecological niches, behavioral patterns, body plans and organismal complexity, as well as metabolic needs and genetics. In this review, we will discuss that diversity also exists in a key biochemical process, translation, across eukaryotes. Translation is a fundamental process for all forms of life, and the basic components and mechanisms of translation in eukaryotes have been largely established upon the study of traditional, so-called model organisms. By using modern genome-wide, high-throughput technologies, recent studies of many nonmodel eukaryotes have unveiled a surprising diversity in the configuration of the translation apparatus across eukaryotes, showing that this apparatus is far from being evolutionarily static. For some of the components of this machinery, functional differences between different species have also been found. The recent research reviewed in this article highlights the molecular and functional diversification the translational machinery has undergone during eukaryotic evolution. A better understanding of all aspects of organismal diversity is key to a more profound knowledge of life.

  17. Integrated diversification of locomotion and feeding in labrid fishes.

    Science.gov (United States)

    Collar, David C; Wainwright, Peter C; Alfaro, Michael E

    2008-02-23

    An organism's performance of any ecological task involves coordination of multiple functional systems. Feeding performance is influenced by locomotor abilities which are used during search and capture of prey, as well as cranial mechanics, which affect prey capture and processing. But, does this integration of functional systems manifest itself during evolution? We asked whether the locomotor and feeding systems evolved in association in one of the most prominent and diverse reef fish radiations, the Labridae. We examined features of the pectoral fins that affect swimming performance and aspects of the skull that describe force and motion of the jaws. We applied a recent phylogeny, calculated independent contrasts for 60 nodes and performed principal components analyses separately on contrasts for fin and skull traits. The major axes of fin and skull diversification are highly correlated; modifications of the skull to amplify the speed of jaw movements are correlated with changes in the pectoral fins that increase swimming speed, and increases in force capacity of the skull are associated with changes towards fins that produce high thrust at slow speeds. These results indicate that the labrid radiation involved a strong connection between locomotion and feeding abilities.

  18. The impact of internationalization and diversification on construction industry performance

    NARCIS (Netherlands)

    Horta, Isabel M.; Kapelko, Magdalena; Oude Lansink, Alfons; Camanho, Ana S.

    2016-01-01

    This paper investigates the impact of internationalization and diversification strategies on the financial performance of construction industry companies. The results obtained can guide the design of strategies to pursue company growth and achieve competitive advantage. The evaluation of

  19. Viviparity stimulates diversification in an order of fish.

    Science.gov (United States)

    Helmstetter, Andrew J; Papadopulos, Alexander S T; Igea, Javier; Van Dooren, Tom J M; Leroi, Armand M; Savolainen, Vincent

    2016-04-12

    Species richness is distributed unevenly across the tree of life and this may be influenced by the evolution of novel phenotypes that promote diversification. Viviparity has originated ∼150 times in vertebrates and is considered to be an adaptation to highly variable environments. Likewise, possessing an annual life cycle is common in plants and insects, where it enables the colonization of seasonal environments, but rare in vertebrates. The extent to which these reproductive life-history traits have enhanced diversification and their relative importance in the process remains unknown. We show that convergent evolution of viviparity causes bursts of diversification in fish. We built a phylogenetic tree for Cyprinodontiformes, an order in which both annualism and viviparity have arisen, and reveal that while both traits have evolved multiple times, only viviparity played a major role in shaping the patterns of diversity. These results demonstrate that changes in reproductive life-history strategy can stimulate diversification.

  20. Promoting structural transformation: Strategic diversification vs laissez-faire approach

    NARCIS (Netherlands)

    Freire Junior, Clovis

    2017-01-01

    Economic development is associated with structural transformation and the increase of complexity of production and exports. This paper examines whether strategic diversification is required to increase economic complexity or whether market incentives would be sufficient to drive this process of

  1. Viviparity stimulates diversification in an order of fish

    Science.gov (United States)

    Helmstetter, Andrew J.; Papadopulos, Alexander S. T.; Igea, Javier; Van Dooren, Tom J. M.; Leroi, Armand M.; Savolainen, Vincent

    2016-01-01

    Species richness is distributed unevenly across the tree of life and this may be influenced by the evolution of novel phenotypes that promote diversification. Viviparity has originated ∼150 times in vertebrates and is considered to be an adaptation to highly variable environments. Likewise, possessing an annual life cycle is common in plants and insects, where it enables the colonization of seasonal environments, but rare in vertebrates. The extent to which these reproductive life-history traits have enhanced diversification and their relative importance in the process remains unknown. We show that convergent evolution of viviparity causes bursts of diversification in fish. We built a phylogenetic tree for Cyprinodontiformes, an order in which both annualism and viviparity have arisen, and reveal that while both traits have evolved multiple times, only viviparity played a major role in shaping the patterns of diversity. These results demonstrate that changes in reproductive life-history strategy can stimulate diversification. PMID:27070759

  2. Asynchronous diversification in a specialized plant-pollinator mutualism.

    Science.gov (United States)

    Ramírez, Santiago R; Eltz, Thomas; Fujiwara, Mikiko K; Gerlach, Günter; Goldman-Huertas, Benjamin; Tsutsui, Neil D; Pierce, Naomi E

    2011-09-23

    Most flowering plants establish mutualistic associations with insect pollinators to facilitate sexual reproduction. However, the evolutionary processes that gave rise to these associations remain poorly understood. We reconstructed the times of divergence, diversification patterns, and interaction networks of a diverse group of specialized orchids and their bee pollinators. In contrast to a scenario of coevolution by race formation, we show that fragrance-producing orchids originated at least three times independently after their fragrance-collecting bee mutualists. Whereas orchid diversification has apparently tracked the diversification of orchids' bee pollinators, bees appear to have depended on the diverse chemical environment of neotropical forests. We corroborated this apparent asymmetrical dependency by simulating co-extinction cascades in real interaction networks that lacked reciprocal specialization. These results suggest that the diversification of insect-pollinated angiosperms may have been facilitated by the exploitation of preexisting sensory biases of insect pollinators.

  3. Economy diversification: a potent tool for tourism development in ...

    African Journals Online (AJOL)

    Economy diversification: a potent tool for tourism development in Nigeria. ... AFRREV STECH: An International Journal of Science and Technology ... The diversity of cultural attractions, the friendly disposition of the people, revamped National ...

  4. Problems and Instruments of Product and Technological Diversification of Manufacturing

    Directory of Open Access Journals (Sweden)

    Kuzmin Oleg Ye.

    2015-03-01

    Full Text Available The purpose of the article involves identification of objectives and development of instruments for product and technological diversification aimed at updating the range of products and introducing innovative technologies, which will ensure a high level of competitiveness and create preconditions for steady development of the enterprise. As a result of studying the literary sources the objectives and instruments for development of enterprises by means of product and technological diversification have been defined. The article suggests effective instruments of product and technological diversification of manufacturing, namely: the model of expansion of the product range, multi-criteria model of optimization of the product range, a modified model of Kantorovich-Koopmans for implementing new production technologies with set limits on the product output. Further research relate to formation of instruments for manufacturing diversification by means of introducing new types of production.

  5. Chromatin modification of Notch targets in olfactory receptor neuron diversification

    Czech Academy of Sciences Publication Activity Database

    Endo, K.; Karim, M. R.; Taniguchi, H.; Krejčí, Alena; Kinameri, E.; Siebert, M.; Ito, K.; Bray, S. J.; Moore, A. W.

    2012-01-01

    Roč. 15, č. 2 (2012), s. 224-233 ISSN 1097-6256 Institutional research plan: CEZ:AV0Z50070508 Keywords : neuron diversification Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 15.251, year: 2012

  6. Diversification of visual media retrieval results using saliency detection

    Science.gov (United States)

    Muratov, Oleg; Boato, Giulia; De Natale, Franesco G. B.

    2013-03-01

    Diversification of retrieval results allows for better and faster search. Recently there has been proposed different methods for diversification of image retrieval results mainly utilizing text information and techniques imported from natural language processing domain. However, images contain visual information that is impossible to describe in text and the use of visual features is inevitable. Visual saliency is information about the main object of an image implicitly included by humans while creating visual content. For this reason it is naturally to exploit this information for the task of diversification of the content. In this work we study whether visual saliency can be used for the task of diversification and propose a method for re-ranking image retrieval results using saliency. The evaluation has shown that the use of saliency information results in higher diversity of retrieval results.

  7. Tourism Diversification and Its Implications for Smart Specialisation

    Directory of Open Access Journals (Sweden)

    Adi Weidenfeld

    2018-01-01

    Full Text Available The complex nature of tourism, its strong inter-sectoral relationships and regional dimension challenge innovation. The advent of smart specialisation, which focuses on regional diversification across sectors, offers considerable and hitherto largely unrealized potential for developing innovative tourism policies within this new agenda. This paper addresses the understudied concept of tourism diversification and its unrealized relevance to smart specialisation, which has emerged as a mainstream logic underpinning EU Cohesion Policy reforms and has diffused into other OECD countries. It provides a theoretical framework for studying product, market, sectoral and regional diversification as well as related variety in tourism. Some policy implications for realizing tourism diversification and for the potential role of tourism in smart specialisation strategies in particular are suggested.

  8. Portfolio Diversification with Commodity Futures: Properties of Levered Futures

    NARCIS (Netherlands)

    Woodard, J.D.; Egelkraut, T.M.; Garcia, P.; Pennings, J.M.E.

    2005-01-01

    Portfolio Diversification with Commodity Futures: Properties of Levered Futures This study extends previous work on the impact of commodity futures on portfolio performance by explicitly incorporating levered futures into the portfolio optimization problem. Using data on nine individual commodity

  9. Phenotypic Covariation And Morphological Diversification In The Ruminant Skull

    OpenAIRE

    Haber, Annat

    2015-01-01

    Differences among clades in their diversification patterns result from a combination of extrinsic and intrinsic factors. In this study I examined the role of intrinsic factors in the morphological diversification of ruminants in general, and in the differences between bovids and cervids in particular. Using skull morphology, which embodies many of the adaptations that distinguish bovids and cervids, I examined 132 of the 200 extant ruminant species. As a proxy for intrinsic constraints I quan...

  10. Product diversification and bank performance: does ownership structure matter?

    OpenAIRE

    Saghi-Zedek , Nadia

    2016-01-01

    International audience; Using detailed data on control chains of 710 European commercial banks, we test whether the presence of some categories of controlling shareholders affects product diversification performance. We find that when banks have no controlling shareholder or have only family and state shareholders activity diversification yields diseconomies. However, as long as the control chain involves banking institutions, institutional investors, industrial companies or any other combina...

  11. Does internationalisation of technology determine technological diversification in large firms?

    OpenAIRE

    Christian Le Bas; Pari Patel

    2005-01-01

    The purpose of the paper is to examine the relationship between technological diversification and internationalisation of technology for large multinational firms, operating at the world technological frontier. More precisely we address the question as to whether internationalisation determines diversification. The analysis is based on a rich database of the European patenting activity of 345 large multinational firms with the highest levels of patenting over two periods of time (1988-1990 an...

  12. Can Google Trends search queries contribute to risk diversification?

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav

    2013-01-01

    Roč. 3, č. 2713 (2013), s. 1-5 ISSN 2045-2322 R&D Projects: GA ČR GA402/09/0965 Institutional support: RVO:67985556 Keywords : Google Trends * diversification * portfolio Subject RIV: AH - Economics Impact factor: 5.078, year: 2013 http://library.utia.cas.cz/separaty/2013/E/kristoufek-can google trends search queries contribute to risk diversification.pdf

  13. Tourism Diversification and Its Implications for Smart Specialisation

    OpenAIRE

    Adi Weidenfeld

    2018-01-01

    The complex nature of tourism, its strong inter-sectoral relationships and regional dimension challenge innovation. The advent of smart specialisation, which focuses on regional diversification across sectors, offers considerable and hitherto largely unrealized potential for developing innovative tourism policies within this new agenda. This paper addresses the understudied concept of tourism diversification and its unrealized relevance to smart specialisation, which has emerged as a mainstre...

  14. Character combinations, convergence and diversification in ectoparasitic arthropods.

    Science.gov (United States)

    Poulin, Robert

    2009-08-01

    Different lineages of organisms diversify over time at different rates, in part as a consequence of the characteristics of the species in these lineages. Certain suites of traits possessed by species within a clade may determine rates of diversification, with some particular combinations of characters acting synergistically to either limit or promote diversification; the most successful combinations may also emerge repeatedly in different clades via convergent evolution. Here, the association between species characters and diversification is investigated amongst 21 independent lineages of arthropods ectoparasitic on vertebrate hosts. Using nine characters (each with two to four states) that capture general life history strategy, transmission mode and host-parasite interaction, each lineage was described by the set of character states it possesses. The results show, firstly, that most possible pair-wise combinations of character states have been adopted at least once, sometimes several times independently by different lineages; thus, ectoparasitic arthropods have explored most of the life history character space available to them. Secondly, lineages possessing commonly observed combinations of character states are not necessarily the ones that have experienced the highest rates of diversification (measured as a clade's species-per-genus ratio). Thirdly, some specific traits are associated with higher rates of diversification. Using more than one host per generation, laying eggs away from the host and intermediate levels of fecundity are features that appear to have promoted diversification. These findings indicate that particular species characters may be evolutionary drivers of diversity, whose effects could also apply in other taxa.

  15. Diversification and Community Bank Performance during a Financial Crisis

    Directory of Open Access Journals (Sweden)

    Kathy Estes

    2014-11-01

    Full Text Available Many U.S. banks failed or performed poorly during the recent financial crisis.  Although the costliest failures were large institutions, the majority of failures were community banks (less than $1 billion in total assets.  Community banks, which are considered instrumental in small business lending and employment growth, face different risks and challenges than their larger counterparts, including a lack of economies of scale and scope and exclusion from “too-big-to-fail” status.  These challenges, coupled with the recent failures, motivate research into potential strategies managers can use to improve performance.  This study examined the relationship between three potential diversification strategies and community bank risk-adjusted performance from 2007 to 2011.  Understanding these relationships could improve management’s decision-making, allowing them to choose risk-mitigating strategies during a severe economic downturn.  Herfindahl-Hirschman Indexes (HHIs were calculated as proxies for geographic, activity, and asset diversification.  Multiple regression models for each of the five years were used to calculate the impact of diversification variables on risk-adjusted ROA.  The results show that diversification in all areas is directly related to performance; however, only the asset diversification relationship is significant.  To the extent possible for community banks, diversification may improve risk-adjusted performance.

  16. Structuring evolution: biochemical networks and metabolic diversification in birds.

    Science.gov (United States)

    Morrison, Erin S; Badyaev, Alexander V

    2016-08-25

    Recurrence and predictability of evolution are thought to reflect the correspondence between genomic and phenotypic dimensions of organisms, and the connectivity in deterministic networks within these dimensions. Direct examination of the correspondence between opportunities for diversification imbedded in such networks and realized diversity is illuminating, but is empirically challenging because both the deterministic networks and phenotypic diversity are modified in the course of evolution. Here we overcome this problem by directly comparing the structure of a "global" carotenoid network - comprising of all known enzymatic reactions among naturally occurring carotenoids - with the patterns of evolutionary diversification in carotenoid-producing metabolic networks utilized by birds. We found that phenotypic diversification in carotenoid networks across 250 species was closely associated with enzymatic connectivity of the underlying biochemical network - compounds with greater connectivity occurred the most frequently across species and were the hotspots of metabolic pathway diversification. In contrast, we found no evidence for diversification along the metabolic pathways, corroborating findings that the utilization of the global carotenoid network was not strongly influenced by history in avian evolution. The finding that the diversification in species-specific carotenoid networks is qualitatively predictable from the connectivity of the underlying enzymatic network points to significant structural determinism in phenotypic evolution.

  17. Factors affecting farm diversification in rice-wheat

    International Nuclear Information System (INIS)

    Ashfaq, M.; Hassan, S.; Naseer, M.Z.; Baig, I.A.; Asma, J.

    2008-01-01

    The risk in agriculture sector is due to various factors like weather and market conditions, particularly the demand of the commodities. This uncertainty can result in variable returns (farm income) to the decisions that farmers make in a particular season. Diversification is a frequently used risk management strategy that involves participation in more than one activity. It has the added advantage of mitigating price risk as well as fluctuations in outputs. The main purpose of this paper was to determine the factors affecting crop diversification. For determining the effect of different factors on diversification a multiple regression model was used. The values of Entropy index computed for measuring horizontal diversification were taken as dependent variable and different factors affecting diversification were taken as independent variables. The results showed that the main factors affecting diversification were size of land holding, age of respondent, education level of respondent, farming experience of respondent, off farm income of respondent, distance of farm from main road, distance of farm from main market and farm machinery. (author)

  18. Epistasis can accelerate adaptive diversification in haploid asexual populations.

    Science.gov (United States)

    Griswold, Cortland K

    2015-03-07

    A fundamental goal of the biological sciences is to determine processes that facilitate the evolution of diversity. These processes can be separated into ecological, physiological, developmental and genetic. An ecological process that facilitates diversification is frequency-dependent selection caused by competition. Models of frequency-dependent adaptive diversification have generally assumed a genetic basis of phenotype that is non-epistatic. Here, we present a model that indicates diversification is accelerated by an epistatic basis of phenotype in combination with a competition model that invokes frequency-dependent selection. Our model makes use of a genealogical model of epistasis and insights into the effects of balancing selection on the genealogical structure of a population to understand how epistasis can facilitate diversification. The finding that epistasis facilitates diversification may be informative with respect to empirical results that indicate an epistatic basis of phenotype in experimental bacterial populations that experienced adaptive diversification. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  19. Distinct Processes Drive Diversification in Different Clades of Gesneriaceae.

    Science.gov (United States)

    Roalson, Eric H; Roberts, Wade R

    2016-07-01

    Using a time-calibrated phylogenetic hypothesis including 768 Gesneriaceae species (out of [Formula: see text]3300 species) and more than 29,000 aligned bases from 26 gene regions, we test Gesneriaceae for diversification rate shifts and the possible proximal drivers of these shifts: geographic distributions, growth forms, and pollination syndromes. Bayesian Analysis of Macroevolutionary Mixtures analyses found five significant rate shifts in Beslerieae, core Nematanthus, core Columneinae, core Streptocarpus, and Pacific Cyrtandra These rate shifts correspond with shifts in diversification rates, as inferred by Binary State Speciation and Extinction Model and Geographic State Speciation and Extinction model, associated with hummingbird pollination, epiphytism, unifoliate growth, and geographic area. Our results suggest that diversification processes are extremely variable across Gesneriaceae clades with different combinations of characters influencing diversification rates in different clades. Diversification patterns between New and Old World lineages show dramatic differences, suggesting that the processes of diversification in Gesneriaceae are very different in these two geographic regions. © The Author(s) 2016. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. What Explains Patterns of Diversification and Richness among Animal Phyla?

    Science.gov (United States)

    Jezkova, Tereza; Wiens, John J

    2017-03-01

    Animal phyla vary dramatically in species richness (from one species to >1.2 million), but the causes of this variation remain largely unknown. Animals have also evolved striking variation in morphology and ecology, including sessile marine taxa lacking heads, eyes, limbs, and complex organs (e.g., sponges), parasitic worms (e.g., nematodes, platyhelminths), and taxa with eyes, skeletons, limbs, and complex organs that dominate terrestrial ecosystems (arthropods, chordates). Relating this remarkable variation in traits to the diversification and richness of animal phyla is a fundamental yet unresolved problem in biology. Here, we test the impacts of 18 traits (including morphology, ecology, reproduction, and development) on diversification and richness of extant animal phyla. Using phylogenetic multiple regression, the best-fitting model includes five traits that explain ∼74% of the variation in diversification rates (dioecy, parasitism, eyes/photoreceptors, a skeleton, nonmarine habitat). However, a model including just three (skeleton, parasitism, habitat) explains nearly as much variation (∼67%). Diversification rates then largely explain richness patterns. Our results also identify many striking traits that have surprisingly little impact on diversification (e.g., head, limbs, and complex circulatory and digestive systems). Overall, our results reveal the key factors that shape large-scale patterns of diversification and richness across >80% of all extant, described species.

  1. Linking Cellular Mechanisms to Behavior: Entorhinal Persistent Spiking and Membrane Potential Oscillations May Underlie Path Integration, Grid Cell Firing, and Episodic Memory

    Directory of Open Access Journals (Sweden)

    Michael E. Hasselmo

    2008-01-01

    Full Text Available The entorhinal cortex plays an important role in spatial memory and episodic memory functions. These functions may result from cellular mechanisms for integration of the afferent input to entorhinal cortex. This article reviews physiological data on persistent spiking and membrane potential oscillations in entorhinal cortex then presents models showing how both these cellular mechanisms could contribute to properties observed during unit recording, including grid cell firing, and how they could underlie behavioural functions including path integration. The interaction of oscillations and persistent firing could contribute to encoding and retrieval of trajectories through space and time as a mechanism relevant to episodic memory.

  2. Functional characterization of c-Mpl ectodomain mutations that underlie congenital amegakaryocytic thrombocytopenia.

    Science.gov (United States)

    Varghese, Leila N; Zhang, Jian-Guo; Young, Samuel N; Willson, Tracy A; Alexander, Warren S; Nicola, Nicos A; Babon, Jeffrey J; Murphy, James M

    2014-02-01

    Activation of the cell surface receptor, c-Mpl, by the cytokine, thrombopoietin (TPO), underpins megakaryocyte and platelet production in mammals. In humans, mutations in c-Mpl have been identified as the molecular basis of Congenital Amegakaryocytic Thrombocytopenia (CAMT). Here, we show that CAMT-associated mutations in c-Mpl principally lead to defective receptor presentation on the cell surface. In contrast, one CAMT mutant c-Mpl, F104S, was expressed on the cell surface, but showed defective TPO binding and receptor activation. Using mutational analyses, we examined which residues adjacent to F104 within the membrane-distal cytokine receptor homology module (CRM) of c-Mpl comprise the TPO-binding epitope, revealing residues within the predicted Domain 1 E-F and A-B loops and Domain 2 F'-G' loop as key TPO-binding determinants. These studies underscore the importance of the c-Mpl membrane-distal CRM to TPO-binding and suggest that mutations within this CRM that perturb TPO binding could give rise to CAMT.

  3. Defensive traits exhibit an evolutionary trade-off and drive diversification in ants.

    Science.gov (United States)

    Blanchard, Benjamin D; Moreau, Corrie S

    2017-02-01

    Evolutionary biologists have long predicted that evolutionary trade-offs among traits should constrain morphological divergence and species diversification. However, this prediction has yet to be tested in a broad evolutionary context in many diverse clades, including ants. Here, we reconstruct an expanded ant phylogeny representing 82% of ant genera, compile a new family-wide trait database, and conduct various trait-based analyses to show that defensive traits in ants do exhibit an evolutionary trade-off. In particular, the use of a functional sting negatively correlates with a suite of other defensive traits including spines, large eye size, and large colony size. Furthermore, we find that several of the defensive traits that trade off with a sting are also positively correlated with each other and drive increased diversification, further suggesting that these traits form a defensive suite. Our results support the hypothesis that trade-offs in defensive traits significantly constrain trait evolution and influence species diversification in ants. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

  4. Evolution of multicellularity coincided with increased diversification of cyanobacteria and the Great Oxidation Event

    Science.gov (United States)

    Schirrmeister, Bettina E.; de Vos, Jurriaan M.; Antonelli, Alexandre; Bagheri, Homayoun C.

    2013-01-01

    Cyanobacteria are among the most diverse prokaryotic phyla, with morphotypes ranging from unicellular to multicellular filamentous forms, including those able to terminally (i.e., irreversibly) differentiate in form and function. It has been suggested that cyanobacteria raised oxygen levels in the atmosphere around 2.45–2.32 billion y ago during the Great Oxidation Event (GOE), hence dramatically changing life on the planet. However, little is known about the temporal evolution of cyanobacterial lineages, and possible interplay between the origin of multicellularity, diversification of cyanobacteria, and the rise of atmospheric oxygen. We estimated divergence times of extant cyanobacterial lineages under Bayesian relaxed clocks for a dataset of 16S rRNA sequences representing the entire known diversity of this phylum. We tested whether the evolution of multicellularity overlaps with the GOE, and whether multicellularity is associated with significant shifts in diversification rates in cyanobacteria. Our results indicate an origin of cyanobacteria before the rise of atmospheric oxygen. The evolution of multicellular forms coincides with the onset of the GOE and an increase in diversification rates. These results suggest that multicellularity could have played a key role in triggering cyanobacterial evolution around the GOE. PMID:23319632

  5. Matrix metalloproteinases: structures, evolution, and diversification.

    Science.gov (United States)

    Massova, I; Kotra, L P; Fridman, R; Mobashery, S

    1998-09-01

    A comprehensive sequence alignment of 64 members of the family of matrix metalloproteinases (MMPs) for the entire sequences, and subsequently the catalytic and the hemopexin-like domains, have been performed. The 64 MMPs were selected from plants, invertebrates, and vertebrates. The analyses disclosed that as many as 23 distinct subfamilies of these proteins are known to exist. Information from the sequence alignments was correlated with structures, both crystallographic as well as computational, of the catalytic domains for the 23 representative members of the MMP family. A survey of the metal binding sites and two loops containing variable sequences of amino acids, which are important for substrate interactions, are discussed. The collective data support the proposal that the assembly of the domains into multidomain enzymes was likely to be an early evolutionary event. This was followed by diversification, perhaps in parallel among the MMPs, in a subsequent evolutionary time scale. Analysis indicates that a retrograde structure simplification may have accounted for the evolution of MMPs with simple domain constituents, such as matrilysin, from the larger and more elaborate enzymes.

  6. Evolution, diversification and expression of KNOX proteins in plants

    Directory of Open Access Journals (Sweden)

    Jie eGao

    2015-10-01

    Full Text Available The KNOX (KNOTTED1-like homeobox transcription factors play a pivotal role in leaf and meristem development. The majority of these proteins are characterized by the KNOX1, KNOX2, ELK and homeobox domains whereas the proteins of the KNATM family contain only the KNOX domains. We carried out an extensive inventory of these proteins and here report on a total of 394 KNOX proteins from 48 species. The land plant proteins fall into two classes (I and II as previously shown where the class I family seems to be most closely related to the green algae homologs. The KNATM proteins are restricted to Eudicots and some species have multiple paralogs of this protein. Certain plants are characterized by a significant increase in the number of KNOX paralogs; one example is Glycine max. Through the analysis of public gene expression data we show that the class II proteins of this plant have a relatively broad expression specificity as compared to class I proteins, consistent with previous studies of other plants. In G. max, class I protein are mainly distributed in axis tissues and KNATM paralogs are overall poorly expressed; highest expression is in the early plumular axis. Overall, analysis of gene expression in G. max demonstrates clearly that the expansion in gene number is associated with functional diversification.

  7. Diversification of Root Hair Development Genes in Vascular Plants.

    Science.gov (United States)

    Huang, Ling; Shi, Xinhui; Wang, Wenjia; Ryu, Kook Hui; Schiefelbein, John

    2017-07-01

    The molecular genetic program for root hair development has been studied intensively in Arabidopsis ( Arabidopsis thaliana ). To understand the extent to which this program might operate in other plants, we conducted a large-scale comparative analysis of root hair development genes from diverse vascular plants, including eudicots, monocots, and a lycophyte. Combining phylogenetics and transcriptomics, we discovered conservation of a core set of root hair genes across all vascular plants, which may derive from an ancient program for unidirectional cell growth coopted for root hair development during vascular plant evolution. Interestingly, we also discovered preferential diversification in the structure and expression of root hair development genes, relative to other root hair- and root-expressed genes, among these species. These differences enabled the definition of sets of genes and gene functions that were acquired or lost in specific lineages during vascular plant evolution. In particular, we found substantial divergence in the structure and expression of genes used for root hair patterning, suggesting that the Arabidopsis transcriptional regulatory mechanism is not shared by other species. To our knowledge, this study provides the first comprehensive view of gene expression in a single plant cell type across multiple species. © 2017 American Society of Plant Biologists. All Rights Reserved.

  8. Can you sequence ecology? Metagenomics of adaptive diversification.

    Science.gov (United States)

    Marx, Christopher J

    2013-01-01

    Few areas of science have benefited more from the expansion in sequencing capability than the study of microbial communities. Can sequence data, besides providing hypotheses of the functions the members possess, detect the evolutionary and ecological processes that are occurring? For example, can we determine if a species is adapting to one niche, or if it is diversifying into multiple specialists that inhabit distinct niches? Fortunately, adaptation of populations in the laboratory can serve as a model to test our ability to make such inferences about evolution and ecology from sequencing. Even adaptation to a single niche can give rise to complex temporal dynamics due to the transient presence of multiple competing lineages. If there are multiple niches, this complexity is augmented by segmentation of the population into multiple specialists that can each continue to evolve within their own niche. For a known example of parallel diversification that occurred in the laboratory, sequencing data gave surprisingly few obvious, unambiguous signs of the ecological complexity present. Whereas experimental systems are open to direct experimentation to test hypotheses of selection or ecological interaction, the difficulty in "seeing ecology" from sequencing for even such a simple system suggests translation to communities like the human microbiome will be quite challenging. This will require both improved empirical methods to enhance the depth and time resolution for the relevant polymorphisms and novel statistical approaches to rigorously examine time-series data for signs of various evolutionary and ecological phenomena within and between species.

  9. The vertebrate Hox gene regulatory network for hindbrain segmentation: Evolution and diversification: Coupling of a Hox gene regulatory network to hindbrain segmentation is an ancient trait originating at the base of vertebrates.

    Science.gov (United States)

    Parker, Hugo J; Bronner, Marianne E; Krumlauf, Robb

    2016-06-01

    Hindbrain development is orchestrated by a vertebrate gene regulatory network that generates segmental patterning along the anterior-posterior axis via Hox genes. Here, we review analyses of vertebrate and invertebrate chordate models that inform upon the evolutionary origin and diversification of this network. Evidence from the sea lamprey reveals that the hindbrain regulatory network generates rhombomeric compartments with segmental Hox expression and an underlying Hox code. We infer that this basal feature was present in ancestral vertebrates and, as an evolutionarily constrained developmental state, is fundamentally important for patterning of the vertebrate hindbrain across diverse lineages. Despite the common ground plan, vertebrates exhibit neuroanatomical diversity in lineage-specific patterns, with different vertebrates revealing variations of Hox expression in the hindbrain that could underlie this diversification. Invertebrate chordates lack hindbrain segmentation but exhibit some conserved aspects of this network, with retinoic acid signaling playing a role in establishing nested domains of Hox expression. © 2016 WILEY Periodicals, Inc.

  10. Ants sow the seeds of global diversification in flowering plants.

    Directory of Open Access Journals (Sweden)

    Szabolcs Lengyel

    Full Text Available The extraordinary diversification of angiosperm plants in the Cretaceous and Tertiary periods has produced an estimated 250,000-300,000 living angiosperm species and has fundamentally altered terrestrial ecosystems. Interactions with animals as pollinators or seed dispersers have long been suspected as drivers of angiosperm diversification, yet empirical examples remain sparse or inconclusive. Seed dispersal by ants (myrmecochory may drive diversification as it can reduce extinction by providing selective advantages to plants and can increase speciation by enhancing geographical isolation by extremely limited dispersal distances.Using the most comprehensive sister-group comparison to date, we tested the hypothesis that myrmecochory leads to higher diversification rates in angiosperm plants. As predicted, diversification rates were substantially higher in ant-dispersed plants than in their non-myrmecochorous relatives. Data from 101 angiosperm lineages in 241 genera from all continents except Antarctica revealed that ant-dispersed lineages contained on average more than twice as many species as did their non-myrmecochorous sister groups. Contrasts in species diversity between sister groups demonstrated that diversification rates did not depend on seed dispersal mode in the sister group and were higher in myrmecochorous lineages in most biogeographic regions.Myrmecochory, which has evolved independently at least 100 times in angiosperms and is estimated to be present in at least 77 families and 11 000 species, is a key evolutionary innovation and a globally important driver of plant diversity. Myrmecochory provides the best example to date for a consistent effect of any mutualism on large-scale diversification.

  11. Diversification patterns in cosmopolitan earthworms: similar mode but different tempo.

    Science.gov (United States)

    Fernández, Rosa; Novo, Marta; Marchán, Daniel F; Díaz Cosín, Darío J

    2016-01-01

    Comparative phylogeography of widespread species that span the same geographic areas can elucidate the influence of historical events on current patterns of biodiversity, identify patterns of co-vicariance, and therefore aid the understanding of general evolutionary processes. Soil-dwelling animals present characteristics that make them suitable for testing the effect of the palaeogeographical events on their distribution and diversification, such as their low vagility and population structure. In this study, we shed light on the spatial lineage diversification and cladogenesis of two widely-distributed cosmopolitan and invasive earthworms (Aporrectodea rosea and A. trapezoides) in their putative ancestral area of origin, the Western Palearctic, and a few populations in North America. Molecular analyses were conducted on mitochondrial and nuclear markers from 220 (A. rosea) and 198 (A. trapezoides) individuals collected in 56 and 57 localities, respectively. We compared the lineage diversification pattern, genetic variability and cladogenesis in both species. Our findings showed that both species underwent a similar diversification from the Western Mediterranean plates to (i) Northern Europe and (ii) the Iberian Peninsula, establishing their two main lineages. Their diversification was in concordance with the main palaeogeographical events in the Iberian Peninsula and Western Mediterranean, followed by a later colonization of North America from individuals derived exclusively from the Eurosiberian lineage. Their diversification occurred at different times, with the diversification of A. rosea being potentially more ancient. Cladogenesis in both species seems to have been modelled only by the Mediterranean plate shifts, ignoring historical climatic oscillations such as the Messinian salinity crisis. Their high genetic variability, strong population structure, lack of gene flow and stepping-stone-like cladogenesis suggest the existence of different cryptic lineages

  12. Darwinism for the Genomic Age: Connecting Mutation to Diversification.

    Science.gov (United States)

    Hua, Xia; Bromham, Lindell

    2017-01-01

    A growing body of evidence suggests that rates of diversification of biological lineages are correlated with differences in genome-wide mutation rate. Given that most research into differential patterns of diversification rate have focused on species traits or ecological parameters, a connection to the biochemical processes of genome change is an unexpected observation. While the empirical evidence for a significant association between mutation rate and diversification rate is mounting, there has been less effort in explaining the factors that mediate this connection between genetic change and species richness. Here we draw together empirical studies and theoretical concepts that may help to build links in the explanatory chain that connects mutation to diversification. First we consider the way that mutation rates vary between species. We then explore how differences in mutation rates have flow-through effects to the rate at which populations acquire substitutions, which in turn influences the speed at which populations become reproductively isolated from each other due to the acquisition of genomic incompatibilities. Since diversification rate is commonly measured from phylogenetic analyses, we propose a conceptual approach for relating events of reproductive isolation to bifurcations on molecular phylogenies. As we examine each of these relationships, we consider theoretical models that might shine a light on the observed association between rate of molecular evolution and diversification rate, and critically evaluate the empirical evidence for these links, focusing on phylogenetic comparative studies. Finally, we ask whether we are getting closer to a real understanding of the way that the processes of molecular evolution connect to the observable patterns of diversification.

  13. Evolutionary Roots and Diversification of the Genus Aeromonas.

    Science.gov (United States)

    Sanglas, Ariadna; Albarral, Vicenta; Farfán, Maribel; Lorén, J G; Fusté, M C

    2017-01-01

    Despite the importance of diversification rates in the study of prokaryote evolution, they have not been quantitatively assessed for the majority of microorganism taxa. The investigation of evolutionary patterns in prokaryotes constitutes a challenge due to a very scarce fossil record, limited morphological differentiation and frequently complex taxonomic relationships, which make even species recognition difficult. Although the speciation models and speciation rates in eukaryotes have traditionally been established by analyzing the fossil record data, this is frequently incomplete, and not always available. More recently, several methods based on molecular sequence data have been developed to estimate speciation and extinction rates from phylogenies reconstructed from contemporary taxa. In this work, we determined the divergence time and temporal diversification of the genus Aeromonas by applying these methods widely used with eukaryotic taxa. Our analysis involved 150 Aeromonas strains using the concatenated sequences of two housekeeping genes (approximately 2,000 bp). Dating and diversification model analyses were performed using two different approaches: obtaining the consensus sequence from the concatenated sequences corresponding to all the strains belonging to the same species, or generating the species tree from multiple alignments of each gene. We used BEAST to perform a Bayesian analysis to estimate both the phylogeny and the divergence times. A global molecular clock cannot be assumed for any gene. From the chronograms obtained, we carried out a diversification analysis using several approaches. The results suggest that the genus Aeromonas began to diverge approximately 250 millions of years (Ma) ago. All methods used to determine Aeromonas diversification gave similar results, suggesting that the speciation process in this bacterial genus followed a rate-constant (Yule) diversification model, although there is a small probability that a slight

  14. Carotenogenesis diversification in phylogenetic lineages of Rhodophyta.

    Science.gov (United States)

    Takaichi, Shinichi; Yokoyama, Akiko; Mochimaru, Mari; Uchida, Hiroko; Murakami, Akio

    2016-06-01

    Carotenoid composition is very diverse in Rhodophyta. In this study, we investigated whether this variation is related to the phylogeny of this group. Rhodophyta consists of seven classes, and they can be divided into two groups on the basis of their morphology. The unicellular group (Cyanidiophyceae, Porphyridiophyceae, Rhodellophyceae, and Stylonematophyceae) contained only β-carotene and zeaxanthin, "ZEA-type carotenoids." In contrast, within the macrophytic group (Bangiophyceae, Compsopogonophyceae, and Florideophyceae), Compsopogonophyceae contained antheraxanthin in addition to ZEA-type carotenoids, "ANT-type carotenoids," whereas Bangiophyceae contained α-carotene and lutein along with ZEA-type carotenoids, "LUT-type carotenoids." Florideophyceae is divided into five subclasses. Ahnfeltiophycidae, Hildenbrandiophycidae, and Nemaliophycidae contained LUT-type carotenoids. In Corallinophycidae, Hapalidiales and Lithophylloideae in Corallinales contained LUT-type carotenoids, whereas Corallinoideae in Corallinales contained ANT-type carotenoids. In Rhodymeniophycidae, most orders contained LUT-type carotenoids; however, only Gracilariales contained ANT-type carotenoids. There is a clear relationship between carotenoid composition and phylogenetics in Rhodophyta. Furthermore, we searched open genome databases of several red algae for references to the synthetic enzymes of the carotenoid types detected in this study. β-Carotene and zeaxanthin might be synthesized from lycopene, as in land plants. Antheraxanthin might require zeaxanthin epoxydase, whereas α-carotene and lutein might require two additional enzymes, as in land plants. Furthermore, Glaucophyta contained ZEA-type carotenoids, and Cryptophyta contained β-carotene, α-carotene, and alloxanthin, whose acetylenic group might be synthesized from zeaxanthin by an unknown enzyme. Therefore, we conclude that the presence or absence of the four enzymes is related to diversification of carotenoid

  15. Portfolio Diversification in the South-East European Equity Markets

    Directory of Open Access Journals (Sweden)

    Zaimovic Azra

    2017-04-01

    Full Text Available Diversification potential enables investors to manage their risk and decrease risk exposure. Good diversification policy is a safety net that prevents a portfolio from losing its value. A well-diversified portfolio consists of different categories of property with low correlations, while highly correlated markets have the feature of low possibilities for diversification. The biggest riddle in the world of investments is to find the optimal portfolio within a set of available assets with limited capital. There are numerous studies and mathematical models that deal with portfolio investment strategies. These strategies take advantage of diversification by spreading risk over several financial assets. Modern portfolio theory seeks to find the optimal model with the best results. This paper tries to identify relationships between returns of companies traded in South-East European equity markets. A Markowitz mean-variance (MV portfolio optimization method is used to identify possibilities for diversification among these markets and world leading capital markets. This research also offers insight into to the level of integration of South-East European equity markets. Principal component analysis (PCA is used to determine components that describe the strong patterns and co-movements of the dataset. Finally, we combined MV efficient frontier and equity, which represent PCA components, to draw conclusions. Our findings show that PC analysis substantially simplifies asset selection process in portfolio management. The results of the paper have practical applications for portfolio investors.

  16. Heterostyly accelerates diversification via reduced extinction in primroses

    Science.gov (United States)

    de Vos, Jurriaan M.; Hughes, Colin E.; Schneeweiss, Gerald M.; Moore, Brian R.; Conti, Elena

    2014-01-01

    The exceptional species diversity of flowering plants, exceeding that of their sister group more than 250-fold, is especially evident in floral innovations, interactions with pollinators and sexual systems. Multiple theories, emphasizing flower–pollinator interactions, genetic effects of mating systems or high evolvability, predict that floral evolution profoundly affects angiosperm diversification. However, consequences for speciation and extinction dynamics remain poorly understood. Here, we investigate trajectories of species diversification focusing on heterostyly, a remarkable floral syndrome where outcrossing is enforced via cross-compatible floral morphs differing in placement of their respective sexual organs. Heterostyly evolved at least 20 times independently in angiosperms. Using Darwin's model for heterostyly, the primrose family, we show that heterostyly accelerates species diversification via decreasing extinction rates rather than increasing speciation rates, probably owing to avoidance of the negative genetic effects of selfing. However, impact of heterostyly appears to differ over short and long evolutionary time-scales: the accelerating effect of heterostyly on lineage diversification is manifest only over long evolutionary time-scales, whereas recent losses of heterostyly may prompt ephemeral bursts of speciation. Our results suggest that temporal or clade-specific conditions may ultimately determine the net effects of specific traits on patterns of species diversification. PMID:24759859

  17. Increased diversification rates follow shifts to bisexuality in liverworts.

    Science.gov (United States)

    Laenen, Benjamin; Machac, Antonin; Gradstein, S Robbert; Shaw, Blanka; Patiño, Jairo; Désamoré, Aurélie; Goffinet, Bernard; Cox, Cymon J; Shaw, A Jonathan; Vanderpoorten, Alain

    2016-05-01

    Shifts in sexual systems are one of the key drivers of species diversification. In contrast to angiosperms, unisexuality prevails in bryophytes. Here, we test the hypotheses that bisexuality evolved from an ancestral unisexual condition and is a key innovation in liverworts. We investigate whether shifts in sexual systems influence diversification using hidden state speciation and extinction analysis (HiSSE). This new method compares the effects of the variable of interest to the best-fitting latent variable, yielding robust and conservative tests. We find that the transitions in sexual systems are significantly biased toward unisexuality, even though bisexuality is coupled with increased diversification. Sexual systems are strongly conserved deep within the liverwort tree but become much more labile toward the present. Bisexuality appears to be a key innovation in liverworts. Its effects on diversification are presumably mediated by the interplay of high fertilization rates, massive spore production and long-distance dispersal, which may separately or together have facilitated liverwort speciation, suppressed their extinction, or both. Importantly, shifts in liverwort sexual systems have the opposite effect when compared to angiosperms, leading to contrasting diversification patterns between the two groups. The high prevalence of unisexuality among liverworts suggests, however, a strong selection for sexual dimorphism. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  18. Diversification of clearwing butterflies with the rise of the Andes.

    Science.gov (United States)

    De-Silva, Donna Lisa; Elias, Marianne; Willmott, Keith; Mallet, James; Day, Julia J

    2016-01-01

    Despite the greatest butterfly diversity on Earth occurring in the Neotropical Andes and Amazonia, there is still keen debate about the origins of this exceptional biota. A densely sampled calibrated phylogeny for a widespread butterfly subtribe, Oleriina (Nymphalidae: Ithomiini) was used to estimate the origin, colonization history and diversification of this species-rich group. Neotropics. Ancestral elevation and biogeographical ranges were reconstructed using data generated from detailed range maps and applying the dispersal-extinction-cladogenesis model using stratified palaeogeographical time slice matrices. The pattern of diversification through time was examined by comparing constant and variable rate models. We also tested the hypothesis that a change in elevation is associated with speciation. The Oleriina likely originated in the Andes in the Early to Middle Miocene and rapidly diversified to include four genera all of which also originated in the Andes. These clades, together with four species groups, experienced varying spatial and temporal patterns of diversification. An overall early burst and decreasing diversification rate is identified, and this pattern is reflected for most subclades. Changes in the palaeogeological landscape, particularly the prolonged uplift of the Andes, had a profound impact on the diversification of the subtribe. The Oleriina mostly remained within the Andes and vicariant speciation resulted in some instances. Dynamic dispersal occurred with the disappearance of geological barriers such as the Acre System and the subtribe exploited newly available habitats. Our results confirm the role of the Andean uplift in the evolution of Neotropical biodiversity.

  19. Independent evolution of the sexes promotes amphibian diversification

    Science.gov (United States)

    De Lisle, Stephen P.; Rowe, Locke

    2015-01-01

    Classic ecological theory predicts that the evolution of sexual dimorphism constrains diversification by limiting morphospace available for speciation. Alternatively, sexual selection may lead to the evolution of reproductive isolation and increased diversification. We test contrasting predictions of these hypotheses by examining the relationship between sexual dimorphism and diversification in amphibians. Our analysis shows that the evolution of sexual size dimorphism (SSD) is associated with increased diversification and speciation, contrary to the ecological theory. Further, this result is unlikely to be explained by traditional sexual selection models because variation in amphibian SSD is unlikely to be driven entirely by sexual selection. We suggest that relaxing a central assumption of classic ecological models—that the sexes share a common adaptive landscape—leads to the alternative hypothesis that independent evolution of the sexes may promote diversification. Once the constraints of sexual conflict are relaxed, the sexes can explore morphospace that would otherwise be inaccessible. Consistent with this novel hypothesis, the evolution of SSD in amphibians is associated with reduced current extinction threat status, and an historical reduction in extinction rate. Our work reconciles conflicting predictions from ecological and evolutionary theory and illustrates that the ability of the sexes to evolve independently is associated with a spectacular vertebrate radiation. PMID:25694616

  20. The evolutionary legacy of diversification predicts ecosystem function

    Czech Academy of Sciences Publication Activity Database

    Yguel, B.; Jactel, H.; Pearse, I. S.; Moen, D.; Winter, M.; Hortal, J.; Helmus, M. R.; Kühn, I.; Pavoine, S.; Purschke, O.; Weiher, E.; Violle, C.; Ozinga, W.; Brändle, M.; Bartish, Igor; Prinzing, A.

    2016-01-01

    Roč. 188, č. 4 (2016), s. 398-410 ISSN 0003-0147 Grant - others:AV ČR(CZ) Fellowship J. E. Purkyně Institutional support: RVO:67985939 Keywords : community ecology * evolutionary history * phylogenetic diversity Subject RIV: EF - Botanics Impact factor: 4.167, year: 2016

  1. Cubozoan genome illuminates functional diversification of opsins and photoreceptor evolution

    Czech Academy of Sciences Publication Activity Database

    Liegertová, Michaela; Pergner, Jiří; Kozmiková, Iryna; Fabian, Peter; Pombinho, António R.; Strnad, Hynek; Pačes, Jan; Vlček, Čestmír; Bartůněk, Petr; Kozmik, Zbyněk

    2015-01-01

    Roč. 5, Jul 8 (2015) ISSN 2045-2322 R&D Projects: GA ČR GAP305/10/2141; GA MŠk LO1220 Institutional support: RVO:68378050 Keywords : Cubozoan genome * opsins * photoreceptor * evolution Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.228, year: 2015

  2. Diversification of the muscle proteome through alternative splicing.

    Science.gov (United States)

    Nakka, Kiran; Ghigna, Claudia; Gabellini, Davide; Dilworth, F Jeffrey

    2018-03-06

    Skeletal muscles express a highly specialized proteome that allows the metabolism of energy sources to mediate myofiber contraction. This muscle-specific proteome is partially derived through the muscle-specific transcription of a subset of genes. Surprisingly, RNA sequencing technologies have also revealed a significant role for muscle-specific alternative splicing in generating protein isoforms that give specialized function to the muscle proteome. In this review, we discuss the current knowledge with respect to the mechanisms that allow pre-mRNA transcripts to undergo muscle-specific alternative splicing while identifying some of the key trans-acting splicing factors essential to the process. The importance of specific splicing events to specialized muscle function is presented along with examples in which dysregulated splicing contributes to myopathies. Though there is now an appreciation that alternative splicing is a major contributor to proteome diversification, the emergence of improved "targeted" proteomic methodologies for detection of specific protein isoforms will soon allow us to better appreciate the extent to which alternative splicing modifies the activity of proteins (and their ability to interact with other proteins) in the skeletal muscle. In addition, we highlight a continued need to better explore the signaling pathways that contribute to the temporal control of trans-acting splicing factor activity to ensure specific protein isoforms are expressed in the proper cellular context. An understanding of the signal-dependent and signal-independent events driving muscle-specific alternative splicing has the potential to provide us with novel therapeutic strategies to treat different myopathies.

  3. Diversification as a Circumvention Strategy to Institutional Constraints in China

    DEFF Research Database (Denmark)

    Xie, Peihong; Li, Xin; Wu, Sibin

    While unrelated diversification (i.e., conglomeration) is deemed value-destroying in the West, many Chinese private firms have been enthusiastically pursuing such a growth strategy. Conventional institutional view of diversification sees conglomerates as responses to market imperfections...... in emerging economies and believes conglomeration is value-creating because conglomerates can effectively fill the institutional voids in the emerging markets. Our literature review shows that the conventional institutional view on conglomeration mainly focuses on the value-creating aspects while neglects...... the socially counterproductive rent-seeking aspects of conglomeration strategy in institution-weak countries (Khanna & Palepu, 2000). In this paper, we fill the gap by examining some unconventional diversifications and point out their rent-seeking nature in China. We have proposed an official...

  4. Can Google Trends search queries contribute to risk diversification?

    Science.gov (United States)

    Kristoufek, Ladislav

    2013-01-01

    Portfolio diversification and active risk management are essential parts of financial analysis which became even more crucial (and questioned) during and after the years of the Global Financial Crisis. We propose a novel approach to portfolio diversification using the information of searched items on Google Trends. The diversification is based on an idea that popularity of a stock measured by search queries is correlated with the stock riskiness. We penalize the popular stocks by assigning them lower portfolio weights and we bring forward the less popular, or peripheral, stocks to decrease the total riskiness of the portfolio. Our results indicate that such strategy dominates both the benchmark index and the uniformly weighted portfolio both in-sample and out-of-sample.

  5. A glimpse on the pattern of rodent diversification

    DEFF Research Database (Denmark)

    Fabre, Pierre-Henri Fréderic; Hautier, Lionel; Dimitrov, Dimitar Stefanov

    2012-01-01

    BACKGROUND:Development of phylogenetic methods that do not rely on fossils for the study of evolutionary processes through time have revolutionized the field of evolutionary biology and resulted in an unprecedented expansion of our knowledge about the tree of life. These methods have helped to shed...... molecular works. A relaxed molecular clock dating approach provided a time framework for speciation events. We found that the Myomorpha clade shows a greater degree of variation in diversification rates than Sciuroidea, Caviomorpha, Castorimorpha and Anomaluromorpha. We identified a number of shifts...... imbalances and the time line we discuss the potential role of different diversification factors that might have shaped the rodents radiation. CONCLUSIONS:The present glimpse on the diversification pattern of rodents can be used for further comparative meta-analyses. Muroid lineages have a greater degree...

  6. Diversification of gas supplies to Romania: options and constraints

    International Nuclear Information System (INIS)

    Kramer, A.

    1996-01-01

    The issue of diversifying natural gas supply to Romania gained importance after 1989. Currently, there are several factors which reinforce the need for the diversification: energy consumption structure; ratio of domestic production to import and traditionally strong natural gas industry. The mentioned points lead to the conclusion that ROMGAZ has to integrate further into the European gas market, to diversify sources of supply and to attract foreign investments. It is clear that the supply diversification depends on three crucial factors: economic recovery (partially achieved after 1992); general price stability (ending permanent depreciation of lev against US dollar); and raising natural gas prices to economic levels. Once those factors are in place, the possibility of gas supply diversification would become more tangible

  7. The challenges of diversification of technologies and markets

    International Nuclear Information System (INIS)

    Bollini, G.

    2003-01-01

    For several years, Tecnatom has been developing a technology and market diversification strategy based on its corporate vision of technological leadership in the services and products it supplies on the national an international nuclear market. Starting with the historical development of these technologies, this article describes how diversification in the global market is initiated and identifies the industrial market segments where the provision of services and the supply of high-tech products can be expanded. It also includes the diversification strategies in these new markets, and presents some of the results obtained in the aeronautical and aerospace market, the transportation market, the industrial processes market, etc. Finally, it provides some examples of the development of new virtual reality and enhanced reality technologies and how these new capabilities are fed back to the nuclear market. (Author)

  8. Left insular cortex and left SFG underlie prismatic adaptation effects on time perception: evidence from fMRI.

    Science.gov (United States)

    Magnani, Barbara; Frassinetti, Francesca; Ditye, Thomas; Oliveri, Massimiliano; Costantini, Marcello; Walsh, Vincent

    2014-05-15

    Prismatic adaptation (PA) has been shown to affect left-to-right spatial representations of temporal durations. A leftward aftereffect usually distorts time representation toward an underestimation, while rightward aftereffect usually results in an overestimation of temporal durations. Here, we used functional magnetic resonance imaging (fMRI) to study the neural mechanisms that underlie PA effects on time perception. Additionally, we investigated whether the effect of PA on time is transient or stable and, in the case of stability, which cortical areas are responsible of its maintenance. Functional brain images were acquired while participants (n=17) performed a time reproduction task and a control-task before, immediately after and 30 min after PA inducing a leftward aftereffect, administered outside the scanner. The leftward aftereffect induced an underestimation of time intervals that lasted for at least 30 min. The left anterior insula and the left superior frontal gyrus showed increased functional activation immediately after versus before PA in the time versus the control-task, suggesting these brain areas to be involved in the executive spatial manipulation of the representation of time. The left middle frontal gyrus showed an increase of activation after 30 min with respect to before PA. This suggests that this brain region may play a key role in the maintenance of the PA effect over time. Copyright © 2014. Published by Elsevier Inc.

  9. Energetic diversification in the interconnected electric system

    International Nuclear Information System (INIS)

    Villanueva M, C.; Beltran M, H.; Serrano G, J.A.

    2007-01-01

    In the interconnected electric system of Mexico the demanded electricity in different timetable periods it is synthesized in the annual curve of load duration, which is characterized by three regions. The energy in every period is quantified according to the under curve areas in each region, which depend of the number of hours in that the power demand exceeds the minimum and the intermediate demands respectively that are certain percentages of the yearly maximum demand. In that context, the generating power stations are dispatched according to the marginal costs of the produced electricity and the electric power to be generated every year by each type of central it is located in some of the regions of the curve of load duration, as they are their marginal costs and their operation characteristic techniques. By strategic reasons it is desirable to diversify the primary energy sources that are used in the national interconnected system to generate the electricity that demand the millions of consumers that there are in Mexico. On one hand, when intensifying the use of renewable sources and of nucleo electric centrals its decrease the import volumes of natural gas, which has very volatile prices and it is a fuel when burning in the power stations produces hothouse gases that are emitted to the atmosphere. On the other hand, when diversifying the installed capacity of the different central types in the interconnected system, a better adaptation of the produced electricity volumes is achieved by each type to the timetable variation, daily, weekly and seasonal of the electric demand, as one manifests this in the curve of load duration. To exemplify a possible diversification plan of the installed capacity in the national interconnected system that includes nucleo electric centrals and those that use renewable energy, charts are presented that project of 2005 at 2015 the capacity, energy and ost of the electricity of different central types, located in each one of the

  10. Early diversification trend and Asian origin for extent bat lineages.

    Science.gov (United States)

    Yu, W; Wu, Y; Yang, G

    2014-10-01

    Bats are a unique mammalian group, which belong to one of the largest and most diverse mammalian radiations, but their early diversification is still poorly understood, and conflicting hypotheses have emerged regarding their biogeographic history. Understanding their diversification is crucial for untangling the enigmatic evolutionary history of bats. In this study, we elucidated the rate of diversification and the biogeographic history of extant bat lineages using genus-level chronograms. The results suggest that a rapid adaptive radiation persisted from the emergence of crown bats until the Early Eocene Climatic Optimum, whereas there was a major deceleration in diversification around 35-49 Ma. There was a positive association between changes in the palaeotemperature and the net diversification rate until 35 Ma, which suggests that the palaeotemperature may have played an important role in the regulation of ecological opportunities. By contrast, there were unexpectedly higher diversification rates around 25-35 Ma during a period characterized by intense and long-lasting global cooling, which implies that intrinsic innovations or adaptations may have released some lineages from the intense selective pressures associated with these severe conditions. Our reconstruction of the ancestral distribution suggests an Asian origin for bats, thereby indicating that the current panglobal but disjunct distribution pattern of extant bats may be related to events involving seriate cross-continental dispersal and local extinction, as well as the influence of geological events and the expansion and contraction of megathermal rainforests during the Tertiary. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  11. Temporal patterns of diversification across global cichlid biodiversity (Acanthomorpha: Cichlidae.

    Directory of Open Access Journals (Sweden)

    Caleb D McMahan

    Full Text Available The contrasting distribution of species diversity across the major lineages of cichlids makes them an ideal group for investigating macroevolutionary processes. In this study, we investigate whether different rates of diversification may explain the disparity in species richness across cichlid lineages globally. We present the most taxonomically robust time-calibrated hypothesis of cichlid evolutionary relationships to date. We then utilize this temporal framework to investigate whether both species-rich and depauperate lineages are associated with rapid shifts in diversification rates and if exceptional species richness can be explained by clade age alone. A single significant rapid rate shift increase is detected within the evolutionary history of the African subfamily Pseudocrenilabrinae, which includes the haplochromins of the East African Great Lakes. Several lineages from the subfamilies Pseudocrenilabrinae (Australotilapiini, Oreochromini and Cichlinae (Heroini exhibit exceptional species richness given their clade age, a net rate of diversification, and relative rates of extinction, indicating that clade age alone is not a sufficient explanation for their increased diversity. Our results indicate that the Neotropical Cichlinae includes lineages that have not experienced a significant rapid burst in diversification when compared to certain African lineages (rift lake. Neotropical cichlids have remained comparatively understudied with regard to macroevolutionary patterns relative to African lineages, and our results indicate that of Neotropical lineages, the tribe Heroini may have an elevated rate of diversification in contrast to other Neotropical cichlids. These findings provide insight into our understanding of the diversification patterns across taxonomically disparate lineages in this diverse clade of freshwater fishes and one of the most species-rich families of vertebrates.

  12. Multiple Continental Radiations and Correlates of Diversification in Lupinus (Leguminosae): Testing for Key Innovation with Incomplete Taxon Sampling

    Science.gov (United States)

    Drummond, Christopher S.; Eastwood, Ruth J.; Miotto, Silvia T. S.; Hughes, Colin E.

    2012-01-01

    Replicate radiations provide powerful comparative systems to address questions about the interplay between opportunity and innovation in driving episodes of diversification and the factors limiting their subsequent progression. However, such systems have been rarely documented at intercontinental scales. Here, we evaluate the hypothesis of multiple radiations in the genus Lupinus (Leguminosae), which exhibits some of the highest known rates of net diversification in plants. Given that incomplete taxon sampling, background extinction, and lineage-specific variation in diversification rates can confound macroevolutionary inferences regarding the timing and mechanisms of cladogenesis, we used Bayesian relaxed clock phylogenetic analyses as well as MEDUSA and BiSSE birth–death likelihood models of diversification, to evaluate the evolutionary patterns of lineage accumulation in Lupinus. We identified 3 significant shifts to increased rates of net diversification (r) relative to background levels in the genus (r = 0.18–0.48 lineages/myr). The primary shift occurred approximately 4.6 Ma (r = 0.48–1.76) in the montane regions of western North America, followed by a secondary shift approximately 2.7 Ma (r = 0.89–3.33) associated with range expansion and diversification of allopatrically distributed sister clades in the Mexican highlands and Andes. We also recovered evidence for a third independent shift approximately 6.5 Ma at the base of a lower elevation eastern South American grassland and campo rupestre clade (r = 0.36–1.33). Bayesian ancestral state reconstructions and BiSSE likelihood analyses of correlated diversification indicated that increased rates of speciation are strongly associated with the derived evolution of perennial life history and invasion of montane ecosystems. Although we currently lack hard evidence for “replicate adaptive radiations” in the sense of convergent morphological and ecological trajectories among species in different

  13. Increased diversification rates follow shifts to bisexuality in liverworts

    DEFF Research Database (Denmark)

    Laenen, Benjamin; Machac, Antonin; Gradstein, S. Robbert

    2016-01-01

    on diversification are presumably mediated by the interplay of high fertilization rates, massive spore production and long-distance dispersal, which may separately or together have facilitated liverwort speciation, suppressed their extinction, or both. Importantly, shifts in liverwort sexual systems have...... shifts in sexual systems influence diversification using hidden state speciation and extinction analysis (HiSSE). This new method compares the effects of the variable of interest to the best-fitting latent variable, yielding robust and conservative tests. We find that the transitions in sexual systems...

  14. REVENUE DIVERSIFICATION, PERFORMANCE, AND BANK RISK: EVIDENCE FROM INDONESIA

    Directory of Open Access Journals (Sweden)

    Mutiara Nur Hafidiyah

    2016-12-01

    Full Text Available This paper examines the effect of revenue diversification on bank performance and bank risk by studying 101 conventional commercial banks in Indonesia over the period of 2010-2014 resulting in 505 observations. By employing panel least square technique, our results show that revenue diversification negatively affects bank performance. Moreover, it is found that diversified banks are riskier than specialized banks. The risk is diminished when state-owned banks diversify their business. Joint venture banks are riskier than other banks when they engage in non-interest income activities.

  15. Industrial diversification and performance in an emerging market

    Directory of Open Access Journals (Sweden)

    Yücel Emel

    2016-01-01

    Full Text Available In this study, we investigated the relationship between industrial diversification and firm performance using a market-based performance measure and an accounting measure. We used the data of the firms listed on Borsa Istanbul during the period between 2006 and 2012. The results of the panel data indicate that there is a significant positive relationship between diversification and performance. We found that diversified firms outperformed the single firms. As is compatible with a resource-based approach, it was found that diversified firms tended to use their resources more efficiently compared to single firms.

  16. Diversification and strategic management of LLNL's R ampersand D portfolio

    International Nuclear Information System (INIS)

    Glinsky, M.E.

    1994-12-01

    Strategic management of LLNL's research effort is addressed. A general framework is established by presenting the McKinsey/BCG Matrix Analysis as it applies to the research portfolio. The framework is used to establish the need for the diversification into new attractive areas of research and for the improvement of the market position of existing research in those attractive areas. With the need for such diversification established, attention is turned to optimizing it. There are limited resources available. It is concluded that LLNL should diversify into only a few areas and try to obtain full market share as soon as possible

  17. Unrelated Diversification and Firm Performance: 1980-2007 Evidence from Italy

    Directory of Open Access Journals (Sweden)

    Raffaele Staglianò

    2012-03-01

    Full Text Available The goal of this article is to examine the relationship between unrelated diversification and performance. Results indicate that diversified firms, investing in activities far from the corebusiness, have high performance. Unrelated diversification positively affects firms’ performance. In addition, the estimation methods applied are fundamental in order to verify if there are endogeneity problems in the diversification decision and evaluate the effective role of diversification on performance.

  18. Discovery of Conservation and Diversification of miR171 Genes by Phylogenetic Analysis based on Global Genomes

    Directory of Open Access Journals (Sweden)

    Xudong Zhu

    2015-07-01

    Full Text Available The microRNA171 (miR171 family is widely distributed and highly conserved in a range of species and plays critical roles in regulating plant growth and development through repressing expression of ( transcription factors. However, information on the evolutionary conservation and functional diversification of the miRNA171 family members remains scanty. We reconstructed the phylogenetic relationships among miR171 precursor and mature sequences so as to investigate the extent and degree of evolutionary conservation of miR171 in (L. Heynh. (ath, grape ( L. (vvi, poplar ( Torr. & A.Gray ex Hook. (ptc, and rice ( L. (osa. Despite strong conservation of over 80%, some mature miR171 sequences, such as , and and , -, and -, have undergone critical sequence variation, leading to functional diversification, since they target non gene transcript(s. Phylogenetic analyses revealed a combination of old ancestral relationships and recent lineage-specific diversification in the miR171 family within the four model plants. The -regulatory motifs on the upstream promoter sequences of genes were highly divergent and shared some similar elements, indicating their possible contribution to the functional variation observed within the miR171 family. This study will buttress our understanding of the functional differentiation of miRNAs and the relationships of miRNA–target pairs based on the evolutionary history of genes.

  19. Curriculum Diversification Re-examined--A Case Study of Sierra Leone.

    Science.gov (United States)

    Wright, Cream A. H.

    This paper deals with a case study of secondary curriculum diversification as a vocationalization strategy in Sierra Leone. It explores diversification issues from four crucial standpoints that are distinct but highly interrelated. First, diversification is dealt with as a policy that was adopted and actively pursued by Sierra Leone for over a…

  20. Tightly congruent bursts of lineage and phenotypic diversification identified in a continental ant radiation

    NARCIS (Netherlands)

    Price, Shauna L; Etienne, Rampal S; Powell, Scott

    Adaptive diversification is thought to be shaped by ecological opportunity. A prediction of this ecological process of diversification is that it should result in congruent bursts of lineage and phenotypic diversification, but few studies have found this expected association. Here, we study the

  1. Complex dynamics underlie the evolution of imperfect wing pattern convergence in butterflies.

    Science.gov (United States)

    Finkbeiner, Susan D; Briscoe, Adriana D; Mullen, Sean P

    2017-04-01

    Adaptive radiation is characterized by rapid diversification that is strongly associated with ecological specialization. However, understanding the evolutionary mechanisms fueling adaptive diversification requires a detailed knowledge of how natural selection acts at multiple life-history stages. Butterflies within the genus Adelpha represent one of the largest and most diverse butterfly lineages in the Neotropics. Although Adelpha species feed on an extraordinary diversity of larval hosts, convergent evolution is widespread in this group, suggesting that selection for mimicry may contribute to adaptive divergence among species. To investigate this hypothesis, we conducted predation studies in Costa Rica using artificial butterfly facsimiles. Specifically, we predicted that nontoxic, palatable Adelpha species that do not feed on host plants in the family Rubiaceae would benefit from sharing a locally convergent wing pattern with the presumably toxic Rubiaceae-feeding species via reduced predation. Contrary to expectations, we found that the presumed mimic was attacked significantly more than its locally convergent model at a frequency paralleling attack rates on both novel and palatable prey. Although these data reveal the first evidence for protection from avian predators by the supposed toxic, Rubiaceae-feeding Adelpha species, we conclude that imprecise mimetic patterns have high costs for Batesian mimics in the tropics. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  2. Phylogenetic analysis reveals conservation and diversification of micro RNA166 genes among diverse plant species.

    Science.gov (United States)

    Barik, Suvakanta; SarkarDas, Shabari; Singh, Archita; Gautam, Vibhav; Kumar, Pramod; Majee, Manoj; Sarkar, Ananda K

    2014-01-01

    Similar to the majority of the microRNAs, mature miR166s are derived from multiple members of MIR166 genes (precursors) and regulate various aspects of plant development by negatively regulating their target genes (Class III HD-ZIP). The evolutionary conservation or functional diversification of miRNA166 family members remains elusive. Here, we show the phylogenetic relationships among MIR166 precursor and mature sequences from three diverse model plant species. Despite strong conservation, some mature miR166 sequences, such as ppt-miR166m, have undergone sequence variation. Critical sequence variation in ppt-miR166m has led to functional diversification, as it targets non-HD-ZIPIII gene transcript (s). MIR166 precursor sequences have diverged in a lineage specific manner, and both precursors and mature osa-miR166i/j are highly conserved. Interestingly, polycistronic MIR166s were present in Physcomitrella and Oryza but not in Arabidopsis. The nature of cis-regulatory motifs on the upstream promoter sequences of MIR166 genes indicates their possible contribution to the functional variation observed among miR166 species. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Ubiquity of Polynucleobacter necessarius subspecies asymbioticus results from ecological diversification

    Czech Academy of Sciences Publication Activity Database

    Jezbera, Jan; Jezberová, Jitka; Brandt, U.; Hahn, M.W.

    2011-01-01

    Roč. 13, č. 4 (2011), s. 922-931 ISSN 1462-2912 R&D Projects: GA ČR(CZ) GAP504/10/0566; GA MŠk(CZ) MEB060901 Institutional research plan: CEZ:AV0Z60170517 Keywords : ubiquity * Polynucleobacter * ecological diversification Subject RIV: EE - Microbiology, Virology Impact factor: 5.843, year: 2011

  4. THEORETICAL BASES OF DIVERSIFICATION OF PENITENTIARY EDUCATIONAL SYSTEM

    Directory of Open Access Journals (Sweden)

    Нэилэ Каюмовна Щепкина

    2013-08-01

    Full Text Available The article deals with the main results of scientific research devoted to the question of theoretical bases of diversification of penitentiary educational system in institutions of confinement.The urgency of scientific research reveals through the social importance of convicts’ education.The article draws attention to the fact that the problem of diversification of penitentiary educational system hasn’t been considered in pedagogy yet.  It also identifies the main contradictions, tasks and methods of scientific research.Retrospective analysis of criminal system inRussiahelps to define the existing tendencies of convicts’ education, unsolved problems in this field of science and formulate perspective ideas to modernize the penitentiary educational system.The item tells about the main point of diversification of penitentiary educational system and presents it in a model. It gives detailed analysis of model’s components and depicts some practical ways of its embodiment in institutions of confinement. Moreover the article describes the determinants of diversification of penitentiary educational system which are seemed to be the factors and conditions of its effective development.DOI: http://dx.doi.org/10.12731/2218-7405-2013-6-20

  5. New insights into diversification of hyper-heuristics.

    Science.gov (United States)

    Ren, Zhilei; Jiang, He; Xuan, Jifeng; Hu, Yan; Luo, Zhongxuan

    2014-10-01

    There has been a growing research trend of applying hyper-heuristics for problem solving, due to their ability of balancing the intensification and the diversification with low level heuristics. Traditionally, the diversification mechanism is mostly realized by perturbing the incumbent solutions to escape from local optima. In this paper, we report our attempt toward providing a new diversification mechanism, which is based on the concept of instance perturbation. In contrast to existing approaches, the proposed mechanism achieves the diversification by perturbing the instance under solving, rather than the solutions. To tackle the challenge of incorporating instance perturbation into hyper-heuristics, we also design a new hyper-heuristic framework HIP-HOP (recursive acronym of HIP-HOP is an instance perturbation-based hyper-heuristic optimization procedure), which employs a grammar guided high level strategy to manipulate the low level heuristics. With the expressive power of the grammar, the constraints, such as the feasibility of the output solution could be easily satisfied. Numerical results and statistical tests over both the Ising spin glass problem and the p -median problem instances show that HIP-HOP is able to achieve promising performances. Furthermore, runtime distribution analysis reveals that, although being relatively slow at the beginning, HIP-HOP is able to achieve competitive solutions once given sufficient time.

  6. Farm Diversification into Tourism--Implications for Social Identity?

    Science.gov (United States)

    Brandth, Berit; Haugen, Marit S.

    2011-01-01

    This article deals with how diversification and transformation of farming into tourism may influence the social identity of farmers. Based on a study of 19 farms run by couples engaged with agritourism, it shows how the development of tourism on the farms can be understood in a perspective of repeasantization; and how the couples draw on their…

  7. A Real Options Perspective On R&D Portfolio Diversification

    NARCIS (Netherlands)

    S. van Bekkum (Sjoerd); H.P.G. Pennings (Enrico); J.T.J. Smit (Han)

    2009-01-01

    textabstractThis paper shows that the conditionality of investment decisions in R&D has a critical impact on portfolio risk, and implies that traditional diversification strategies should be reevaluated when a portfolio is constructed. Real option theory argues that research projects have

  8. A Real Options Perspective on R&D Portfolio Diversification

    NARCIS (Netherlands)

    S. van Bekkum (Sjoerd); H.P.G. Pennings (Enrico); J.T.J. Smit (Han)

    2008-01-01

    textabstractThis paper shows that the presence of conditional staging in R&D (Research & Development) has a critical impact on portfolio risk, and changes diversification arguments when a portfolio is constructed. When R&D projects exhibit option-like characteristics, correlation between projects

  9. Livelihood Diversification Sources of Female Household Heads in ...

    African Journals Online (AJOL)

    Majority (65.8%) of FHH did not have external sources of financial assistance while 21.7% were supported by their children. The study concluded that livelihoods of FHH were diversified mainly within agriculture and trading enterprises. Key words: Livelihood diversification, Female household heads, Rural communities.

  10. Promoting Entrepreneurship and Diversification as a Strategy for ...

    African Journals Online (AJOL)

    Promoting Entrepreneurship and Diversification as a Strategy for Climate Change Adaptation among Rural Women in Anambra State, Nigeria. ... They were involved in enterprises such as planting of crops (88.1%), marketing of farm produce (79.2%), rearing of farm animals (42.2%), petty trading (58.2%), among others.

  11. ANALYSIS OF INVESTMENT DIVERSIFICATION OF THE PRECIOUS METALS

    Directory of Open Access Journals (Sweden)

    Ivan I. Agafonov

    2013-01-01

    Full Text Available Analysis of the impact of investment portfolio of precious metals on its minimum risk with limited mean income is carried out based on the data from the beginning of 2009 to the July of 2013. Vector and matrix criteria of assessment of the effects of investment diversification at the precious metals market are offered.

  12. 84 income and crop diversification among farming households in a ...

    African Journals Online (AJOL)

    OLUWOLE AKINNAGBE

    This is often necessary in agriculture based peasant economies because of risks such as variability in soil quality, household and crop diseases, price shock, unpredictable rainfall and other weather related events. Income diversification can be achieved by producing a variety of crops and/or pursuing off-farm employment.

  13. Early Cretaceous greenhouse pumped higher taxa diversification in spiders.

    Science.gov (United States)

    Shao, Lili; Li, Shuqiang

    2018-05-24

    The Cretaceous experienced one of the most remarkable greenhouse periods in geological history. During this time, ecosystem reorganizations significantly impacted the diversification of many groups of organisms. The rise of angiosperms marked a major biome turnover. Notwithstanding, relatively little remains known about how the Cretaceous global ecosystem impacted the evolution of spiders, which constitute one of the most abundant groups of predators. Herein, we evaluate the transcriptomes of 91 taxa representing more than half of the spider families. We add 23 newly sequenced taxa to the existing database to obtain a robust phylogenomic assessment. Phylogenetic reconstructions using different datasets and methods obtain novel placements of some groups, especially in the Synspermiata and the group having a retrolateral tibial apophysis (RTA). Molecular analyses indicate an expansion of the RTA clade at the Early Cretaceous with a hunting predatory strategy shift. Fossil analyses show a 7-fold increase of diversification rate at the same period, but this likely owes to the first occurrences spider in amber deposits. Additional analyses of fossil abundance show an accumulation of spider lineages in the Early Cretaceous. We speculate that the establishment of a warm greenhouse climate pumped the diversification of spiders, in particular among webless forms tracking the abundance of insect prey. Our study offers a new pathway for future investigations of spider phylogeny and diversification. Copyright © 2018. Published by Elsevier Inc.

  14. Energy diversification and renewable energies for the coming decade

    International Nuclear Information System (INIS)

    Plumejeaud, D.

    1999-01-01

    In the last issue of Gaz d'Aujourd'hui, the relation between energy and ethics during the next century was discussed. This article pursues this reflection, focusing on the problems raised by energy diversification through the use of renewable energies. It presents the main points raised during a meeting held on this topic. (author)

  15. Classroom Diversification: A Strategic View of Educational Productivity

    Science.gov (United States)

    Lopez, Omar S.

    2007-01-01

    This article advances a theory of educational productivity based on a paradigm of classroom diversification that defines a strategic view of the education production process. The paradigm's underlying premise is that classroom student performance, and the instructional interactions that produce such outcomes, depend on economies derived from the…

  16. European Market Portfolio Diversification Strategies across the GFC

    NARCIS (Netherlands)

    D.E. Allen (David); M.J. McAleer (Michael); R.J. Powell (Robert); A.K. Singh (Abhay)

    2014-01-01

    markdownabstract__Abstract__ is paper features an analysis of the effectiveness of a range of portfolio diversification strategies as applied to a set of daily arithmetically compounded returns on a set of ten market indices representing the major European markets for a nine year period from the

  17. Income and crop diversification among farming households in a ...

    African Journals Online (AJOL)

    Both strategies were analyzed based on empirical data collected from rural households. The analysis was done using the Simpson Index of Diversity (SID) and Ordinary least square (OLS) regression analysis. The results revealed that diversification into a number of income sources and crops grown were very high.

  18. The Downside Risk of Heavy Tails induces Low Diversification

    NARCIS (Netherlands)

    N. Hyung (Namwon); C.G. de Vries (Casper)

    2010-01-01

    textabstractActual portfolios contain fewer stocks than are implied by standard financial analysis that balances the costs of diversification against the benefits in terms of the standard deviation of the returns. Suppose a safety first investor cares about downside risk and recognizes the heavy

  19. Constraints to livelihood diversification among rural households in ...

    African Journals Online (AJOL)

    Low farm productivity due to environmental degradation had made rural dwellers in Nigeria to diversify into other business besides agricultural production so as to liberate them from poverty. However, there are various challenges to livelihood diversification among the rural dwellers. This study therefore, identifies ...

  20. Constraints to Occupational Diversification among Rural Women in ...

    African Journals Online (AJOL)

    The mean of farm income was .31,022.8 while the mean of non-farm income was .125,364 (t= 12.136; p=0.05). The study recommends the inclusion of non-farm occupations in rural extension services especially value chain of cash crops as a means of improving income generation. Key words: Occupation, diversification, ...

  1. Enhancing agricultural value chain for economic diversification in ...

    African Journals Online (AJOL)

    This study examined how enhancing the agricultural value chain can contribute to rapid economic diversification in Nigeria within the period of 1981-2015. The autoregressive distributed lag (ARDL) model was employed as the econometric method of estimation. The inferences were drawn at 5% significant level. The result ...

  2. Culture du bambou : diversification des moyens de subsistance des ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Culture du bambou : diversification des moyens de subsistance des petits producteurs de tabac du sud de la province de Nyanza, au Kenya - phase II. Au cours de la première phase du projet (projet no 103765), les chercheurs ont effectué une analyse de marché pour le bambou et les produits du bambou, comparé les ...

  3. Burning phylogenies: fire, molecular evolutionary rates, and diversification.

    Science.gov (United States)

    Verdú, Miguel; Pausas, Juli G; Segarra-Moragues, José Gabriel; Ojeda, Fernando

    2007-09-01

    Mediterranean-type ecosystems are among the most remarkable plant biodiversity "hot spots" on the earth, and fire has traditionally been invoked as one of the evolutionary forces explaining this exceptional diversity. In these ecosystems, adult plants of some species are able to survive after fire (resprouters), whereas in other species fire kills the adults and populations are only maintained by an effective post-fire recruitment (seeders). Seeders tend to have shorter generation times than resprouters, particularly under short fire return intervals, thus potentially increasing their molecular evolutionary rates and, ultimately, their diversification. We explored whether seeder lineages actually have higher rates of molecular evolution and diversification than resprouters. Molecular evolutionary rates in different DNA regions were compared in 45 phylogenetically paired congeneric taxa from fire-prone Mediterranean-type ecosystems with contrasting seeder and resprouter life histories. Differential diversification was analyzed with both topological and chronological approaches in five genera (Banksia, Daviesia, Lachnaea, Leucadendron, and Thamnochortus) from two fire-prone regions (Australia and South Africa). We found that seeders had neither higher molecular rates nor higher diversification than resprouters. Such lack of differences in molecular rates between seeders and resprouters-which did not agree with theoretical predictions-may occur if (1) the timing of the switch from seeding to resprouting (or vice versa) occurs near the branch tip, so that most of the branch length evolves under the opposite life-history form; (2) resprouters suffer more somatic mutations and therefore counterbalancing the replication-induced mutations of seeders; and (3) the rate of mutations is not related to shorter generation times because plants do not undergo determinate germ-line replication. The absence of differential diversification is to be expected if seeders and resprouters

  4. SRSF1-3 contributes to diversification of the immunoglobulin variable region gene by promoting accumulation of AID in the nucleus

    OpenAIRE

    Kawaguchi, Yuka; Nariki, Hiroaki; Kawamoto, Naoko; Kanehiro, Yuichi; Miyazaki, Satoshi; Suzuki, Mari; Magari, Masaki; Tokumitsu, Hiroshi; Kanayama, Naoki

    2017-01-01

     Activation-induced cytidine deaminase (AID) is essential for diversification of the Ig variable region (IgV). AID is excluded from the nucleus, where it normally functions. However, the molecular mechanisms responsible for regulating AID localization remain to be elucidated. The SR-protein splicing factor SRSF1 is a nucleocytoplasmic shuttling protein, a splicing isoform of which called SRSF1-3, has previously been shown to contribute to IgV diversification in chicken DT40 cells. In this stu...

  5. Recreational stimulants, herbal, and spice cannabis: The core psychobiological processes that underlie their damaging effects.

    Science.gov (United States)

    Parrott, Andrew C; Hayley, Amie C; Downey, Luke A

    2017-05-01

    Recreational drugs are taken for their positive mood effects, yet their regular usage damages well-being. The psychobiological mechanisms underlying these damaging effects will be debated. The empirical literature on recreational cannabinoids and stimulant drugs is reviewed. A theoretical explanation for how they cause similar types of damage is outlined. All psychoactive drugs cause moods and psychological states to fluctuate. The acute mood gains underlie their recreational usage, while the mood deficits on withdrawal explain their addictiveness. Cyclical mood changes are found with every central nervous system stimulant and also occur with cannabis. These mood state changes provide a surface index for more profound psychobiological fluctuations. Homeostatic balance is altered, with repetitive disturbances of the hypothalamic-pituitary-adrenal axis, and disrupted cortisol-neurohormonal secretions. Hence, these drugs cause increased stress, disturbed sleep, neurocognitive impairments, altered brain activity, and psychiatric vulnerability. Equivalent deficits occur with novel psychoactive stimulants such as mephedrone and artificial "spice" cannabinoids. These psychobiological fluctuations underlie drug dependency and make cessation difficult. Psychobiological stability and homeostatic balance are optimally restored by quitting psychoactive drugs. Recreational stimulants such as cocaine or MDMA (3.4-methylenedioxymethamphetamine) and sedative drugs such as cannabis damage human homeostasis and well-being through similar core psychobiological mechanisms. Copyright © 2017 John Wiley & Sons, Ltd.

  6. Structure versus time in the evolutionary diversification of avian carotenoid metabolic networks.

    Science.gov (United States)

    Morrison, Erin S; Badyaev, Alexander V

    2018-05-01

    Historical associations of genes and proteins are thought to delineate pathways available to subsequent evolution; however, the effects of past functional involvements on contemporary evolution are rarely quantified. Here, we examined the extent to which the structure of a carotenoid enzymatic network persists in avian evolution. Specifically, we tested whether the evolution of carotenoid networks was most concordant with phylogenetically structured expansion from core reactions of common ancestors or with subsampling of biochemical pathway modules from an ancestral network. We compared structural and historical associations in 467 carotenoid networks of extant and ancestral species and uncovered the overwhelming effect of pre-existing metabolic network structure on carotenoid diversification over the last 50 million years of avian evolution. Over evolutionary time, birds repeatedly subsampled and recombined conserved biochemical modules, which likely maintained the overall structure of the carotenoid metabolic network during avian evolution. These findings explain the recurrent convergence of evolutionary distant species in carotenoid metabolism and weak phylogenetic signal in avian carotenoid evolution. Remarkable retention of an ancient metabolic structure throughout extensive and prolonged ecological diversification in avian carotenoid metabolism illustrates a fundamental requirement of organismal evolution - historical continuity of a deterministic network that links past and present functional associations of its components. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology.

  7. Identifying the valuation effects and agency costs of corporate diversification : Evidence from the geographic diversification of U.S. banks

    NARCIS (Netherlands)

    Laeven, L.; Goetz, M.; Levine, R.

    2013-01-01

    This paper assesses the impact of the geographic diversification of bank holding company (BHC) assets across the United States on their market valuations. Using two new identification strategies based on the dynamic process of interstate bank deregulation, we find that exogenous increases in

  8. SRSF1-3 contributes to diversification of the immunoglobulin variable region gene by promoting accumulation of AID in the nucleus.

    Science.gov (United States)

    Kawaguchi, Yuka; Nariki, Hiroaki; Kawamoto, Naoko; Kanehiro, Yuichi; Miyazaki, Satoshi; Suzuki, Mari; Magari, Masaki; Tokumitsu, Hiroshi; Kanayama, Naoki

    2017-04-01

    Activation-induced cytidine deaminase (AID) is essential for diversification of the Ig variable region (IgV). AID is excluded from the nucleus, where it normally functions. However, the molecular mechanisms responsible for regulating AID localization remain to be elucidated. The SR-protein splicing factor SRSF1 is a nucleocytoplasmic shuttling protein, a splicing isoform of which called SRSF1-3, has previously been shown to contribute to IgV diversification in chicken DT40 cells. In this study, we examined whether SRSF1-3 functions in IgV diversification by promoting nuclear localization of AID. AID expressed alone was localized predominantly in the cytoplasm. In contrast, co-expression of AID with SRSF1-3 led to the nuclear accumulation of both AID and SRSF1-3 and the formation of a protein complex that contained them both, although SRSF1-3 was dispensable for nuclear import of AID. Expression of either SRSF1-3 or a C-terminally-truncated AID mutant increased IgV diversification in DT40 cells. However, overexpression of exogenous SRSF1-3 was unable to further enhance IgV diversification in DT40 cells expressing the truncated AID mutant, although SRSF1-3 was able to form a protein complex with the AID mutant. These results suggest that SRSF1-3 promotes nuclear localization of AID probably by forming a nuclear protein complex, which might stabilize nuclear AID and induce IgV diversification in an AID C-terminus-dependent manner. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Diversification and control in emerging markets: The case of Chilean firms

    Directory of Open Access Journals (Sweden)

    Mauricio Jara-Bertin

    2015-10-01

    Full Text Available We analyze the effect of two types of corporate diversification (business diversification and ownership diversification on the market value of the Chilean firms. For a sample of 83 nonfinancial firms listed on the Santiago Stock Market from 2005 to 2013, we find a discount for both business and ownership diversification, which is consistent with that reported for other economic or institutional settings. Second, we find that the business diversification discount is related to the ownership structure and is due to the excess of the largest shareholders’ control rights. Third, we find that the ownership diversification discount becomes a premium when the ownership diversification enables the control of the affiliated firms. This effect can be explained by the improvement of internal capital markets that allows overcoming the limitations of Chilean external capital markets.

  10. LASER: A Maximum Likelihood Toolkit for Detecting Temporal Shifts in Diversification Rates From Molecular Phylogenies

    Directory of Open Access Journals (Sweden)

    Daniel L. Rabosky

    2006-01-01

    Full Text Available Rates of species origination and extinction can vary over time during evolutionary radiations, and it is possible to reconstruct the history of diversification using molecular phylogenies of extant taxa only. Maximum likelihood methods provide a useful framework for inferring temporal variation in diversification rates. LASER is a package for the R programming environment that implements maximum likelihood methods based on the birth-death process to test whether diversification rates have changed over time. LASER contrasts the likelihood of phylogenetic data under models where diversification rates have changed over time to alternative models where rates have remained constant over time. Major strengths of the package include the ability to detect temporal increases in diversification rates and the inference of diversification parameters under multiple rate-variable models of diversification. The program and associated documentation are freely available from the R package archive at http://cran.r-project.org.

  11. DIVERSIFICATION AS A TOOL OF ANTI-CRISIS STRATEGY OF DEVELOPMENT OF RURAL TERRITORIES IN UKRAINE

    Directory of Open Access Journals (Sweden)

    Arthur Ilnitsky

    2015-11-01

    one of the tools of anti-crisis strategy. The effectiveness of diversification depends on timely guidance on the types of goods and services that are in demand or close to the level of competitiveness. The practical value. Thus, our proposed mechanism for developing a program of social development will help meet the needs of the population in social infrastructure, solve the problem of territorial distribution of these facilities, to develop concrete measures to improve the functioning of the social infrastructure for various purposes and most importantly – to find ways financing of such programs will allow overcoming disparities of regions of Ukraine in general and the regions and districts to provide people with jobs. Value/originality. Diversification of the rural economy is the key to a significant decrease dependence on agriculture and the development of new economic activities, creating new businesses and investments. It can also help increase employment and income of rural population increased output of high value added, improving the quality of human capital and, finally, help boost rural development.

  12. Sensorimotor simulations underlie conceptual representations: modality-specific effects of prior activation.

    Science.gov (United States)

    Pecher, Diane; Zeelenberg, René; Barsalou, Lawrence W

    2004-02-01

    According to the perceptual symbols theory (Barsalou, 1999), sensorimotor simulations underlie the representation of concepts. Simulations are componential in the sense that they vary with the context in which the concept is presented. In the present study, we investigated whether representations are affected by recent experiences with a concept. Concept names (e.g., APPLE) were presented twice in a property verification task with a different property on each occasion. The two properties were either from the same perceptual modality (e.g., green, shiny) or from different modalities (e.g., tart, shiny). All stimuli were words. There was a lag of several intervening trials between the first and second presentation. Verification times and error rates for the second presentation of the concept were higher if the properties were from different modalities than if they were from the same modality.

  13. Protecting the Innocence of Youth: Moral Sanctity Values Underlie Censorship From Young Children.

    Science.gov (United States)

    Anderson, Rajen A; Masicampo, E J

    2017-11-01

    Three studies examined the relationship between people's moral values (drawing on moral foundations theory) and their willingness to censor immoral acts from children. Results revealed that diverse moral values did not predict censorship judgments. It was not the case that participants who valued loyalty and authority, respectively, sought to censor depictions of disloyal and disobedient acts. Rather, censorship intentions were predicted by a single moral value-sanctity. The more people valued sanctity, the more willing they were to censor from children, regardless of the types of violations depicted (impurity, disloyalty, disobedience, etc.). Furthermore, people who valued sanctity objected to indecent exposure only to apparently innocent and pure children-those who were relatively young and who had not been previously exposed to immoral acts. These data suggest that sanctity, purity, and the preservation of innocence underlie intentions to censor from young children.

  14. Activity of the anterior cingulate cortex and ventral hippocampus underlie increases in contextual fear generalization.

    Science.gov (United States)

    Cullen, Patrick K; Gilman, T Lee; Winiecki, Patrick; Riccio, David C; Jasnow, Aaron M

    2015-10-01

    Memories for context become less specific with time resulting in animals generalizing fear from training contexts to novel contexts. Though much attention has been given to the neural structures that underlie the long-term consolidation of a context fear memory, very little is known about the mechanisms responsible for the increase in fear generalization that occurs as the memory ages. Here, we examine the neural pattern of activation underlying the expression of a generalized context fear memory in male C57BL/6J mice. Animals were context fear conditioned and tested for fear in either the training context or a novel context at recent and remote time points. Animals were sacrificed and fluorescent in situ hybridization was performed to assay neural activation. Our results demonstrate activity of the prelimbic, infralimbic, and anterior cingulate (ACC) cortices as well as the ventral hippocampus (vHPC) underlie expression of a generalized fear memory. To verify the involvement of the ACC and vHPC in the expression of a generalized fear memory, animals were context fear conditioned and infused with 4% lidocaine into the ACC, dHPC, or vHPC prior to retrieval to temporarily inactivate these structures. The results demonstrate that activity of the ACC and vHPC is required for the expression of a generalized fear memory, as inactivation of these regions returned the memory to a contextually precise form. Current theories of time-dependent generalization of contextual memories do not predict involvement of the vHPC. Our data suggest a novel role of this region in generalized memory, which should be incorporated into current theories of time-dependent memory generalization. We also show that the dorsal hippocampus plays a prolonged role in contextually precise memories. Our findings suggest a possible interaction between the ACC and vHPC controls the expression of fear generalization. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Emergence, development and diversification of the TGF-beta signalling pathway within the animal kingdom.

    Science.gov (United States)

    Huminiecki, Lukasz; Goldovsky, Leon; Freilich, Shiri; Moustakas, Aristidis; Ouzounis, Christos; Heldin, Carl-Henrik

    2009-02-03

    The question of how genomic processes, such as gene duplication, give rise to co-ordinated organismal properties, such as emergence of new body plans, organs and lifestyles, is of importance in developmental and evolutionary biology. Herein, we focus on the diversification of the transforming growth factor-beta (TGF-beta) pathway -- one of the fundamental and versatile metazoan signal transduction engines. After an investigation of 33 genomes, we show that the emergence of the TGF-beta pathway coincided with appearance of the first known animal species. The primordial pathway repertoire consisted of four Smads and four receptors, similar to those observed in the extant genome of the early diverging tablet animal (Trichoplax adhaerens). We subsequently retrace duplications in ancestral genomes on the lineage leading to humans, as well as lineage-specific duplications, such as those which gave rise to novel Smads and receptors in teleost fishes. We conclude that the diversification of the TGF-beta pathway can be parsimoniously explained according to the 2R model, with additional rounds of duplications in teleost fishes. Finally, we investigate duplications followed by accelerated evolution which gave rise to an atypical TGF-beta pathway in free-living bacterial feeding nematodes of the genus Rhabditis. Our results challenge the view of well-conserved developmental pathways. The TGF-beta signal transduction engine has expanded through gene duplication, continually adopting new functions, as animals grew in anatomical complexity, colonized new environments, and developed an active immune system.

  16. Hold it! The influence of lingering rewards on choice diversification and persistence.

    Science.gov (United States)

    Schulze, Christin; van Ravenzwaaij, Don; Newell, Ben R

    2017-11-01

    Learning to choose adaptively when faced with uncertain and variable outcomes is a central challenge for decision makers. This study examines repeated choice in dynamic probability learning tasks in which outcome probabilities changed either as a function of the choices participants made or independently of those choices. This presence/absence of sequential choice-outcome dependencies was implemented by manipulating a single task aspect between conditions: the retention/withdrawal of reward across individual choice trials. The study addresses how people adapt to these learning environments and to what extent they engage in 2 choice strategies often contrasted as paradigmatic examples of striking violation of versus nominal adherence to rational choice: diversification and persistent probability maximizing, respectively. Results show that decisions approached adaptive choice diversification and persistence when sufficient feedback was provided on the dynamic rules of the probabilistic environments. The findings of divergent behavior in the 2 environments indicate that diversified choices represented a response to the reward retention manipulation rather than to the mere variability of outcome probabilities. Choice in both environments was well accounted for by the generalized matching law, and computational modeling-based strategy analyses indicated that adaptive choice arose mainly from reliance on reinforcement learning strategies. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  17. Hill-Climbing search and diversification within an evolutionary approach to protein structure prediction.

    Science.gov (United States)

    Chira, Camelia; Horvath, Dragos; Dumitrescu, D

    2011-07-30

    Proteins are complex structures made of amino acids having a fundamental role in the correct functioning of living cells. The structure of a protein is the result of the protein folding process. However, the general principles that govern the folding of natural proteins into a native structure are unknown. The problem of predicting a protein structure with minimum-energy starting from the unfolded amino acid sequence is a highly complex and important task in molecular and computational biology. Protein structure prediction has important applications in fields such as drug design and disease prediction. The protein structure prediction problem is NP-hard even in simplified lattice protein models. An evolutionary model based on hill-climbing genetic operators is proposed for protein structure prediction in the hydrophobic - polar (HP) model. Problem-specific search operators are implemented and applied using a steepest-ascent hill-climbing approach. Furthermore, the proposed model enforces an explicit diversification stage during the evolution in order to avoid local optimum. The main features of the resulting evolutionary algorithm - hill-climbing mechanism and diversification strategy - are evaluated in a set of numerical experiments for the protein structure prediction problem to assess their impact to the efficiency of the search process. Furthermore, the emerging consolidated model is compared to relevant algorithms from the literature for a set of difficult bidimensional instances from lattice protein models. The results obtained by the proposed algorithm are promising and competitive with those of related methods.

  18. Fishing for leadership: The role diversification plays in facilitating change agents.

    Science.gov (United States)

    Stoll, Joshua S

    2017-09-01

    Leadership is often viewed as being critical to successful natural resource management. This research focuses on a set of leaders identified through a social network analysis of fishers in a rural coastal region. Leaders' connections to different fisheries are evaluated, and these actors are found to be significantly more diversified than other fishers in the area. Drawing on theory related to institutional entrepreneurship and a series of in-depth interviews with these actors, this paper puts forward several hypotheses to explain how diverse social-ecological connections facilitate leadership. Three mechanisms are identified. Being diversified facilitates: (1) production of alternative visions; (2) framing of tractable strategies to sustain local marine resource; and (3) participation in the management process. While more research is needed to understand the relationship between diversification and leadership, these exploratory results suggest that leadership is, in part, a manifestation of ecological circumstance, supporting recent assertions that scholarship on leadership in natural resource management settings could benefit from being more attentive to the processes that shape leadership rather than fixating on individuals and their personal attributes. Given that fisheries policies increasingly constrain diversification, policymakers and managers should consider how specialization of fishers might change the form and function of leaders in the future. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Diversification Models of Sales Activity for Steady Development of an Enterprise

    Directory of Open Access Journals (Sweden)

    Nestor Shpak

    2016-04-01

    Full Text Available The paper substantiates the importance of the optimal directionality choice of sales activity as one of the main lines of enterprise activity, the functioning of which should be complete, synchronous and complementary. Diversification is one of the powerful instruments to ensure the steady development of the sales activity of an enterprise. Three models of sales activity diversification of an enterprise are developed. The first model is based on unveiling the potential of sales channels and allows us to show the peculiarities of their use. The second model of the optimal quantitative distribution of production between sales channels is based on profit maximization. This approach not only takes into account the evaluation of the prescribed parameters of sales channels, but also provides the high profitability of each assortment item and of the whole enterprise. The third model of the optimal distribution of production between sales channels accounts for the experience of collaboration between the enterprise and sales channels during the past period and ensures the minimal risk and appropriate profitability for each sales channel. The proposed models are tested and compared to actual data of the enterprise; the advantages and peculiarities of each model are discussed.

  20. Hill-Climbing search and diversification within an evolutionary approach to protein structure prediction

    Directory of Open Access Journals (Sweden)

    Chira Camelia

    2011-07-01

    Full Text Available Abstract Proteins are complex structures made of amino acids having a fundamental role in the correct functioning of living cells. The structure of a protein is the result of the protein folding process. However, the general principles that govern the folding of natural proteins into a native structure are unknown. The problem of predicting a protein structure with minimum-energy starting from the unfolded amino acid sequence is a highly complex and important task in molecular and computational biology. Protein structure prediction has important applications in fields such as drug design and disease prediction. The protein structure prediction problem is NP-hard even in simplified lattice protein models. An evolutionary model based on hill-climbing genetic operators is proposed for protein structure prediction in the hydrophobic - polar (HP model. Problem-specific search operators are implemented and applied using a steepest-ascent hill-climbing approach. Furthermore, the proposed model enforces an explicit diversification stage during the evolution in order to avoid local optimum. The main features of the resulting evolutionary algorithm - hill-climbing mechanism and diversification strategy - are evaluated in a set of numerical experiments for the protein structure prediction problem to assess their impact to the efficiency of the search process. Furthermore, the emerging consolidated model is compared to relevant algorithms from the literature for a set of difficult bidimensional instances from lattice protein models. The results obtained by the proposed algorithm are promising and competitive with those of related methods.

  1. Flood protection diversification to reduce probabilities of extreme losses.

    Science.gov (United States)

    Zhou, Qian; Lambert, James H; Karvetski, Christopher W; Keisler, Jeffrey M; Linkov, Igor

    2012-11-01

    Recent catastrophic losses because of floods require developing resilient approaches to flood risk protection. This article assesses how diversification of a system of coastal protections might decrease the probabilities of extreme flood losses. The study compares the performance of portfolios each consisting of four types of flood protection assets in a large region of dike rings. A parametric analysis suggests conditions in which diversifications of the types of included flood protection assets decrease extreme flood losses. Increased return periods of extreme losses are associated with portfolios where the asset types have low correlations of economic risk. The effort highlights the importance of understanding correlations across asset types in planning for large-scale flood protection. It allows explicit integration of climate change scenarios in developing flood mitigation strategy. © 2012 Society for Risk Analysis.

  2. Diversification vs diversity : what will drive diversity in the future

    International Nuclear Information System (INIS)

    Brummell, A.

    1998-01-01

    The issue of what the energy industry of the future will look like was discussed. The core competencies needed for the future, the ways in which they could change the business model for energy companies, and the history of the industry vis-a-vis diversification were outlined. The current forces driving the change towards diversification were identified as technology impacts, deregulation and open competition. The implication of these forces on the structure of the industry were probed. It was concluded that future opportunities for the industry will be influenced by these forces, but the major beneficiaries will be companies that will rely on knowledge not only of technology, but new competencies and business ideas, the ability to develop new markets, new products and emphasize knowledge to leverage assets

  3. Host shifts enhance diversification of ectomycorrhizal fungi: diversification rate analysis of the ectomycorrhizal fungal genera Strobilomyces and Afroboletus with an 80-gene phylogeny.

    Science.gov (United States)

    Sato, Hirotoshi; Tanabe, Akifumi S; Toju, Hirokazu

    2017-04-01

    Mutualisms with new host lineages can provide symbionts with novel ecological opportunities to expand their geographical distribution, thereby leading to evolutionary diversification. Because ectomycorrhizal (ECM) fungi provide ideal opportunities to test the relationship between host shifts and diversification, we tested whether mutualism with new host lineages could increase the diversification rates of ECM fungi. Using a Bayesian tree inferred from 23 027-base nucleotide sequences of 80 single-copy genes, we tested whether the diversification rate had changed through host-shift events in the monophyletic clade containing the ECM fungal genera Strobilomyces and Afroboletus. The results indicated that these fungi were initially associated with Caesalpinioideae/Monotoideae in Africa, acquired associations with Dipterocarpoideae in tropical Asia, and then switched to Fagaceae/Pinaceae and Nothofagaceae/Eucalyptus. Fungal lineages associated with Fagaceae/Pinaceae were inferred to have approximately four-fold and two-fold greater diversification rates than those associated with Caesalpinioideae/Monotoideae and Dipterocarpoideae or Nothofagaceae/Eucalyptus, respectively. Moreover, the diversification rate shift was inferred to follow the host shift to Fagaceae/Pinaceae. Our study suggests that host-shift events, particularly those occurring with respect to Fagaceae/Pinaceae, can provide ecological opportunities for the rapid diversification of Strobilomyces-Afroboletus. Although further studies are needed for generalization, we propose a possible diversification scenario of ECM fungi. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  4. Tightly congruent bursts of lineage and phenotypic diversification identified in a continental ant radiation.

    Science.gov (United States)

    Price, Shauna L; Etienne, Rampal S; Powell, Scott

    2016-04-01

    Adaptive diversification is thought to be shaped by ecological opportunity. A prediction of this ecological process of diversification is that it should result in congruent bursts of lineage and phenotypic diversification, but few studies have found this expected association. Here, we study the relationship between rates of lineage diversification and body size evolution in the turtle ants, a diverse Neotropical clade. Using a near complete, time-calibrated phylogeny we investigated lineage diversification dynamics and body size disparity through model fitting analyses and estimation of per-lineage rates of cladogenesis and phenotypic evolution. We identify an exceptionally high degree of congruence between the high rates of lineage and body size diversification in a young clade undergoing renewed diversification in the ecologically distinct Chacoan biogeographical region of South America. It is likely that the region presented turtle ants with novel ecological opportunity, which facilitated a nested burst of diversification and phenotypic evolution within the group. Our results provide a compelling quantitative example of tight congruence between rates of lineage and phenotypic diversification, meeting the key predicted pattern of adaptive diversification shaped by ecological opportunity. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

  5. Economic Diversification in the GCC; Past, Present, and Future

    OpenAIRE

    Tim Callen; Reda Cherif; Fuad Hasanov; Amgad Hegazy; Padamja Khandelwal

    2014-01-01

    Abstract: The economies of the six Gulf Cooperation Council (GCC) countries are heavily reliant on oil. Greater economic diversification would reduce their exposure to volatility and uncertainty in the global oil market, help create jobs in the private sector, increase productivity and sustainable growth, and help create the non-oil economy that will be needed in the future when oil revenues start to dwindle. The GCC countries have followed many of the standard policies that are usually thoug...

  6. Biogeography and diversification dynamics of the African woodpeckers.

    Science.gov (United States)

    Fuchs, Jérôme; Pons, Jean-Marc; Bowie, Rauri C K

    2017-03-01

    The dynamics of species accumulation of African terrestrial vertebrates over time remains underexplored in comparison with those in the New World, despite Africa hosting about 25% of the world's avian diversity. This lack of knowledge hampers our understanding of the fundamental processes that drive biodiversity and the dynamics of speciation. To begin to address this gap, we reconstructed species-level phylogenies of two unrelated clades of African woodpeckers (12 species of Geocolaptes/Campethera and 13 species of Chloropicus/Mesopicos/Dendropicos/Ipophilus) that diverged from their closest Indo-Malayan relatives at similar times. Our results demonstrate that the current taxonomy is misleading: three (Campethera, Dendropicos and Mesopicos) out of four polytpic genera/subgenera are not monophyletic. Our results also show that current estimates of diversity at the species level are significantly understated, as up to 18 species for the 'Campethera clade' and 19 for the 'Dendropicos clade' could be recognized. The first splits within both clades involve species that are largely restricted to the Guineo-Congolian biogeographic regions, followed by later adaptations to particular habitats (forest versus savannah) and colonization of other regions (e.g. Southern Africa), each of which occurred multiple times in both clades. Assuming a conservative species delimitation scheme, our results indicate that diversification rates are decreasing through time for both clades. Applying a more extreme species recognition scheme (18 and 19 species for the Campethera and Dendropicos clades, respectively), our results support a decrease in diversification rates only for the Dendropicos clade and thus underline the importance of the number of species included in our diversification analyses. Greater ecological diversity of the Campethera clade where multiple species exhibit either an arboreal or terrestrial foraging strategy might explain the constant diversification rates through

  7. Resbuffling of the electric power industries: internationalization new players, diversification

    International Nuclear Information System (INIS)

    Chevalier, J.M.; Salaun, D.

    1995-01-01

    The changes that are being brought in the forms of organization of the power industry lead to a global restructuring of the industry. Traditional players are forced to redefine their strategies concerning vertical and horizontal integration and also diversification. They tend to internationalize their business but they are facing aggressive new-comers. The future structure of the industry is not yet determined but there will be a great number of very different corporate players. (authors). 1 fig

  8. KirCII- promising tool for polyketide diversification

    DEFF Research Database (Denmark)

    Musiol-Kroll, Ewa Maria; Härtner, Thomas; Kulik, Andreas

    2014-01-01

    Kirromycin is produced by Streptomyces collinus Tü 365. This compound is synthesized by a large assembly line of type I polyketide synthases and non-ribosomal peptide synthetases (PKS I/NRPS), encoded by the genes kirAI-kirAVI and kirB. The PKSs KirAI-KirAV have no acyltransferase domains integra...... introducing the non-native substrates in an in vivo context. Thus, KirCII represents a promising tool for polyketide diversification....

  9. Macroevolutionary dynamics in the early diversification of Asteraceae.

    Science.gov (United States)

    Panero, Jose L; Crozier, Bonnie S

    2016-06-01

    Spatial and temporal differences in ecological opportunity can result in disparity of net species diversification rates and consequently uneven distribution of taxon richness across the tree of life. The largest eudicotyledonous plant family Asteraceae has a global distribution and at least 460 times more species than its South American endemic sister family Calyceraceae. In this study, diversification rate dynamics across Asteraceae are examined in light of the several hypothesized causes for the family's evolutionary success that could be responsible for rate change. The innovations of racemose capitulum and pappus, and a whole genome duplication event occurred near the origin of the family, yet we found the basal lineages of Asteraceae that evolved in South America share background diversification rates with Calyceraceae and their Australasian sister Goodeniaceae. Instead we found diversification rates increased gradually from the origin of Asteraceae approximately 69.5Ma in the late Cretaceous through the Early Eocene Climatic Optimum at least. In contrast to earlier studies, significant rate shifts were not strongly correlated with intercontinental dispersals or polyploidization. The difference is due primarily to sampling more backbone nodes, as well as calibrations placed internally in Asteraceae that resulted in earlier divergence times than those found in most previous relaxed clock studies. Two clades identified as having transformed rate processes are the Vernonioid Clade and a clade within the Heliantheae alliance characterized by phytomelanic fruit (PF Clade) that represents an American radiation. In Africa, subfamilies Carduoideae, Pertyoideae, Gymnarrhenoideae, Cichorioideae, Corymbioideae, and Asteroideae diverged in a relatively short span of only 6.5millionyears during the Middle Eocene. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Activity diversification and performance of Islamic banks in Malaysia

    OpenAIRE

    CHATTI, Mohamed Ali; KABLAN, Sandrine; YOUSFI, Ouidad

    2010-01-01

    The current paper analyzes the performance and the choice of portfolio in Islamic banks. We consider a sample of 8 Malaysian universal Islamic banks between 2004 and 2008. We use the Herfindahl-Hirschman Index (HHI) as an indicator of the degree of diversification. The performance of the banks is measured by the return on assets ratio (ROA) and the Risk Adjusted Return On Capital ratio (RAROC). Finally, we use the Modern Portfolio Theory (MPT) of Markowitz to define the efficient frontier and...

  11. Financial education, investor protection and international portfolio diversification

    OpenAIRE

    Maela Giofré

    2012-01-01

    This paper investigates the tension between regulation and financial education in explaining one of the major puzzles in international finance, that is the lack of international diversification. We show that both dimensions are relevant: higher investor’s financial education fosters international investment and stronger minority investor protection legislation attracts inward investment. More interestingly, these factors appear to be substitute in enhancing investor’s portfolio diversificatio...

  12. The Effectiveness of Catastrophe Bonds in Portfolio Diversification

    OpenAIRE

    Mariani, Massimo; Amoruso, Paola

    2016-01-01

    The rapid growth of catastrophe bonds in financial markets is due to increasing environmental disasters and consequent economic losses, barely covered by insurance and reinsurance companies. These securities represent an effective solution, allowing the risk transfer to the capital market. The objective of this paper is to prove real advantages of the investor who operates in this market segment, in terms of portfolio diversification. The present work indeed shows how investing in catastrophe...

  13. Ecological opportunity and the adaptive diversification of lineages.

    Science.gov (United States)

    Wellborn, Gary A; Langerhans, R Brian

    2015-01-01

    The tenet that ecological opportunity drives adaptive diversification has been central to theories of speciation since Darwin, yet no widely accepted definition or mechanistic framework for the concept currently exists. We propose a definition for ecological opportunity that provides an explicit mechanism for its action. In our formulation, ecological opportunity refers to environmental conditions that both permit the persistence of a lineage within a community, as well as generate divergent natural selection within that lineage. Thus, ecological opportunity arises from two fundamental elements: (1) niche availability, the ability of a population with a phenotype previously absent from a community to persist within that community and (2) niche discordance, the diversifying selection generated by the adaptive mismatch between a population's niche-related traits and the newly encountered ecological conditions. Evolutionary response to ecological opportunity is primarily governed by (1) spatiotemporal structure of ecological opportunity, which influences dynamics of selection and development of reproductive isolation and (2) diversification potential, the biological properties of a lineage that determine its capacity to diversify. Diversification under ecological opportunity proceeds as an increase in niche breadth, development of intraspecific ecotypes, speciation, and additional cycles of diversification that may themselves be triggered by speciation. Extensive ecological opportunity may exist in depauperate communities, but it is unclear whether ecological opportunity abates in species-rich communities. Because ecological opportunity should generally increase during times of rapid and multifarious environmental change, human activities may currently be generating elevated ecological opportunity - but so far little work has directly addressed this topic. Our framework highlights the need for greater synthesis of community ecology and evolutionary biology, unifying

  14. Market reactions to Telecom diversification in the smartphone era

    OpenAIRE

    Svendsen, Frid Marie; Kolstad, Elisabeth Vie

    2017-01-01

    Masteroppgave(MSc) in Master of Science in Business, Finance - Handelshøyskolen BI, 2017 In this research, we examine abnormal returns from diversifying acquisition announcements in the period 2000-2016 in the telecom industry. The goal of the research is to shed some light on what impact industry conditions might have on market reactions to diversification. We apply event study methodology on acquisition announcements on a sample of telecom operators and S&P Global 100 compani...

  15. Market reactions to Telecom diversification in the smartphone era

    OpenAIRE

    Svendsen, Frid Marie; Kolstad, Elisabeth Vie

    2017-01-01

    In this research, we examine abnormal returns from diversifying acquisition announcements in the period 2000-2016 in the telecom industry. The goal of the research is to shed some light on what impact industry conditions might have on market reactions to diversification. We apply event study methodology on acquisition announcements on a sample of telecom operators and S&P Global 100 companies. The research find no evidence supporting higher cumulative abnormal return from diver...

  16. Opportunism and diversification : entrepreneurship and livelihood strategies in uncertain times

    OpenAIRE

    Knight, Daniel Martyn

    2015-01-01

    As economic crisis deepens across Europe people are forced to find innovative strategies to accommodate circumstances of chronic uncertainty. Even with a second multi-billion euro bailout package secured for Greece, the prospects of a sustainable recovery in the near future look bleak. However, crisis has also created dynamic spaces for entrepreneurial opportunism and diversification resulting in social mobility, relocation, shifts in livelihood strategy and a burgeoning informal economy. Alt...

  17. Diversification rates and phenotypic evolution in venomous snakes (Elapidae).

    Science.gov (United States)

    Lee, Michael S Y; Sanders, Kate L; King, Benedict; Palci, Alessandro

    2016-01-01

    The relationship between rates of diversification and of body size change (a common proxy for phenotypic evolution) was investigated across Elapidae, the largest radiation of highly venomous snakes. Time-calibrated phylogenetic trees for 175 species of elapids (more than 50% of known taxa) were constructed using seven mitochondrial and nuclear genes. Analyses using these trees revealed no evidence for a link between speciation rates and changes in body size. Two clades (Hydrophis, Micrurus) show anomalously high rates of diversification within Elapidae, yet exhibit rates of body size evolution almost identical to the general elapid 'background' rate. Although correlations between speciation rates and rates of body size change exist in certain groups (e.g. ray-finned fishes, passerine birds), the two processes appear to be uncoupled in elapid snakes. There is also no detectable shift in diversification dynamics associated with the colonization of Australasia, which is surprising given that elapids appear to be the first clade of venomous snakes to reach the continent.

  18. Internal Interface Diversification as a Security Measure in Sensor Networks

    Directory of Open Access Journals (Sweden)

    Sampsa Rauti

    2018-03-01

    Full Text Available More actuator and sensor devices are connected to the Internet of Things (IoT every day, and the network keeps growing, while software security of the devices is often incomplete. Sensor networks and the IoT in general currently cover a large number of devices with an identical internal interface structure. By diversifying the internal interfaces, the interfaces on each node of the network are made unique, and it is possible to break the software monoculture of easily exploitable identical systems. This paper proposes internal interface diversification as a security measure for sensor networks. We conduct a study on diversifiable internal interfaces in 20 IoT operating systems. We also present two proof-of-concept implementations and perform experiments to gauge the feasibility in the IoT environment. Internal interface diversification has practical limitations, and not all IoT operating systems have that many diversifiable interfaces. However, because of low resource requirements, compatibility with other security measures and wide applicability to several interfaces, we believe internal interface diversification is a promising and effective approach for securing nodes in sensor networks.

  19. Ecological specialization and morphological diversification in Greater Antillean boas.

    Science.gov (United States)

    Reynolds, R Graham; Collar, David C; Pasachnik, Stesha A; Niemiller, Matthew L; Puente-Rolón, Alberto R; Revell, Liam J

    2016-08-01

    Colonization of islands can dramatically influence the evolutionary trajectories of organisms, with both deterministic and stochastic processes driving adaptation and diversification. Some island colonists evolve extremely large or small body sizes, presumably in response to unique ecological circumstances present on islands. One example of this phenomenon, the Greater Antillean boas, includes both small (<90 cm) and large (4 m) species occurring on the Greater Antilles and Bahamas, with some islands supporting pairs or trios of body-size divergent species. These boas have been shown to comprise a monophyletic radiation arising from a Miocene dispersal event to the Greater Antilles, though it is not known whether co-occurrence of small and large species is a result of dispersal or in situ evolution. Here, we provide the first comprehensive species phylogeny for this clade combined with morphometric and ecological data to show that small body size evolved repeatedly on separate islands in association with specialization in substrate use. Our results further suggest that microhabitat specialization is linked to increased rates of head shape diversification among specialists. Our findings show that ecological specialization following island colonization promotes morphological diversity through deterministic body size evolution and cranial morphological diversification that is contingent on island- and species-specific factors. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

  20. Structural change and agricultural diversification since China’s reforms

    Directory of Open Access Journals (Sweden)

    Lihua Li

    2017-01-01

    Full Text Available Structural change is considered the major engine in fostering a country’s growth. In the agricultural sector, diversification is the commonly used development strategy to increase rural sector’s flexibility, and to respond to improving technologies and market conditions. This study examined agricultural development and transformation during China’s socio-economic reforms. In particular, it empirically investigated whether the change of China’s agricultural structure is consistent with structural change theory and observed outcomes from other countries. The degree of agricultural diversification was quantitatively measured at a regional scale using the Herfindahl index. An underdeveloped province in northwest China was studied to provide insights into the interaction among structural change, agricultural diversification, and implemented development policies. Aggregate-level analyses suggest that China’s agricultural transformation pattern is consistent with those of other developing countries. A specific provincial-level analysis shows that environmentally and economically disadvantaged regions are slower to diversify their economy than better endorsed regions.

  1. Tempo of trophic evolution and its impact on mammalian diversification.

    Science.gov (United States)

    Price, Samantha A; Hopkins, Samantha S B; Smith, Kathleen K; Roth, V Louise

    2012-05-01

    Mammals are characterized by the complex adaptations of their dentition, which are an indication that diet has played a critical role in their evolutionary history. Although much attention has focused on diet and the adaptations of specific taxa, the role of diet in large-scale diversification patterns remains unresolved. Contradictory hypotheses have been proposed, making prediction of the expected relationship difficult. We show that net diversification rate (the cumulative effect of speciation and extinction), differs significantly among living mammals, depending upon trophic strategy. Herbivores diversify fastest, carnivores are intermediate, and omnivores are slowest. The tempo of transitions between the trophic strategies is also highly biased: the fastest rates occur into omnivory from herbivory and carnivory and the lowest transition rates are between herbivory and carnivory. Extant herbivore and carnivore diversity arose primarily through diversification within lineages, whereas omnivore diversity evolved by transitions into the strategy. The ability to specialize and subdivide the trophic niche allowed herbivores and carnivores to evolve greater diversity than omnivores.

  2. Spatially heterogeneous stochasticity and the adaptive diversification of dormancy.

    Science.gov (United States)

    Rajon, E; Venner, S; Menu, F

    2009-10-01

    Diversified bet-hedging, a strategy that leads several individuals with the same genotype to express distinct phenotypes in a given generation, is now well established as a common evolutionary response to environmental stochasticity. Life-history traits defined as diversified bet-hedging (e.g. germination or diapause strategies) display marked differences between populations in spatial proximity. In order to find out whether such differences can be explained by local adaptations to spatially heterogeneous environmental stochasticity, we explored the evolution of bet-hedging dormancy strategies in a metapopulation using a two-patch model with patch differences in stochastic juvenile survival. We found that spatial differences in the level of environmental stochasticity, restricted dispersal, increased fragmentation and intermediate survival during dormancy all favour the adaptive diversification of bet-hedging dormancy strategies. Density dependency also plays a major role in the diversification of dormancy strategies because: (i) it may interact locally with environmental stochasticity and amplify its effects; however, (ii) it can also generate chaotic population dynamics that may impede diversification. Our work proposes new hypotheses to explain the spatial patterns of bet-hedging strategies that we hope will encourage new empirical studies of this topic.

  3. Orchid phylogenomics and multiple drivers of their extraordinary diversification

    Science.gov (United States)

    Givnish, Thomas J.; Spalink, Daniel; Ames, Mercedes; Lyon, Stephanie P.; Hunter, Steven J.; Zuluaga, Alejandro; Iles, William J. D.; Clements, Mark A.; Arroyo, Mary T. K.; Leebens-Mack, James; Endara, Lorena; Kriebel, Ricardo; Neubig, Kurt M.; Whitten, W. Mark; Williams, Norris H.; Cameron, Kenneth M.

    2015-01-01

    Orchids are the most diverse family of angiosperms, with over 25 000 species, more than mammals, birds and reptiles combined. Tests of hypotheses to account for such diversity have been stymied by the lack of a fully resolved broad-scale phylogeny. Here, we provide such a phylogeny, based on 75 chloroplast genes for 39 species representing all orchid subfamilies and 16 of 17 tribes, time-calibrated against 17 angiosperm fossils. A supermatrix analysis places an additional 144 species based on three plastid genes. Orchids appear to have arisen roughly 112 million years ago (Mya); the subfamilies Orchidoideae and Epidendroideae diverged from each other at the end of the Cretaceous; and the eight tribes and three previously unplaced subtribes of the upper epidendroids diverged rapidly from each other between 37.9 and 30.8 Mya. Orchids appear to have undergone one significant acceleration of net species diversification in the orchidoids, and two accelerations and one deceleration in the upper epidendroids. Consistent with theory, such accelerations were correlated with the evolution of pollinia, the epiphytic habit, CAM photosynthesis, tropical distribution (especially in extensive cordilleras), and pollination via Lepidoptera or euglossine bees. Deceit pollination appears to have elevated the number of orchid species by one-half but not via acceleration of the rate of net diversification. The highest rate of net species diversification within the orchids (0.382 sp sp−1 My−1) is 6.8 times that at the Asparagales crown. PMID:26311671

  4. Cretaceous origin and repeated tertiary diversification of the redefined butterflies.

    Science.gov (United States)

    Heikkilä, Maria; Kaila, Lauri; Mutanen, Marko; Peña, Carlos; Wahlberg, Niklas

    2012-03-22

    Although the taxonomy of the ca 18 000 species of butterflies and skippers is well known, the family-level relationships are still debated. Here, we present, to our knowledge, the most comprehensive phylogenetic analysis of the superfamilies Papilionoidea, Hesperioidea and Hedyloidea to date based on morphological and molecular data. We reconstructed their phylogenetic relationships using parsimony and Bayesian approaches. We estimated times and rates of diversification along lineages in order to reconstruct their evolutionary history. Our results suggest that the butterflies, as traditionally understood, are paraphyletic, with Papilionidae being the sister-group to Hesperioidea, Hedyloidea and all other butterflies. Hence, the families in the current three superfamilies should be placed in a single superfamily Papilionoidea. In addition, we find that Hedylidae is sister to Hesperiidae, and this novel relationship is supported by two morphological characters. The families diverged in the Early Cretaceous but diversified after the Cretaceous-Palaeogene event. The diversification of butterflies is characterized by a slow speciation rate in the lineage leading to Baronia brevicornis, a period of stasis by the skippers after divergence and a burst of diversification in the lineages leading to Nymphalidae, Riodinidae and Lycaenidae.

  5. Eocene diversification of crown group rails (Aves: Gruiformes: Rallidae).

    Science.gov (United States)

    García-R, Juan C; Gibb, Gillian C; Trewick, Steve A

    2014-01-01

    Central to our understanding of the timing of bird evolution is debate about an apparent conflict between fossil and molecular data. A deep age for higher level taxa within Neoaves is evident from molecular analyses but much remains to be learned about the age of diversification in modern bird families and their evolutionary ecology. In order to better understand the timing and pattern of diversification within the family Rallidae we used a relaxed molecular clock, fossil calibrations, and complete mitochondrial genomes from a range of rallid species analysed in a Bayesian framework. The estimated time of origin of Rallidae is Eocene, about 40.5 Mya, with evidence of intrafamiliar diversification from the Late Eocene to the Miocene. This timing is older than previously suggested for crown group Rallidae, but fossil calibrations, extent of taxon sampling and substantial sequence data give it credence. We note that fossils of Eocene age tentatively assigned to Rallidae are consistent with our findings. Compared to available studies of other bird lineages, the rail clade is old and supports an inference of deep ancestry of ground-dwelling habits among Neoaves.

  6. Do holocentric chromosomes represent an evolutionary advantage? A study of paired analyses of diversification rates of lineages with holocentric chromosomes and their monocentric closest relatives.

    Science.gov (United States)

    Márquez-Corro, José Ignacio; Escudero, Marcial; Luceño, Modesto

    2017-10-17

    Despite most of the cytogenetic research is focused on monocentric chromosomes, chromosomes with kinetochoric activity localized in a single centromere, several studies have been centered on holocentric chromosomes which have diffuse kinetochoric activity along the chromosomes. The eukaryotic organisms that present this type of chromosomes have been relatively understudied despite they constitute rather diversified species lineages. On the one hand, holocentric chromosomes may present intrinsic benefits (chromosome mutations such as fissions and fusions are potentially neutral in holocentrics). On the other hand, they present restrictions to the spatial separation of the functions of recombination and segregation during meiotic divisions (functions that may interfere), separation that is found in monocentric chromosomes. In this study, we compare the diversification rates of all known holocentric lineages in animals and plants with their most related monocentric lineages in order to elucidate whether holocentric chromosomes constitute an evolutionary advantage in terms of diversification and species richness. The results showed that null hypothesis of equal mean diversification rates cannot be rejected, leading us to surmise that shifts in diversification rates between holocentric and monocentric lineages might be due to other factors, such as the idiosyncrasy of each lineage or the interplay of evolutionary selections with the benefits of having either monocentric or holocentric chromosomes.

  7. Measuring energy security: Trends in the diversification of oil and natural gas supplies

    International Nuclear Information System (INIS)

    Cohen, Gail; Joutz, Frederick; Loungani, Prakash

    2011-01-01

    We present evidence on one facet of energy security in OECD economies-the extent of diversification in sources of oil and natural gas supplies. Viewed from the perspective of the energy-importing countries as a whole, there has not been much change in diversification in oil supplies over the last decade, but diversification in sources of natural gas supplies has increased steadily. We document the considerable cross-country heterogeneity in the extent of diversification. We also show how the extent of diversification changes if account is taken of the political risk attached to suppliers; the size of the importing country; and transportation risk. - Highlights: → Global diversification is constant but large differences exist among countries. → Political risk and distance have large impacts on diversity measures. → Size has little impact on diversity measures. → France, US, and UK show low vulnerability for both fuels. → Smaller European countries show high vulnerability for both fuels.

  8. How much diversification potential is there in a single market? Evidence from the Australian Stock Exchange

    OpenAIRE

    Yang, Libin; Rea, William; Rea, Alethea

    2015-01-01

    We present four methods of assessing the diversification potential within a stock market, two of these are based on principal component analysis. They were applied to the Australian stock exchange for the years 2000 to 2014 and all show a consistent picture. The potential for diversification declined almost monotonically in the three years prior to the 2008 financial crisis. On one of the measures the diversification potential declined even further in the 2011 European debt crisis and the Ame...

  9. Vulnerabilities in Bytecode Removed by Analysis, Nuanced Confinement and Diversification (VIBRANCE)

    Science.gov (United States)

    2015-06-01

    AFRL-RY-WP-TR-2015-0019 VULNERABILITIES IN BYTECODE REMOVED BY ANALYSIS, NUANCED CONFINEMENT AND DIVERSIFICATION (VIBRANCE) Alessandro...REMOVED BY ANALYSIS, NUANCED CONFINEMENT AND DIVERSIFICATION (VIBRANCE) 5a. CONTRACT NUMBER FA8650-10-C-7026 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...in Bytecode Removed by Analysis, Nuanced Confinement, and Diversification ), is to track the provenance of each piece of data, and defer the

  10. Quantifying the effects of the break up of Pangaea on global terrestrial diversification with neutral theory

    OpenAIRE

    Jordan, S; Barraclough, T; Rosindell, JL

    2016-01-01

    The historic richness of most taxonomic groups increases substantially over geological time. Explanations for this fall broadly into two categories: bias in the fossil record and elevated net rates of diversification in recent periods. For example, the break up of Pangaea and isolation between continents might have increased net diversification rates. In this study, we investigate the effect on terrestrial diversification rates of the increased isolation between land masses brought about by c...

  11. Bank Diversification Effects on Bank Performance and Risk Profile of Bank in Indonesia

    Directory of Open Access Journals (Sweden)

    Anthony Lukmawijaya

    2015-05-01

    Full Text Available We investigate the relationship of Indonesian bank diversification towards its long term performance and risk profile with Indonesian bank data from 2009 to 2013. Non-interest income to total operating income of the bank measures its bank diversification level. Bank value is measured by the adjusted Tobin's Q and risk profile which is broken down into total risk, idiosyncratic risk, and systematic risk. The result shows that bank non-interest income diversification has a positive influence on its franchise value. There is, however, no strong evidence that diversification can lower a bank's risk profile.

  12. Scaling and universality in urban economic diversification.

    Science.gov (United States)

    Youn, Hyejin; Bettencourt, Luís M A; Lobo, José; Strumsky, Deborah; Samaniego, Horacio; West, Geoffrey B

    2016-01-01

    Understanding cities is central to addressing major global challenges from climate change to economic resilience. Although increasingly perceived as fundamental socio-economic units, the detailed fabric of urban economic activities is only recently accessible to comprehensive analyses with the availability of large datasets. Here, we study abundances of business categories across US metropolitan statistical areas, and provide a framework for measuring the intrinsic diversity of economic activities that transcends scales of the classification scheme. A universal structure common to all cities is revealed, manifesting self-similarity in internal economic structure as well as aggregated metrics (GDP, patents, crime). We present a simple mathematical derivation of the universality, and provide a model, together with its economic implications of open-ended diversity created by urbanization, for understanding the observed empirical distribution. Given the universal distribution, scaling analyses for individual business categories enable us to determine their relative abundances as a function of city size. These results shed light on the processes of economic differentiation with scale, suggesting a general structure for the growth of national economies as integrated urban systems. © 2016 The Authors.

  13. Convergences in the diversification of bats

    Directory of Open Access Journals (Sweden)

    M. Brock FENTON

    2010-08-01

    Full Text Available Twenty-five characters or suites of characters from bats are considered in light of changes in bat classification. The characters include some associated with flower-visiting (two, echolocation (12, roosting (six, reproduction (two and three are of unknown adaptive function. In both the 1998 and 2006 classifications of bats into suborders (Megachiroptera and Microchiroptera versus Yinpterochiroptera and Yangochiroptera, respectively, some convergences between suborders are the same (e.g., foliage roosting, tent building, but others associated with echolocation differ substantially. In the 1998 phylogeny convergences associated with echolocation (high duty cycle echolocation, nasal emission of echolocation calls occurred among the Microchiroptera. In the 2006 phylogeny, they occur between Yinpterochiroptera and Yangochiroptera. While some traits apparently arose independently in two suborders (e.g., foliage-roosting, tent building, low intensity echolocation calls, noseleafs, nasal emission of echolocation calls, high duty cycle echolocation behaviour, others appear to have been ancestral (roosting in narrow spaces, laryngeal echolocation, stylohyal-tympanic contact, oral emission of echolocation calls, and small litter size. A narrow profile through the chest is typical of bats reflecting the thoracic skeleton. This feature suggests that the ancestors of bats spent the day in small crevices. Features associated with laryngeal echolocation appear to be ancestral, suggesting that echolocation evolved early in bats but was subsequently lost in one yinpterochiropteran lineage [Current Zoology 56 (4: 454–468, 2010].

  14. Planning-related motor processes underlie mental practice and imitation learning.

    Science.gov (United States)

    Bach, Patric; Allami, Bassem Khalaf; Tucker, Mike; Ellis, Rob

    2014-06-01

    It is still controversial whether mental practice-the internal rehearsal of movements to improve later performance-relies on processes engaged during physical motor performance and, if so, which processes these are. We report data from 5 experiments, in which participants mentally practiced complex rhythms with either feet or hands while using the same or different body parts to respond to unrelated sounds. We found that responses were impaired for those body parts that were concurrently used in mental practice, suggesting a binding of body-part-specific motor processes to action plans. This result was found when participants mentally trained to memorize the rhythms, to merely improve their performance, when mental practice and execution directly followed one another and when separated by a different task. Finally, it was found irrespective of whether participants practiced on the basis of a symbolic rhythm description and when they practiced by watching somebody perform the rhythms (imitation learning). The effect was eliminated only when the requirement for mental practice was eliminated from the task while keeping visual stimulation identical. These data link mental practice not to execution but planning related motor processes and reveal that these planning processes underlie both mental practice and imitation learning. PsycINFO Database Record (c) 2014 APA, all rights reserved.

  15. Distinct neural and neuromuscular strategies underlie independent evolution of simplified advertisement calls.

    Science.gov (United States)

    Leininger, Elizabeth C; Kelley, Darcy B

    2013-04-07

    Independent or convergent evolution can underlie phenotypic similarity of derived behavioural characters. Determining the underlying neural and neuromuscular mechanisms sheds light on how these characters arose. One example of evolutionarily derived characters is a temporally simple advertisement call of male African clawed frogs (Xenopus) that arose at least twice independently from a more complex ancestral pattern. How did simplification occur in the vocal circuit? To distinguish shared from divergent mechanisms, we examined activity from the calling brain and vocal organ (larynx) in two species that independently evolved simplified calls. We find that each species uses distinct neural and neuromuscular strategies to produce the simplified calls. Isolated Xenopus borealis brains produce fictive vocal patterns that match temporal patterns of actual male calls; the larynx converts nerve activity faithfully into muscle contractions and single clicks. In contrast, fictive patterns from isolated Xenopus boumbaensis brains are short bursts of nerve activity; the isolated larynx requires stimulus bursts to produce a single click of sound. Thus, unlike X. borealis, the output of the X. boumbaensis hindbrain vocal pattern generator is an ancestral burst-type pattern, transformed by the larynx into single clicks. Temporally simple advertisement calls in genetically distant species of Xenopus have thus arisen independently via reconfigurations of central and peripheral vocal neuroeffectors.

  16. Rat hippocampal alterations could underlie behavioral abnormalities induced by exposure to moderate noise levels.

    Science.gov (United States)

    Uran, S L; Aon-Bertolino, M L; Caceres, L G; Capani, F; Guelman, L R

    2012-08-30

    Noise exposure is known to affect auditory structures in living organisms. However, it should not be ignored that many of the effects of noise are extra-auditory. Previous findings of our laboratory demonstrated that noise was able to induce behavioral alterations that are mainly related to the cerebellum (CE) and the hippocampus (HC). Therefore, the aim of this work was to reveal new data about the vulnerability of developing rat HC to moderate noise levels through the assessment of potential histological changes and hippocampal-related behavioral alterations. Male Wistar rats were exposed to noise (95-97 dB SPL, 2h daily) either for 1 day (acute noise exposure, ANE) or between postnatal days 15 and 30 (sub-acute noise exposure, SANE). Hippocampal histological evaluation as well as short (ST) and long term (LT) habituation and recognition memory assessments were performed. Results showed a mild disruption in the different hippocampal regions after ANE and SANE schemes, along with significant behavioral abnormalities. These data suggest that exposure of developing rats to noise levels of moderate intensity is able to trigger changes in the HC, an extra-auditory structure of the Central Nervous System (CNS), that could underlie the observed behavioral effects. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Co-Option and De Novo Gene Evolution Underlie Molluscan Shell Diversity

    Science.gov (United States)

    Aguilera, Felipe; McDougall, Carmel

    2017-01-01

    Abstract Molluscs fabricate shells of incredible diversity and complexity by localized secretions from the dorsal epithelium of the mantle. Although distantly related molluscs express remarkably different secreted gene products, it remains unclear if the evolution of shell structure and pattern is underpinned by the differential co-option of conserved genes or the integration of lineage-specific genes into the mantle regulatory program. To address this, we compare the mantle transcriptomes of 11 bivalves and gastropods of varying relatedness. We find that each species, including four Pinctada (pearl oyster) species that diverged within the last 20 Ma, expresses a unique mantle secretome. Lineage- or species-specific genes comprise a large proportion of each species’ mantle secretome. A majority of these secreted proteins have unique domain architectures that include repetitive, low complexity domains (RLCDs), which evolve rapidly, and have a proclivity to expand, contract and rearrange in the genome. There are also a large number of secretome genes expressed in the mantle that arose before the origin of gastropods and bivalves. Each species expresses a unique set of these more ancient genes consistent with their independent co-option into these mantle gene regulatory networks. From this analysis, we infer lineage-specific secretomes underlie shell diversity, and include both rapidly evolving RLCD-containing proteins, and the continual recruitment and loss of both ancient and recently evolved genes into the periphery of the regulatory network controlling gene expression in the mantle epithelium. PMID:28053006

  18. Genetic Defects Underlie the Non-syndromic Autosomal Recessive Intellectual Disability (NS-ARID

    Directory of Open Access Journals (Sweden)

    Saleha Shamim

    2017-05-01

    Full Text Available Intellectual disability (ID is a neurodevelopmental disorder which appears frequently as the result of genetic mutations and may be syndromic (S-ID or non-syndromic (NS-ID. ID causes an important economic burden, for patient's family, health systems, and society. Identifying genes that cause S-ID can easily be evaluated due to the clinical symptoms or physical anomalies. However, in the case of NS-ID due to the absence of co-morbid features, the latest molecular genetic techniques can be used to understand the genetic defects that underlie it. Recent studies have shown that non-syndromic autosomal recessive (NS-ARID is extremely heterogeneous and contributes much more than X-linked ID. However, very little is known about the genes and loci involved in NS-ARID relative to X-linked ID, and whose complete genetic etiology remains obscure. In this review article, the known genetic etiology of NS-ARID and possible relationships between genes and the associated molecular pathways of their encoded proteins has been reviewed which will enhance our understanding about the underlying genes and mechanisms in NS-ARID.

  19. Brain mechanisms that underlie the effects of motivational audiovisual stimuli on psychophysiological responses during exercise.

    Science.gov (United States)

    Bigliassi, Marcelo; Silva, Vinícius B; Karageorghis, Costas I; Bird, Jonathan M; Santos, Priscila C; Altimari, Leandro R

    2016-05-01

    Motivational audiovisual stimuli such as music and video have been widely used in the realm of exercise and sport as a means by which to increase situational motivation and enhance performance. The present study addressed the mechanisms that underlie the effects of motivational stimuli on psychophysiological responses and exercise performance. Twenty-two participants completed fatiguing isometric handgrip-squeezing tasks under two experimental conditions (motivational audiovisual condition and neutral audiovisual condition) and a control condition. Electrical activity in the brain and working muscles was analyzed by use of electroencephalography and electromyography, respectively. Participants were asked to squeeze the dynamometer maximally for 30s. A single-item motivation scale was administered after each squeeze. Results indicated that task performance and situational motivational were superior under the influence of motivational stimuli when compared to the other two conditions (~20% and ~25%, respectively). The motivational stimulus downregulated the predominance of low-frequency waves (theta) in the right frontal regions of the cortex (F8), and upregulated high-frequency waves (beta) in the central areas (C3 and C4). It is suggested that motivational sensory cues serve to readjust electrical activity in the brain; a mechanism by which the detrimental effects of fatigue on the efferent control of working muscles is ameliorated. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Long-Term Synaptic Changes in Two Input Pathways into the Lateral Nucleus of the Amygdala Underlie Fear Extinction

    Science.gov (United States)

    Park, Junchol; Choi, June-Seek

    2010-01-01

    Plasticity in two input pathways into the lateral nucleus of the amygdala (LA), the medial prefrontal cortex (mPFC) and the sensory thalamus, have been suggested to underlie extinction, suppression of a previously acquired conditioned response (CR) following repeated presentations of the conditioned stimulus (CS). However, little is known about…

  1. Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere

    Directory of Open Access Journals (Sweden)

    Antonietta Quigg

    2012-05-01

    Full Text Available The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of inorganic nutrients to carbon in the diversification of the marine biosphere. Nutrient availability and phytoplankton stoichiometry played a critical role in the initial diversification of the marine biosphere during the Neoproterozoic. Initial biosphere expansion during this time resulted in the massive sequestration of nutrients into biomass which, along with the geologically slow input of nutrients from land, set the stage for severe nutrient limitation and relatively constant marine biodiversity during the rest of the Paleozoic. Given the slow nutrient inputs from land and low recycling rates, the growth of early-to-middle Paleozoic metazoans remained limited by their having to expend energy to first “burn off” (respire excess carbon in food before the associated nutrients could be utilized for growth and reproduction; the relative equilibrium in marine biodiversity during the Paleozoic therefore appears to be real. Limited nutrient availability and the consequent nutrient imbalance may have delayed the appearance of more advanced carnivores until the Permo-Carboniferous, when widespread orogeny, falling sea level, the spread of forests, greater weathering rates, enhanced ocean circulation, oxygenation, and upwelling all combined to increase nutrient availability. During the Meso-Cenozoic, rising oxygen levels, the continued nutrient input from land, and, especially, increasing rates of bioturbation, enhanced nutrient availability, increasing the nutrient content of phytoplankton that fueled the diversification of the Modern Fauna.

  2. Impact of whole-genome duplication events on diversification rates in angiosperms.

    Science.gov (United States)

    Landis, Jacob B; Soltis, Douglas E; Li, Zheng; Marx, Hannah E; Barker, Michael S; Tank, David C; Soltis, Pamela S

    2018-03-01

    Polyploidy or whole-genome duplication (WGD) pervades the evolutionary history of angiosperms. Despite extensive progress in our understanding of WGD, the role of these events in promoting diversification is still not well understood. We seek to clarify the possible association between WGD and diversification rates in flowering plants. Using a previously published phylogeny spanning all land plants (31,749 tips) and WGD events inferred from analyses of the 1000 Plants (1KP) transcriptome data, we analyzed the association of WGDs and diversification rates following numerous WGD events across the angiosperms. We used a stepwise AIC approach (MEDUSA), a Bayesian mixture model approach (BAMM), and state-dependent diversification analyses (MuSSE) to investigate patterns of diversification. Sister-clade comparisons were used to investigate species richness after WGDs. Based on the density of 1KP taxon sampling, 106 WGDs were unambiguously placed on the angiosperm phylogeny. We identified 334-530 shifts in diversification rates. We found that 61 WGD events were tightly linked to changes in diversification rates, and state-dependent diversification analyses indicated higher speciation rates for subsequent rounds of WGD. Additionally, 70 of 99 WGD events showed an increase in species richness compared to the sister clade. Forty-six of the 106 WGDs analyzed appear to be closely associated with upshifts in the rate of diversification in angiosperms. Shifts in diversification do not appear more likely than random within a four-node lag phase following a WGD; however, younger WGD events are more likely to be followed by an upshift in diversification than older WGD events. © 2018 Botanical Society of America.

  3. Diversification and autonomy: axes in Argentine rapprochement to Southeast Asia

    Directory of Open Access Journals (Sweden)

    María Florencia Rubiolo

    2017-04-01

    Full Text Available From 2007 onwards, with the change of presidency in Argentina and the consolidation of the internal recovery, the orientation of foreign policy acquires more autonomist nuances. It is in this scenario that the links with less developed countries - or of the South - should be understood, including the ties with the economies of Southeast Asia. Our objective in this work is to analyze the current state of Argentina’s bilateral ties with Southeast Asia - with special emphasis on the Philippines -analyzing these bonds as an alternative for insertion within a strategy of selective diversification and extension of margins of autonomy.

  4. Evolution of exploitative interactions during diversification in Bacillus subtilis biofilms

    DEFF Research Database (Denmark)

    Dragoš, Anna; Lakshmanan, Nivedha; Martin, Marivic

    2018-01-01

    variants. These variants can settle in alternative biofilm niches and develop new types of interactions that greatly influence population productivity. Here, we explore the evolutionary diversification of pellicle biofilms of the Gram positive, spore-forming bacterium Bacillus subtilis. We discover that......-similarly to other species-B. subtilis diversifies into distinct colony variants. These variants dramatically differ in biofilm formation abilities and expression of biofilm-related genes. In addition, using a quantitative approach, we reveal striking differences in surface complexity and hydrophobicity...

  5. Rapid diversification of Tragopogon and ecological associates in Eurasia.

    Science.gov (United States)

    Bell, C D; Mavrodiev, E V; Soltis, P S; Calaminus, A K; Albach, D C; Cellinese, N; Garcia-Jacas, N; Soltis, D E

    2012-12-01

    Tragopogon comprises approximately 150 described species distributed throughout Eurasia from Ireland and the UK to India and China with a few species in North Africa. Most of the species diversity is found in Eastern Europe to Western Asia. Previous phylogenetic analyses identified several major clades, generally corresponding to recognized taxonomic sections, although relationships both among these clades and among species within clades remain largely unresolved. These patterns are consistent with rapid diversification following the origin of Tragopogon, and this study addresses the timing and rate of diversification in Tragopogon. Using BEAST to simultaneously estimate a phylogeny and divergence times, we estimate the age of a major split and subsequent rapid divergence within Tragopogon to be ~2.6 Ma (and 1.7-5.4 Ma using various clock estimates). Based on the age estimates obtained with BEAST (HPD 1.7-5.4 Ma) for the origin of crown group Tragopogon and 200 estimated species (to accommodate a large number of cryptic species), the diversification rate of Tragopogon is approximately 0.84-2.71 species/Myr for the crown group, assuming low levels of extinction. This estimate is comparable in rate to a rapid Eurasian radiation in Dianthus (0.66-3.89 species/Myr), which occurs in the same or similar habitats. Using available data, we show that subclades of various plant taxa that occur in the same semi-arid habitats of Eurasia also represent rapid radiations occurring during roughly the same window of time (1.7-5.4 Ma), suggesting similar causal events. However, not all species-rich plant genera from the same habitats diverged at the same time, or at the same tempo. Radiations of several other clades in this same habitat (e.g. Campanula, Knautia, Scabiosa) occurred at earlier dates (45-4.28 Ma). Existing phylogenetic data and diversification estimates therefore indicate that, although some elements of these semi-arid communities radiated during the Plio

  6. Diversification through Catastrophe Bonds: Lessons from the Subprime Financial Crisis

    OpenAIRE

    Peter Carayannopoulos; M Fabricio Perez

    2015-01-01

    Are catastrophe bonds (CAT bonds) zero-beta investments? Are they a valuable new source of diversification for investors? We study these questions by analysing the dynamic relations of CAT bond returns and the returns of the stock, corporate bond and government bond markets. Our multivariate GARCH model results provide evidence that CAT bonds are zero-beta assets only in non-crisis periods. We document that CAT bonds were not immune to the effects of the recent financial crisis. With the coll...

  7. X-y interactions underlie sperm head abnormality in hybrid male house mice.

    Science.gov (United States)

    Campbell, Polly; Nachman, Michael W

    2014-04-01

    The genetic basis of hybrid male sterility in house mice is complex, highly polygenic, and strongly X linked. Previous work suggested that there might be interactions between the Mus musculus musculus X and the M. m. domesticus Y with a large negative effect on sperm head morphology in hybrid males with an F1 autosomal background. To test this, we introgressed the M. m. domesticus Y onto a M. m. musculus background and measured the change in sperm morphology, testis weight, and sperm count across early backcross generations and in 11th generation backcross males in which the opportunity for X-autosome incompatibilities is effectively eliminated. We found that abnormality in sperm morphology persists in M. m. domesticus Y introgression males, and that this phenotype is rescued by M. m. domesticus introgressions on the X chromosome. In contrast, the severe reductions in testis weight and sperm count that characterize F1 males were eliminated after one generation of backcrossing. These results indicate that X-Y incompatibilities contribute specifically to sperm morphology. In contrast, X-autosome incompatibilities contribute to low testis weight, low sperm count, and sperm morphology. Restoration of normal testis weight and sperm count in first generation backcross males suggests that a small number of complex incompatibilities between loci on the M. m. musculus X and the M. m. domesticus autosomes underlie F1 male sterility. Together, these results provide insight into the genetic architecture of F1 male sterility and help to explain genome-wide patterns of introgression across the house mouse hybrid zone.

  8. Is agriculture driving the diversification of the Bemisia tabaci species complex (Hemiptera: Sternorrhyncha: Aleyrodidae)?: Dating, diversification and biogeographic evidence revealed.

    Science.gov (United States)

    Boykin, Laura M; Bell, Charles D; Evans, Gregory; Small, Ian; De Barro, Paul J

    2013-10-18

    Humans and insect herbivores are competing for the same food crops and have been for thousands of years. Despite considerable advances in crop pest management, losses due to insects remain considerable. The global homogenisation of agriculture has supported the range expansion of numerous insect pests and has been driven in part by human-assisted dispersal supported through rapid global trade and low-cost air passenger transport. One of these pests, is the whitefly, Bemisia tabaci, a cryptic species complex that contains some of the world's most damaging pests of agriculture. The complex shows considerable genetic diversity and strong phylogeographic relationships. One consequence of the considerable impact that members of the B. tabaci complex have on agriculture, is the view that human activity, particularly in relation to agricultural practices, such as use of insecticides, has driven the diversification found within the species complex. This has been particularly so in the case of two members of the complex, Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED), which have become globally distributed invasive species. An alternative hypothesis is that diversification is due to paleogeographic and paleoclimatological changes. The idea that human activity is driving speciation within the B. tabaci complex has never been tested, but the increased interest in fossil whiteflies and the growth in molecular data have enabled us to apply a relaxed molecular clock and so estimate divergence dates for the major lineages within the B. tabaci species complex. The divergence estimates do not support the view that human activity has been a major driver of diversification. Our analysis suggests that the major lineages within the complex arose approximately 60-30 mya and the highly invasive MED and MEAM1 split from the rest of the species complex around 12 mya well before the evolution of Homo sapiens and agriculture. Furthermore, the divergence dates coincide with a period

  9. Diversification of oil import sources and energy security. A key strategy or an elusive objective?

    International Nuclear Information System (INIS)

    Vivoda, Vlado

    2009-01-01

    This paper explores the relationship between the diversification of sources of imported oil and energy security of oil-importing countries. It examines the importance of diversification policy for oil importers, explains why oil importers implement oil diversification policy, and contextualizes the oil import diversification strategy in the overall energy security policy of oil importers. The paper analyzes the factors and the contexts that affect the level of importance assigned to oil import diversification policy in oil-importing countries, and the limitations that may affect the successful implication of oil import diversification policy. The examples are drawn from the world's top three oil importers, the United States, Japan, and China. The policymakers in these and other oil-importing countries place much importance on energy security. The diversification of oil import sources is used as one of the strategies to enhance energy security in oil-importing countries. This paper is important for policymakers in oil-importing countries as it provides them with a qualitative conceptual framework with which to evaluate the need to diversify their countries' sources of imported oil, and with which to identify the likely limitations to the successful implementation of oil import diversification policy. (author)

  10. Down-side Risk Metrics as Portfolio Diversification Strategies across the GFC

    NARCIS (Netherlands)

    D.E. Allen (David); M.J. McAleer (Michael); R.J. Powell (Robert); A.K. Singh (Abhay)

    2015-01-01

    textabstractThis paper features an analysis of the effectiveness of a range of portfolio diversification strategies, with a focus on down-side risk metrics, as a portfolio diversification strategy in a European market context. We apply these measures to a set of daily arithmetically compounded

  11. Uganda Country Economic Memorandum : Economic Diversification and Growth in the Era of Oil and Volatility

    OpenAIRE

    World Bank; Government of Uganda

    2015-01-01

    The objective of the Ugandan government is to make Uganda an upper - middle income country within thirty years. Economic diversification is a key component of that strategy. The country economic memorandum (CEM) report discusses how the emergence of oil and mineral production can contribute to Uganda’s effort to promote economic diversification as a means to achieve sustainable and shared ...

  12. The Impact of Business Diversification on Performance of IDX Listed Firms

    Directory of Open Access Journals (Sweden)

    Ony Humarseno

    2013-07-01

    Full Text Available Normal 0 false false false EN-US X-NONE X-NONE This study analyzes the correlation between business diversification and performances in Indonesian listed companies from 2006-2011. In addition to observing business diversification impact on company’s performance in term of Return on Assets (ROA and Tobin’s Q, this research also observes the business diversification impact on the performances of different companies at different level. The result of this research indicates that diversification gives negative effect to ROA and Tobin’s Q, while for higher level of diversification, the effect on Tobin’s Q is relatively high. The negative effect of diversification on ROA is higher in the group of companies with higher ROA. The different results show that when using Tobin’s Q as a measure of companies’ performances, diversification gives negative impact to companies’ performance in the intermediate level.   Keywords: Diversification, companies’ performance, ROA, quantile regression, Tobin’s Q

  13. 75 FR 3871 - Promoting Diversification of Ownership in Broadcast Services; Suspension of Filing Date

    Science.gov (United States)

    2010-01-25

    ... FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 73 [MB Docket Nos. 07-294, 06-121, 02-277, 04-228; MM Docket Nos. 01-235, 01-317, 00-244; DA 09-2618] Promoting Diversification of Ownership in...); Promoting Diversification in the Broadcasting Services, Order, DA 09-2165 (rel. Oct. 2, 2009). See also...

  14. 13 CFR 107.740 - Portfolio diversification (“overline” limitation).

    Science.gov (United States)

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Portfolio diversification (âoverlineâ limitation). 107.740 Section 107.740 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION... Eligibility of A Small Business for Sbic Financing § 107.740 Portfolio diversification (“overline” limitation...

  15. Estimating diversification rates for higher taxa: BAMM can give problematic estimates of rates and rate shifts.

    Science.gov (United States)

    Meyer, Andreas L S; Wiens, John J

    2018-01-01

    Estimates of diversification rates are invaluable for many macroevolutionary studies. Recently, an approach called BAMM (Bayesian Analysis of Macro-evolutionary Mixtures) has become widely used for estimating diversification rates and rate shifts. At the same time, several articles have concluded that estimates of net diversification rates from the method-of-moments (MS) estimators are inaccurate. Yet, no studies have compared the ability of these two methods to accurately estimate clade diversification rates. Here, we use simulations to compare their performance. We found that BAMM yielded relatively weak relationships between true and estimated diversification rates. This occurred because BAMM underestimated the number of rates shifts across each tree, and assigned high rates to small clades with low rates. Errors in both speciation and extinction rates contributed to these errors, showing that using BAMM to estimate only speciation rates is also problematic. In contrast, the MS estimators (particularly using stem group ages), yielded stronger relationships between true and estimated diversification rates, by roughly twofold. Furthermore, the MS approach remained relatively accurate when diversification rates were heterogeneous within clades, despite the widespread assumption that it requires constant rates within clades. Overall, we caution that BAMM may be problematic for estimating diversification rates and rate shifts. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  16. Global patterns of insect diversification: towards a reconciliation of fossil and molecular evidence?

    Science.gov (United States)

    Condamine, Fabien L; Clapham, Matthew E; Kergoat, Gael J

    2016-01-18

    Macroevolutionary studies of insects at diverse taxonomic scales often reveal dynamic evolutionary patterns, with multiple inferred diversification rate shifts. Responses to major past environmental changes, such as the Cretaceous Terrestrial Revolution, or the development of major key innovations, such as wings or complete metamorphosis are usually invoked as potential evolutionary triggers. However this view is partially contradicted by studies on the family-level fossil record showing that insect diversification was relatively constant through time. In an attempt to reconcile both views, we investigate large-scale insect diversification dynamics at family level using two distinct types of diversification analyses on a molecular timetree representing ca. 82% of the extant families, and reassess the insect fossil diversity using up-to-date records. Analyses focusing on the fossil record recovered an early burst of diversification, declining to low and steady rates through time, interrupted by extinction events. Phylogenetic analyses showed that major shifts of diversification rates only occurred in the four richest holometabolous orders. Both suggest that neither the development of flight or complete metamorphosis nor the Cretaceous Terrestrial Revolution environmental changes induced immediate changes in diversification regimes; instead clade-specific innovations likely promoted the diversification of major insect orders.

  17. 7 CFR 4290.740 - Portfolio diversification (“overline” limitation).

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Portfolio diversification (âoverlineâ limitation). 4290.740 Section 4290.740 Agriculture Regulations of the Department of Agriculture (Continued) RURAL... Enterprise for Rbic Financing § 4290.740 Portfolio diversification (“overline” limitation). (a) Without the...

  18. 13 CFR 108.740 - Portfolio diversification (“overline” limitation).

    Science.gov (United States)

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Portfolio diversification (âoverlineâ limitation). 108.740 Section 108.740 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION... Determining the Eligibility of A Small Business for Nmvc Financing § 108.740 Portfolio diversification...

  19. Patterns of diversification in islands: A comparative study across three gecko genera in the Socotra Archipelago.

    Science.gov (United States)

    Garcia-Porta, Joan; Morales, Hernán E; Gómez-Díaz, Elena; Sindaco, Roberto; Carranza, Salvador

    2016-05-01

    In this study we used the complete fauna of geckos of the Socotra Archipelago to test whether the three gecko genera co-occurring in the islands (Pristurus, Hemidactylus and Haemodracon) produced similar outcomes of morphological and climatic diversification. To test this, we produced a time-calibrated tree of 346 geckos including all 16 endemic species of the archipelago and 26 potential close-relatives in the continent. Our dating estimates revealed that most of the diversity of geckos in the archipelago was the consequence of in situ diversification. However not all genera shared similar patterns of diversification. While in Hemidactylus and Haemodracon this involved great differences in body size and low levels of climatic diversification (mostly involving sympatric distributions), an opposite pattern appeared in Pristurus in which most of the diversification involved shifts in climatic envelopes (mostly involving allopatric and parapatric distributions) but almost no size differentiation. Consistently with this, Pristurus was the only genus in which rates of size diversification in islands were substantially lower than in the continent. This illustrates how different groups can greatly differ in their patterns of intra-island diversification and highlights the importance of taxon-dependent factors at determining different patterns of diversification in the same insular context. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Paleoclimate determines diversification patterns in the fossorial snake family Uropeltidae Cuvier, 1829.

    Science.gov (United States)

    Cyriac, Vivek Philip; Kodandaramaiah, Ullasa

    2017-11-01

    Understanding how and why diversification rates vary across evolutionary time is central to understanding how biodiversity is generated and maintained. Recent mathematical models that allow estimation of diversification rates across time from reconstructed phylogenies have enabled us to make inferences on how biodiversity copes with environmental change. Here, we explore patterns of temporal diversification in Uropeltidae, a diverse fossorial snake family. We generate a time-calibrated phylogenetic hypothesis for Uropeltidae and show a significant correlation between diversification rate and paleotemperature during the Cenozoic. We show that the temporal diversification pattern of this group is punctuated by one rate shift event with a decrease in diversification and turnover rate between ca. 11Ma to present, but there is no strong support for mass extinction events. The analysis indicates higher turnover during periods of drastic climatic fluctuations and reduced diversification rates associated with contraction and fragmentation of forest habitats during the late Miocene. Our study highlights the influence of environmental fluctuations on diversification rates in fossorial taxa such as uropeltids, and raises conservation concerns related to present rate of climate change. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Diversification rates are more strongly related to microhabitat than climate in squamate reptiles (lizards and snakes).

    Science.gov (United States)

    Bars-Closel, Melissa; Kohlsdorf, Tiana; Moen, Daniel S; Wiens, John J

    2017-09-01

    Patterns of species richness among clades can be directly explained by the ages of clades or their rates of diversification. The factors that most strongly influence diversification rates remain highly uncertain, since most studies typically consider only a single predictor variable. Here, we explore the relative impacts of macroclimate (i.e., occurring in tropical vs. temperate regions) and microhabitat use (i.e., terrestrial, fossorial, arboreal, aquatic) on diversification rates of squamate reptile clades (lizards and snakes). We obtained data on microhabitat, macroclimatic distribution, and phylogeny for >4000 species. We estimated diversification rates of squamate clades (mostly families) from a time-calibrated tree, and used phylogenetic methods to test relationships between diversification rates and microhabitat and macroclimate. Across 72 squamate clades, the best-fitting model included microhabitat but not climatic distribution. Microhabitat explained ∼37% of the variation in diversification rates among clades, with a generally positive impact of arboreal microhabitat use on diversification, and negative impacts of fossorial and aquatic microhabitat use. Overall, our results show that the impacts of microhabitat on diversification rates can be more important than those of climate, despite much greater emphasis on climate in previous studies. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  2. Landscape properties as drivers for farm diversification: A Dutch case study

    NARCIS (Netherlands)

    Pfeifer, C.; Jongeneel, R.A.; Sonneveld, M.P.W.; Stoorvogel, J.J.

    2009-01-01

    Farm diversification is stimulated by the societal demand to transform production countryside into consumption countryside. In most empirical studies on farmers¿ decision making for diversification, geographical information is either omitted or reduced to a variable that links the farm to an

  3. INDUSTRIAL DIVERSIFICATION IN NONMETROPOLITAN COUNTIES AND ITS EFFECT ON ECONOMIC STABILITY

    OpenAIRE

    Smith, Stephen M.; Gibson, Cosette M.

    1988-01-01

    Applying indexes of economic instability and industrial diversification to Idaho's forty-three nonmetropolitan counties, this paper tests the hypothesis that unemployment is more stable in a more diverse economy. While results support the hypothesis, other aspects of a county's economic structure are just as influential. Indiscriminate diversification will not necessarily bring economic stability.

  4. Phenotypic Covariation and Morphological Diversification in the Ruminant Skull.

    Science.gov (United States)

    Haber, Annat

    2016-05-01

    Differences among clades in their diversification patterns result from a combination of extrinsic and intrinsic factors. In this study, I examined the role of intrinsic factors in the morphological diversification of ruminants, in general, and in the differences between bovids and cervids, in particular. Using skull morphology, which embodies many of the adaptations that distinguish bovids and cervids, I examined 132 of the 200 extant ruminant species. As a proxy for intrinsic constraints, I quantified different aspects of the phenotypic covariation structure within species and compared them with the among-species divergence patterns, using phylogenetic comparative methods. My results show that for most species, divergence is well aligned with their phenotypic covariance matrix and that those that are better aligned have diverged further away from their ancestor. Bovids have dispersed into a wider range of directions in morphospace than cervids, and their overall disparity is higher. This difference is best explained by the lower eccentricity of bovids' within-species covariance matrices. These results are consistent with the role of intrinsic constraints in determining amount, range, and direction of dispersion and demonstrate that intrinsic constraints can influence macroevolutionary patterns even as the covariance structure evolves.

  5. Information diversification for intelligent diagnosis of nuclear plants

    International Nuclear Information System (INIS)

    Furukawa, Hiroshi; Kuchimura, Keiji; Kitamura, Masaharu; Washio, Takashi.

    1995-01-01

    A general framework for future development of intelligent operator support systems in nuclear plants is proposed in this paper. The central idea in the framework is the decision-making through consensus among multiple agents, each conducting diagnosis on the basis of mutually different, i.e. diverse, principle by focusing dissimilar symptoms obtained from the plant. The applicability and credibility of the operator support system are expected to be significantly improved by implementing the proposed scheme. The effectiveness of diversification in symptom description independently of the effect of reasoning methods was mainly evaluated in this paper. A prototype system was developed for the subtask of fault diagnosis by multiple neural networks emulating the diagnostic agents. The advantage of the proposed framework, together with the related technique of symptom diversification and consensus, was clearly demonstrated through numerical evaluations simulating anomalies in a pressurized water reactor. The obtained results validate, at least to same extent, the present claim of combining multiple and diverse perspectives for reliable decision-making in high-hazard artifacts. (author)

  6. Modular diversification of the locomotor system in damselfishes (Pomacentridae).

    Science.gov (United States)

    Aguilar-Medrano, Rosalía; Frédérich, Bruno; Barber, Paul H

    2016-05-01

    As fish move and interact with their aquatic environment by swimming, small morphological variations of the locomotor system can have profound implications on fitness. Damselfishes (Pomacentridae) have inhabited coral reef ecosystems for more than 50 million years. As such, habitat preferences and behavior could significantly constrain the morphology and evolvability of the locomotor system. To test this hypothesis, we used phylogenetic comparative methods on morphometric, ecological and behavioral data. While body elongation represented the primary source of variation in the locomotor system of damselfishes, results also showed a diverse suite of morphological combinations between extreme morphologies. Results show clear associations between behavior, habitat preferences, and morphology, suggesting ecological constraints on shape diversification of the locomotor system. In addition, results indicate that the three modules of the locomotor system are weakly correlated, resulting in versatile and independent characters. These results suggest that Pomacentridae is shape may result from the interaction between (1) integrated parts of morphological variation that maintain overall swimming ability and (2) relatively independent parts of the morphology that facilitate adaptation and diversification. © 2016 Wiley Periodicals, Inc.

  7. A statistical design for testing apomictic diversification through linkage analysis.

    Science.gov (United States)

    Zeng, Yanru; Hou, Wei; Song, Shuang; Feng, Sisi; Shen, Lin; Xia, Guohua; Wu, Rongling

    2014-03-01

    The capacity of apomixis to generate maternal clones through seed reproduction has made it a useful characteristic for the fixation of heterosis in plant breeding. It has been observed that apomixis displays pronounced intra- and interspecific diversification, but the genetic mechanisms underlying this diversification remains elusive, obstructing the exploitation of this phenomenon in practical breeding programs. By capitalizing on molecular information in mapping populations, we describe and assess a statistical design that deploys linkage analysis to estimate and test the pattern and extent of apomictic differences at various levels from genotypes to species. The design is based on two reciprocal crosses between two individuals each chosen from a hermaphrodite or monoecious species. A multinomial distribution likelihood is constructed by combining marker information from two crosses. The EM algorithm is implemented to estimate the rate of apomixis and test its difference between two plant populations or species as the parents. The design is validated by computer simulation. A real data analysis of two reciprocal crosses between hickory (Carya cathayensis) and pecan (C. illinoensis) demonstrates the utilization and usefulness of the design in practice. The design provides a tool to address fundamental and applied questions related to the evolution and breeding of apomixis.

  8. Does density-dependent diversification mirror ecological competitive exclusion?

    Directory of Open Access Journals (Sweden)

    Melanie J Monroe

    Full Text Available Density-dependence is a term used in ecology to describe processes such as birth and death rates that are regulated by the number of individuals in a population. Evolutionary biologists have borrowed the term to describe decreasing rates of species accumulation, suggesting that speciation and extinction rates depend on the total number of species in a clade. If this analogy with ecological density-dependence holds, diversification of clades is restricted because species compete for limited resources. We hypothesize that such competition should not only affect numbers of species, but also prevent species from being phenotypically similar. Here, we present a method to detect whether competitive interactions between species have ordered phenotypic traits on a phylogeny, assuming that competition prevents related species from having identical trait values. We use the method to analyze clades of birds and mammals, with body size as the phenotypic trait. We find no sign that competition has prevented species from having the same body size. Thus, since body size is a key ecological trait and competition does not seem to be responsible for differences in body size between species, we conclude that the diversification slowdown that is prevalent in these clades is unlikely due to the ecological interference implied by the term density dependence.

  9. Genetic Diversification and Dispersal of Taro (Colocasia esculenta (L. Schott.

    Directory of Open Access Journals (Sweden)

    H Chaïr

    Full Text Available Taro (Colocasia esculenta (L. Schott is widely distributed in tropical and sub-tropical areas. However, its origin, diversification and dispersal remain unclear. While taro genetic diversity has been documented at the country and regional levels in Asia and the Pacific, few reports are available from Americas and Africa where it has been introduced through human migrations. We used eleven microsatellite markers to investigate the diversity and diversification of taro accessions from nineteen countries in Asia, the Pacific, Africa and America. The highest genetic diversity and number of private alleles were observed in Asian accessions, mainly from India. While taro has been diversified in Asia and the Pacific mostly via sexual reproduction, clonal reproduction with mutation appeared predominant in African and American countries investigated. Bayesian clustering revealed a first genetic group of diploids from the Asia-Pacific region and to a second diploid-triploid group mainly from India. Admixed cultivars between the two genetic pools were also found. In West Africa, most cultivars were found to have originated from India. Only one multi-locus lineage was assigned to the Asian pool, while cultivars in Madagascar originated from India and Indonesia. The South African cultivars shared lineages with Japan. The Caribbean Islands cultivars were found to have originated from the Pacific, while in Costa Rica they were from India or admixed between Indian and Asian groups. Taro dispersal in the different areas of Africa and America is thus discussed in the light of available records of voyages and settlements.

  10. DIVERSIFICATION OF FINANCIAL FLOWS IN THE PROMOTION OF ECONOMIC DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    T. Paentko

    2013-08-01

    Full Text Available The article is devoted to the problems of stimulating economic development. International experience of state regulation of economic development is studied. The optimal financing of economic development at the expense of economic entities and the state is justified. Applying of new software to quickly processing and interpreting data, which substantially reduces the time for making financial decisions and reduces the risk of errors. Prospects for further research study identified diversification of financial flows for various real economics industries through the application of information technology. To stimulate the development of the real economy to direct budget investments in terms of growth, which will provide impetus for economic development? In order to overcome the negative impact of institutional deformations in expenditure propose to use the mechanism of diversification of financial flows. Its essence is that the priorities of economic activities funded under the co-financing: budget grant and equity investors. To achieve sustainable GDP growth state should maintain the ratio of budget investments and investments for its own account enterprises in a certain percentage in the form of budget investments and investments on their own businesses.

  11. Ubiquity of Polynucleobacter necessarius subspecies asymbioticus results from ecological diversification

    Science.gov (United States)

    Jezbera, Jan; Jezberová, Jitka; Brandt, Ulrike; Hahn, Martin W

    2011-01-01

    The subspecies Polynucleobacter necessarius asymbioticus (> 99% 16S rRNA similarity) has a cosmopolitan distribution and a ubiquitous occurrence in lentic freshwater habitats. We tested if the observed ubiquity of these free-living planktonic freshwater bacteria results from a euryoecious (generalist) adaptation of P. n. asymbioticus strains, or from ecological diversification within the subspecies. We developed a reverse line blot hybridization assay enabling the cultivation-independent detection of 13 groups within the subspecies in environmental samples. A set of 121 lentic freshwater habitats, spanning a broad variety of habitat types (e.g. pH levels ranging from 3.8 to 8.5) was investigated for the presence of these 13 P. n. asymbioticus groups. Statistical analyses of the reverse line blot hybridization detections revealed pronounced differences in habitat preferences of several of the groups. Their preferences differed regarding pH, conductivity, dissolved organic carbon and oxygen concentration of habitats. For some groups, differences in environmental preferences resulted even in complete niche separation between them. The revealed differences in habitat preferences suggest that the previously reported ubiquity of P. n. asymbioticus results from ecological diversification within the taxon and not from generalist adaptation of strains. PMID:21208356

  12. Divergence and diversification in North American Psoraleeae (Fabaceae) due to climate change

    Science.gov (United States)

    Egan, Ashley N; Crandall, Keith A

    2008-01-01

    Background Past studies in the legume family (Fabaceae) have uncovered several evolutionary trends including differential mutation and diversification rates across varying taxonomic levels. The legume tribe Psoraleeae is shown herein to exemplify these trends at the generic and species levels. This group includes a sizable diversification within North America dated at approximately 6.3 million years ago with skewed species distribution to the most recently derived genus, Pediomelum, suggesting a diversification rate shift. We estimate divergence dates of North American (NAm) Psoraleeae using Bayesian MCMC sampling in BEAST based on eight DNA regions (ITS, waxy, matK, trnD-trnT, trnL-trnF, trnK, trnS-trnG, and rpoB-trnC). We also test the hypothesis of a diversification rate shift within NAm Psoraleeae using topological and temporal methods. We investigate the impact of climate change on diversification in this group by (1) testing the hypothesis that a shift from mesic to xeric habitats acted as a key innovation and (2) investigating diversification rate shifts along geologic time, discussing the impact of Quaternary climate oscillations on diversification. Results NAm Psoraleeae represents a recent, rapid radiation with several genera originating during the Pleistocene, 1 to 2 million years ago. A shift in diversification rate is supported by both methods with a 2.67-fold increase suggested around 2 million years ago followed by a 8.73-fold decrease 440,000 years ago. The hypothesis that a climate regime shift from mesic to xeric habitats drove increased diversification in affected taxa was not supported. Timing of the diversification rate increase supports the hypothesis that glaciation-induced climate changes during the Quaternary influenced diversification of the group. Nonrandom spatial diversification also exists, with greater species richness in the American Southwest. Conclusion This study outlines NAm Psoraleeae as a model example of a recent, rapid

  13. Divergence and diversification in North American Psoraleeae (Fabaceae due to climate change

    Directory of Open Access Journals (Sweden)

    Crandall Keith A

    2008-12-01

    Full Text Available Abstract Background Past studies in the legume family (Fabaceae have uncovered several evolutionary trends including differential mutation and diversification rates across varying taxonomic levels. The legume tribe Psoraleeae is shown herein to exemplify these trends at the generic and species levels. This group includes a sizable diversification within North America dated at approximately 6.3 million years ago with skewed species distribution to the most recently derived genus, Pediomelum, suggesting a diversification rate shift. We estimate divergence dates of North American (NAm Psoraleeae using Bayesian MCMC sampling in BEAST based on eight DNA regions (ITS, waxy, matK, trnD-trnT, trnL-trnF, trnK, trnS-trnG, and rpoB-trnC. We also test the hypothesis of a diversification rate shift within NAm Psoraleeae using topological and temporal methods. We investigate the impact of climate change on diversification in this group by (1 testing the hypothesis that a shift from mesic to xeric habitats acted as a key innovation and (2 investigating diversification rate shifts along geologic time, discussing the impact of Quaternary climate oscillations on diversification. Results NAm Psoraleeae represents a recent, rapid radiation with several genera originating during the Pleistocene, 1 to 2 million years ago. A shift in diversification rate is supported by both methods with a 2.67-fold increase suggested around 2 million years ago followed by a 8.73-fold decrease 440,000 years ago. The hypothesis that a climate regime shift from mesic to xeric habitats drove increased diversification in affected taxa was not supported. Timing of the diversification rate increase supports the hypothesis that glaciation-induced climate changes during the Quaternary influenced diversification of the group. Nonrandom spatial diversification also exists, with greater species richness in the American Southwest. Conclusion This study outlines NAm Psoraleeae as a model example

  14. Tempo of Diversification of Global Amphibians: One-Constant Rate, One-Continuous Shift or Multiple-Discrete Shifts?

    OpenAIRE

    Youhua Chen

    2014-01-01

    In this brief report, alternative time-varying diversification rate models were fitted onto the phylogeny of global amphibians by considering one-constant-rate (OCR), one-continuous-shift (OCS) and multiplediscrete- shifts (MDS) situations. The OCS diversification model was rejected by γ statistic (γ=-5.556, p⁄ 0.001), implying the existence of shifting diversification rates for global amphibian phylogeny. Through model selection, MDS diversification model outperformed OCS and OCR...

  15. Size, Diversification and Risk: Preliminary Evidence from Commercial Banks in Pakistan

    Directory of Open Access Journals (Sweden)

    Ayesha Afzal

    2012-12-01

    Full Text Available The aim of this paper is to provide some preliminary evidence on relation between size, diversification and risk in commercial banks of Pakistan. Using a panel of Pakistani banks, we investigated whether bigger banks are better diversified than smaller banks.The results suggested that larger banks were more diversified than their smaller counterparts mainly on account of their outreach and size of credit portfolio. On the risk side, based on accounting and market based risk measures, we explored if there is any impact of diversification on risk. We could not deduce significant result in favor of accounting risk measure of impaired lending signaling that banks find no incentive in diversification of credit books. The market based measures of VaR and Default indicator were significantly related to diversification signifying that market participants consider diversification as a relevant tool for risk mitigation. These findings have policy implications for regulators and risk management to ensure stability in financial system.

  16. Determinants of Export Diversification in Nigeria: Any Special Role for Foreign Direct Investment (FDI?

    Directory of Open Access Journals (Sweden)

    Damilola Felix Arawomo

    2014-12-01

    Full Text Available The importance of export diversification is presently taking a center stage in trade literature. This paper contributed to the evolving literature by examining the extent of export diversification in Nigeria and also analyzed the impact of foreign direct investment on it. Two major methods of export diversification: export count (horizontal and Herfindahl Index were used. Nigeria’s exports flows based on 4-digit SICT product classification were used. The Generalized Moment Methods (GMM was used to analyze our specified model. Empirical analysis showed that foreign direct investment discourages export diversification in Nigeria, while domestic investment promotes it. Exchange rate and democratic accountability are other factors that discourage export diversification in Nigeria. No evidence was found on the impact of per capita GDP, trade openness and natural resource.

  17. Has frugivory influenced the macroecology and diversification of a tropical keystone plant family?

    Directory of Open Access Journals (Sweden)

    W. Daniel Kissling

    2017-07-01

    Full Text Available Seed dispersal by fruit-eating animals is a pivotal ecosystem function in tropical forests, but the role that frugivores have played in the biogeography and macroevolution of species-rich tropical plant families remains largely unexplored. This project investigates how frugivory-relevant plant traits (e.g. fruit size, fruit color, fruit shape etc. are distributed within the angiosperm family of palms (Arecaceae, how this relates to diversification rates, and whether and how it coincides with the global biogeographic distribution of vertebrate frugivores (birds, bats, primates, other frugivorous mammals and their ecological traits (e.g. diet specialization, body size, flight ability, color vision etc.. Palms are particularly suitable because they are well studied, species-rich, characteristic of tropical rainforests, and dispersed by all groups of vertebrate seed dispersers. Using newly compiled data on species distributions and ecological traits in combination with phylogenies we will test (1 how fruit trait variability relates to palm phylogeny and other aspects of plant morphology (e.g. leaf size, plant height, growth form, (2 whether geographic variability in fruit traits correlates with geographic distributions of animal consumers and their traits, and (3 to what extent interaction-relevant plant traits are related to palm diversification rates. This combined macroecological and macroevolutionary approach allows novel insights into the global ecology and the evolution of a tropical keystone plant family. This is important for the conservation and sustainable management of tropical rainforests because palms are often key components of subsistence economies, ecosystem dynamics and carbon storage and therefore help to enhance nature’s goods, benefits and services to humanity.

  18. Emergence, development and diversification of the TGF-β signalling pathway within the animal kingdom

    Directory of Open Access Journals (Sweden)

    Moustakas Aristidis

    2009-02-01

    Full Text Available Abstract Background The question of how genomic processes, such as gene duplication, give rise to co-ordinated organismal properties, such as emergence of new body plans, organs and lifestyles, is of importance in developmental and evolutionary biology. Herein, we focus on the diversification of the transforming growth factor-β (TGF-β pathway – one of the fundamental and versatile metazoan signal transduction engines. Results After an investigation of 33 genomes, we show that the emergence of the TGF-β pathway coincided with appearance of the first known animal species. The primordial pathway repertoire consisted of four Smads and four receptors, similar to those observed in the extant genome of the early diverging tablet animal (Trichoplax adhaerens. We subsequently retrace duplications in ancestral genomes on the lineage leading to humans, as well as lineage-specific duplications, such as those which gave rise to novel Smads and receptors in teleost fishes. We conclude that the diversification of the TGF-β pathway can be parsimoniously explained according to the 2R model, with additional rounds of duplications in teleost fishes. Finally, we investigate duplications followed by accelerated evolution which gave rise to an atypical TGF-β pathway in free-living bacterial feeding nematodes of the genus Rhabditis. Conclusion Our results challenge the view of well-conserved developmental pathways. The TGF-β signal transduction engine has expanded through gene duplication, continually adopting new functions, as animals grew in anatomical complexity, colonized new environments, and developed an active immune system.

  19. Kv4 channels underlie the subthreshold-operating A-type K+-current in nociceptive dorsal root ganglion neurons

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    Thanawath R Na Phuket

    2009-07-01

    Full Text Available The dorsal root ganglion (DRG contains heterogeneous populations of sensory neurons including primary nociceptive neurons and C-fibers implicated in pain signaling.  Recent studies have demonstrated DRG hyperexcitability associated with downregulation of A-type K+ channels; however, the molecular correlate of the corresponding A-type K+ current (IA has remained hypothetical.  Kv4 channels may underlie the IA in DRG neurons.  We combined electrophysiology, molecular biology (whole-tissue and single-cell RT-PCR and immunohistochemistry to investigate the molecular basis of the IA in acutely dissociated DRG neurons from 7-8 day-old rats.  Whole-cell recordings demonstrate a robust tetraethylammonium-resistant (20 mM and 4-aminopyridine-sensitive (5 mM IA.  Matching Kv4 channel properties, activation and inactivation of this IA occur in the subthreshold range of membrane potentials and the rate of recovery from inactivation is rapid and voltage-dependent.  Among Kv4 transcripts, the DRG expresses significant levels of Kv4.1 and Kv4.3 mRNAs.  Also, single small-medium diameter DRG neurons (~30 mm exhibit correlated frequent expression of mRNAs encoding Kv4.1 and Nav1.8, a known nociceptor marker.  In contrast, the expressions of Kv1.4 and Kv4.2 mRNAs at the whole-tissue and single-cell levels are relatively low and infrequent.  Kv4 protein expression in nociceptive DRG neurons was confirmed by immunohistochemistry, which demonstrates colocalization of Kv4.3 and Nav1.8, and negligible expression of Kv4.2.  Furthermore, specific dominant-negative suppression and overexpression strategies confirmed the contribution of Kv4 channels to IA in DRG neurons.  Contrasting the expression patterns of Kv4 channels in the central and peripheral nervous systems, we discuss possible functional roles of these channels in primary sensory neurons.

  20. [Methodological aspects of the reconstitution and evaluation of the behavioral theories that underlie population policy].

    Science.gov (United States)

    Leeuw, F

    1991-09-01

    This work discusses methodological aspects of the articulation and evaluation of behavioral theories underlying demographic policies. Such theories, called "policy theories" among other terms, may be defined as a group of hypotheses explicitly translated into predictions about behavior that underlie policy measures and that concern the relations between the measure and the objective to be attained. Interest in policy theories has been reflected in the writings of such demographers as D. Bogue, J. Blake, and T. Burch, and of researchers from other social science disciplines. 2 examples of policy theories from the Netherlands are presented to illustrate the discussion, 1 describing family planning communication programs that were intended to reduce the number of unwanted and unplanned pregnancies, and the other describing measures to increase availability of child care services in order to facilitate labor force participation of women and ultimately to increase the birth rate. Both theories are found to be comprised of 2 main parallel theories and several related hypotheses. Because political authorities do not usually make explicit the hypotheses that support political measures, their hypotheses must be articulated and reconstituted through attention to debates, written communications, interviews, and other means. The reconstitution must be done as objectively as possible, which implies the need to follow some methodologic rules. Examples are cited of principles advanced by researchers in management science, market research, and political science. 7 methodological rules or steps are then suggested for articulating policy theories: 1) identify statements relative to the political problem, such as excessive or inadequate fertility rates; 2) use the sources to identify reasons for undertaking concrete policy measures; 3) describe the role of the official in the political process; 4) inventory all declarations concerning the relationship between the objective and the

  1. Evolutionary Diversification of Alanine Transaminases in Yeast: Catabolic Specialization and Biosynthetic Redundancy

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    Ximena Escalera-Fanjul

    2017-06-01

    % identity with LkAlt1 and 66% with KlAlt1, suggests that ScAlt2 diversified after the ancestral hybrid was formed. ScALT2 functional diversification resulted in loss of both alanine transaminase activity and the additional alanine-independent LkAlt1 function, since ScALT2 did not complement the Lkalt1Δ phenotype. It can be concluded that LkALT1 and KlLALT1 functional role as alanine transaminases was delegated to ScALT1, while ScALT2 lost this role during diversification.

  2. Scaffold diversification enhances effectiveness of a superlibrary of hyperthermophilic proteins.

    Science.gov (United States)

    Hussain, Mahmud; Gera, Nimish; Hill, Andrew B; Rao, Balaji M

    2013-01-18

    The use of binding proteins from non-immunoglobulin scaffolds has become increasingly common in biotechnology and medicine. Typically, binders are isolated from a combinatorial library generated by mutating a single scaffold protein. In contrast, here we generated a "superlibrary" or "library-of-libraries" of 4 × 10(8) protein variants by mutagenesis of seven different hyperthermophilic proteins; six of the seven proteins have not been used as scaffolds prior to this study. Binding proteins for five different model targets were successfully isolated from this library. Binders obtained were derived from five out of the seven scaffolds. Strikingly, binders from this modestly sized superlibrary have affinities comparable or higher than those obtained from a library with 1000-fold higher sequence diversity but derived from a single stable scaffold. Thus scaffold diversification, i.e., randomization of multiple different scaffolds, is a powerful alternate strategy for combinatorial library construction.

  3. Higher Education Student Body Diversification as Glocal Practice

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    José Gerardo Alvarado

    2012-07-01

    Full Text Available Georg Simmel's assertion that strangeness organizes nearness and remoteness helps to understand how the social category of First Generation College Student (FGCS, first in the family to attend college is used at a public university in the United States southwest. Membership Categorization Analysis (MCA is applied to ethnographic data. Difference categories and devices morph into those of distance in an interaction where a recruitment convention substitutes for a handshake between a boy and some adults in the hallway of a student center. These changes imbricate with those found in the analysis of a student-persistence sequence of an educational marketing recruitment DVD. As evidence of glocal practice or the global impact of local contact gestures of student body diversification or massification policies directed at FGCSs (and others, they appear to coincide with distribution and recognition social justice projects that are inviting us to reach out across distances, short and long.

  4. Team-up Crop Diversification and Weed Management: PRODIVA

    DEFF Research Database (Denmark)

    Gerowitt, B.; Melander, B.; Krawczyk, R.

    2015-01-01

    The research-network PRODIVA focuses on a better utilization of crop diversification for weed management in North European arable cropping systems. The goal is to maintain diverse arable weed vegetation that is manageable in the long-term and could fulfil other necessary systemfunctions including...... support of beneficial organisms. The partners in PRODIVA will synthesize knowledge from terminated and running research projects and set-up selected new experiments on cover crops and variety resp. crop mixtures. Moreover, we will interact with partners from farming practice and extension services...... in organic agriculture. Regional fields will be surveyed for weeds to safeguard the relevance of the experimental research. Current cropping practices and their influence on weed pressure and weed diversity will be identified. The project will involve relevant stakeholders from the participating countries...

  5. Diversification in toxicology: man and environment. EUROTOX proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Seiler, J.P. [Intercantonal Office for the Control of Medicines (IOCM), Bern (Switzerland); Autrup, J.L.; Autrup, H. [eds.] [Aarhus Univ. (Denmark). Steno Inst. of Public Health

    1998-12-31

    This volume contains the main papers presented at the 1997 EUROTOX Congress, Aaarhus, Denmark, 24-28 June 1997. Diversification in toxicology is not seen as splitting into subfields, but as the application of basic science to such diverse areas as man and his environment. The pressing issues which have been dealt with not only include reproductive effects of environmental chemicals (`xenoestrogens`), but also receptor-mediated toxic responses, new frontiers in human and ecological toxicology, chemoprevention of cancer and molecular approaches in toxicological research. The practical and ethical facets of toxicology, e.g. ecotoxicological risk assessment, biomarkers of exposure, complex chemical mixtures as well as animal welfare and the ethics of animal experimentation, are also treated. (orig.)

  6. International portfolio diversification: United States and south Asian equity markets

    Directory of Open Access Journals (Sweden)

    Mushtaq Rizwan

    2014-01-01

    Full Text Available This paper explores the dynamic liaison between US and three developing South Asian equity markets in short and long term. To gauge the long-term relationship, we applied Johansen co-integration procedure as all the representative indices are found to be non-stationary at level. The findings illustrate that the US equity market index exhibits a reasonably different movement over time in contrast to the three developing equity markets under consideration. However, the Granger-causality test divulge that the direction of causality scamper from US equity market to the three South Asian markets. It further indicates that within the three developing equity markets the direction of causality emanates from Bombay stock market to Karachi and Colombo. Overall, the results of the study suggest that the American investors can get higher returns through international diversification into developing equity markets, while the US stock market would also be a gainful upshot for South Asian investors.

  7. Comparative analysis reveals that polyploidy does not decelerate diversification in fish.

    Science.gov (United States)

    Zhan, S H; Glick, L; Tsigenopoulos, C S; Otto, S P; Mayrose, I

    2014-02-01

    While the proliferation of the species-rich teleost fish has been ascribed to an ancient genome duplication event at the base of this group, the broader impact of polyploidy on fish evolution and diversification remains poorly understood. Here, we investigate the association between polyploidy and diversification in several fish lineages: the sturgeons (Acipenseridae: Acipenseriformes), the botiid loaches (Botiidae: Cypriniformes), Cyprininae fishes (Cyprinidae: Cypriniformes) and the salmonids (Salmonidae: Salmoniformes). Using likelihood-based evolutionary methodologies, we co-estimate speciation and extinction rates associated with polyploid vs. diploid fish lineages. Family-level analysis of Acipenseridae and Botiidae revealed no significant difference in diversification rates between polyploid and diploid relatives, while analysis of the subfamily Cyprininae revealed higher polyploid diversification. Additionally, order-level analysis of the polyploid Salmoniformes and its diploid sister clade, the Esociformes, did not support a significantly different net diversification rate between the two groups. Taken together, our results suggest that polyploidy is generally not associated with decreased diversification in fish - a pattern that stands in contrast to that previously observed in plants. While there are notable differences in the time frame examined in the two studies, our results suggest that polyploidy is associated with different diversification patterns in these two major branches of the eukaryote tree of life. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  8. Ecological opportunities, habitat, and past climatic fluctuations influenced the diversification of modern turtles.

    Science.gov (United States)

    Rodrigues, João Fabrício Mota; Diniz-Filho, José Alexandre Felizola

    2016-08-01

    Habitat may be viewed as an important life history component potentially related to diversification patterns. However, differences in diversification rates between aquatic and terrestrial realms are still poorly explored. Testudines is a group distributed worldwide that lives in aquatic and terrestrial environments, but until now no-one has evaluated the diversification history of the group as a whole. We aim here to investigate the diversification history of turtles and to test if habitat influenced speciation rate in these animals. We reconstructed the phylogeny of the modern species of chelonians and estimated node divergence dates using molecular markers and a Bayesian approach. Then, we used Bayesian Analyses of Macroevolutionary Mixtures to evaluate the diversification history of turtles and evaluate the effect of habitat on this pattern. Our reconstructed phylogeny covered 300 species (87% of the total diversity of the group). We found that the emydid subfamily Deirochelyinae, which forms the turtle hotspot in south-eastern United States, had an increase in its speciation rate, and that Galapagos tortoises had similar increases. Current speciation rates are lower in terrestrial turtles, contradicting studies supporting the idea terrestrial animals diversify more than aquatic species. Our results suggest that habitat, ecological opportunities, island invasions, and climatic factors are important drivers of diversification in modern turtles and reinforce the importance of habitat as a diversification driver. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. DETERMINANTS OF INCOME DIVERSIFICATION AMONG MAIZE FARM HOUSEHOLDS IN THE GARU-TEMPANE DISTRICT, GHANA

    Directory of Open Access Journals (Sweden)

    Gilbert DAGUNGA

    2018-03-01

    Full Text Available This study explores the determinants of income diversification using a sample of 200 farm-level data collected from households in the Garu-Tampane district, Ghana. The Simpson Index of Diversification was used to determine the extent of income diversification while Fractional Response Model, particularly Generalized Linear Model (GLM was employed to identify the determinants of income diversification. Results from the Simpson Index of Diversification showed that the average income diversification index was 0.65 with the minimum and maximum of 0.13 and 0.83, respectively. No farm household was found to depend solely on a single source of income for its survival. The results from the Generalized Linear Model revealed that extension services, attendance to demonstration fields, membership of Farmer-based Organizations (FBOs, farmer accessibility to credit, the number of days spent on on-farm activities per month and the number of years in maize farming significantly influence income diversification. The study, therefore, concludes that farm-level policies geared towards alternative sources of income for the rural farm household should focus on improving extension services, the formation of farmer-based organizations, use of demonstration fields as well as ensuring farmers’ accessibility to credit.

  10. 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.

  11. Exploring Diversification as A Management Strategy in Substance Use Disorder Treatment Organizations.

    Science.gov (United States)

    Fields, Dail; Riesenmy, Kelly; Roman, Paul M

    2015-10-01

    Implementation of the Affordable Care Act (ACA) creates both environmental uncertainties and opportunities for substance use disorder (SUD) treatment providers. One managerial response to uncertainties and emergent opportunities is strategic diversification of various dimensions of organizational activity. This paper explored organizational outcomes related to diversification of funding sources, services offered, and referral sources in a national sample of 590 SUD treatment organizations. Funding diversification was related to higher average levels of census, organization size, and recent expansion of operations. Service diversification was related to higher average levels of use of medication-assisted treatment (MAT), organization size, and expansion. Referral source diversification was related only to greater average use of MAT. Overall, strategic diversification in the three areas explored was related to positive organizational outcomes. Considering alternative strategies of diversification may help position SUD treatment centers to deliver more innovative treatments such as MAT as well as enhance capacity to satisfy current unmet treatment needs of individuals with behavioral health coverage provided under the ACA. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Into and out of the tropics: global diversification patterns in a hyperdiverse clade of ectomycorrhizal fungi.

    Science.gov (United States)

    Looney, Brian P; Ryberg, Martin; Hampe, Felix; Sánchez-García, Marisol; Matheny, P Brandon

    2016-01-01

    Ectomycorrhizal (ECM) fungi, symbiotic mutualists of many dominant tree and shrub species, exhibit a biogeographic pattern counter to the established latitudinal diversity gradient of most macroflora and fauna. However, an evolutionary basis for this pattern has not been explicitly tested in a diverse lineage. In this study, we reconstructed a mega-phylogeny of a cosmopolitan and hyperdiverse genus of ECM fungi, Russula, sampling from annotated collections and utilizing publically available sequences deposited in GenBank. Metadata from molecular operational taxonomic unit cluster sets were examined to infer the distribution and plant association of the genus. This allowed us to test for differences in patterns of diversification between tropical and extratropical taxa, as well as how their associations with different plant lineages may be a driver of diversification. Results show that Russula is most species-rich at temperate latitudes and ancestral state reconstruction shows that the genus initially diversified in temperate areas. Migration into and out of the tropics characterizes the early evolution of the genus, and these transitions have been frequent since this time. We propose the 'generalized diversification rate' hypothesis to explain the reversed latitudinal diversity gradient pattern in Russula as we detect a higher net diversification rate in extratropical lineages. Patterns of diversification with plant associates support host switching and host expansion as driving diversification, with a higher diversification rate in lineages associated with Pinaceae and frequent transitions to association with angiosperms. © 2015 John Wiley & Sons Ltd.

  13. Contrasting patterns of Andean diversification among three diverse clades of Neotropical clearwing butterflies.

    Science.gov (United States)

    Chazot, Nicolas; De-Silva, Donna Lisa; Willmott, Keith R; Freitas, André V L; Lamas, Gerardo; Mallet, James; Giraldo, Carlos E; Uribe, Sandra; Elias, Marianne

    2018-04-01

    The Neotropical region is the most biodiverse on Earth, in a large part due to the highly diverse tropical Andean biota. The Andes are a potentially important driver of diversification within the mountains and for neighboring regions. We compared the role of the Andes in diversification among three subtribes of Ithomiini butterflies endemic to the Neotropics, Dircennina, Oleriina, and Godyridina. The diversification patterns of Godyridina have been studied previously. Here, we generate the first time-calibrated phylogeny for the largest ithomiine subtribe, Dircennina, and we reanalyze a published phylogeny of Oleriina to test different biogeographic scenarios involving the Andes within an identical framework. We found common diversification patterns across the three subtribes, as well as major differences. In Dircennina and Oleriina, our results reveal a congruent pattern of diversification related to the Andes with an Andean origin, which contrasts with the Amazonian origin and multiple Andean colonizations of Godyridina. In each of the three subtribes, a clade diversified in the Northern Andes at a faster rate. Diversification within Amazonia occurred in Oleriina and Godyridina, while virtually no speciation occurred in Dircennina in this region. Dircennina was therefore characterized by higher diversification rates within the Andes compared to non-Andean regions, while in Oleriina and Godyridina, we found no difference between these regions. Our results and discussion highlight the importance of comparative approaches in biogeographic studies.

  14. Diversity Dynamics in Nymphalidae Butterflies: Effect of Phylogenetic Uncertainty on Diversification Rate Shift Estimates

    Science.gov (United States)

    Peña, Carlos; Espeland, Marianne

    2015-01-01

    The species rich butterfly family Nymphalidae has been used to study evolutionary interactions between plants and insects. Theories of insect-hostplant dynamics predict accelerated diversification due to key innovations. In evolutionary biology, analysis of maximum credibility trees in the software MEDUSA (modelling evolutionary diversity using stepwise AIC) is a popular method for estimation of shifts in diversification rates. We investigated whether phylogenetic uncertainty can produce different results by extending the method across a random sample of trees from the posterior distribution of a Bayesian run. Using the MultiMEDUSA approach, we found that phylogenetic uncertainty greatly affects diversification rate estimates. Different trees produced diversification rates ranging from high values to almost zero for the same clade, and both significant rate increase and decrease in some clades. Only four out of 18 significant shifts found on the maximum clade credibility tree were consistent across most of the sampled trees. Among these, we found accelerated diversification for Ithomiini butterflies. We used the binary speciation and extinction model (BiSSE) and found that a hostplant shift to Solanaceae is correlated with increased net diversification rates in Ithomiini, congruent with the diffuse cospeciation hypothesis. Our results show that taking phylogenetic uncertainty into account when estimating net diversification rate shifts is of great importance, as very different results can be obtained when using the maximum clade credibility tree and other trees from the posterior distribution. PMID:25830910

  15. Using phylogenomics to understand the link between biogeographic origins and regional diversification in ratsnakes.

    Science.gov (United States)

    Chen, Xin; Lemmon, Alan R; Lemmon, Emily Moriarty; Pyron, R Alexander; Burbrink, Frank T

    2017-06-01

    Globally distributed groups may show regionally distinct rates of diversification, where speciation is elevated given timing and sources of ecological opportunity. However, for most organisms, nearly complete sampling at genomic-data scales to reduce topological error in all regions is unattainable, thus hampering conclusions related to biogeographic origins and rates of diversification. We explore processes leading to the diversity of global ratsnakes and test several important hypotheses related to areas of origin and enhanced diversification upon colonizing new continents. We estimate species trees inferred from phylogenomic scale data (304 loci) while exploring several strategies that consider topological error from each individual gene tree. With a dated species tree, we examine taxonomy and test previous hypotheses that suggest the ratsnakes originated in the Old World (OW) and dispersed to New World (NW). Furthermore, we determine if dispersal to the NW represented a source of ecological opportunity, which should show elevated rates of species diversification. We show that ratsnakes originated in the OW during the mid-Oligocene and subsequently dispersed to the NW by the mid-Miocene; diversification was also elevated in a subclade of NW taxa. Finally, the optimal biogeographic region-dependent speciation model shows that the uptick in ratsnake diversification was associated with colonization of the NW. We consider several alternative explanations that account for regionally distinct diversification rates. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. A parametric method for assessing diversification-rate variation in phylogenetic trees.

    Science.gov (United States)

    Shah, Premal; Fitzpatrick, Benjamin M; Fordyce, James A

    2013-02-01

    Phylogenetic hypotheses are frequently used to examine variation in rates of diversification across the history of a group. Patterns of diversification-rate variation can be used to infer underlying ecological and evolutionary processes responsible for patterns of cladogenesis. Most existing methods examine rate variation through time. Methods for examining differences in diversification among groups are more limited. Here, we present a new method, parametric rate comparison (PRC), that explicitly compares diversification rates among lineages in a tree using a variety of standard statistical distributions. PRC can identify subclades of the tree where diversification rates are at variance with the remainder of the tree. A randomization test can be used to evaluate how often such variance would appear by chance alone. The method also allows for comparison of diversification rate among a priori defined groups. Further, the application of the PRC method is not restricted to monophyletic groups. We examined the performance of PRC using simulated data, which showed that PRC has acceptable false-positive rates and statistical power to detect rate variation. We apply the PRC method to the well-studied radiation of North American Plethodon salamanders, and support the inference that the large-bodied Plethodon glutinosus clade has a higher historical rate of diversification compared to other Plethodon salamanders. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

  17. Phylogenetic diversification patterns and divergence times in ground beetles (Coleoptera: Carabidae: Harpalinae

    Directory of Open Access Journals (Sweden)

    Ober Karen A

    2010-08-01

    Full Text Available Abstract Background Harpalinae is a species rich clade of carabid beetles with many unusual morphological forms and ecological interactions. How this diversity evolved has been difficult to reconstruct, perhaps because harpalines underwent a rapid burst of diversification early in their evolutionary history. Here we investigate the tempo of evolution in harpalines using molecular divergence dating techniques and explore the rates of lineage accumulation in harpalines and their sister group. Results According to molecular divergence date estimates, harpalines originated in the mid Cretaceous but did not diversify extensively until the late Cretaceous or early Paleogene about 32 million years after their origin. In a relatively small window of time, harpalines underwent rapid speciation. Harpalines have a relative high net diversification rate and increased cladogenesis in some regions of the clade. We did not see a significant decrease in diversification rate through time in the MCCR test, but a model of diversification with two shift points to lower diversification rates fit the harpaline lineage accumulation through time the best. Conclusions Our results indicate harpalines are significantly more diverse and have higher diversification than their sistergroup. Instead of an immediate burst of explosive diversification, harpalines may have had a long "fuse" before major lineages diversified during the early Paleogene when other taxa such as mammals, birds, and some flowering plants were also rapidly diversifying.

  18. Phylogenetic diversification patterns and divergence times in ground beetles (Coleoptera: Carabidae: Harpalinae).

    Science.gov (United States)

    Ober, Karen A; Heider, Thomas N

    2010-08-27

    Harpalinae is a species rich clade of carabid beetles with many unusual morphological forms and ecological interactions. How this diversity evolved has been difficult to reconstruct, perhaps because harpalines underwent a rapid burst of diversification early in their evolutionary history. Here we investigate the tempo of evolution in harpalines using molecular divergence dating techniques and explore the rates of lineage accumulation in harpalines and their sister group. According to molecular divergence date estimates, harpalines originated in the mid Cretaceous but did not diversify extensively until the late Cretaceous or early Paleogene about 32 million years after their origin. In a relatively small window of time, harpalines underwent rapid speciation. Harpalines have a relative high net diversification rate and increased cladogenesis in some regions of the clade. We did not see a significant decrease in diversification rate through time in the MCCR test, but a model of diversification with two shift points to lower diversification rates fit the harpaline lineage accumulation through time the best. Our results indicate harpalines are significantly more diverse and have higher diversification than their sistergroup. Instead of an immediate burst of explosive diversification, harpalines may have had a long "fuse" before major lineages diversified during the early Paleogene when other taxa such as mammals, birds, and some flowering plants were also rapidly diversifying.

  19. Diversity dynamics in Nymphalidae butterflies: effect of phylogenetic uncertainty on diversification rate shift estimates.

    Directory of Open Access Journals (Sweden)

    Carlos Peña

    Full Text Available The species rich butterfly family Nymphalidae has been used to study evolutionary interactions between plants and insects. Theories of insect-hostplant dynamics predict accelerated diversification due to key innovations. In evolutionary biology, analysis of maximum credibility trees in the software MEDUSA (modelling evolutionary diversity using stepwise AIC is a popular method for estimation of shifts in diversification rates. We investigated whether phylogenetic uncertainty can produce different results by extending the method across a random sample of trees from the posterior distribution of a Bayesian run. Using the MultiMEDUSA approach, we found that phylogenetic uncertainty greatly affects diversification rate estimates. Different trees produced diversification rates ranging from high values to almost zero for the same clade, and both significant rate increase and decrease in some clades. Only four out of 18 significant shifts found on the maximum clade credibility tree were consistent across most of the sampled trees. Among these, we found accelerated diversification for Ithomiini butterflies. We used the binary speciation and extinction model (BiSSE and found that a hostplant shift to Solanaceae is correlated with increased net diversification rates in Ithomiini, congruent with the diffuse cospeciation hypothesis. Our results show that taking phylogenetic uncertainty into account when estimating net diversification rate shifts is of great importance, as very different results can be obtained when using the maximum clade credibility tree and other trees from the posterior distribution.

  20. Conservation and diversification of Msx protein in metazoan evolution.

    Science.gov (United States)

    Takahashi, Hirokazu; Kamiya, Akiko; Ishiguro, Akira; Suzuki, Atsushi C; Saitou, Naruya; Toyoda, Atsushi; Aruga, Jun

    2008-01-01

    Msx (/msh) family genes encode homeodomain (HD) proteins that control ontogeny in many animal species. We compared the structures of Msx genes from a wide range of Metazoa (Porifera, Cnidaria, Nematoda, Arthropoda, Tardigrada, Platyhelminthes, Mollusca, Brachiopoda, Annelida, Echiura, Echinodermata, Hemichordata, and Chordata) to gain an understanding of the role of these genes in phylogeny. Exon-intron boundary analysis suggested that the position of the intron located N-terminally to the HDs was widely conserved in all the genes examined, including those of cnidarians. Amino acid (aa) sequence comparison revealed 3 new evolutionarily conserved domains, as well as very strong conservation of the HDs. Two of the three domains were associated with Groucho-like protein binding in both a vertebrate and a cnidarian Msx homolog, suggesting that the interaction between Groucho-like proteins and Msx proteins was established in eumetazoan ancestors. Pairwise comparison among the collected HDs and their C-flanking aa sequences revealed that the degree of sequence conservation varied depending on the animal taxa from which the sequences were derived. Highly conserved Msx genes were identified in the Vertebrata, Cephalochordata, Hemichordata, Echinodermata, Mollusca, Brachiopoda, and Anthozoa. The wide distribution of the conserved sequences in the animal phylogenetic tree suggested that metazoan ancestors had already acquired a set of conserved domains of the current Msx family genes. Interestingly, although strongly conserved sequences were recovered from the Vertebrata, Cephalochordata, and Anthozoa, the sequences from the Urochordata and Hydrozoa showed weak conservation. Because the Vertebrata-Cephalochordata-Urochordata and Anthozoa-Hydrozoa represent sister groups in the Chordata and Cnidaria, respectively, Msx sequence diversification may have occurred differentially in the course of evolution. We speculate that selective loss of the conserved domains in Msx family

  1. Phylogenetic relationships, diversification and expansion of chili peppers (Capsicum, Solanaceae)

    Science.gov (United States)

    Carrizo García, Carolina; Barfuss, Michael H. J.; Sehr, Eva M.; Barboza, Gloria E.; Samuel, Rosabelle; Moscone, Eduardo A.; Ehrendorfer, Friedrich

    2016-01-01

    Background and Aims Capsicum (Solanaceae), native to the tropical and temperate Americas, comprises the well-known sweet and hot chili peppers and several wild species. So far, only partial taxonomic and phylogenetic analyses have been done for the genus. Here, the phylogenetic relationships between nearly all taxa of Capsicum were explored to test the monophyly of the genus and to obtain a better knowledge of species relationships, diversification and expansion. Methods Thirty-four of approximately 35 Capsicum species were sampled. Maximum parsimony and Bayesian inference analyses were performed using two plastid markers (matK and psbA-trnH) and one single-copy nuclear gene (waxy). The evolutionary changes of nine key features were reconstructed following the parsimony ancestral states method. Ancestral areas were reconstructed through a Bayesian Markov chain Monte Carlo analysis. Key Results Capsicum forms a monophyletic clade, with Lycianthes as a sister group, following both phylogenetic approaches. Eleven well-supported clades (four of them monotypic) can be recognized within Capsicum, although some interspecific relationships need further analysis. A few features are useful to characterize different clades (e.g. fruit anatomy, chromosome base number), whereas some others are highly homoplastic (e.g. seed colour). The origin of Capsicum is postulated in an area along the Andes of western to north-western South America. The expansion of the genus has followed a clockwise direction around the Amazon basin, towards central and south-eastern Brazil, then back to western South America, and finally northwards to Central America. Conclusions New insights are provided regarding interspecific relationships, character evolution, and geographical origin and expansion of Capsicum. A clearly distinct early-diverging clade can be distinguished, centred in western–north-western South America. Subsequent rapid speciation has led to the origin of the remaining clades. The

  2. Phenotypic and genetic diversification of Pseudanabaena spp. (cyanobacteria).

    Science.gov (United States)

    Acinas, Silvia G; Haverkamp, Thomas H A; Huisman, Jef; Stal, Lucas J

    2009-01-01

    Pseudanabaena species are poorly known filamentous bloom-forming cyanobacteria closely related to Limnothrix. We isolated 28 Pseudanabaena strains from the Baltic Sea (BS) and the Albufera de Valencia (AV; Spain). By combining phenotypic and genotypic approaches, the phylogeny, diversity and evolutionary diversification of these isolates were explored. Analysis of the in vivo absorption spectra of the Pseudanabaena strains revealed two coexisting pigmentation phenotypes: (i) phycocyanin-rich (PC-rich) strains and (ii) strains containing both PC and phycoerythrin (PE). Strains of the latter phenotype were all capable of complementary chromatic adaptation (CCA). About 65 kb of the Pseudanabaena genomes were sequenced through a multilocus sequencing approach including the sequencing of the16 and 23S rRNA genes, the ribosomal intergenic spacer (IGS), internal transcribed spacer 1 (ITS-1), the cpcBA operon encoding PC and the IGS between cpcA and cpcB. In addition, the presence of nifH, one of the structural genes of nitrogenase, was investigated. Sequence analysis of ITS and cpcBA-IGS allowed the differentiation between Pseudanabaena isolates exhibiting high levels of microdiversity. This multilocus sequencing approach revealed specific clusters for the BS, the AV and a mixed cluster with strains from both ecosystems. The latter comprised exclusively CCA phenotypes. The phylogenies of the 16 and 23S rRNA genes are consistent, but analysis of other loci indicated the loss of substructure, suggesting that the recombination between these loci has occurred. Our preliminary results on population genetic analyses of the PC genes suggest an evolutionary diversification of Pseudanabaena through purifying selection.

  3. Are rates of species diversification and body size evolution coupled in the ferns?

    Science.gov (United States)

    Testo, Weston L; Sundue, Michael A

    2018-03-01

    Understanding the relationship between phenotypic evolution and lineage diversification is a central goal of evolutionary biology. To extend our understanding of the role morphological evolution plays in the diversification of plants, we examined the relationship between leaf size evolution and lineage diversification across ferns. We tested for an association between body size evolution and lineage diversification using a comparative phylogenetic approach that combined a time-calibrated phylogeny and leaf size data set for 2654 fern species. Rates of leaf size change and lineage diversification were estimated using BAMM, and rate correlations were performed for rates obtained for all families and individual species. Rates and patterns of rate-rate correlation were also analyzed separately for terrestrial and epiphytic taxa. We find no significant correlation between rates of leaf area change and lineage diversification, nor was there a difference in this pattern when growth habit is considered. Our results are consistent with the findings of an earlier study that reported decoupled rates of body size evolution and diversification in the Polypodiaceae, but conflict with a recent study that reported a positive correlation between body size evolution and lineage diversification rates in the tree fern family Cyatheaceae. Our findings indicate that lineage diversification in ferns is largely decoupled from shifts in body size, in contrast to several other groups of organisms. Speciation in ferns appears to be primarily driven by hybridization and isolation along elevational gradients, rather than adaptive radiations featuring prominent morphological restructuring. The exceptional diversity of leaf morphologies in ferns appears to reflect a combination of ecophysiological constraints and adaptations that are not key innovations. © 2018 Botanical Society of America.

  4. Global diversification of a tropical plant growth form: environmental correlates and historical contingencies in climbing palms.

    Science.gov (United States)

    Couvreur, Thomas L P; Kissling, W Daniel; Condamine, Fabien L; Svenning, Jens-Christian; Rowe, Nick P; Baker, William J

    2014-01-01

    Tropical rain forests (TRF) are the most diverse terrestrial biome on Earth, but the diversification dynamics of their constituent growth forms remain largely unexplored. Climbing plants contribute significantly to species diversity and ecosystem processes in TRF. We investigate the broad-scale patterns and drivers of species richness as well as the diversification history of climbing and non-climbing palms (Arecaceae). We quantify to what extent macroecological diversity patterns are related to contemporary climate, forest canopy height, and paleoclimatic changes. We test whether diversification rates are higher for climbing than non-climbing palms and estimate the origin of the climbing habit. Climbers account for 22% of global palm species diversity, mostly concentrated in Southeast Asia. Global variation in climbing palm species richness can be partly explained by past and present-day climate and rain forest canopy height, but regional differences in residual species richness after accounting for current and past differences in environment suggest a strong role of historical contingencies in climbing palm diversification. Climbing palms show a higher net diversification rate than non-climbers. Diversification analyses of palms detected a diversification rate increase along the branches leading to the most species-rich clade of climbers. Ancestral character reconstructions revealed that the climbing habit originated between early Eocene and Miocene. These results imply that changes from non-climbing to climbing habits may have played an important role in palm diversification, resulting in the origin of one fifth of all palm species. We suggest that, in addition to current climate and paleoclimatic changes after the late Neogene, present-day diversity of climbing palms can be explained by morpho-anatomical innovations, the biogeographic history of Southeast Asia, and/or ecological opportunities due to the diversification of high-stature dipterocarps in Asian TRFs.

  5. High tropical net diversification drives the New World latitudinal gradient in palm (Arecaceae) species richness

    DEFF Research Database (Denmark)

    Svenning, J.-C.; Borchsenius, Finn; Bjorholm, Stine Wendelboe

    2008-01-01

    /temperature and water availability. These patterns therefore reflect net diversification at both deep and shallow levels in the phylogeny. Richness also increased with range in elevation, but this was only reflected in the MS/G pattern and therefore reflects recent diversification. Main conclusions The geographical......Aim Species richness exhibits striking geographical variation, but the processes that drive this variation are unresolved. We investigated the relative importance of two hypothesized evolutionary causes for the variation in palm species richness across the New World: time for diversification...

  6. The evolutionary diversification of LSF and Grainyhead transcription factors preceded the radiation of basal animal lineages

    Directory of Open Access Journals (Sweden)

    Kaufman Les

    2010-04-01

    Full Text Available Abstract Background The transcription factors of the LSF/Grainyhead (GRH family are characterized by the possession of a distinctive DNA-binding domain that bears no clear relationship to other known DNA-binding domains, with the possible exception of the p53 core domain. In triploblastic animals, the LSF and GRH subfamilies have diverged extensively with respect to their biological roles, general expression patterns, and mechanism of DNA binding. For example, Grainyhead (GRH homologs are expressed primarily in the epidermis, and they appear to play an ancient role in maintaining the epidermal barrier. By contrast, LSF homologs are more widely expressed, and they regulate general cellular functions such as cell cycle progression and survival in addition to cell-lineage specific gene expression. Results To illuminate the early evolution of this family and reconstruct the functional divergence of LSF and GRH, we compared homologs from 18 phylogenetically diverse taxa, including four basal animals (Nematostella vectensis, Vallicula multiformis, Trichoplax adhaerens, and Amphimedon queenslandica, a choanoflagellate (Monosiga brevicollis and several fungi. Phylogenetic and bioinformatic analyses of these sequences indicate that (1 the LSF/GRH gene family originated prior to the animal-fungal divergence, and (2 the functional diversification of the LSF and GRH subfamilies occurred prior to the divergence between sponges and eumetazoans. Aspects of the domain architecture of LSF/GRH proteins are well conserved between fungi, choanoflagellates, and metazoans, though within the Metazoa, the LSF and GRH families are clearly distinct. We failed to identify a convincing LSF/GRH homolog in the sequenced genomes of the algae Volvox carteri and Chlamydomonas reinhardtii or the amoebozoan Dictyostelium purpureum. Interestingly, the ancestral GRH locus has become split into two separate loci in the sea anemone Nematostella, with one locus encoding a DNA binding

  7. Conservation and diversification of the miR166 family in soybean and potential roles of newly identified miR166s.

    Science.gov (United States)

    Li, Xuyan; Xie, Xin; Li, Ji; Cui, Yuhai; Hou, Yanming; Zhai, Lulu; Wang, Xiao; Fu, Yanli; Liu, Ranran; Bian, Shaomin

    2017-02-01

    microRNA166 (miR166) is a highly conserved family of miRNAs implicated in a wide range of cellular and physiological processes in plants. miR166 family generally comprises multiple miR166 members in plants, which might exhibit functional redundancy and specificity. The soybean miR166 family consists of 21 members according to the miRBase database. However, the evolutionary conservation and functional diversification of miR166 family members in soybean remain poorly understood. We identified five novel miR166s in soybean by data mining approach, thus enlarging the size of miR166 family from 21 to 26 members. Phylogenetic analyses of the 26 miR166s and their precursors indicated that soybean miR166 family exhibited both evolutionary conservation and diversification, and ten pairs of miR166 precursors with high sequence identity were individually grouped into a discrete clade in the phylogenetic tree. The analysis of genomic organization and evolution of MIR166 gene family revealed that eight segmental duplications and four tandem duplications might occur during evolution of the miR166 family in soybean. The cis-elements in promoters of MIR166 family genes and their putative targets pointed to their possible contributions to the functional conservation and diversification. The targets of soybean miR166s were predicted, and the cleavage of ATHB14-LIKE transcript was experimentally validated by RACE PCR. Further, the expression patterns of the five newly identified MIR166s and 12 target genes were examined during seed development and in response to abiotic stresses, which provided important clues for dissecting their functions and isoform specificity. This study enlarged the size of soybean miR166 family from 21 to 26 members, and the 26 soybean miR166s exhibited evolutionary conservation and diversification. These findings have laid a foundation for elucidating functional conservation and diversification of miR166 family members, especially during seed development or

  8. Different Signal Enhancement Pathways of Attention and Consciousness Underlie Perception in Humans.

    Science.gov (United States)

    van Boxtel, Jeroen J A

    2017-06-14

    It is not yet known whether attention and consciousness operate through similar or largely different mechanisms. Visual processing mechanisms are routinely characterized by measuring contrast response functions (CRFs). In this report, behavioral CRFs were obtained in humans (both males and females) by measuring afterimage durations over the entire range of inducer stimulus contrasts to reveal visual mechanisms behind attention and consciousness. Deviations relative to the standard CRF, i.e., gain functions, describe the strength of signal enhancement, which were assessed for both changes due to attentional task and conscious perception. It was found that attention displayed a response-gain function, whereas consciousness displayed a contrast-gain function. Through model comparisons, which only included contrast-gain modulations, both contrast-gain and response-gain effects can be explained with a two-level normalization model, in which consciousness affects only the first level and attention affects only the second level. These results demonstrate that attention and consciousness can effectively show different gain functions because they operate through different signal enhancement mechanisms. SIGNIFICANCE STATEMENT The relationship between attention and consciousness is still debated. Mapping contrast response functions (CRFs) has allowed (neuro)scientists to gain important insights into the mechanistic underpinnings of visual processing. Here, the influence of both attention and consciousness on these functions were measured and they displayed a strong dissociation. First, attention lowered CRFs, whereas consciousness raised them. Second, attention manifests itself as a response-gain function, whereas consciousness manifests itself as a contrast-gain function. Extensive model comparisons show that these results are best explained in a two-level normalization model in which consciousness affects only the first level, whereas attention affects only the second level

  9. Shark IgW C region diversification through RNA processing and isotype switching.

    Science.gov (United States)

    Zhang, Cecilia; Du Pasquier, Louis; Hsu, Ellen

    2013-09-15

    Sharks and skates represent the earliest vertebrates with an adaptive immune system based on lymphocyte Ag receptors generated by V(D)J recombination. Shark B cells express two classical Igs, IgM and IgW, encoded by an early, alternative gene organization consisting of numerous autonomous miniloci, where the individual gene cluster carries a few rearranging gene segments and one C region, μ or ω. We have characterized eight distinct Ig miniloci encoding the nurse shark ω H chain. Each cluster consists of VH, D, and JH segments and six to eight C domain exons. Two interspersed secretory exons, in addition to the 3'-most C exon with tailpiece, provide the gene cluster with the ability to generate at least six secreted isoforms that differ as to polypeptide length and C domain combination. All clusters appear to be functional, as judged by the capability for rearrangement and absence of defects in the deduced amino acid sequence. We previously showed that IgW VDJ can perform isotype switching to μ C regions; in this study, we found that switching also occurs between ω clusters. Thus, C region diversification for any IgW VDJ can take place at the DNA level by switching to other ω or μ C regions, as well as by RNA processing to generate different C isoforms. The wide array of pathogens recognized by Abs requires different disposal pathways, and our findings demonstrate complex and unique pathways for C effector function diversity that evolved independently in cartilaginous fishes.

  10. Diversification of defensins and NLRs in Arabidopsis species by different evolutionary mechanisms.

    Science.gov (United States)

    Mondragón-Palomino, Mariana; Stam, Remco; John-Arputharaj, Ajay; Dresselhaus, Thomas

    2017-12-15

    natural selection. Their heterogeneous expression pattern suggests that transcriptional divergence probably made the major contribution to functional diversification. In comparison to smaller families encoding pathogenesis-related (PR) proteins under positive selection, DEFLs are involved in a wide variety of processes that altogether might pose structural and functional trade-offs to their family-wide pattern of evolution.

  11. The 8 Learning Events Model: a Pedagogic Conceptual Tool Supporting Diversification of Learning Methods

    NARCIS (Netherlands)

    Verpoorten, Dominique; Poumay, M; Leclercq, D

    2006-01-01

    Please, cite this publication as: Verpoorten, D., Poumay, M., & Leclercq, D. (2006). The 8 Learning Events Model: a Pedagogic Conceptual Tool Supporting Diversification of Learning Methods. Proceedings of International Workshop in Learning Networks for Lifelong Competence Development, TENCompetence

  12. Acquisition versus greenfield foreign entry : diversification mode choice in Central and Eastern Europe

    NARCIS (Netherlands)

    Dikova, Desislava; Witteloostuijn, Adriaan van

    2005-01-01

    Departing from the traditional transaction cost approach in diversification mode literature, this study investigates the influence of experimental organizational learning on the choice between acquisition and a greenfield investment. We provide empirical support that prior experience with

  13. Diversification of companies' activity of the Arctic fuel and energy complex

    Directory of Open Access Journals (Sweden)

    Fedoseev S. V.

    2015-09-01

    Full Text Available The analysis of diversification role in company's activity has been considered. Special attention has been paid to the levels of strategy for a diversified company of the fuel and energy complex

  14. Non-farm diversification and its impacts on income inequality and ...

    African Journals Online (AJOL)

    Non-farm diversification and its impacts on income inequality and poverty: evidence from rural Ethiopia. ... Ethiopian Journal of Development Research ... non-farm sector can provide a feasible option to tackling rural poverty and vulnerabilities ...

  15. Estimation of main diversification time-points of hantaviruses using phylogenetic analyses of complete genomes.

    Science.gov (United States)

    Castel, Guillaume; Tordo, Noël; Plyusnin, Alexander

    2017-04-02

    Because of the great variability of their reservoir hosts, hantaviruses are excellent models to evaluate the dynamics of virus-host co-evolution. Intriguing questions remain about the timescale of the diversification events that influenced this evolution. In this paper we attempted to estimate the first ever timing of hantavirus diversification based on thirty five available complete genomes representing five major groups of hantaviruses and the assumption of co-speciation of hantaviruses with their respective mammal hosts. Phylogenetic analyses were used to estimate the main diversification points during hantavirus evolution in mammals while host diversification was mostly estimated from independent calibrators taken from fossil records. Our results support an earlier developed hypothesis of co-speciation of known hantaviruses with their respective mammal hosts and hence a common ancestor for all hantaviruses carried by placental mammals. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Assessment of criteria and farming activities for tobacco diversification using the Analytical Hierarchical Process (AHP) technique

    NARCIS (Netherlands)

    Chavez, M.D.; Berentsen, P.B.M.; Oude Lansink, A.G.J.M.

    2012-01-01

    Continuous monocropping of tobacco, excessive tillage and inadequate irrigation management have caused soil degradation in tobacco farms in the Valle de Lerma. Soil degradation due to tobacco monocropping and uncertain economic perspectives for tobacco farming call for diversification strategies for

  17. Biogeography of species richness gradients : Linking adaptive traits, demography and diversification

    NARCIS (Netherlands)

    Carnicer, Jofre; Brotons, Lluis; Stefanescu, Constanti; Penuelas, Josep

    Here we review how adaptive traits contribute to the emergence and maintenance of species richness gradients through their influence on demographic and diversification processes. We start by reviewing how demographic dynamics change along species richness gradients. Empirical studies show that

  18. Does Money Grow on Trees? The Diversification Properties of US Timberland Investments

    NARCIS (Netherlands)

    Scholtens, Bert; Spierdijk, Laura

    This paper quantifies the diversification potential of timberland investments in a meanvariance framework. The starting point is a broad set of benchmark assets represented by various indexes. Including publicly traded timberland investments in the portfolio does not significantly increase

  19. Foxp3(+) T cells regulate immunoglobulin a selection and facilitate diversification of bacterial species responsible for immune homeostasis.

    Science.gov (United States)

    Kawamoto, Shimpei; Maruya, Mikako; Kato, Lucia M; Suda, Wataru; Atarashi, Koji; Doi, Yasuko; Tsutsui, Yumi; Qin, Hongyan; Honda, Kenya; Okada, Takaharu; Hattori, Masahira; Fagarasan, Sidonia

    2014-07-17

    Foxp3(+) T cells play a critical role for the maintenance of immune tolerance. Here we show that in mice, Foxp3(+) T cells contributed to diversification of gut microbiota, particularly of species belonging to Firmicutes. The control of indigenous bacteria by Foxp3(+) T cells involved regulatory functions both outside and inside germinal centers (GCs), consisting of suppression of inflammation and regulation of immunoglobulin A (IgA) selection in Peyer's patches, respectively. Diversified and selected IgAs contributed to maintenance of diversified and balanced microbiota, which in turn facilitated the expansion of Foxp3(+) T cells, induction of GCs, and IgA responses in the gut through a symbiotic regulatory loop. Thus, the adaptive immune system, through cellular and molecular components that are required for immune tolerance and through the diversification as well as selection of antibody repertoire, mediates host-microbial symbiosis by controlling the richness and balance of bacterial communities required for homeostasis. Copyright © 2014 Elsevier Inc. All rights reserved.

  20. Parallel Expansions of Sox Transcription Factor Group B Predating the Diversifications of the Arthropods and Jawed Vertebrates

    Science.gov (United States)

    Zhong, Lei; Wang, Dengqiang; Gan, Xiaoni; Yang, Tong; He, Shunping

    2011-01-01

    Group B of the Sox transcription factor family is crucial in embryo development in the insects and vertebrates. Sox group B, unlike the other Sox groups, has an unusually enlarged functional repertoire in insects, but the timing and mechanism of the expansion of this group were unclear. We collected and analyzed data for Sox group B from 36 species of 12 phyla representing the major metazoan clades, with an emphasis on arthropods, to reconstruct the evolutionary history of SoxB in bilaterians and to date the expansion of Sox group B in insects. We found that the genome of the bilaterian last common ancestor probably contained one SoxB1 and one SoxB2 gene only and that tandem duplications of SoxB2 occurred before the arthropod diversification but after the arthropod-nematode divergence, resulting in the basal repertoire of Sox group B in diverse arthropod lineages. The arthropod Sox group B repertoire expanded differently from the vertebrate repertoire, which resulted from genome duplications. The parallel increases in the Sox group B repertoires of the arthropods and vertebrates are consistent with the parallel increases in the complexity and diversification of these two important organismal groups. PMID:21305035

  1. Reforms, agricultural risks and agro-industrial diversification in rural China: Evidence from Chinese Provinces

    OpenAIRE

    Weiyong YANG

    2003-01-01

    Since the implementation of the economic reforms in 1978, there is a remarkable diversification trend in rural China characterized by an impressive development of rural enterprises. The main objective of this paper is to understand the forces driving this agro-industrial diversification which has important impact on the employment, incomes and welfare of rural residents. A particular attention has been paid to two categories of factors, agricultural income risks and institutional factors such...

  2. Lead Diversification through a Prins-Driven Macrocyclization Strategy: Application to C13-Diversified Bryostatin Analogues.

    Science.gov (United States)

    Wender, Paul A; Billingsley, Kelvin L

    2013-01-01

    The design, synthesis, and biological evaluation of a novel class of C13-diversified bryostatin analogues are described. An innovative and general strategy based on a Prins macrocyclization-nucleophilic trapping cascade was used to achieve late-stage diversification. In vitro analysis of selected library members revealed that modification at the C13 position of the bryostatin scaffold can be used as a diversification handle to regulate biological activity.

  3. Diversification: A Value-Creating or Value-Destroying Strategy? Evidence from the Eurozone Countries

    OpenAIRE

    Gálvan Antonio; Pindado Julio; De La Torre Chabela

    2014-01-01

    In this paper, we provide evidence on how diversification strategy impacts on excess value in a sample of Eurozone firms by using the data panel methodology. Specifically, we study the effect of the levels and types of the product diversification on the premium or discount that diversified firms trade at. Preliminary results are consistent with the value-destroying expectations and show that diversified companies trade at a discount in the Eurozone countries. However, a more accurate analysis...

  4. Product Diversification in the European Banking Industry: Risk and Loan Pricing Implications

    OpenAIRE

    Lepetit , Laetitia; Nys , Emmanuelle; Rous , Philippe; Tarazi , Amine

    2005-01-01

    The purpose of this paper is to investigate the relationship between bank risk and product diversification in the changing structure of the European banking industry. Based on a broad set of European banks for the period 1996-2002, our study shows that banks expanding into non-interest income activities present higher risk than banks which mainly supply loans. Whereas previous studies (mainly on U.S. banks) focused on portfolio diversification effects we explore risk implications of cross-sel...

  5. Detecting Hidden Diversification Shifts in Models of Trait-Dependent Speciation and Extinction.

    Science.gov (United States)

    Beaulieu, Jeremy M; O'Meara, Brian C

    2016-07-01

    The distribution of diversity can vary considerably from clade to clade. Attempts to understand these patterns often employ state-dependent speciation and extinction models to determine whether the evolution of a particular novel trait has increased speciation rates and/or decreased extinction rates. It is still unclear, however, whether these models are uncovering important drivers of diversification, or whether they are simply pointing to more complex patterns involving many unmeasured and co-distributed factors. Here we describe an extension to the popular state-dependent speciation and extinction models that specifically accounts for the presence of unmeasured factors that could impact diversification rates estimated for the states of any observed trait, addressing at least one major criticism of BiSSE (Binary State Speciation and Extinction) methods. Specifically, our model, which we refer to as HiSSE (Hidden State Speciation and Extinction), assumes that related to each observed state in the model are "hidden" states that exhibit potentially distinct diversification dynamics and transition rates than the observed states in isolation. We also demonstrate how our model can be used as character-independent diversification models that allow for a complex diversification process that is independent of the evolution of a character. Under rigorous simulation tests and when applied to empirical data, we find that HiSSE performs reasonably well, and can at least detect net diversification rate differences between observed and hidden states and detect when diversification rate differences do not correlate with the observed states. We discuss the remaining issues with state-dependent speciation and extinction models in general, and the important ways in which HiSSE provides a more nuanced understanding of trait-dependent diversification. © The Author(s) 2016. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved

  6. Phylogenetic estimates of diversification rate are affected by molecular rate variation.

    Science.gov (United States)

    Duchêne, D A; Hua, X; Bromham, L

    2017-10-01

    Molecular phylogenies are increasingly being used to investigate the patterns and mechanisms of macroevolution. In particular, node heights in a phylogeny can be used to detect changes in rates of diversification over time. Such analyses rest on the assumption that node heights in a phylogeny represent the timing of diversification events, which in turn rests on the assumption that evolutionary time can be accurately predicted from DNA sequence divergence. But there are many influences on the rate of molecular evolution, which might also influence node heights in molecular phylogenies, and thus affect estimates of diversification rate. In particular, a growing number of studies have revealed an association between the net diversification rate estimated from phylogenies and the rate of molecular evolution. Such an association might, by influencing the relative position of node heights, systematically bias estimates of diversification time. We simulated the evolution of DNA sequences under several scenarios where rates of diversification and molecular evolution vary through time, including models where diversification and molecular evolutionary rates are linked. We show that commonly used methods, including metric-based, likelihood and Bayesian approaches, can have a low power to identify changes in diversification rate when molecular substitution rates vary. Furthermore, the association between the rates of speciation and molecular evolution rate can cause the signature of a slowdown or speedup in speciation rates to be lost or misidentified. These results suggest that the multiple sources of variation in molecular evolutionary rates need to be considered when inferring macroevolutionary processes from phylogenies. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

  7. Evolutionary history, immigration history, and the extent of diversification in community assembly.

    Science.gov (United States)

    Knope, Matthew L; Forde, Samantha E; Fukami, Tadashi

    2011-01-01

    During community assembly, species may accumulate not only by immigration, but also by in situ diversification. Diversification has intrigued biologists because its extent varies even among closely related lineages under similar ecological conditions. Recent research has suggested that some of this puzzling variation may be caused by stochastic differences in the history of immigration (relative timing and order of immigration by founding populations), indicating that immigration and diversification may affect community assembly interactively. However, the conditions under which immigration history affects diversification remain unclear. Here we propose the hypothesis that whether or not immigration history influences the extent of diversification depends on the founding populations' prior evolutionary history, using evidence from a bacterial experiment. To create genotypes with different evolutionary histories, replicate populations of Pseudomonas fluorescens were allowed to adapt to a novel environment for a short or long period of time (approximately 10 or 100 bacterial generations) with or without exploiters (viral parasites). Each evolved genotype was then introduced to a new habitat either before or after a standard competitor genotype. Most genotypes diversified to a greater extent when introduced before, rather than after, the competitor. However, introduction order did not affect the extent of diversification when the evolved genotype had previously adapted to the environment for a long period of time without exploiters. Diversification of these populations was low regardless of introduction order. These results suggest that the importance of immigration history in diversification can be predicted by the immigrants' evolutionary past. The hypothesis proposed here may be generally applicable in both micro- and macro-organisms.

  8. Asset Allocation:diversification dan Rebalancing sebagai Bagian dari Proses Perencanaan Keuangan (suatu Kajian Pustaka)

    OpenAIRE

    Dewi, Vera Intanie

    2013-01-01

    Financial planning is the process of designing an investmentstrategy that can helps an individual to achieve financial goals. Asset allocation, diversification and rebalancing is a particularly important steps of investment strategy process. By doing asset allocation and diversification among a variety of different asset categories such as bonds,stocks,mutual funds and saving can helps minimize risk and maximize return. And the goal of rebalancing is to move the current asset allocation back ...

  9. The Effects of Market Properties on Portfolio Diversification in the Korean and Japanese Stock Markets

    OpenAIRE

    Cheoljun Eom; Jongwon Park; Woo-Sung Jung; Taisei Kaizoji; Yong H. Kim

    2009-01-01

    In this study, we have investigated empirically the effects of market properties on the degree of diversification of investment weights among stocks in a portfolio. The weights of stocks within a portfolio were determined on the basis of Markowitz's portfolio theory. We identified that there was a negative relationship between the influence of market properties and the degree of diversification of the weights among stocks in a portfolio. Furthermore, we noted that the random matrix theory met...

  10. TIME VARIATION AND ASYMMETRY IN THE WORLD PRICE OF COVARIANCE RISK: THE IMPLICATIONS FOR INTERNATIONAL DIVERSIFICATION

    OpenAIRE

    Olan T. Henry; Nilss Olekalns; Kalvinder Shields

    2004-01-01

    The International Capital Asset Pricing Model measures country risk in terms of the conditional covariance of national returns with the world return. Using impulse responses from a multivariate nonlinear model we provide evidence of time variation and asymmetry in the measure of country risk. and the implied benefit to international diversification. The evidence implies that the price of risk and the benefits from diversification may differ in a statistically and economically meaningful fashi...

  11. Climate change adaptation in Ethiopia: to what extent does social protection influence livelihood diversification?

    DEFF Research Database (Denmark)

    Weldegebriel, Zerihun; Prowse, Martin Philip

    2013-01-01

    Social-protection programmes like the Productive Safety-Net Programme (PSNP) in Ethiopia can play a positive role in promoting livelihoods and enhancing risk management. This article uses propensity score matching to estimate its effect on income diversification. The results suggest that receiving...... in a positive manner for climate adaptation. The article concludes by arguing for the promotion of positive forms of income diversification and the further investigation of the PSNP’s influence on autonomous adaptation strategies....

  12. Antibody maturation and viral diversification in HIV-infected women.

    Directory of Open Access Journals (Sweden)

    Maria M James

    Full Text Available The Post-exposure Prophylaxis in Infants (PEPI-Malawi trial evaluated infant antiretroviral regimens for prevention of post-natal HIV transmission. A multi-assay algorithm (MAA that includes the BED capture immunoassay, an avidity assay, CD4 cell count, and viral load was used to identify women who were vs. were not recently infected at the time of enrollment (MAA recent, N = 73; MAA non-recent, N = 2,488; a subset of the women in the MAA non-recent group known to have been HIV infected for at least 2 years before enrollment (known non-recent, N = 54. Antibody maturation and viral diversification were examined in these women.Samples collected at enrollment (N = 2,561 and 12-24 months later (N = 1,306 were available for serologic analysis using the BED and avidity assays. A subset of those samples was used for analysis of viral diversity, which was performed using a high resolution melting (HRM diversity assay. Viral diversity analysis was performed using all available samples from women in the MAA recent group (61 enrollment samples, 38 follow-up samples and the known non-recent group (43 enrollment samples, 22 follow-up samples. Diversity data from PEPI-Malawi were also compared to similar data from 169 adults in the United States (US with known recent infection (N = 102 and known non-recent infection (N = 67.In PEPI-Malawi, results from the BED and avidity assays increased over time in the MAA recent group, but did not change significantly in the MAA non-recent group. At enrollment, HIV diversity was lower in the MAA recent group than in the known non-recent group. HRM diversity assay results from women in PEPI-Malawi were similar to those from adults in the US with known duration of HIV infection.Antibody maturation and HIV diversification patterns in African women provide additional support for use of the MAA to identify populations with recent HIV infection.

  13. [Diversification is the financial alternative for family planning].

    Science.gov (United States)

    Castro Villamil, R

    1991-12-01

    donations accounted for 47.3% of PROFAMILIA income and PROFAMILIA contributed the rest. 18.1% came from family planning activities, 20.2% from surgical procedures, consultations, sales of medications, and laboratory services, and 20.2% from service contracts, national donations, interest, and other sources. In the same year, family planning programs accounted for 68.9% of expenditures, diversification programs for 11.5%, technical assistance for 8.6%, and administration for 11%. The income and expenditure data indicate that the diversification programs make a significant financial contribution to the family planning program, at the same time reducing dependency on international donor agencies.

  14. Strategies for improving approximate Bayesian computation tests for synchronous diversification.

    Science.gov (United States)

    Overcast, Isaac; Bagley, Justin C; Hickerson, Michael J

    2017-08-24

    Estimating the variability in isolation times across co-distributed taxon pairs that may have experienced the same allopatric isolating mechanism is a core goal of comparative phylogeography. The use of hierarchical Approximate Bayesian Computation (ABC) and coalescent models to infer temporal dynamics of lineage co-diversification has been a contentious topic in recent years. Key issues that remain unresolved include the choice of an appropriate prior on the number of co-divergence events (Ψ), as well as the optimal strategies for data summarization. Through simulation-based cross validation we explore the impact of the strategy for sorting summary statistics and the choice of prior on Ψ on the estimation of co-divergence variability. We also introduce a new setting (β) that can potentially improve estimation of Ψ by enforcing a minimal temporal difference between pulses of co-divergence. We apply this new method to three empirical datasets: one dataset each of co-distributed taxon pairs of Panamanian frogs and freshwater fishes, and a large set of Neotropical butterfly sister-taxon pairs. We demonstrate that the choice of prior on Ψ has little impact on inference, but that sorting summary statistics yields substantially more reliable estimates of co-divergence variability despite violations of assumptions about exchangeability. We find the implementation of β improves estimation of Ψ, with improvement being most dramatic given larger numbers of taxon pairs. We find equivocal support for synchronous co-divergence for both of the Panamanian groups, but we find considerable support for asynchronous divergence among the Neotropical butterflies. Our simulation experiments demonstrate that using sorted summary statistics results in improved estimates of the variability in divergence times, whereas the choice of hyperprior on Ψ has negligible effect. Additionally, we demonstrate that estimating the number of pulses of co-divergence across co-distributed taxon

  15. Phylogenetic relationships, diversification and expansion of chili peppers (Capsicum, Solanaceae).

    Science.gov (United States)

    Carrizo García, Carolina; Barfuss, Michael H J; Sehr, Eva M; Barboza, Gloria E; Samuel, Rosabelle; Moscone, Eduardo A; Ehrendorfer, Friedrich

    2016-07-01

    Capsicum (Solanaceae), native to the tropical and temperate Americas, comprises the well-known sweet and hot chili peppers and several wild species. So far, only partial taxonomic and phylogenetic analyses have been done for the genus. Here, the phylogenetic relationships between nearly all taxa of Capsicum were explored to test the monophyly of the genus and to obtain a better knowledge of species relationships, diversification and expansion. Thirty-four of approximately 35 Capsicum species were sampled. Maximum parsimony and Bayesian inference analyses were performed using two plastid markers (matK and psbA-trnH) and one single-copy nuclear gene (waxy). The evolutionary changes of nine key features were reconstructed following the parsimony ancestral states method. Ancestral areas were reconstructed through a Bayesian Markov chain Monte Carlo analysis. Capsicum forms a monophyletic clade, with Lycianthes as a sister group, following both phylogenetic approaches. Eleven well-supported clades (four of them monotypic) can be recognized within Capsicum, although some interspecific relationships need further analysis. A few features are useful to characterize different clades (e.g. fruit anatomy, chromosome base number), whereas some others are highly homoplastic (e.g. seed colour). The origin of Capsicum is postulated in an area along the Andes of western to north-western South America. The expansion of the genus has followed a clockwise direction around the Amazon basin, towards central and south-eastern Brazil, then back to western South America, and finally northwards to Central America. New insights are provided regarding interspecific relationships, character evolution, and geographical origin and expansion of Capsicum A clearly distinct early-diverging clade can be distinguished, centred in western-north-western South America. Subsequent rapid speciation has led to the origin of the remaining clades. The diversification of Capsicum has culminated in the origin

  16. 'Fish' (Actinopterygii and Elasmobranchii) diversification patterns through deep time.

    Science.gov (United States)

    Guinot, Guillaume; Cavin, Lionel

    2016-11-01

    Actinopterygii (ray-finned fishes) and Elasmobranchii (sharks, skates and rays) represent more than half of today's vertebrate taxic diversity (approximately 33000 species) and form the largest component of vertebrate diversity in extant aquatic ecosystems. Yet, patterns of 'fish' evolutionary history remain insufficiently understood and previous studies generally treated each group independently mainly because of their contrasting fossil record composition and corresponding sampling strategies. Because direct reading of palaeodiversity curves is affected by several biases affecting the fossil record, analytical approaches are needed to correct for these biases. In this review, we propose a comprehensive analysis based on comparison of large data sets related to competing phylogenies (including all Recent and fossil taxa) and the fossil record for both groups during the Mesozoic-Cainozoic interval. This approach provides information on the 'fish' fossil record quality and on the corrected 'fish' deep-time phylogenetic palaeodiversity signals, with special emphasis on diversification events. Because taxonomic information is preserved after analytical treatment, identified palaeodiversity events are considered both quantitatively and qualitatively and put within corresponding palaeoenvironmental and biological settings. Results indicate a better fossil record quality for elasmobranchs due to their microfossil-like fossil distribution and their very low diversity in freshwater systems, whereas freshwater actinopterygians are diverse in this realm with lower preservation potential. Several important diversification events are identified at familial and generic levels for elasmobranchs, and marine and freshwater actinopterygians, namely in the Early-Middle Jurassic (elasmobranchs), Late Jurassic (actinopterygians), Early Cretaceous (elasmobranchs, freshwater actinopterygians), Cenomanian (all groups) and the Paleocene-Eocene interval (all groups), the latter two

  17. Interpreting the gamma statistic in phylogenetic diversification rate studies: a rate decrease does not necessarily indicate an early burst.

    Directory of Open Access Journals (Sweden)

    James A Fordyce

    Full Text Available BACKGROUND: Phylogenetic hypotheses are increasingly being used to elucidate historical patterns of diversification rate-variation. Hypothesis testing is often conducted by comparing the observed vector of branching times to a null, pure-birth expectation. A popular method for inferring a decrease in speciation rate, which might suggest an early burst of diversification followed by a decrease in diversification rate is the gamma statistic. METHODOLOGY: Using simulations under varying conditions, I examine the sensitivity of gamma to the distribution of the most recent branching times. Using an exploratory data analysis tool for lineages through time plots, tree deviation, I identified trees with a significant gamma statistic that do not appear to have the characteristic early accumulation of lineages consistent with an early, rapid rate of cladogenesis. I further investigated the sensitivity of the gamma statistic to recent diversification by examining the consequences of failing to simulate the full time interval following the most recent cladogenic event. The power of gamma to detect rate decrease at varying times was assessed for simulated trees with an initial high rate of diversification followed by a relatively low rate. CONCLUSIONS: The gamma statistic is extraordinarily sensitive to recent diversification rates, and does not necessarily detect early bursts of diversification. This was true for trees of various sizes and completeness of taxon sampling. The gamma statistic had greater power to detect recent diversification rate decreases compared to early bursts of diversification. Caution should be exercised when interpreting the gamma statistic as an indication of early, rapid diversification.

  18. Interpreting the gamma statistic in phylogenetic diversification rate studies: a rate decrease does not necessarily indicate an early burst.

    Science.gov (United States)

    Fordyce, James A

    2010-07-23

    Phylogenetic hypotheses are increasingly being used to elucidate historical patterns of diversification rate-variation. Hypothesis testing is often conducted by comparing the observed vector of branching times to a null, pure-birth expectation. A popular method for inferring a decrease in speciation rate, which might suggest an early burst of diversification followed by a decrease in diversification rate is the gamma statistic. Using simulations under varying conditions, I examine the sensitivity of gamma to the distribution of the most recent branching times. Using an exploratory data analysis tool for lineages through time plots, tree deviation, I identified trees with a significant gamma statistic that do not appear to have the characteristic early accumulation of lineages consistent with an early, rapid rate of cladogenesis. I further investigated the sensitivity of the gamma statistic to recent diversification by examining the consequences of failing to simulate the full time interval following the most recent cladogenic event. The power of gamma to detect rate decrease at varying times was assessed for simulated trees with an initial high rate of diversification followed by a relatively low rate. The gamma statistic is extraordinarily sensitive to recent diversification rates, and does not necessarily detect early bursts of diversification. This was true for trees of various sizes and completeness of taxon sampling. The gamma statistic had greater power to detect recent diversification rate decreases compared to early bursts of diversification. Caution should be exercised when interpreting the gamma statistic as an indication of early, rapid diversification.

  19. Non-reef environments impact the diversification of extant jacks, remoras and allies (Carangoidei, Percomorpha).

    Science.gov (United States)

    Frédérich, Bruno; Marramà, Giuseppe; Carnevale, Giorgio; Santini, Francesco

    2016-11-16

    Various factors may impact the processes of diversification of a clade. In the marine realm, it has been shown that coral reef environments have promoted diversification in various fish groups. With the exception of requiem sharks, all the groups showing a higher level of diversity in reefs than in non-reef habitats have diets based predominantly on plankton, algae or benthic invertebrates. Here we explore the pattern of diversification of carangoid fishes, a clade that includes numerous piscivorous species (e.g. trevallies, jacks and dolphinfishes), using time-calibrated phylogenies as well as ecological and morphological data from both extant and fossil species. The study of carangoid morphospace suggests that reef environments played a role in their early radiation during the Eocene. However, contrary to the hypothesis of a reef-association-promoting effect, we show that habitat shifts to non-reef environments have increased the rates of morphological diversification (i.e. size and body shape) in extant carangoids. Piscivory did not have a major impact on the tempo of diversification of this group. Through the ecological radiation of carangoid fishes, we demonstrate that non-reef environments may sustain and promote processes of diversification of different marine fish groups, at least those including a large proportion of piscivorous species. © 2016 The Author(s).

  20. Evidence for determinism in species diversification and contingency in phenotypic evolution during adaptive radiation.

    Science.gov (United States)

    Burbrink, Frank T; Chen, Xin; Myers, Edward A; Brandley, Matthew C; Pyron, R Alexander

    2012-12-07

    Adaptive radiation (AR) theory predicts that groups sharing the same source of ecological opportunity (EO) will experience deterministic species diversification and morphological evolution. Thus, deterministic ecological and morphological evolution should be correlated with deterministic patterns in the tempo and mode of speciation for groups in similar habitats and time periods. We test this hypothesis using well-sampled phylogenies of four squamate groups that colonized the New World (NW) in the Late Oligocene. We use both standard and coalescent models to assess species diversification, as well as likelihood models to examine morphological evolution. All squamate groups show similar early pulses of speciation, as well as diversity-dependent ecological limits on clade size at a continental scale. In contrast, processes of morphological evolution are not easily predictable and do not show similar pulses of early and rapid change. Patterns of morphological and species diversification thus appear uncoupled across these groups. This indicates that the processes that drive diversification and disparification are not mechanistically linked, even among similar groups of taxa experiencing the same sources of EO. It also suggests that processes of phenotypic diversification cannot be predicted solely from the existence of an AR or knowledge of the process of diversification.

  1. Old lineages in a new ecosystem: diversification of arcellinid amoebae (Amoebozoa and peatland mosses.

    Directory of Open Access Journals (Sweden)

    Omar Fiz-Palacios

    Full Text Available Arcellinid testate amoebae (Amoebozoa form a group of free-living microbial eukaryotes with one of the oldest fossil records known, yet several aspects of their evolutionary history remain poorly understood. Arcellinids occur in a range of terrestrial, freshwater and even brackish habitats; however, many arcellinid morphospecies such as Hyalosphenia papilio are particularly abundant in Sphagnum-dominated peatlands, a relatively new ecosystem that appeared during the diversification of Sphagnum species in the Miocene (5-20 Myr ago. Here, we reconstruct divergence times in arcellinid testate amoebae after selecting several fossils for clock calibrations and then infer whether or not arcellinids followed a pattern of diversification that parallels the pattern described for Sphagnum. We found that the diversification of core arcellinids occurred during the Phanerozoic, which is congruent with most arcellinid fossils but not with the oldest known amoebozoan fossil (i.e. at ca. 662 or ca. 750 Myr. Overall, Sphagnum and the Hyalospheniidae exhibit different patterns of diversification. However, an extensive molecular phylogenetic analysis of distinct clades within H. papilio species complex demonstrated a correlation between the recent diversification of H. papilio, the recent diversification of Sphagnum mosses, and the establishment of peatlands.

  2. Temperate radiations and dying embers of a tropical past: the diversification of Viburnum.

    Science.gov (United States)

    Spriggs, Elizabeth L; Clement, Wendy L; Sweeney, Patrick W; Madriñán, Santiago; Edwards, Erika J; Donoghue, Michael J

    2015-07-01

    We used a near-complete phylogeny for the angiosperm clade Viburnum to assess lineage diversification rates, and to examine possible morphological and ecological factors driving radiations. Maximum-likelihood and Bayesian approaches identified shifts in diversification rate and possible links to character evolution. We inferred the ancestral environment for Viburnum and changes in diversification dynamics associated with subsequent biome shifts. Viburnum probably diversified in tropical forests of Southeast Asia in the Eocene, with three subsequent radiations in temperate clades during the Miocene. Four traits (purple fruits, extrafloral nectaries, bud scales and toothed leaves) were statistically associated with higher rates of diversification. However, we argue that these traits are unlikely to be driving diversification directly. Instead, two radiations were associated with the occupation of mountainous regions and a third with repeated shifts between colder and warmer temperate forests. Early-branching depauperate lineages imply that the rare lowland tropical species are 'dying embers' of once more diverse lineages; net diversification rates in Viburnum likely decreased in these tropical environments after the Oligocene. We suggest that 'taxon pulse' dynamics might characterize other temperate plant lineages. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  3. Adaptive radiation versus 'radiation' and 'explosive diversification': why conceptual distinctions are fundamental to understanding evolution.

    Science.gov (United States)

    Givnish, Thomas J

    2015-07-01

    Adaptive radiation is the rise of a diversity of ecological roles and role-specific adaptations within a lineage. Recently, some researchers have begun to use 'adaptive radiation' or 'radiation' as synonymous with 'explosive species diversification'. This essay aims to clarify distinctions between these concepts, and the related ideas of geographic speciation, sexual selection, key innovations, key landscapes and ecological keys. Several examples are given to demonstrate that adaptive radiation and explosive diversification are not the same phenomenon, and that focusing on explosive diversification and the analysis of phylogenetic topology ignores much of the rich biology associated with adaptive radiation, and risks generating confusion about the nature of the evolutionary forces driving species diversification. Some 'radiations' involve bursts of geographic speciation or sexual selection, rather than adaptive diversification; some adaptive radiations have little or no effect on speciation, or even a negative effect. Many classic examples of 'adaptive radiation' appear to involve effects driven partly by geographic speciation, species' dispersal abilities, and the nature of extrinsic dispersal barriers; partly by sexual selection; and partly by adaptive radiation in the classical sense, including the origin of traits and invasion of adaptive zones that result in decreased diversification rates but add to overall diversity. © 2015 The Author. New Phytologist © 2015 New Phytologist Trust.

  4. Elevated Extinction Rates as a Trigger for Diversification Rate Shifts: Early Amniotes as a Case Study

    Science.gov (United States)

    Brocklehurst, Neil; Ruta, Marcello; Müller, Johannes; Fröbisch, Jörg

    2015-01-01

    Tree shape analyses are frequently used to infer the location of shifts in diversification rate within the Tree of Life. Many studies have supported a causal relationship between shifts and temporally coincident events such as the evolution of “key innovations”. However, the evidence for such relationships is circumstantial. We investigated patterns of diversification during the early evolution of Amniota from the Carboniferous to the Triassic, subjecting a new supertree to analyses of tree balance in order to infer the timing and location of diversification shifts. We investigated how uneven origination and extinction rates drive diversification shifts, and use two case studies (herbivory and an aquatic lifestyle) to examine whether shifts tend to be contemporaneous with evolutionary novelties. Shifts within amniotes tend to occur during periods of elevated extinction, with mass extinctions coinciding with numerous and larger shifts. Diversification shifts occurring in clades that possess evolutionary innovations do not coincide temporally with the appearance of those innovations, but are instead deferred to periods of high extinction rate. We suggest such innovations did not cause increases in the rate of cladogenesis, but allowed clades to survive extinction events. We highlight the importance of examining general patterns of diversification before interpreting specific shifts. PMID:26592209

  5. Uplift-driven diversification in the Hengduan Mountains, a temperate biodiversity hotspot.

    Science.gov (United States)

    Xing, Yaowu; Ree, Richard H

    2017-04-25

    A common hypothesis for the rich biodiversity found in mountains is uplift-driven diversification-that orogeny creates conditions favoring rapid in situ speciation of resident lineages. We tested this hypothesis in the context of the Qinghai-Tibetan Plateau (QTP) and adjoining mountain ranges, using the phylogenetic and geographic histories of multiple groups of plants to infer the tempo (rate) and mode (colonization versus in situ diversification) of biotic assembly through time and across regions. We focused on the Hengduan Mountains region, which in comparison with the QTP and Himalayas was uplifted more recently (since the late Miocene) and is smaller in area and richer in species. Time-calibrated phylogenetic analyses show that about 8 million y ago the rate of in situ diversification increased in the Hengduan Mountains, significantly exceeding that in the geologically older QTP and Himalayas. By contrast, in the QTP and Himalayas during the same period the rate of in situ diversification remained relatively flat, with colonization dominating lineage accumulation. The Hengduan Mountains flora was thus assembled disproportionately by recent in situ diversification, temporally congruent with independent estimates of orogeny. This study shows quantitative evidence for uplift-driven diversification in this region, and more generally, tests the hypothesis by comparing the rate and mode of biotic assembly jointly across time and space. It thus complements the more prevalent method of examining endemic radiations individually and could be used as a template to augment such studies in other biodiversity hotspots.

  6. A Robust Semi-Parametric Test for Detecting Trait-Dependent Diversification.

    Science.gov (United States)

    Rabosky, Daniel L; Huang, Huateng

    2016-03-01

    Rates of species diversification vary widely across the tree of life and there is considerable interest in identifying organismal traits that correlate with rates of speciation and extinction. However, it has been challenging to develop methodological frameworks for testing hypotheses about trait-dependent diversification that are robust to phylogenetic pseudoreplication and to directionally biased rates of character change. We describe a semi-parametric test for trait-dependent diversification that explicitly requires replicated associations between character states and diversification rates to detect effects. To use the method, diversification rates are reconstructed across a phylogenetic tree with no consideration of character states. A test statistic is then computed to measure the association between species-level traits and the corresponding diversification rate estimates at the tips of the tree. The empirical value of the test statistic is compared to a null distribution that is generated by structured permutations of evolutionary rates across the phylogeny. The test is applicable to binary discrete characters as well as continuous-valued traits and can accommodate extremely sparse sampling of character states at the tips of the tree. We apply the test to several empirical data sets and demonstrate that the method has acceptable Type I error rates. © The Author(s) 2015. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  7. Evidence for determinism in species diversification and contingency in phenotypic evolution during adaptive radiation

    Science.gov (United States)

    Burbrink, Frank T.; Chen, Xin; Myers, Edward A.; Brandley, Matthew C.; Pyron, R. Alexander

    2012-01-01

    Adaptive radiation (AR) theory predicts that groups sharing the same source of ecological opportunity (EO) will experience deterministic species diversification and morphological evolution. Thus, deterministic ecological and morphological evolution should be correlated with deterministic patterns in the tempo and mode of speciation for groups in similar habitats and time periods. We test this hypothesis using well-sampled phylogenies of four squamate groups that colonized the New World (NW) in the Late Oligocene. We use both standard and coalescent models to assess species diversification, as well as likelihood models to examine morphological evolution. All squamate groups show similar early pulses of speciation, as well as diversity-dependent ecological limits on clade size at a continental scale. In contrast, processes of morphological evolution are not easily predictable and do not show similar pulses of early and rapid change. Patterns of morphological and species diversification thus appear uncoupled across these groups. This indicates that the processes that drive diversification and disparification are not mechanistically linked, even among similar groups of taxa experiencing the same sources of EO. It also suggests that processes of phenotypic diversification cannot be predicted solely from the existence of an AR or knowledge of the process of diversification. PMID:23034709

  8. Machine Learning Biogeographic Processes from Biotic Patterns: A New Trait-Dependent Dispersal and Diversification Model with Model Choice By Simulation-Trained Discriminant Analysis.

    Science.gov (United States)

    Sukumaran, Jeet; Economo, Evan P; Lacey Knowles, L

    2016-05-01

    Current statistical biogeographical analysis methods are limited in the ways ecology can be related to the processes of diversification and geographical range evolution, requiring conflation of geography and ecology, and/or assuming ecologies that are uniform across all lineages and invariant in time. This precludes the possibility of studying a broad class of macroevolutionary biogeographical theories that relate geographical and species histories through lineage-specific ecological and evolutionary dynamics, such as taxon cycle theory. Here we present a new model that generates phylogenies under a complex of superpositioned geographical range evolution, trait evolution, and diversification processes that can communicate with each other. We present a likelihood-free method of inference under our model using discriminant analysis of principal components of summary statistics calculated on phylogenies, with the discriminant functions trained on data generated by simulations under our model. This approach of model selection by classification of empirical data with respect to data generated under training models is shown to be efficient, robust, and performs well over a broad range of parameter space defined by the relative rates of dispersal, trait evolution, and diversification processes. We apply our method to a case study of the taxon cycle, that is testing for habitat and trophic level constraints in the dispersal regimes of the Wallacean avifaunal radiation. ©The Author(s) 2015. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  9. Multilocus phylogeny, divergence times, and a major role for the benthic-to-pelagic axis in the diversification of grunts (Haemulidae).

    Science.gov (United States)

    Tavera, Jose; Acero P, Arturo; Wainwright, Peter C

    2018-04-01

    We present a phylogenetic analysis with divergence time estimates, and an ecomorphological assessment of the role of the benthic-to-pelagic axis of diversification in the history of haemulid fishes. Phylogenetic analyses were performed on 97 grunt species based on sequence data collected from seven loci. Divergence time estimation indicates that Haemulidae originated during the mid Eocene (54.7-42.3 Ma) but that the major lineages were formed during the mid-Oligocene 30-25 Ma. We propose a new classification that reflects the phylogenetic history of grunts. Overall the pattern of morphological and functional diversification in grunts appears to be strongly linked with feeding ecology. Feeding traits and the first principal component of body shape strongly separate species that feed in benthic and pelagic habitats. The benthic-to-pelagic axis has been the major axis of ecomorphological diversification in this important group of tropical shoreline fishes, with about 13 transitions between feeding habitats that have had major consequences for head and body morphology. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Integrating Diverse Types of Genomic Data to Identify Genes that Underlie Adverse Pregnancy Phenotypes.

    Directory of Open Access Journals (Sweden)

    Jibril Hirbo

    Full Text Available Progress in understanding complex genetic diseases has been bolstered by synthetic approaches that overlay diverse data types and analyses to identify functionally important genes. Pre-term birth (PTB, a major complication of pregnancy, is a leading cause of infant mortality worldwide. A major obstacle in addressing PTB is that the mechanisms controlling parturition and birth timing remain poorly understood. Integrative approaches that overlay datasets derived from comparative genomics with function-derived ones have potential to advance our understanding of the genetics of birth timing, and thus provide insights into the genes that may contribute to PTB. We intersected data from fast evolving coding and non-coding gene regions in the human and primate lineage with data from genes expressed in the placenta, from genes that show enriched expression only in the placenta, as well as from genes that are differentially expressed in four distinct PTB clinical subtypes. A large fraction of genes that are expressed in placenta, and differentially expressed in PTB clinical subtypes (23-34% are fast evolving, and are associated with functions that include adhesion neurodevelopmental and immune processes. Functional categories of genes that express fast evolution in coding regions differ from those linked to fast evolution in non-coding regions. Finally, there is a surprising lack of overlap between fast evolving genes that are differentially expressed in four PTB clinical subtypes. Integrative approaches, especially those that incorporate evolutionary perspectives, can be successful in identifying potential genetic contributions to complex genetic diseases, such as PTB.

  11. Apathy and Reduced Speed of Processing Underlie Decline in Verbal Fluency following DBS

    Science.gov (United States)

    Foltynie, Tom; Zrinzo, Ludvic; Hyam, Jonathan A.; Limousin, Patricia

    2017-01-01

    Objective. Reduced verbal fluency is a strikingly uniform finding following deep brain stimulation (DBS) for Parkinson's disease (PD). The precise cognitive mechanism underlying this reduction remains unclear, but theories have suggested reduced motivation, linguistic skill, and/or executive function. It is of note, however, that previous reports have failed to consider the potential role of any changes in speed of processing. Thus, the aim of this study was to examine verbal fluency changes with a particular focus on the role of cognitive speed. Method. In this study, 28 patients with PD completed measures of verbal fluency, motivation, language, executive functioning, and speed of processing, before and after DBS. Results. As expected, there was a marked decline in verbal fluency but also in a timed test of executive functions and two measures of speed of processing. Verbal fluency decline was associated with markers of linguistic and executive functioning, but not after speed of processing was statistically controlled for. In contrast, greater decline in verbal fluency was associated with higher levels of apathy at baseline, which was not associated with changes in cognitive speed. Discussion. Reduced generativity and processing speed may account for the marked reduction in verbal fluency commonly observed following DBS. PMID:28408788

  12. Mitochondrial phenylalanyl-tRNA synthetase mutations underlie fatal infantile Alpers encephalopathy

    DEFF Research Database (Denmark)

    Elo, Jenni M; Yadavalli, Srujana S; Euro, Liliya

    2012-01-01

    was impaired. Our results imply that the three FARS2 mutations directly impair aminoacylation function and stability of mtPheRS, leading to a decrease in overall tRNA charging capacity. This study establishes a new genetic cause of infantile mitochondrial Alpers encephalopathy and reports a new mitochondrial...

  13. Apathy and Reduced Speed of Processing Underlie Decline in Verbal Fluency following DBS

    Directory of Open Access Journals (Sweden)

    Jennifer A. Foley

    2017-01-01

    Full Text Available Objective. Reduced verbal fluency is a strikingly uniform finding following deep brain stimulation (DBS for Parkinson’s disease (PD. The precise cognitive mechanism underlying this reduction remains unclear, but theories have suggested reduced motivation, linguistic skill, and/or executive function. It is of note, however, that previous reports have failed to consider the potential role of any changes in speed of processing. Thus, the aim of this study was to examine verbal fluency changes with a particular focus on the role of cognitive speed. Method. In this study, 28 patients with PD completed measures of verbal fluency, motivation, language, executive functioning, and speed of processing, before and after DBS. Results. As expected, there was a marked decline in verbal fluency but also in a timed test of executive functions and two measures of speed of processing. Verbal fluency decline was associated with markers of linguistic and executive functioning, but not after speed of processing was statistically controlled for. In contrast, greater decline in verbal fluency was associated with higher levels of apathy at baseline, which was not associated with changes in cognitive speed. Discussion. Reduced generativity and processing speed may account for the marked reduction in verbal fluency commonly observed following DBS.

  14. Apathy and Reduced Speed of Processing Underlie Decline in Verbal Fluency following DBS.

    Science.gov (United States)

    Foley, Jennifer A; Foltynie, Tom; Zrinzo, Ludvic; Hyam, Jonathan A; Limousin, Patricia; Cipolotti, Lisa

    2017-01-01

    Objective . Reduced verbal fluency is a strikingly uniform finding following deep brain stimulation (DBS) for Parkinson's disease (PD). The precise cognitive mechanism underlying this reduction remains unclear, but theories have suggested reduced motivation, linguistic skill, and/or executive function. It is of note, however, that previous reports have failed to consider the potential role of any changes in speed of processing. Thus, the aim of this study was to examine verbal fluency changes with a particular focus on the role of cognitive speed. Method . In this study, 28 patients with PD completed measures of verbal fluency, motivation, language, executive functioning, and speed of processing, before and after DBS. Results . As expected, there was a marked decline in verbal fluency but also in a timed test of executive functions and two measures of speed of processing. Verbal fluency decline was associated with markers of linguistic and executive functioning, but not after speed of processing was statistically controlled for. In contrast, greater decline in verbal fluency was associated with higher levels of apathy at baseline, which was not associated with changes in cognitive speed. Discussion . Reduced generativity and processing speed may account for the marked reduction in verbal fluency commonly observed following DBS.

  15. Subfield profitability analysis reveals an economic case for cropland diversification

    Science.gov (United States)

    Brandes, E.; McNunn, G. S.; Schulte, L. A.; Bonner, I. J.; Muth, D. J.; Babcock, B. A.; Sharma, B.; Heaton, E. A.

    2016-01-01

    Public agencies and private enterprises increasingly desire to achieve ecosystem service outcomes in agricultural systems, but are limited by perceived conflicts between economic and ecosystem service goals and a lack of tools enabling effective operational management. Here we use Iowa—an agriculturally homogeneous state representative of the Maize Belt—to demonstrate an economic rationale for cropland diversification at the subfield scale. We used a novel computational framework that integrates disparate but publicly available data to map ˜3.3 million unique potential management polygons (9.3 Mha) and reveal subfield opportunities to increase overall field profitability. We analyzed subfield profitability for maize/soybean fields during 2010-2013—four of the most profitable years in recent history—and projected results for 2015. While cropland operating at a loss of US 250 ha-1 or more was negligible between 2010 and 2013 at 18 000-190 000 ha (profitable areas, incorporating conservation management that breaks even (e.g., planting low-input perennials), into low-yielding portions of fields could increase overall cropland profitability by 80%. This approach is applicable to the broader region and differs substantially from the status quo of ‘top-down’ land management for conservation by harnessing private interest to align profitability with the production of ecosystem services.

  16. Inferring the dynamics of diversification: a coalescent approach.

    Science.gov (United States)

    Morlon, Hélène; Potts, Matthew D; Plotkin, Joshua B

    2010-09-28

    Recent analyses of the fossil record and molecular phylogenies suggest that there are fundamental limits to biodiversity, possibly arising from constraints in the availability of space, resources, or ecological niches. Under this hypothesis, speciation rates decay over time and biodiversity eventually saturates, with new species emerging only when others are driven to extinction. This view of macro-evolution contradicts an alternative hypothesis that biodiversity is unbounded, with species ever accumulating as they find new niches to occupy. These contrasting theories of biodiversity dynamics yield fundamentally different explanations for the disparity in species richness across taxa and regions. Here, we test whether speciation rates have decayed or remained constant over time, and whether biodiversity is saturated or still expanding. We first derive a general likelihood expression for internode distances in a phylogeny, based on the well-known coalescent process from population genetics. This expression accounts for either time-constant or time-variable rates, time-constant or time-variable diversity, and completely or incompletely sampled phylogenies. We then compare the performance of different diversification scenarios in explaining a set of 289 phylogenies representing amphibians, arthropods, birds, mammals, mollusks, and flowering plants. Our results indicate that speciation rates typically decay over time, but that diversity is still expanding at present. The evidence for expanding-diversity models suggests that an upper limit to biodiversity has not yet been reached, or that no such limit exists.

  17. Top predators induce the evolutionary diversification of intermediate predator species.

    Science.gov (United States)

    Zu, Jian; Yuan, Bo; Du, Jianqiang

    2015-12-21

    We analyze the evolutionary branching phenomenon of intermediate predator species in a tritrophic food chain model by using adaptive dynamics theory. Specifically, we consider the adaptive diversification of an intermediate predator species that feeds on a prey species and is fed upon by a top predator species. We assume that the intermediate predator׳s ability to forage on the prey can adaptively improve, but this comes at the cost of decreased defense ability against the top predator. First, we identify the general properties of trade-off relationships that lead to a continuously stable strategy or to evolutionary branching in the intermediate predator species. We find that if there is an accelerating cost near the singular strategy, then that strategy is continuously stable. In contrast, if there is a mildly decelerating cost near the singular strategy, then that strategy may be an evolutionary branching point. Second, we find that after branching has occurred, depending on the specific shape and strength of the trade-off relationship, the intermediate predator species may reach an evolutionarily stable dimorphism or one of the two resultant predator lineages goes extinct. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  18. Going All In: Unfavorable Sex Ratios Attenuate Choice Diversification.

    Science.gov (United States)

    Ackerman, Joshua M; Maner, Jon K; Carpenter, Stephanie M

    2016-06-01

    When faced with risky decisions, people typically choose to diversify their choices by allocating resources across a variety of options and thus avoid putting "all their eggs in one basket." The current research revealed that this tendency is reversed when people face an important cue to mating-related risk: skew in the operational sex ratio, or the ratio of men to women in the local environment. Counter to the typical strategy of choice diversification, findings from four studies demonstrated that the presence of romantically unfavorable sex ratios (those featuring more same-sex than opposite-sex individuals) led heterosexual people to diversify financial resources less and instead concentrate investment in high-risk/high-return options when making lottery, stock-pool, retirement-account, and research-funding decisions. These studies shed light on a key process by which people manage risks to mating success implied by unfavorable interpersonal environments. These choice patterns have important implications for mating behavior as well as other everyday forms of decision making. © The Author(s) 2016.

  19. Ubx regulates differential enlargement and diversification of insect hind legs.

    Directory of Open Access Journals (Sweden)

    Najmus Mahfooz

    2007-09-01

    Full Text Available Differential enlargement of hind (T3 legs represents one of the hallmarks of insect evolution. However, the actual mechanism(s responsible are yet to be determined. To address this issue, we have now studied the molecular basis of T3 leg enlargement in Oncopeltus fasciatus (milkweed bug and Acheta domesticus (house cricket. In Oncopeltus, the T3 tibia displays a moderate increase in size, whereas in Acheta, the T3 femur, tibia, and tarsus are all greatly enlarged. Here, we show that the hox gene Ultrabithorax (Ubx is expressed in the enlarged segments of hind legs. Furthermore, we demonstrate that depletion of Ubx during embryogenesis has a primary effect in T3 legs and causes shortening of leg segments that are enlarged in a wild type. This result shows that Ubx is regulating the differential growth and enlargement of T3 legs in both Oncopeltus and Acheta. The emerging view suggests that Ubx was co-opted for a novel role in regulating leg growth and that the transcriptional modification of its expression may be a universal mechanism for the evolutionary diversification of insect hind legs.

  20. Archaeobatrachian paraphyly and pangaean diversification of crown-group frogs.

    Science.gov (United States)

    Roelants, Kim; Bossuyt, Franky

    2005-02-01

    Current models for the early diversification of living frogs inferred from morphological, ontogenetic, or DNA sequence data invoke very different scenarios of character evolution and biogeography. To explore central controversies on the phylogeny of Anura, we analyzed nearly 4000 base pairs of mitochondrial and nuclear DNA for the major frog lineages. Likelihood-based analyses of this data set are congruent with morphological evidence in supporting a paraphyletic arrangement of archaeobatrachian frogs, with an (Ascaphus + Leiopelma) clade as the sister-group of all other living anurans. The stability of this outcome is reinforced by screening for phylogenetic bias resulting from site-specific rate variation, homoplasy, or the obligatory use of distantly related outgroups. Twenty-one alternative branching and rooting hypotheses were evaluated using a nonparametric multicomparison test and parametric bootstrapping. Relaxed molecular clock estimates situate the emergence of crown-group anurans in the Triassic, approximately 55 million years prior to their first appearance in the fossil record. The existence of at least four extant frog lineages on the supercontinent Pangaea before its breakup gains support from the estimation that three early splits between Laurasia- and Gondwana-associated families coincide with the initial rifting of these landmasses. This observation outlines the potential significance of this breakup event in the formation of separate Mesozoic faunal assemblages in both hemispheres.

  1. Starvation induces phenotypic diversification and convergent evolution in Vibrio vulnificus.

    Directory of Open Access Journals (Sweden)

    Hwajiun Chen

    Full Text Available Starvation is a common stress experienced by bacteria living in natural environments and the ability to adapt to and survive intense stress is of paramount importance for any bacterial population. A series of starvation experiments were conducted using V. vulnificus 93U204 in phosphate-buffered saline and seawater. The starved population entered the death phase during the first week and approximately 1% of cells survived. After that the population entered a long-term stationary phase, and could survive for years. Starvation-induced diversification (SID of phenotypes was observed in starved populations and phenotypic variants (PVs appeared in less than 8 days. The cell density, rather than the population size, had a major effect on the extent of SID. SID was also observed in strain YJ016, where it evolved at a faster pace. PVs appeared to emerge in a fixed order: PV with reduced motility, PV with reduced proteolytic activity, and PV with reduced hemolytic activity. All of the tested PVs had growth advantages in the stationary phase phenotypes and increased fitness compared with 93U204 cells in co-culture competition experiments, which indicates that they had adapted to starvation. We also found that SID occurred in natural seawater with a salinity of 1%-3%, so this mechanism may facilitate bacterial adaptation in natural environments.

  2. The oldest parareptile and the early diversification of reptiles.

    Science.gov (United States)

    Modesto, Sean P; Scott, Diane M; MacDougall, Mark J; Sues, Hans-Dieter; Evans, David C; Reisz, Robert R

    2015-02-22

    Amniotes, tetrapods that evolved the cleidoic egg and thus independence from aquatic larval stages, appeared ca 314 Ma during the Coal Age. The rapid diversification of amniotes and other tetrapods over the course of the Late Carboniferous period was recently attributed to the fragmentation of coal-swamp rainforests ca 307 Ma. However, the amniote fossil record during the Carboniferous is relatively sparse, with ca 33% of the diversity represented by single specimens for each species. We describe here a new species of reptilian amniote that was collected from uppermost Carboniferous rocks of Prince Edward Island, Canada. Erpetonyx arsenaultorum gen. et sp. nov. is a new parareptile distinguished by 29 presacral vertebrae and autapomorphies of the carpus. Phylogenetic analyses of parareptiles reveal E. arsenaultorum as the closest relative of bolosaurids. Stratigraphic calibration of our results indicates that parareptiles began their evolutionary radiation before the close of the Carboniferous Period, and that the diversity of end-Carboniferous reptiles is 80% greater than suggested by previous work. Latest Carboniferous reptiles were still half as diverse as synapsid amniotes, a disparity that may be attributable to preservational biases, to collecting biases, to the origin of herbivory in tetrapods or any combination of these factors. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  3. Diversification of fuel costs accounting for load variation

    International Nuclear Information System (INIS)

    Ruangpattana, Suriya; Preckel, Paul V.; Gotham, Douglas J.; Muthuraman, Kumar; Velástegui, Marco; Morin, Thomas L.; Uhan, Nelson A.

    2012-01-01

    A practical mathematical programming model for the strategic fuel diversification problem is presented. The model is designed to consider the tradeoffs between the expected costs of investments in capacity, operating and maintenance costs, average fuel costs, and the variability of fuel costs. In addition, the model is designed to take the load curve into account at a high degree of resolution, while keeping the computational burden at a practical level. The model is illustrated with a case study for Indiana's power generation system. The model reveals that an effective means of reducing the volatility of the system-level fuel costs is through the reduction of dependence on coal-fired generation with an attendant shift towards nuclear generation. Model results indicate that about a 25% reduction in the standard deviation of the generation costs can be achieved with about a 20–25% increase in average fuel costs. Scenarios that incorporate costs for carbon dioxide emissions or a moratorium on nuclear capacity additions are also presented. Highlights: ► We propose a fuel price risk management model for generation investments accounting for load shape. ► The formulation incorporates a highly refined load curve while maintaining tractability. ► We demonstrate the model for planning generation investments in the state of Indiana for 2025. ► Scenarios reflect charges for CO 2 emissions and a moratorium on new nuclear power.

  4. Comparative Analysis of Risk, Return and Diversification of Mutual Fund

    Directory of Open Access Journals (Sweden)

    Rais Ahmad

    2015-01-01

    Full Text Available Mutual Funds have become a widely popular and effective way for investors to participate in financial markets in an easy, low-cost fashion, while muting risk characteristics by spreading the investment across different types of securities, also known as diversification. It can play a central role in an individual's investment strategy. With the plethora of schemes available in the Indian markets, an investors needs to evaluate and consider various factors before making an investment decision. The present investigation is aimed to examine the performance of safest investment instrument in the security market in the eyes of investors. Five mutual fund large cap scheme have been selected for this purpose. The examination is achieved by assessing various financial tests like Sharpe Ratio, Standard Deviation, Alpha, and Beta. Furthermore, in-depth analysis also has been done by considering return over the period of last five years on various basis, expenses ratio, corpus-size etc. The data has been taken from various websites of mutual fund schemes and from www.valueresearch.com. The study will be helpful for the researchers and financial analysts to analyze various securities or funds while selecting the best investment alternative out of the galaxy of investment alternatives.

  5. Origin and Diversification of Dung Beetles in Madagascar

    Directory of Open Access Journals (Sweden)

    Andreia Miraldo

    2011-04-01

    Full Text Available Madagascar has a rich fauna of dung beetles (Scarabaeinae and Aphodiinae withalmost 300 species described to date. Like most other taxa in Madagascar, dung beetles exhibit an exceptionally high level of endemism (96% of the species. Here,we review the current knowledge of the origin and diversification of Malagasy dung beetles. Based on molecular phylogenies, the extant dung beetles originate from eight colonizations, of which four have given rise to extensive radiations. These radiations have occurred in wet forests, while the few extant species in the less successfulradiations occur in open and semi-open habitats. We discuss the likely mechanisms of speciation and the ecological characteristics of the extant communities, emphasizing the role of adaptation along environmental gradients and allopatric speciation in generating the exceptionally high beta diversity in Malagasy dung beetles. Phylogeographic analyses of selected species reveal complex patterns with evidence for genetic introgression between old taxa. The introduction of cattle to Madagascar 1500 years ago created a new abundant resource, onto which a few species haveshifted and thereby been able to greatly expand their geographical ranges.

  6. Capital Strategy in Diversification Farming Efforts Using SWOT Analysis

    Science.gov (United States)

    Damanhuri; Setyohadi, D. P. S.; Utami, M. M. D.; Kurnianto, M. F.; Hariono, B.

    2018-01-01

    Wetland farm diversification program in the district of Bojonegoro, Tulungagung, and Ponorogo can not provide an optimal contribution to the income of farmers caused because farmers are not able to cultivate high value-added commodities due to limited capital. This study aims to identify the characteristics of farming, capital pattern, stakeholder role, to analyze farming to know the pattern of planting suggestions and prospects, and to formulate capital facilitation strategy. Farming capital is obtained through loans in financial institutions with different patterns. Small farmers tend to utilize savings and credit cooperatives, microcredit, and loan sharks, while farmers with large wetland holdings tend to utilize commercial banks. P enelitian using descriptive method of farming profit analysis, and SWOT. The government through the banking institutions have provided much facilitation in the form of low-interest loans with flexible payment method. The generic strategy of selected capital facilitation is to empower farmers through farmer groups who have the capability in managing the capital needs of their members.

  7. The Diversification Benefits of Including Carbon Assets in Financial Portfolios

    Directory of Open Access Journals (Sweden)

    Yinpeng Zhang

    2017-03-01

    Full Text Available Carbon allowances traded in the EU-Emission Trading Scheme (EU-ETS were initially designed as an economic motivation for efficiently curbing greenhouse as emissions, but now it mimics quite a few characteristics of financial assets, and have now been used as a candidate product in building financial portfolios. In this study, we examine the time-varying correlations between carbon allowance prices with other financial indices, during the third phase of EU-ETS. The results show that, at the beginning of this period, carbon price was still strongly corrected with other financial indices. However, this connection was weakened over time. Given the relative independence of carbon assets from other financial assets, we argue for the diversification benefits of including carbon assets in financial portfolios, and building such portfolios, respectively, with the traditional global minimum variance (GMV strategy, the mean-variance-OGARCH (MV-OGARCH strategy, and the dynamic conditional correlation (DCC strategy. It is shown that the portfolio built with the MV-OGARCH strategy far out-performs the others and that including carbon assets in financial portfolios does help reduce investment risks.

  8. Different brain circuits underlie motor and perceptual representations of temporal intervals

    DEFF Research Database (Denmark)

    Bueti, Doemnica; Walsh, Vincent; Frith, Christopher

    2008-01-01

    V5/MT. Our findings point to a role for the parietal cortex as an interface between sensory and motor processes and suggest that it may be a key node in translation of temporal information into action. Furthermore, we discuss the potential importance of the extrastriate cortex in processing visual......In everyday life, temporal information is used for both perception and action, but whether these two functions reflect the operation of similar or different neural circuits is unclear. We used functional magnetic resonance imaging to investigate the neural correlates of processing temporal...... information when either a motor or a perceptual representation is used. Participants viewed two identical sequences of visual stimuli and used the information differently to perform either a temporal reproduction or a temporal estimation task. By comparing brain activity evoked by these tasks and control...

  9. Separate neural mechanisms underlie choices and strategic preferences in risky decision making.

    Science.gov (United States)

    Venkatraman, Vinod; Payne, John W; Bettman, James R; Luce, Mary Frances; Huettel, Scott A

    2009-05-28

    Adaptive decision making in real-world contexts often relies on strategic simplifications of decision problems. Yet, the neural mechanisms that shape these strategies and their implementation remain largely unknown. Using an economic decision-making task, we dissociate brain regions that predict specific choices from those predicting an individual's preferred strategy. Choices that maximized gains or minimized losses were predicted by functional magnetic resonance imaging activation in ventromedial prefrontal cortex or anterior insula, respectively. However, choices that followed a simplifying strategy (i.e., attending to overall probability of winning) were associated with activation in parietal and lateral prefrontal cortices. Dorsomedial prefrontal cortex, through differential functional connectivity with parietal and insular cortex, predicted individual variability in strategic preferences. Finally, we demonstrate that robust decision strategies follow from neural sensitivity to rewards. We conclude that decision making reflects more than compensatory interaction of choice-related regions; in addition, specific brain systems potentiate choices depending on strategies, traits, and context.

  10. Tempo of Diversification of Global Amphibians: One-Constant Rate, One-Continuous Shift or Multiple-Discrete Shifts?

    Directory of Open Access Journals (Sweden)

    Youhua Chen

    2014-01-01

    Full Text Available In this brief report, alternative time-varying diversification rate models were fitted onto the phylogeny of global amphibians by considering one-constant-rate (OCR, one-continuous-shift (OCS and multiplediscrete- shifts (MDS situations. The OCS diversification model was rejected by γ statistic (γ=-5.556, p⁄ 0.001, implying the existence of shifting diversification rates for global amphibian phylogeny. Through model selection, MDS diversification model outperformed OCS and OCR models using “laser” package under R environment. Moreover, MDS models, implemented using another R package “MEDUSA”, indicated that there were sixteen shifts over the internal nodes for amphibian phylogeny. Conclusively, both OCS and MDS models are recommended to compare so as to better quantify rate-shifting trends of species diversification. MDS diversification models should be preferential for large phylogenies using “MEDUSA” package in which any arbitrary numbers of shifts are allowed to model.

  11. Molecular evolution and diversification of snake toxin genes, revealed by analysis of intron sequences.

    Science.gov (United States)

    Fujimi, T J; Nakajyo, T; Nishimura, E; Ogura, E; Tsuchiya, T; Tamiya, T

    2003-08-14

    The genes encoding erabutoxin (short chain neurotoxin) isoforms (Ea, Eb, and Ec), LsIII (long chain neurotoxin) and a novel long chain neurotoxin pseudogene were cloned from a Laticauda semifasciata genomic library. Short and long chain neurotoxin genes were also cloned from the genome of Laticauda laticaudata, a closely related species of L. semifasciata, by PCR. A putative matrix attached region (MAR) sequence was found in the intron I of the LsIII gene. Comparative analysis of 11 structurally relevant snake toxin genes (three-finger-structure toxins) revealed the molecular evolution of these toxins. Three-finger-structure toxin genes diverged from a common ancestor through two types of evolutionary pathways (long and short types), early in the course of evolution. At a later stage of evolution in each gene, the accumulation of mutations in the exons, especially exon II, by accelerated evolution may have caused the increased diversification in their functions. It was also revealed that the putative MAR sequence found in the LsIII gene was integrated into the gene after the species-level divergence.

  12. Evolutionary diversification of protein-protein interactions by interface add-ons.

    Science.gov (United States)

    Plach, Maximilian G; Semmelmann, Florian; Busch, Florian; Busch, Markus; Heizinger, Leonhard; Wysocki, Vicki H; Merkl, Rainer; Sterner, Reinhard

    2017-10-03

    Cells contain a multitude of protein complexes whose subunits interact with high specificity. However, the number of different protein folds and interface geometries found in nature is limited. This raises the question of how protein-protein interaction specificity is achieved on the structural level and how the formation of nonphysiological complexes is avoided. Here, we describe structural elements called interface add-ons that fulfill this function and elucidate their role for the diversification of protein-protein interactions during evolution. We identified interface add-ons in 10% of a representative set of bacterial, heteromeric protein complexes. The importance of interface add-ons for protein-protein interaction specificity is demonstrated by an exemplary experimental characterization of over 30 cognate and hybrid glutamine amidotransferase complexes in combination with comprehensive genetic profiling and protein design. Moreover, growth experiments showed that the lack of interface add-ons can lead to physiologically harmful cross-talk between essential biosynthetic pathways. In sum, our complementary in silico, in vitro, and in vivo analysis argues that interface add-ons are a practical and widespread evolutionary strategy to prevent the formation of nonphysiological complexes by specializing protein-protein interactions.

  13. Diversification of DnaA dependency for DNA replication in cyanobacterial evolution.

    Science.gov (United States)

    Ohbayashi, Ryudo; Watanabe, Satoru; Ehira, Shigeki; Kanesaki, Yu; Chibazakura, Taku; Yoshikawa, Hirofumi

    2016-05-01

    Regulating DNA replication is essential for all living cells. The DNA replication initiation factor DnaA is highly conserved in prokaryotes and is required for accurate initiation of chromosomal replication at oriC. DnaA-independent free-living bacteria have not been identified. The dnaA gene is absent in plastids and some symbiotic bacteria, although it is not known when or how DnaA-independent mechanisms were acquired. Here, we show that the degree of dependency of DNA replication on DnaA varies among cyanobacterial species. Deletion of the dnaA gene in Synechococcus elongatus PCC 7942 shifted DNA replication from oriC to a different site as a result of the integration of an episomal plasmid. Moreover, viability during the stationary phase was higher in dnaA disruptants than in wild-type cells. Deletion of dnaA did not affect DNA replication or cell growth in Synechocystis sp. PCC 6803 or Anabaena sp. PCC 7120, indicating that functional dependency on DnaA was already lost in some nonsymbiotic cyanobacterial lineages during diversification. Therefore, we proposed that cyanobacteria acquired DnaA-independent replication mechanisms before symbiosis and such an ancestral cyanobacterium was the sole primary endosymbiont to form a plastid precursor.

  14. Reward salience and risk aversion underlie differential ACC activity in substance dependence.

    Science.gov (United States)

    Alexander, William H; Fukunaga, Rena; Finn, Peter; Brown, Joshua W

    2015-01-01

    The medial prefrontal cortex, especially the dorsal anterior cingulate cortex (ACC), has long been implicated in cognitive control and error processing. Although the association between ACC and behavior has been established, it is less clear how ACC contributes to dysfunctional behavior such as substance dependence. Evidence from neuroimaging studies investigating ACC function in substance users is mixed, with some studies showing disengagement of ACC in substance dependent individuals (SDs), while others show increased ACC activity related to substance use. In this study, we investigate ACC function in SDs and healthy individuals performing a change signal task for monetary rewards. Using a priori predictions derived from a recent computational model of ACC, we find that ACC activity differs between SDs and controls in factors related to reward salience and risk aversion between SDs and healthy individuals. Quantitative fits of a computational model to fMRI data reveal significant differences in best fit parameters for reward salience and risk preferences. Specifically, the ACC in SDs shows greater risk aversion, defined as concavity in the utility function, and greater attention to rewards relative to reward omission. Furthermore, across participants risk aversion and reward salience are positively correlated. The results clarify the role that ACC plays in both the reduced sensitivity to omitted rewards and greater reward valuation in SDs. Clinical implications of applying computational modeling in psychiatry are also discussed.

  15. Cognition from life: the two modes of cognition that underlie moral behavior

    Directory of Open Access Journals (Sweden)

    Tjeerd C Andringa

    2015-04-01

    Full Text Available We argue that the capacity to live life to the benefit of self and others originates in the defining properties of life. These lead to two modes of cognition; the coping mode that is preoccupied with the satisfaction of pressing needs and the co-creation mode that aims at the realization of a world where pressing needs occur less frequently. We have used the Rule of Conservative Changes – stating that new functions can only scaffold on evolutionary older, yet highly stable functions – to predict that the interplay of these two modes define a number of core functions in psychology associated with moral behavior. We explore this prediction with five examples reflecting different theoretical approaches to human cognition and action selection. We conclude the paper with the observation that science is currently dominated by the coping mode and that the benefits of the co-creation mode may be necessary to generate realistic prospects for a modern synthesis in the sciences of the mind.

  16. Moving Forward: Age Effects on the Cerebellum Underlie Cognitive and Motor Declines

    Science.gov (United States)

    Bernard, Jessica A.; Seidler, Rachael D.

    2014-01-01

    Though the cortical contributions to age-related declines in motor and cognitive performance are well-known, the potential contributions of the cerebellum are less clear. The diverse functions of the cerebellum make it an important structure to investigate in aging. Here, we review the extant literature on this topic. To date, there is evidence to indicate that there are morphological age differences in the cerebellum that are linked to motor and cognitive behavior. Cerebellar morphology is often as good as -- or even better -- at predicting performance than the prefrontal cortex. We also touch on the few studies using functional neuroimaging and connectivity analyses that further implicate the cerebellum in age-related performance declines. Importantly, we provide a conceptual framework for the cerebellum influencing age differences in performance, centered on the notion of degraded internal models. The evidence indicating that cerebellar age differences associate with performance highlights the need for additional work in this domain to further elucidate the role of the cerebellum in age differences in movement control and cognitive function. PMID:24594194

  17. Cognition from life: the two modes of cognition that underlie moral behavior.

    Science.gov (United States)

    Andringa, Tjeerd C; Bosch, Kirsten A Van Den; Wijermans, Nanda

    2015-01-01

    We argue that the capacity to live life to the benefit of self and others originates in the defining properties of life. These lead to two modes of cognition; the coping mode that is preoccupied with the satisfaction of pressing needs and the co-creation mode that aims at the realization of a world where pressing needs occur less frequently. We have used the Rule of Conservative Changes - stating that new functions can only scaffold on evolutionary older, yet highly stable functions - to predict that the interplay of these two modes define a number of core functions in psychology associated with moral behavior. We explore this prediction with five examples reflecting different theoretical approaches to human cognition and action selection. We conclude the paper with the observation that science is currently dominated by the coping mode and that the benefits of the co-creation mode may be necessary to generate realistic prospects for a modern synthesis in the sciences of the mind.

  18. The diversification benefits from Islamic investment during the financial turmoil: The case for the US-based equity investors

    Directory of Open Access Journals (Sweden)

    Buerhan Saiti

    2014-12-01

    Our findings based on the Dynamic Conditional Correlation (DCC tend to suggest: both the conventional and Islamic MSCI indices of Japan, GCC ex-Saudi, Indonesia, Malaysia and Taiwan provide better diversification benefits compared to Korea, Hong Kong, China and Turkey. It tends to suggest that the Islamic countries provide better diversification benefits compared to the Far East countries with strong policy implications for the domestic and international investors in their portfolio diversification for hedging against unforeseen risks.

  19. Phylogenetic patterns of geographical and ecological diversification in the subgenus Drosophila.

    Directory of Open Access Journals (Sweden)

    Ramiro Morales-Hojas

    Full Text Available Colonisation of new geographic regions and/or of new ecological resources can result in rapid species diversification into the new ecological niches available. Members of the subgenus Drosophila are distributed across the globe and show a large diversity of ecological niches. Furthermore, taxonomic classification of Drosophila includes the rank radiation, which refers to closely related species groups. Nevertheless, it has never been tested if these taxonomic radiations correspond to evolutionary radiations. Here we present a study of the patterns of diversification of Drosophila to test for increased diversification rates in relation to the geographic and ecological diversification processes. For this, we have estimated and dated a phylogeny of 218 species belonging to the major species groups of the subgenus. The obtained phylogenies are largely consistent with previous studies and indicate that the major groups appeared during the Oligocene/Miocene transition or early Miocene, characterized by a trend of climate warming with brief periods of glaciation. Ancestral reconstruction of geographic ranges and ecological resource use suggest at least two dispersals to the Neotropics from the ancestral Asiatic tropical disribution, and several transitions to specialized ecological resource use (mycophagous and cactophilic. Colonisation of new geographic regions and/or of new ecological resources can result in rapid species diversification into the new ecological niches available. However, diversification analyses show no significant support for adaptive radiations as a result of geographic dispersal or ecological resource shift. Also, cactophily has not resulted in an increase in the diversification rate of the repleta and related groups. It is thus concluded that the taxonomic radiations do not correspond to adaptive radiations.

  20. 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.