WorldWideScience

Sample records for symbiont population densities

  1. Earthworm ecology affects the population structure of their Verminephrobacter symbionts

    DEFF Research Database (Denmark)

    Macedo Viana, Flavia Daniela; Jensen, Christopher Erik; Macey, Michael

    2016-01-01

    . Although several studies have addressed the Verminephrobacter diversity between worm species, the intra-species diversity of the symbiont population has never been investigated. To address symbiont population structure, we used a multi-locus sequence typing (MLST) approach on Verminephrobacter isolated...... from two contrasting ecological types of earthworm hosts: the high population density, fast reproducing compost worms, Eisenia andrei and E. fetida, and the low-density, slow reproducing Aporrectodea tuberculata, commonly found in garden soils; for both types, three distinct populations were...... across host individuals from the same population. Thus, host ecology shapes the population structure of the Verminephrobacter symbionts. The homogeneous symbiont populations in the compost worms indicate that Verminephrobacter can be transferred bi-parentally or via leaky horizontal transmission in high...

  2. Temporal changes of symbiont density and host fitness after rifampicin treatment in a whitefly of the Bemisia tabaci species complex.

    Science.gov (United States)

    Shan, Hong-Wei; Zhang, Chang-Rong; Yan, Ting-Ting; Tang, Hai-Qin; Wang, Xiao-Wei; Liu, Shu-Sheng; Liu, Yin-Quan

    2016-04-01

    Microbial symbionts are essential or important partners to phloem-feeding insects. Antibiotics have been used to selectively eliminate symbionts from their host insects and establish host lines with or without certain symbionts for investigating functions of the symbionts. In this study, using the antibiotic rifampicin we attempted to selectively eliminate certain symbionts from a population of the Middle East-Asia Minor 1 whitefly of the Bemisia tabaci species complex, which harbors the primary symbiont "Candidatus Portiera aleyrodidarum" and two secondary symbionts "Candidatus Hamiltonella defensa" and Rickettsia. Neither the primary nor the secondary symbionts were completely depleted in the adults (F0) that fed for 48 h on a diet treated with rifampicin at concentrations of 1-100 μg/mL. However, both the primary and secondary symbionts were nearly completely depleted in the offspring (F1) of the rifampicin-treated adults. Although the F1 adults produced some eggs (F2), most of the eggs failed to hatch and none of them reached the second instar, and consequently the rifampicin-treated whitefly colony vanished at the F2 generation. Interestingly, quantitative polymerase chain reaction assays showed that in the rifampicin-treated whiteflies, the density of the primary symbiont was reduced at an obviously slower pace than the secondary symbionts. Mating experiments between rifampicin-treated and untreated adults demonstrated that the negative effects of rifampicin on host fitness were expressed when the females were treated by the antibiotic, and whether males were treated or not by the antibiotic had little contribution to the negative effects. These observations indicate that with this whitefly population it is not feasible to selectively eliminate the secondary symbionts using rifampicin without affecting the primary symbiont and establish host lines for experimental studies. However, the extinction of the whitefly colony at the second generation after

  3. Location of Symbionts in the Whitefly Bemisia tabaci Affects Their Densities during Host Development and Environmental Stress

    Science.gov (United States)

    Su, Qi; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Ghanim, Murad; Zhang, Youjun

    2014-01-01

    Bacterial symbionts often enhance the physiological capabilities of their arthropod hosts and enable their hosts to expand into formerly unavailable niches, thus leading to biological diversification. Many arthropods, including the worldwide invasive whitefly Bemisia tabaci, have individuals simultaneously infected with symbionts of multiple genera that occur in different locations in the host. This study examined the population dynamics of symbionts that are located in different areas within B. tabaci. While densities of Portiera and Hamiltonella (which are located in bacteriocytes) appeared to be well-regulated during host development, densities of Rickettsia (which are not located in bacteriocytes) were highly variable among individual hosts during host development. Host mating did not significantly affect symbiont densities. Infection by Tomato yellow leaf curl virus did not affect Portiera and Hamiltonella densities in either sex, but increased Rickettsia densities in females. High and low temperatures did not affect Portiera and Hamiltonella densities, but low temperature (15°C) significantly suppressed Rickettsia densities whereas high temperature (35°C) had little effect on Rickettsia densities. The results are consistent with the view that the population dynamics of bacterial symbionts in B. tabaci are regulated by symbiont location within the host and that the regulation reflects adaptation between the bacteria and insect. PMID:24632746

  4. Recovery from bleaching is mediated by threshold densities of background thermo-tolerant symbiont types in a reef-building coral.

    Science.gov (United States)

    Bay, Line K; Doyle, Jason; Logan, Murray; Berkelmans, Ray

    2016-06-01

    Sensitive molecular analyses show that most corals host a complement of Symbiodinium genotypes that includes thermo-tolerant types in low abundance. While tolerant symbiont types are hypothesized to facilitate tolerance to temperature and recovery from bleaching, empirical data on their distribution and relative abundance in corals under ambient and stress conditions are still rare. We quantified visual bleaching and mortality of coral hosts, along with relative abundance of C- and D-type Symbiodinium cells in 82 Acropora millepora colonies from three locations on the Great Barrier Reef transplanted to a central inshore site over a 13 month period. Our analyses reveal dynamic change in symbiont associations within colonies and among populations over time. Coral bleaching and declines in C- but not D-type symbionts were observed in transplanted corals. Survival and recovery of 25% of corals from one population was associated with either initial D-dominance or an increase in D-type symbionts that could be predicted by a minimum pre-stress D : C ratio of 0.003. One-third of corals from this population became D dominated at the bleached stage despite no initial detection of this symbiont type, but failed to recover and died in mid to late summer. These results provide a predictive threshold minimum density of background D-type symbionts in A. millepora, above which survival following extreme thermal stress is increased.

  5. Worldwide populations of the aphid Aphis craccivora are infected with diverse facultative bacterial symbionts.

    Science.gov (United States)

    Brady, Cristina M; Asplen, Mark K; Desneux, Nicolas; Heimpel, George E; Hopper, Keith R; Linnen, Catherine R; Oliver, Kerry M; Wulff, Jason A; White, Jennifer A

    2014-01-01

    Facultative bacterial endosymbionts can play an important role in the evolutionary trajectory of their hosts. Aphids (Hemiptera: Aphididae) are infected with a wide variety of facultative endosymbionts that can confer ecologically relevant traits, which in turn may drive microevolutionary processes in a dynamic selective environment. However, relatively little is known about how symbiont diversity is structured in most aphid species. Here, we investigate facultative symbiont species richness and prevalence among world-wide populations of the cowpea aphid, Aphis craccivora Koch. We surveyed 44 populations of A. craccivora, and detected 11 strains of facultative symbiotic bacteria, representing six genera. There were two significant associations between facultative symbiont and aphid food plant: the symbiont Arsenophonus was found at high prevalence in A. craccivora populations collected from Robinia sp. (locust), whereas the symbiont Hamiltonella was almost exclusively found in A. craccivora populations from Medicago sativa (alfalfa). Aphids collected from these two food plants also had divergent mitochondrial haplotypes, potentially indicating the formation of specialized aphid lineages associated with food plant (host-associated differentiation). The role of facultative symbionts in this process remains to be determined. Overall, observed facultative symbiont prevalence in A. craccivora was lower than that of some other well-studied aphids (e.g., Aphis fabae and Acyrthosiphon pisum), possibly as a consequence of A. craccivora's almost purely parthenogenetic life history. Finally, most (70 %) of the surveyed populations were polymorphic for facultative symbiont infection, indicating that even when symbiont prevalence is relatively low, symbiont-associated phenotypic variation may allow population-level evolutionary responses to local selection.

  6. Cellular tropism, population dynamics, host range and taxonomic status of an aphid secondary symbiont, SMLS (Sitobion miscanthi L type symbiont.

    Directory of Open Access Journals (Sweden)

    Tong Li

    Full Text Available SMLS (Sitobion miscanthi L type symbiont is a newly reported aphid secondary symbiont. Phylogenetic evidence from molecular markers indicates that SMLS belongs to the Rickettsiaceae and has a sibling relationship with Orientia tsutsugamushi. A comparative analysis of coxA nucleotide sequences further supports recognition of SMLS as a new genus in the Rickettsiaceae. In situ hybridization reveals that SMLS is housed in both sheath cells and secondary bacteriocytes and it is also detected in aphid hemolymph. The population dynamics of SMLS differ from those of Buchnera aphidicola and titer levels of SMLS increase in older aphids. A survey of 13 other aphids reveals that SMLS only occurs in wheat-associated species.

  7. Cellular Tropism, Population Dynamics, Host Range and Taxonomic Status of an Aphid Secondary Symbiont, SMLS (Sitobion miscanthi L Type Symbiont)

    Science.gov (United States)

    Li, Tong; Xiao, Jin-Hua; Xu, Zhao-Huan; Murphy, Robert W.; Huang, Da-Wei

    2011-01-01

    SMLS (Sitobion miscanthi L type symbiont) is a newly reported aphid secondary symbiont. Phylogenetic evidence from molecular markers indicates that SMLS belongs to the Rickettsiaceae and has a sibling relationship with Orientia tsutsugamushi. A comparative analysis of coxA nucleotide sequences further supports recognition of SMLS as a new genus in the Rickettsiaceae. In situ hybridization reveals that SMLS is housed in both sheath cells and secondary bacteriocytes and it is also detected in aphid hemolymph. The population dynamics of SMLS differ from those of Buchnera aphidicola and titer levels of SMLS increase in older aphids. A survey of 13 other aphids reveals that SMLS only occurs in wheat-associated species. PMID:21789197

  8. Population Density Modeling Tool

    Science.gov (United States)

    2012-06-26

    194 POPULATION DENSITY MODELING TOOL by Davy Andrew Michael Knott David Burke 26 June 2012 Distribution...MARYLAND NAWCADPAX/TR-2012/194 26 June 2012 POPULATION DENSITY MODELING TOOL by Davy Andrew Michael Knott David Burke...information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE 26

  9. Farming termites determine the genetic population structure of Termitomyces fungal symbionts

    DEFF Research Database (Denmark)

    Nobre, Tânia; Fernandes, Cecília; Boomsma, Jacobus J

    2011-01-01

    population structure of Termitomyces fungus gardens across 74 colonies of Macrotermes bellicosus in four west and central African countries. We confirm earlier, more limited, studies showing that the Termitomyces symbionts of M. bellicosus are normally transmitted vertically and clonally by dispersing males....... We also document that the symbionts associated with this termite species belong to three main lineages that do not constitute a monophyletic group. The most common lineage occurs over the entire geographical region that we studied, including west, central and southern Africa, where it is also...... associated with the alternative termite hosts Macrotermes subhyalinus and Macrotermes natalensis. While Termitomyces associated with these alternative hosts are horizontally transmitted and recombine freely, the genetic population structure of the same Termitomyces associated with M. bellicosus is consistent...

  10. Nocturnal production of endospores in natural populations of epulopiscium-like surgeonfish symbionts.

    Science.gov (United States)

    Flint, Joseph F; Drzymalski, Dan; Montgomery, W Linn; Southam, Gordon; Angert, Esther R

    2005-11-01

    Prior studies have described a morphologically diverse group of intestinal microorganisms associated with surgeonfish. Despite their diversity of form, 16S rRNA gene surveys and fluorescent in situ hybridizations indicate that these bacteria are low-G+C gram-positive bacteria related to Epulopiscium spp. Many of these bacteria exhibit an unusual mode of reproduction, developing multiple offspring intracellularly. Previous reports have suggested that some Epulopiscium-like symbionts produce dormant or phase-bright intracellular offspring. Close relatives of Epulopiscium, such as Metabacterium polyspora and Clostridium lentocellum, are endospore-forming bacteria, which raises the possibility that the phase-bright offspring are endospores. Structural evidence and the presence of dipicolinic acid demonstrate that phase-bright offspring of Epulopiscium-like bacteria are true endospores. In addition, endospores are formed as part of the normal daily life cycle of these bacteria. In the populations studied, mature endospores were seen only at night and the majority of cells in a given population produced one or two endospores per mother cell. Phylogenetic analyses confirmed the close relationship between the endospore-forming surgeonfish symbionts characterized here and previously described Epulopiscium spp. The broad distribution of endospore formation among the Epulopiscium phylogenetic group raises the possibility that sporulation is a characteristic of the group. We speculate that spore formation in Epulopiscium-like symbionts may be important for dispersal and may also enhance survival in the changing conditions of the fish intestinal tract.

  11. Using color as a proxy for symbiont density to assess health in the facultatively symbiotic northern coral, Astrangia poculata

    Science.gov (United States)

    Seballos, R.; Burmester, E. M.; Rotjan, R. D.

    2016-02-01

    Unlike most tropical corals, the northern star coral, Astrangia poculata, can survive and thrive with and without its photosynthetic endosymbionts, Symbiodinium psygmophilum. The degree of symbiosis is dependent on symbiont cell density, but the measurement of cell density is de facto destructive. We therefore explored the use of color (RGB) as a non-destructive proxy for symbiont state, building on the methods of Dimond and Carrington (2008). RGB color values, derived from a custom image analysis tool built in Matlab, were used to determine the inferred chlorophyll density of corals throughout an 8 week period. We found that non-destructive color analysis was a good metric to describe symbiotic state. To explore this method in an experimental context, we manipulated the impact of host condition (fed vs. starved) on the likelihood of wound healing in both symbiotic and aposymbiotic states. No difference was observed between either wounding or nutrition treatments, indicating that symbiotic state is likely controlled by other factors. In tropical corals, assessing the breakdown of symbiosis is an important predictor of holobiont stress, and colorimetric methods have been used to assess the extent of bleaching. Our method instead explores the spectral quality and extent of pigmentation to infer chlorophyll densities and symbiont cell densities, thereby extending the use of nondestructive methods to explore the strength of symbiosis.

  12. Effects of long-term starvation on a host bivalve (Codakia orbicularis, Lucinidae) and its symbiont population.

    Science.gov (United States)

    Caro, Audrey; Got, Patrice; Bouvy, Marc; Troussellier, Marc; Gros, Olivier

    2009-05-01

    The bivalve Codakia orbicularis, hosting sulfur-oxidizing gill endosymbionts, was starved (in artificial seawater filtered through a 0.22-mum-pore-size membrane) for a long-term experiment (4 months). The effects of starvation were observed using transmission electron microscopy, fluorescence in situ hybridization and catalyzed reporter deposition (CARD-FISH), and flow cytometry to monitor the anatomical and physiological modifications in the gill organization of the host and in the symbiotic population housed in bacteriocytes. The abundance of the symbiotic population decreased through starvation, with a loss of one-third of the bacterial population each month, as shown by CARD-FISH. At the same time, flow cytometry revealed significant changes in the physiology of symbiotic cells, with a decrease in cell size and modifications to the nucleic acid content, while most of the symbionts maintained a high respiratory activity (measured using the 5-cyano-2,3-ditolyl tetrazolium chloride method). Progressively, the number of symbiont subpopulations was reduced, and the subsequent multigenomic state, characteristic of this symbiont in freshly collected clams, turned into one and five equivalent genome copies for the two remaining subpopulations after 3 months. Concomitant structural modifications appeared in the gill organization. Lysosymes became visible in the bacteriocytes, while large symbionts disappeared, and bacteriocytes were gradually replaced by granule cells throughout the entire lateral zone. Those data suggested that host survival under these starvation conditions was linked to symbiont digestion as the main nutritional source.

  13. Nocturnal Production of Endospores in Natural Populations of Epulopiscium-Like Surgeonfish Symbionts

    OpenAIRE

    Flint, Joseph F.; Drzymalski, Dan; Montgomery, W. Linn; Southam, Gordon; Angert, Esther R.

    2005-01-01

    Prior studies have described a morphologically diverse group of intestinal microorganisms associated with surgeonfish. Despite their diversity of form, 16S rRNA gene surveys and fluorescent in situ hybridizations indicate that these bacteria are low-G+C gram-positive bacteria related to Epulopiscium spp. Many of these bacteria exhibit an unusual mode of reproduction, developing multiple offspring intracellularly. Previous reports have suggested that some Epulopiscium-like symbionts produce do...

  14. Global Population Density Grid Time Series Estimates

    Data.gov (United States)

    National Aeronautics and Space Administration — Global Population Density Grid Time Series Estimates provide a back-cast time series of population density grids based on the year 2000 population grid from SEDAC's...

  15. Mechanisms Affecting Population Density in Fragmented Habitat

    Directory of Open Access Journals (Sweden)

    Lutz Tischendorf

    2005-06-01

    Full Text Available We conducted a factorial simulation experiment to analyze the relative importance of movement pattern, boundary-crossing probability, and mortality in habitat and matrix on population density, and its dependency on habitat fragmentation, as well as inter-patch distance. We also examined how the initial response of a species to a fragmentation event may affect our observations of population density in post-fragmentation experiments. We found that the boundary-crossing probability from habitat to matrix, which partly determines the emigration rate, is the most important determinant for population density within habitat patches. The probability of crossing a boundary from matrix to habitat had a weaker, but positive, effect on population density. Movement behavior in habitat had a stronger effect on population density than movement behavior in matrix. Habitat fragmentation and inter-patch distance may have a positive or negative effect on population density. The direction of both effects depends on two factors. First, when the boundary-crossing probability from habitat to matrix is high, population density may decline with increasing habitat fragmentation. Conversely, for species with a high matrix-to-habitat boundary-crossing probability, population density may increase with increasing habitat fragmentation. Second, the initial distribution of individuals across the landscape: we found that habitat fragmentation and inter-patch distance were positively correlated with population density when individuals were distributed across matrix and habitat at the beginning of our simulation experiments. The direction of these relationships changed to negative when individuals were initially distributed across habitat only. Our findings imply that the speed of the initial response of organisms to habitat fragmentation events may determine the direction of observed relationships between habitat fragmentation and population density. The time scale of post

  16. [Population density of Eucalyptus urophylla plantation].

    Science.gov (United States)

    Huang, B; Lu, C

    2000-02-01

    This paper dealt with the relationships and correlation models of the population density of 5.6 years old Eucalyptus urophylla plantation with its crown width, diamter at breast height(DBH), tree height, individual standing volume, stand volume, wood properties and survital rate. The results showed that the population density remarkably affected DBH, individual standing volume, crown width, live branch height, stand volume and wood fiber width; but not affect tree height, basic density of wood, and length of wood fibers. It had a positive relationship with stand volume, live branch height and wood fibers width, and a negative relationship with DBH, individual standing volume and crown width. In addition, E. urophylla had a wide range of reasonable density. For short-rotation puplwoods, the optimum planting density of E. urophylla is 2000 individuals per hectare.

  17. Excess seawater nutrients, enlarged algal symbiont densities and bleaching sensitive reef locations: 2. A regional-scale predictive model for the Great Barrier Reef, Australia.

    Science.gov (United States)

    Wooldridge, Scott A; Heron, Scott F; Brodie, Jon E; Done, Terence J; Masiri, Itsara; Hinrichs, Saskia

    2017-01-15

    A spatial risk assessment model is developed for the Great Barrier Reef (GBR, Australia) that helps identify reef locations at higher or lower risk of coral bleaching in summer heat-wave conditions. The model confirms the considerable benefit of discriminating nutrient-enriched areas that contain corals with enlarged (suboptimal) symbiont densities for the purpose of identifying bleaching-sensitive reef locations. The benefit of the new system-level understanding is showcased in terms of: (i) improving early-warning forecasts of summer bleaching risk, (ii) explaining historical bleaching patterns, (iii) testing the bleaching-resistant quality of the current marine protected area (MPA) network (iv) identifying routinely monitored coral health attributes, such as the tissue energy reserves and skeletal growth characteristics (viz. density and extension rates) that correlate with bleaching resistant reef locations, and (v) targeting region-specific water quality improvement strategies that may increase reef-scale coral health and bleaching resistance. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

  18. Density Estimation in Several Populations With Uncertain Population Membership

    KAUST Repository

    Ma, Yanyuan

    2011-09-01

    We devise methods to estimate probability density functions of several populations using observations with uncertain population membership, meaning from which population an observation comes is unknown. The probability of an observation being sampled from any given population can be calculated. We develop general estimation procedures and bandwidth selection methods for our setting. We establish large-sample properties and study finite-sample performance using simulation studies. We illustrate our methods with data from a nutrition study.

  19. Fine-Scale Biogeographical Boundary Delineation and Sub-population Resolution in the Symbiodinium thermophilum Coral Symbiont Group From the Persian/Arabian Gulf and Gulf of Oman

    KAUST Repository

    Hume, Benjamin C. C.

    2018-04-24

    The adaptation of tropical coral communities to the world\\'s hottest sea, the Persian/Arabian Gulf (PAG), has recently been associated with ecological selection acting on a group of coral-associated algal symbionts, the Symbiodinium thermophilum group. Previous studies have shown that considerable genetic diversity exists within the group and that group members found within the PAG are significantly differentiated from those found externally, in the Gulf of Oman and wider waters. However, little is known about this genetic diversity. As an initial step towards understanding whether this diversity could represent niche adapted, selectable populations within the S. thermophilum group that may act as natural sources of stress tolerant associations to Indo-Pacific reefs, we investigate whether the diversity is structured between populations and where the location of the internal-external genetic partition lies. We use regions of the nuclear ribosomal DNA (ITS1-5.8S-ITS2) and chloroplastic psbA gene (non-coding region) from >100 S. thermophilum group-harbouring Porites spp. (P. lobata, P. lutea, and P. harrisoni) sampled across steep temperature and salinity gradients to conduct analyses of variance and create maximum parsimony networks to assess genetic structure and (dis)similarity within and between populations of S. thermophilum found within the PAG and externally in the Gulf of Oman. Our analyses resolve a sharp genetic boundary between Symbiodinium populations in the western Strait of Hormuz and identify significant genetic structure between populations with as little as 20 km between them demonstrating that differentiation between populations is likely due to factors other than limited connectivity. Further, we hypothesize that genotypes identified outside of the PAG in the Gulf of Oman existing in near-oceanic salinities, yet thermally challenging waters, putatively represent candidates for stress-tolerant symbionts that could act as natural seed populations of

  20. Sampling low-density gypsy moth populations

    Science.gov (United States)

    William E. Wallner; Clive G. Jones; Joseph S. Elkinton; Bruce L. Parker

    1991-01-01

    The techniques and methodology for sampling gypsy moth, Lymantria dispar L., at low densities, less than 100 egg masses/ha (EM/ha), are compared. Forest managers have constraints of time and cost, and need a useful, simple predictable means to assist them in sampling gypsy moth populations. A comparison of various techniques coupled with results of...

  1. Aphid Heritable Symbiont Exploits Defensive Mutualism.

    Science.gov (United States)

    Doremus, Matthew R; Oliver, Kerry M

    2017-04-15

    Insects and other animals commonly form symbioses with heritable bacteria, which can exert large influences on host biology and ecology. The pea aphid, Acyrthosiphon pisum , is a model for studying effects of infection with heritable facultative symbionts (HFS), and each of its seven common HFS species has been reported to provide resistance to biotic or abiotic stresses. However, one common HFS, called X-type, rarely occurs as a single infection in field populations and instead typically superinfects individual aphids with Hamiltonella defensa , another HFS that protects aphids against attack by parasitic wasps. Using experimental aphid lines comprised of all possible infection combinations in a uniform aphid genotype, we investigated whether the most common strain of X-type provides any of the established benefits associated with aphid HFS as a single infection or superinfection with H. defensa We found that X-type does not confer protection to any tested threats, including parasitoid wasps, fungal pathogens, or thermal stress. Instead, component fitness assays identified large costs associated with X-type infection, costs which were ameliorated in superinfected aphids. Together these findings suggest that X-type exploits the aphid/ H. defensa mutualism and is maintained primarily as a superinfection by "hitchhiking" via the mutualistic benefits provided by another HFS. Exploitative symbionts potentially restrict the functions and distributions of mutualistic symbioses with effects that extend to other community members. IMPORTANCE Maternally transmitted bacterial symbionts are widespread and can have major impacts on the biology of arthropods, including insects of medical and agricultural importance. Given that host fitness and symbiont fitness are tightly linked, inherited symbionts can spread within host populations by providing beneficial services. Many insects, however, are frequently infected with multiple heritable symbiont species, providing potential

  2. Evidence of two lineages of the symbiont 'Candidatus Erwinia dacicola' in Italian populations of Bactrocera oleae (Rossi) based on 16S rRNA gene sequences.

    Science.gov (United States)

    Savio, Claudia; Mazzon, Luca; Martinez-Sañudo, Isabel; Simonato, Mauro; Squartini, Andrea; Girolami, Vincenzo

    2012-01-01

    The close association between the olive fly Bactrocera oleae (Rossi) (Diptera: Tephritidae) and bacteria has been known for more than a century. Recently, the presence of a host-specific, hereditary, unculturable symbiotic bacterium, designated 'Candidatus Erwinia dacicola', has been described inside the cephalic organ of the fly, called the oesophageal bulb. In the present study, the 16S rRNA gene sequence variability of 'Ca. E. dacicola' was examined within and between 26 Italian olive fly populations sampled across areas where olive trees occur in the wild and areas where cultivated olive trees have been introduced through history. The bacterial contents of the oesophageal bulbs of 314 olive flies were analysed and a minimum of 781 bp of the 16S rRNA gene was sequenced. The corresponding host fly genotype was assessed by sequencing a 776 bp portion of the mitochondrial genome. Two 'Ca. E. dacicola' haplotypes were found (htA and htB), one being slightly more prevalent than the other (57%). The two haplotypes did not co-exist in the same individuals, as confirmed by cloning. Interestingly, the olive fly populations of the two main Italian islands, Sicily and Sardinia, appeared to be represented exclusively by the htB and htA haplotypes, respectively, while peninsular populations showed both bacterial haplotypes in different proportions. No significant correlation emerged between the two symbiont haplotypes and the 16 host fly haplotypes observed, suggesting evidence for a mixed model of vertical and horizontal transmission of the symbiont during the fly life cycle.

  3. Bird population density estimated from acoustic signals

    Science.gov (United States)

    Dawson, D.K.; Efford, M.G.

    2009-01-01

    Many animal species are detected primarily by sound. Although songs, calls and other sounds are often used for population assessment, as in bird point counts and hydrophone surveys of cetaceans, there are few rigorous methods for estimating population density from acoustic data. 2. The problem has several parts - distinguishing individuals, adjusting for individuals that are missed, and adjusting for the area sampled. Spatially explicit capture-recapture (SECR) is a statistical methodology that addresses jointly the second and third parts of the problem. We have extended SECR to use uncalibrated information from acoustic signals on the distance to each source. 3. We applied this extension of SECR to data from an acoustic survey of ovenbird Seiurus aurocapilla density in an eastern US deciduous forest with multiple four-microphone arrays. We modelled average power from spectrograms of ovenbird songs measured within a window of 0??7 s duration and frequencies between 4200 and 5200 Hz. 4. The resulting estimates of the density of singing males (0??19 ha -1 SE 0??03 ha-1) were consistent with estimates of the adult male population density from mist-netting (0??36 ha-1 SE 0??12 ha-1). The fitted model predicts sound attenuation of 0??11 dB m-1 (SE 0??01 dB m-1) in excess of losses from spherical spreading. 5.Synthesis and applications. Our method for estimating animal population density from acoustic signals fills a gap in the census methods available for visually cryptic but vocal taxa, including many species of bird and cetacean. The necessary equipment is simple and readily available; as few as two microphones may provide adequate estimates, given spatial replication. The method requires that individuals detected at the same place are acoustically distinguishable and all individuals vocalize during the recording interval, or that the per capita rate of vocalization is known. We believe these requirements can be met, with suitable field methods, for a significant

  4. Exploring symbiont management in lichens.

    Science.gov (United States)

    Grube, Martin; Spribille, Toby

    2012-07-01

    Lichens are unique among fungal symbioses in that their mycelial structures are compact and exposed to the light as thallus structures. The myriad intersections of unique fungal species with photosynthetic partner organisms (green algae in 90% of lichens) produce a wide variety of diverse shapes and colours of the fully synthesized lichen thallus when growing in nature. This characteristic complex morphology is, however, not achieved in the fungal axenic state. Even under ideal environmental conditions, the lichen life cycle faces considerable odds: first, meiotic spores are only produced on well-established thalli and often only after achieving considerable age in a stable environment, and second, even then in vivo resynthesis requires the presence of compatible algal strains where fungal spores germinate. Many lichen species have evolved a way around the resynthesis bottleneck by producing asexual propagules for joint propagation of symbionts. These different dispersal strategies ostensibly shape the population genetic structure of lichen symbioses, but the relative contributions of vertical (joint) and horizontal (independent) symbiont transmission have long eluded lichen evolutionary biologists. In this issue of Molecular Ecology, Dal Grande et al. (2012) close in on this question with the lung lichen, Lobaria pulmonaria, a flagship species in the conservation of old growth forests. By capitalizing on available microsatellite markers for both fungal and algal symbionts, they show that while vertical transmission is the predominant mode of reproduction, horizontal transmission is demonstrable and actively shapes population genetic structure. The resulting mixed propagation system is a highly successful balance of safe recruitment of symbiotic clones and endless possibilities for fungal recombination and symbiont shuffling.

  5. Monitoring microbial population dynamics at low densities

    Science.gov (United States)

    Julou, Thomas; Desprat, Nicolas; Bensimon, David; Croquette, Vincent

    2012-07-01

    We propose a new and simple method for the measurement of microbial concentrations in highly diluted cultures. This method is based on an analysis of the intensity fluctuations of light scattered by microbial cells under laser illumination. Two possible measurement strategies are identified and compared using simulations and measurements of the concentration of gold nanoparticles. Based on this comparison, we show that the concentration of Escherichia coli and Saccharomyces cerevisiae cultures can be easily measured in situ across a concentration range that spans five orders of magnitude. The lowest measurable concentration is three orders of magnitude (1000×) smaller than in current optical density measurements. We show further that this method can also be used to measure the concentration of fluorescent microbial cells. In practice, this new method is well suited to monitor the dynamics of population growth at early colonization of a liquid culture medium. The dynamic data thus obtained are particularly relevant for microbial ecology studies.

  6. Interactions among symbionts operate across scales to influence parasite epidemics.

    Science.gov (United States)

    Halliday, Fletcher W; Umbanhowar, James; Mitchell, Charles E

    2017-10-01

    Parasite epidemics may be influenced by interactions among symbionts, which can depend on past events at multiple spatial scales. Within host individuals, interactions can depend on the sequence in which symbionts infect a host, generating priority effects. Across host individuals, interactions can depend on parasite phenology. To test the roles of parasite interactions and phenology in epidemics, we embedded multiple cohorts of sentinel plants, grown from seeds with and without a vertically transmitted symbiont, into a wild host population, and tracked foliar infections caused by three common fungal parasites. Within hosts, parasite growth was influenced by coinfections, but coinfections were often prevented by priority effects among symbionts. Across hosts, parasite phenology altered host susceptibility to secondary infections, symbiont interactions and ultimately the magnitude of parasite epidemics. Together, these results indicate that parasite phenology can influence parasite epidemics by altering the sequence of infection and interactions among symbionts within host individuals. © 2017 John Wiley & Sons Ltd/CNRS.

  7. Gridded Population of the World, Version 4 (GPWv4): Population Density

    Data.gov (United States)

    National Aeronautics and Space Administration — Gridded Population of the World, Version 4 (GPWv4) Population Density consists of estimates of human population density based on counts consistent with national...

  8. Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 10

    Data.gov (United States)

    National Aeronautics and Space Administration — Gridded Population of the World, Version 4 (GPWv4) Population Density, Revision 10 consists of estimates of human population density (number of persons per square...

  9. More than one rabbit out of the hat: Radiation, transgenic and symbiont-based approaches for sustainable management of mosquito and tsetse fly populations

    International Nuclear Information System (INIS)

    Bourtzis, K.; Lees, R.S.; Hendrichs, J.; Vreysen, M.J.B.

    2016-01-01

    Mosquitoes (Diptera: Culicidae) and tsetse flies (Diptera: Glossinidae) are bloodsucking vectors of human and animal pathogens. Mosquito-borne diseases (malaria, filariasis, dengue, chikungunya and Zika) cause severe mortality and morbidity annually, and tsetse fly-borne diseases (African trypanosomes causing sleeping sickness in humans and nagana in livestock) cost Sub-Saharan Africa an estimated US$ 4750 million annually. Current reliance on insecticides for vector control is unsustainable: due to increasing insecticide resistance and growing concerns about health and environmental impacts of chemical control there is a growing need for novel, effective and safe biologically- based methods that are more sustainable. The integration of the sterile insect technique has proven successful to manage crop pests and disease vectors, particularly tsetse flies, and is likely to prove effective against mosquito vectors, particularly once sexseparation methods are improved. Transgenic and symbiont-based approaches are in development, and more advanced in (particularly Aedes) mosquitoes than in tsetse flies; however, issues around stability, sustainability and biosecurity have to be addressed, especially when considering population replacement approaches. Regulatory issues and those relating to intellectual property and economic cost of application must also be overcome. Standardised methods to assess insect quality are required to compare and predict efficacy of the different approaches. Different combinations of these three approaches could be integrated to maximise their benefits, and all have the potential to be used in tsetse and mosquito area-wide integrated pest management programmes. (author)

  10. A mechanistic analysis of density dependence in algal population dynamics

    Directory of Open Access Journals (Sweden)

    Adrian eBorlestean

    2015-04-01

    Full Text Available Population density regulation is a fundamental principle in ecology, but the specific process underlying functional expression of density dependence remains to be fully elucidated. One view contends that patterns of density dependence are largely fixed across a species irrespective of environmental conditions, whereas another is that the strength and expression of density dependence are fundamentally variable depending on the nature of exogenous or endogenous constraints acting on the population. We conducted a study investigating the expression of density dependence in Chlamydomonas spp. grown under a gradient from low to high nutrient density. We predicted that the relationship between per capita growth rate (pgr and population density would vary from concave up to concave down as nutrient density became less limiting and populations experienced weaker density regulation. Contrary to prediction, we found that the relationship between pgr and density became increasingly concave-up as nutrient levels increased. We also found that variation in pgr increased, and pgr levels reached higher maxima in nutrient-limited environments. Most likely, these results are attributable to population growth suppression in environments with high intraspecific competition due to limited nutrient resources. Our results suggest that density regulation is strongly variable depending on exogenous and endogenous processes acting on the population, implying that expression of density dependence depends extensively on local conditions. Additional experimental work should reveal the mechanisms influencing how the expression of density dependence varies across populations through space and time.

  11. More than one rabbit out of the hat: Radiation, transgenic and symbiont-based approaches for sustainable management of mosquito and tsetse fly populations.

    Science.gov (United States)

    Bourtzis, Kostas; Lees, Rosemary Susan; Hendrichs, Jorge; Vreysen, Marc J B

    2016-05-01

    Mosquitoes (Diptera: Culicidae) and tsetse flies (Diptera: Glossinidae) are bloodsucking vectors of human and animal pathogens. Mosquito-borne diseases (malaria, filariasis, dengue, zika, and chikungunya) cause severe mortality and morbidity annually, and tsetse fly-borne diseases (African trypanosomes causing sleeping sickness in humans and nagana in livestock) cost Sub-Saharan Africa an estimated US$ 4750 million annually. Current reliance on insecticides for vector control is unsustainable: due to increasing insecticide resistance and growing concerns about health and environmental impacts of chemical control there is a growing need for novel, effective and safe biologically-based methods that are more sustainable. The integration of the sterile insect technique has proven successful to manage crop pests and disease vectors, particularly tsetse flies, and is likely to prove effective against mosquito vectors, particularly once sex-separation methods are improved. Transgenic and symbiont-based approaches are in development, and more advanced in (particularly Aedes) mosquitoes than in tsetse flies; however, issues around stability, sustainability and biosecurity have to be addressed, especially when considering population replacement approaches. Regulatory issues and those relating to intellectual property and economic cost of application must also be overcome. Standardised methods to assess insect quality are required to compare and predict efficacy of the different approaches. Different combinations of these three approaches could be integrated to maximise their benefits, and all have the potential to be used in tsetse and mosquito area-wide integrated pest management programmes. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  12. Inter cropping and population density effects on yield component ...

    African Journals Online (AJOL)

    These results demonstrate that population density and intercropping may be a viable alternative of manipulating the productivity of these crops through their changes in physiological processes. The Journal of Food Technology in Africa Volume 6 No.3, 2001, pp. 96-103. KEY WORDS: Population density, intercropping ...

  13. Density-dependent feedbacks can mask environmental drivers of populations

    DEFF Research Database (Denmark)

    Dahlgren, Johan Petter

    I present some results from studies identifying environmental drivers of vital rates and population dynamics when controlling for intraspecific density statistically or experimentally, show that density dependence can be strong even in populations of slow-growing species in stressful habitats, an...

  14. Estimating density dependence from time series of population age structure.

    Science.gov (United States)

    Lande, Russell; Engen, Steinar; Saether, Bernt-Erik; Coulson, Tim

    2006-07-01

    Population fluctuations are caused by demographic and environmental stochasticity, time lags due to life history, and density dependence. We model a general life history allowing density dependence within and among age or stage classes in a population undergoing small or moderate fluctuations around a stable equilibrium. We develop a method for estimating the overall strength of density dependence measured by the rate of return toward equilibrium, and we also consider a simplified population description and forecasting using the density-dependent reproductive value. This generality comes at the cost of requiring a time series of the population age or stage structure instead of a univariate time series of adult or total population size. The method is illustrated by analyzing the dynamics of a fully censused population of red deer (Cervus elaphus) based on annual fluctuations of age structure through 21 years.

  15. Patch Size and Population Density: the Effect of Immigration Behavior

    Directory of Open Access Journals (Sweden)

    Jeff Bowman

    2002-06-01

    Full Text Available Many habitat fragmentation experiments make the prediction that animal population density will be positively related to fragment, or patch, size. The mechanism that is supposed to result in this prediction is unclear, but several recent reviews have demonstrated that population density often is negatively related to patch size. Immigration behavior is likely to have an important effect on population density for species that do not show strong edge effects, for species that have low emigration rates, and during short-term habitat fragmentation experiments. We consider the effect that different kinds of immigration behaviors will have on population density and we demonstrate that only a minority of possible scenarios produce positive density vs. patch size relationships. More commonly, these relationships are expected to be negative. Our results demonstrate the importance of considering autecological mechanisms, such as immigration behavior, when developing the predictions that we test in habitat fragmentation or other experiments.

  16. Evidence for density dependent population regulation in southern ...

    African Journals Online (AJOL)

    The means by which populations are regulated form a central theme in conservation biology, and much debate has revolved around density dependence as a mechanism driving population ... A significant increase in adult female survival was evident which is likely to have given rise to recent changes in population growth.

  17. Radial propagation in population dynamics with density-dependent diffusion

    Science.gov (United States)

    Ngamsaad, Waipot

    2014-01-01

    Population dynamics that evolve in a radial symmetric geometry are investigated. The nonlinear reaction-diffusion model, which depends on population density, is employed as the governing equation for this system. The approximate analytical solution to this equation is found. It shows that the population density evolves from the initial state and propagates in a traveling-wave-like manner for a long-time scale. If the distance is insufficiently long, the curvature has an ineluctable influence on the density profile and front speed. In comparison, the analytical solution is in agreement with the numerical solution.

  18. Strict Host-Symbiont Cospeciation and Reductive Genome Evolution in Insect Gut Bacteria

    Science.gov (United States)

    Hosokawa, Takahiro; Kikuchi, Yoshitomo; Nikoh, Naruo; Shimada, Masakazu; Fukatsu, Takema

    2006-01-01

    Host-symbiont cospeciation and reductive genome evolution have been identified in obligate endocellular insect symbionts, but no such example has been identified from extracellular ones. Here we first report such a case in stinkbugs of the family Plataspidae, wherein a specific gut bacterium is vertically transmitted via “symbiont capsule.” In all of the plataspid species, females produced symbiont capsules upon oviposition and their gut exhibited specialized traits for capsule production. Phylogenetic analysis showed that the plataspid symbionts constituted a distinct group in the γ-Proteobacteria, whose sister group was the aphid obligate endocellular symbionts Buchnera. Removal of the symbionts resulted in retarded growth, mortality, and sterility of the insects. The host phylogeny perfectly agreed with the symbiont phylogeny, indicating strict host-symbiont cospeciation despite the extracellular association. The symbionts exhibited AT-biased nucleotide composition, accelerated molecular evolution, and reduced genome size, as has been observed in obligate endocellular insect symbionts. These findings suggest that not the endocellular conditions themselves but the population genetic attributes of the vertically transmitted symbionts are probably responsible for the peculiar genetic traits of these insect symbionts. We proposed the designation “Candidatus Ishikawaella capsulata” for the plataspid symbionts. The plataspid stinkbugs, wherein the host-symbiont associations can be easily manipulated, provide a novel system that enables experimental approaches to previously untouched aspects of the insect-microbe mutualism. Furthermore, comparative analyses of the sister groups, the endocellular Buchnera and the extracellular Ishikawaella, would lead to insights into how the different symbiotic lifestyles have affected their genomic evolution. PMID:17032065

  19. Population density and mortality among individuals in motor vehicle crashes.

    Science.gov (United States)

    Gedeborg, Rolf; Thiblin, Ingemar; Byberg, Liisa; Melhus, Håkan; Lindbäck, Johan; Michaelsson, Karl

    2010-10-01

    To assess whether higher mortality rates among individuals in motor vehicle crashes in areas with low population density depend on injury type and severity or are related to the performance of emergency medical services (EMS). Prehospital and hospital deaths were studied in a population-based cohort of 41,243 motor vehicle crashes that occurred in Sweden between 1998 and 2004. The final multivariable analysis was restricted to 6884 individuals in motor vehicle crashes, to minimise the effects of confounding factors. Crude mortality rates following motor vehicle crashes were inversely related to regional population density. In regions with low population density, the unadjusted rate ratio for prehospital death was 2.2 (95% CI 1.9 to 2.5) and for hospital death 1.5 (95% CI 1.1 to 1.9), compared with a high-density population. However, after controlling for regional differences in age, gender and the type/severity of injuries among 6884 individuals in motor vehicle crashes, low population density was no longer associated with increased mortality. At 25 years of age, predicted prehospital mortality was 9% lower (95% CI 5% to 12%) in regions with low population density compared with high population density. This difference decreased with increasing age, but was still 3% lower (95% CI 0.5% to 5%) at 65 years of age. The inverse relationship between population density and mortality among individuals in motor vehicle crashes is related to pre-crash factors that influence the type and severity of injuries and not to differences in EMS.

  20. Population densities of eastern black rhinoceros : unravelling the controls

    NARCIS (Netherlands)

    Ouma, B.O.

    2014-01-01

    Key words: black rhinoceros, browser, corticosterone, diet, density dependence, minerals, moisture, physiological stress, savanna, soil nutrients, woody cover.   Understanding the forces that cause variability in population sizes is a central theme in ecology. The limiting factor in

  1. The influence of population density and duration of breeding on ...

    African Journals Online (AJOL)

    The influence of population density and duration of breeding on broiler chickens productivity and profitability. S Mitrovic, V Dermanovi c, M Radivojevi c, Z Raji c, D Živkovi c, D Ostoji c, N Filipovi c ...

  2. Inter cropping and population density effects on yield component ...

    African Journals Online (AJOL)

    Population density and intercropping of sorghum {sorghum bicolour (L) and Soybean {Glycine max Merril (L)} may alter their growth and yield patterns through responses to light and physiological attributes as compared to their performance in standard densities and monocultures. There is limited field information on this ...

  3. Dietary niche variation and its relationship to lizard population density.

    Science.gov (United States)

    Novosolov, Maria; Rodda, Gordon H; Gainsbury, Alison M; Meiri, Shai

    2018-01-01

    Insular species are predicted to broaden their niches, in response to having fewer competitors. They can thus exploit a greater proportion of the resource spectrum. In turn, broader niches are hypothesized to facilitate (or be a consequence of) increased population densities. We tested whether insular lizards have broader dietary niches than mainland species, how it relates to competitor and predator richness, and the nature of the relationship between population density and dietary niche breadth. We collected population density and dietary niche breadth data for 36 insular and 59 mainland lizard species, and estimated competitor and predator richness at the localities where diet data were collected. We estimated dietary niche shift by comparing island species to their mainland relatives. We controlled for phylogenetic relatedness, body mass and the size of the plots over which densities were estimated. We found that island and mainland species had similar niche breadths. Dietary niche breadth was unrelated to competitor and predator richness, on both islands and the mainland. Population density was unrelated to dietary niche breadth across island and mainland populations. Our results indicate that dietary generalism is not an effective way of increasing population density nor is it result of lower competitive pressure. A lower variety of resources on islands may prevent insular animals from increasing their niche breadths even in the face of few competitors. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

  4. Nutritional Differences between Two Orangutan Habitats: Implications for Population Density.

    Science.gov (United States)

    Vogel, Erin R; Harrison, Mark E; Zulfa, Astri; Bransford, Timothy D; Alavi, Shauhin E; Husson, Simon; Morrogh-Bernard, Helen; Santiano; Firtsman, Twentinolosa; Utami-Atmoko, Sri Suci; van Noordwijk, Maria A; Farida, Wartika Rosa

    2015-01-01

    Bottom-up regulatory factors have been proposed to exert a strong influence on mammalian population density. Studies relating habitat quality to population density have typically made comparisons among distant species or communities without considering variation in food quality among localities. We compared dietary nutritional quality of two Bornean orangutan populations with differing population densities in peatland habitats, Tuanan and Sabangau, separated by 63 km. We hypothesized that because Tuanan is alluvial, the plant species included in the orangutan diet would be of higher nutritional quality compared to Sabangau, resulting in higher daily caloric intake in Tuanan. We also predicted that forest productivity would be greater in Tuanan compared to Sabangau. In support of these hypotheses, the overall quality of the diet and the quality of matched dietary items were higher in Tuanan, resulting in higher daily caloric intake compared to Sabangau. These differences in dietary nutritional quality may provide insights into why orangutan population density is almost two times greater in Tuanan compared to Sabangau, in agreement with a potentially important influence of diet quality on primate population density.

  5. Modelling interactions of toxicants and density dependence in wildlife populations

    Science.gov (United States)

    Schipper, Aafke M.; Hendriks, Harrie W.M.; Kauffman, Matthew J.; Hendriks, A. Jan; Huijbregts, Mark A.J.

    2013-01-01

    1. A major challenge in the conservation of threatened and endangered species is to predict population decline and design appropriate recovery measures. However, anthropogenic impacts on wildlife populations are notoriously difficult to predict due to potentially nonlinear responses and interactions with natural ecological processes like density dependence. 2. Here, we incorporated both density dependence and anthropogenic stressors in a stage-based matrix population model and parameterized it for a density-dependent population of peregrine falcons Falco peregrinus exposed to two anthropogenic toxicants [dichlorodiphenyldichloroethylene (DDE) and polybrominated diphenyl ethers (PBDEs)]. Log-logistic exposure–response relationships were used to translate toxicant concentrations in peregrine falcon eggs to effects on fecundity. Density dependence was modelled as the probability of a nonbreeding bird acquiring a breeding territory as a function of the current number of breeders. 3. The equilibrium size of the population, as represented by the number of breeders, responded nonlinearly to increasing toxicant concentrations, showing a gradual decrease followed by a relatively steep decline. Initially, toxicant-induced reductions in population size were mitigated by an alleviation of the density limitation, that is, an increasing probability of territory acquisition. Once population density was no longer limiting, the toxicant impacts were no longer buffered by an increasing proportion of nonbreeders shifting to the breeding stage, resulting in a strong decrease in the equilibrium number of breeders. 4. Median critical exposure concentrations, that is, median toxicant concentrations in eggs corresponding with an equilibrium population size of zero, were 33 and 46 μg g−1 fresh weight for DDE and PBDEs, respectively. 5. Synthesis and applications. Our modelling results showed that particular life stages of a density-limited population may be relatively insensitive to

  6. The association between ALS and population density: A population based study.

    Science.gov (United States)

    Scott, Kirsten M; Abhinav, Kumar; Wijesekera, Lokesh; Ganesalingam, Jeban; Goldstein, Laura H; Janssen, Anna; Dougherty, Andrew; Willey, Emma; Stanton, Biba R; Turner, Martin R; Ampong, Mary-Ann; Sakel, Mohammed; Orrell, Richard; Howard, Robin; Shaw, Christopher E; Nigel Leigh, P; Al-Chalabi, Ammar

    2010-10-01

    We aimed to assess whether rural residence is associated with amyotrophic lateral sclerosis in the south-east of England using a population based register. Previous studies in different populations have produced contradictory findings. Residence defined by London borough or non-metropolitan district at time of diagnosis was recorded for each incident case in the South-East England ALS Register between 1995 and 2005. Each of the 26 boroughs or districts of the catchment area of the register was classified according to population density. Age- and sex-adjusted incidence of ALS was calculated for each region and the relationship with population density tested by linear regression, thereby controlling for the underlying population structure. We found that population density in region of residence at diagnosis explained 25% of the variance in ALS rates (r = 0.5, p population density at diagnosis.

  7. Excess seawater nutrients, enlarged algal symbiont densities and bleaching sensitive reef locations: 1. Identifying thresholds of concern for the Great Barrier Reef, Australia.

    Science.gov (United States)

    Wooldridge, Scott A

    2016-05-23

    Here, I contribute new insight into why excess seawater nutrients are an increasingly identified feature at reef locations that have low resistance to thermal stress. Specifically, I link this unfavourable synergism to the development of enlarged (suboptimal) zooxanthellae densities that paradoxically limit the capacity of the host coral to build tissue energy reserves needed to combat periods of stress. I explain how both theoretical predictions and field observations support the existence of species-specific 'optimal' zooxanthellae densities ~1.0-3.0×10 6 cellscm- 2 . For the central Great Barrier Reef (GBR), excess seawater nutrients that permit enlarged zooxanthellae densities beyond this optimum range are linked with seawater chlorophyll a>0.45μg·L -1 ; a eutrophication threshold previously shown to correlate with a significant loss in species for hard corals and phototrophic octocorals on the central GBR, and herein shown to correlate with enhanced bleaching sensitivity during the 1998 and 2002 mass bleaching events. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Assessment of Population Density and Disparity of Village ...

    African Journals Online (AJOL)

    Study of Village weaverbirds Ploceus cucullatus along the roads was necessary in order to provide prospect of their population, density and platform for monitoring their distribution. Data were collected through on-site observations and pointcount method at thirty-four (34) point-count stations. Collected data were subjected ...

  9. Dispersal patterns of red foxes relative to population density

    Science.gov (United States)

    Allen, Stephen H.; Sargeant, Alan B.

    1993-01-01

    Factors affecting red fox (Vulpes vulpes) dispersal patterns are poorly understood but warranted investigation because of the role of dispersal in rebuilding depleted populations and transmission of diseases. We examined dispersal patterns of red foxes in North Dakota based on recoveries of 363 of 854 foxes tagged as pups and relative to fox density. Foxes were recovered up to 8.6 years after tagging; 79% were trapped or shot. Straight-line distances between tagging and recovery locations ranged from 0 to 302 km. Mean recovery distances increased with age and were greater for males than females, but longest individual recovery distances were by females. Dispersal distances were not related to population density for males (P = 0.36) or females (P = 0.96). The proportion of males recovered that dispersed was inversely related to population density (r = -0.94; n = 5; P = 0.02), but not the proportion of females (r = -0.49; n = 5; P = 0.40). Dispersal directions were not uniform for either males (P = 0.003) or females (P = 0.006); littermates tended to disperse in similar directions (P = 0.09). A 4-lane interstate highway altered dispersal directions (P = 0.001). Dispersal is a strong innate behavior of red foxes (especially males) that results in many individuals of both sexes traveling far from natal areas. Because dispersal distance was unaffected by fox density, populations can be rebuilt and diseases transmitted long distances regardless of fox abundance.

  10. Population density and refractive error among Chinese children.

    Science.gov (United States)

    Zhang, Mingzhi; Li, Liping; Chen, Lizhen; Lee, Jack; Wu, Jiasi; Yang, Amy; Chen, Connie; Xu, Daocheng; Lam, Dennis S C; Sharma, Abhishek; Griffiths, Sian; Gao, Yang; Congdon, Nathan

    2010-10-01

    China is urbanizing rapidly, and the prevalence of myopia is high. This study was conducted to identify the reasons for observed differences in the prevalence of myopia among urban versus rural Chinese children. All children with uncorrected acuity of 6/12 or worse and a 50% random sample of children with vision better than 6/12 at all secondary schools in mixed rural-urban Liangying Township, Guangdong, underwent cycloplegic refraction, and provided data on age, gender, parental education, weekly near work and time outdoors, and urban development level of respondents' neighborhoods (12-item questionnaire). Population density of 32 villages and urban zones in Liangying was calculated from census figures (mean population density, 217 persons/km(2); range, 94-957; mean for Guangdong, 486). Among 5844 eligible children, 4612 (78.9%) had parental consent and completed examinations; 2957 were refracted per protocol, and 2480 (83.9%) of these had questionnaire data. Those with completed examinations were more likely to be girls (P population density (P = 0.003), but not development index, parental education, or time outdoors were significantly associated with more myopic refractive error. Higher population density appears to be associated with myopia risk, independent of academic activity, time spent outdoors, familial educational level, or economic development, factors that have been thought to explain higher myopia prevalence among urban children. Mechanisms for this apparent association should be sought.

  11. Population densities of wheat thrips, Haplothrips tritici Kurdjumov ...

    African Journals Online (AJOL)

    Population densities of Haplothrips tritici (H. tritici) Kurdjumov (Thysanoptera: Phlaeothripidae) were studied in Kahramanmaras, Turkey. In 2002, bread wheat cultivars, Bocro 4, Pehlivan and Yüreğir 89, durum wheat cultivars, Balcali 85, Ceylan 95 and Harran 95 and barley cultivars, Esterel and Pacific, were used. In 2003 ...

  12. Effects of population density on agricultural land use and ...

    African Journals Online (AJOL)

    This study examined agricultural land use and productivity with particular reference to its effects on population density in the Nsukka Agricultural Zone of Enugu State, Nigeria. The study involved distribution of questionnaires to 96 respondents, with only 60 being valid. Majority of the respondents had farms of between one ...

  13. Effects of scale of movement, detection probability, and true population density on common methods of estimating population density.

    Science.gov (United States)

    Keiter, David A; Davis, Amy J; Rhodes, Olin E; Cunningham, Fred L; Kilgo, John C; Pepin, Kim M; Beasley, James C

    2017-08-25

    Knowledge of population density is necessary for effective management and conservation of wildlife, yet rarely are estimators compared in their robustness to effects of ecological and observational processes, which can greatly influence accuracy and precision of density estimates. In this study, we simulate biological and observational processes using empirical data to assess effects of animal scale of movement, true population density, and probability of detection on common density estimators. We also apply common data collection and analytical techniques in the field and evaluate their ability to estimate density of a globally widespread species. We find that animal scale of movement had the greatest impact on accuracy of estimators, although all estimators suffered reduced performance when detection probability was low, and we provide recommendations as to when each field and analytical technique is most appropriately employed. The large influence of scale of movement on estimator accuracy emphasizes the importance of effective post-hoc calculation of area sampled or use of methods that implicitly account for spatial variation. In particular, scale of movement impacted estimators substantially, such that area covered and spacing of detectors (e.g. cameras, traps, etc.) must reflect movement characteristics of the focal species to reduce bias in estimates of movement and thus density.

  14. Ambit determination method in estimating rice plant population density

    Directory of Open Access Journals (Sweden)

    Abu Bakar, B.,

    2017-11-01

    Full Text Available Rice plant population density is a key indicator in determining the crop setting and fertilizer application rate. It is therefore essential that the population density is monitored to ensure that a correct crop management decision is taken. The conventional method of determining plant population is by manually counting the total number of rice plant tillers in a 25 cm x 25 cm square frame. Sampling is done by randomly choosing several different locations within a plot to perform tiller counting. This sampling method is time consuming, labour intensive and costly. An alternative fast estimating method was developed to overcome this issue. The method relies on measuring the outer circumference or ambit of the contained rice plants in a 25 cm x 25 cm square frame to determine the number of tillers within that square frame. Data samples of rice variety MR219 were collected from rice plots in the Muda granary area, Sungai Limau Dalam, Kedah. The data were taken at 50 days and 70 days after seeding (DAS. A total of 100 data samples were collected for each sampling day. A good correlation was obtained for the variety of 50 DAS and 70 DAS. The model was then verified by taking 100 samples with the latching strap for 50 DAS and 70 DAS. As a result, this technique can be used as a fast, economical and practical alternative to manual tiller counting. The technique can potentially be used in the development of an electronic sensing system to estimate paddy plant population density.

  15. The relationship between population density and cancer mortality in Taiwan.

    Science.gov (United States)

    Yang, C Y; Hsieh, Y L

    1998-04-01

    Many investigators have examined urbanization gradients in cancer rates. The purpose of this report was to identify urban-rural trends in cancer mortality rates (1982-1991) for municipalities in Taiwan. For this purpose, Taiwan's municipalities were classified as rural, suburban, urban, or metropolitan, using population density as an ordinal indicator of the degree of urbanization. Average annual age-adjusted, site-specific cancer mortality rates were calculated for both sexes within each population density group. Significant increasing trends with more urbanization were observed in mortality rates for cancers of the lung, pancreas, and kidney among both males and females, as well as male prostate cancer, and female breast and ovary cancer. In addition, this study revealed a significant rural excess for nonmelanoma skin cancer among both males and females, as well as male non-Hodgkin's lymphoma, and cancers of the female bone, and female connective tissue. Analytic studies for sites with consistent urban-rural trends may be fruitful in identifying the aspect of population density, or other unmeasured factors, that contribute to these trends.

  16. Relationships between brightness of nighttime lights and population density

    Science.gov (United States)

    Naizhuo, Z.

    2012-12-01

    Brightness of nighttime lights has been proven to be a good proxy for socioeconomic and demographic statistics. Moreover, the satellite nighttime lights data have been used to spatially disaggregate amounts of gross domestic product (GDP), fossil fuel carbon dioxide emission, and electric power consumption (Ghosh et al., 2010; Oda and Maksyutov, 2011; Zhao et al., 2012). Spatial disaggregations were performed in these previous studies based on assumed linear relationships between digital number (DN) value of pixels in the nighttime light images and socioeconomic data. However, reliability of the linear relationships was never tested due to lack of relative high-spatial-resolution (equal to or finer than 1 km × 1 km) statistical data. With the similar assumption that brightness linearly correlates to population, Bharti et al. (2011) used nighttime light data as a proxy for population density and then developed a model about seasonal fluctuations of measles in West Africa. The Oak Ridge National Laboratory used sub-national census population data and high spatial resolution remotely-sensed-images to produce LandScan population raster datasets. The LandScan population datasets have 1 km × 1 km spatial resolution which is consistent with the spatial resolution of the nighttime light images. Therefore, in this study I selected 2008 LandScan population data as baseline reference data and the contiguous United State as study area. Relationships between DN value of pixels in the 2008 Defense Meteorological Satellite Program's Operational Linescan System (DMSP-OLS) stable light image and population density were established. Results showed that an exponential function can more accurately reflect the relationship between luminosity and population density than a linear function. Additionally, a certain number of saturated pixels with DN value of 63 exist in urban core areas. If directly using the exponential function to estimate the population density for the whole brightly

  17. Density regulation in Northeast Atlantic fish populations: Density dependence is stronger in recruitment than in somatic growth.

    Science.gov (United States)

    Zimmermann, Fabian; Ricard, Daniel; Heino, Mikko

    2018-01-30

    Population regulation is a central concept in ecology, yet in many cases its presence and the underlying mechanisms are difficult to demonstrate. The current paradigm maintains that marine fish populations are predominantly regulated by density-dependent recruitment. While it is known that density-dependent somatic growth can be present too, its general importance remains unknown and most practical applications neglect it. This study aimed to close this gap by for the first time quantifying and comparing density dependence in growth and recruitment over a large set of fish populations. We fitted density-dependent models to time-series data on population size, recruitment and age-specific weight from commercially exploited fish populations in the Northeast Atlantic Ocean and the Baltic Sea. Data were standardized to enable a direct comparison within and among populations, and estimated parameters were used to quantify the impact of density regulation on population biomass. Statistically significant density dependence in recruitment was detected in a large proportion of populations (70%), whereas for density dependence in somatic growth the prevalence of density dependence depended heavily on the method (26% and 69%). Despite age-dependent variability, the density dependence in recruitment was consistently stronger among age groups and between alternative approaches that use weight-at-age or weight increments to assess growth. Estimates of density-dependent reduction in biomass underlined these results: 97% of populations with statistically significant parameters for growth and recruitment showed a larger impact of density-dependent recruitment on population biomass. The results reaffirm the importance of density-dependent recruitment in marine fishes, yet they also show that density dependence in somatic growth is not uncommon. Furthermore, the results are important from an applied perspective because density dependence in somatic growth affects productivity and

  18. Population density controls on microbial pollution across the Ganga catchment.

    Science.gov (United States)

    Milledge, D G; Gurjar, S K; Bunce, J T; Tare, V; Sinha, R; Carbonneau, P E

    2018-01-01

    For millions of people worldwide, sewage-polluted surface waters threaten water security, food security and human health. Yet the extent of the problem and its causes are poorly understood. Given rapid widespread global urbanisation, the impact of urban versus rural populations is particularly important but unknown. Exploiting previously unpublished archival data for the Ganga (Ganges) catchment, we find a strong non-linear relationship between upstream population density and microbial pollution, and predict that these river systems would fail faecal coliform standards for irrigation waters available to 79% of the catchment's 500 million inhabitants. Overall, this work shows that microbial pollution is conditioned by the continental-scale network structure of rivers, compounded by the location of cities whose growing populations contribute c. 100 times more microbial pollutants per capita than their rural counterparts. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  19. Quality or quantity: is nutrient transfer driven more by symbiont identity and productivity than by symbiont abundance?

    Science.gov (United States)

    Freeman, Christopher J; Thacker, Robert W; Baker, David M; Fogel, Marilyn L

    2013-06-01

    By forming symbiotic interactions with microbes, many animals and plants gain access to the products of novel metabolic pathways. We investigated the transfer of symbiont-derived carbon and nitrogen to the sponges Aplysina cauliformis, Aplysina fulva, Chondrilla caribensis, Neopetrosia subtriangularis and Xestospongia bocatorensis, all of which host abundant microbial populations, and Niphates erecta, which hosts a sparse symbiont community. We incubated sponges in light and dark bottles containing seawater spiked with (13)C- and (15)N-enriched inorganic compounds and then measured (13)C and (15)N enrichment in the microbial (nutrient assimilation) and sponge (nutrient transfer) fractions. Surprisingly, although most sponges hosting abundant microbial communities were more enriched in (13)C than N. erecta, only N. subtriangularis was more enriched in (15)N than N. erecta. Although photosymbiont abundance varied substantially across species, (13)C and (15)N enrichment was not significantly correlated with photosymbiont abundance. Enrichment was significantly correlated with the ratio of gross productivity to respiration (P:R), which varied across host species and symbiont phylotype. Because irradiance impacts P:R ratios, we also incubated A. cauliformis in (13)C-enriched seawater under different irradiances to determine whether symbiont carbon fixation and transfer are dependent on irradiance. Carbon fixation and transfer to the sponge host occurred in all treatments, but was greatest at higher irradiances and was significantly correlated with P:R ratios. Taken together, these results demonstrate that nutrient transfer from microbial symbionts to host sponges is influenced more by host-symbiont identities and P:R ratios than by symbiont abundance.

  20. Density estimation in tiger populations: combining information for strong inference

    Science.gov (United States)

    Gopalaswamy, Arjun M.; Royle, J. Andrew; Delampady, Mohan; Nichols, James D.; Karanth, K. Ullas; Macdonald, David W.

    2012-01-01

    A productive way forward in studies of animal populations is to efficiently make use of all the information available, either as raw data or as published sources, on critical parameters of interest. In this study, we demonstrate two approaches to the use of multiple sources of information on a parameter of fundamental interest to ecologists: animal density. The first approach produces estimates simultaneously from two different sources of data. The second approach was developed for situations in which initial data collection and analysis are followed up by subsequent data collection and prior knowledge is updated with new data using a stepwise process. Both approaches are used to estimate density of a rare and elusive predator, the tiger, by combining photographic and fecal DNA spatial capture–recapture data. The model, which combined information, provided the most precise estimate of density (8.5 ± 1.95 tigers/100 km2 [posterior mean ± SD]) relative to a model that utilized only one data source (photographic, 12.02 ± 3.02 tigers/100 km2 and fecal DNA, 6.65 ± 2.37 tigers/100 km2). Our study demonstrates that, by accounting for multiple sources of available information, estimates of animal density can be significantly improved.

  1. Population density equations for stochastic processes with memory kernels

    Science.gov (United States)

    Lai, Yi Ming; de Kamps, Marc

    2017-06-01

    We present a method for solving population density equations (PDEs)-a mean-field technique describing homogeneous populations of uncoupled neurons—where the populations can be subject to non-Markov noise for arbitrary distributions of jump sizes. The method combines recent developments in two different disciplines that traditionally have had limited interaction: computational neuroscience and the theory of random networks. The method uses a geometric binning scheme, based on the method of characteristics, to capture the deterministic neurodynamics of the population, separating the deterministic and stochastic process cleanly. We can independently vary the choice of the deterministic model and the model for the stochastic process, leading to a highly modular numerical solution strategy. We demonstrate this by replacing the master equation implicit in many formulations of the PDE formalism by a generalization called the generalized Montroll-Weiss equation—a recent result from random network theory—describing a random walker subject to transitions realized by a non-Markovian process. We demonstrate the method for leaky- and quadratic-integrate and fire neurons subject to spike trains with Poisson and gamma-distributed interspike intervals. We are able to model jump responses for both models accurately to both excitatory and inhibitory input under the assumption that all inputs are generated by one renewal process.

  2. Population density equations for stochastic processes with memory kernels.

    Science.gov (United States)

    Lai, Yi Ming; de Kamps, Marc

    2017-06-01

    We present a method for solving population density equations (PDEs)--a mean-field technique describing homogeneous populations of uncoupled neurons-where the populations can be subject to non-Markov noise for arbitrary distributions of jump sizes. The method combines recent developments in two different disciplines that traditionally have had limited interaction: computational neuroscience and the theory of random networks. The method uses a geometric binning scheme, based on the method of characteristics, to capture the deterministic neurodynamics of the population, separating the deterministic and stochastic process cleanly. We can independently vary the choice of the deterministic model and the model for the stochastic process, leading to a highly modular numerical solution strategy. We demonstrate this by replacing the master equation implicit in many formulations of the PDE formalism by a generalization called the generalized Montroll-Weiss equation-a recent result from random network theory-describing a random walker subject to transitions realized by a non-Markovian process. We demonstrate the method for leaky- and quadratic-integrate and fire neurons subject to spike trains with Poisson and gamma-distributed interspike intervals. We are able to model jump responses for both models accurately to both excitatory and inhibitory input under the assumption that all inputs are generated by one renewal process.

  3. Heat Stress Affects Facultative Symbiont-Mediated Protection from a Parasitoid Wasp.

    Science.gov (United States)

    Heyworth, Eleanor R; Ferrari, Julia

    2016-01-01

    Many insects carry facultative bacterial symbionts, which provide benefits including resistance to natural enemies and abiotic stresses. Little is known about how these beneficial phenotypes are affected when biotic or abiotic threats occur simultaneously. The pea aphid (Acyrthosiphon pisum) can host several well-characterized symbiont species. The symbiont known as X-type can protect against both parasitoid wasps and heat stress. Here, we used three pea aphid genotypes that were naturally infected with X-type and the symbiont Spiroplasma sp. We compared aphids coinfected with these two symbionts with those cured from X-type and infected with only Spiroplasma to investigate the ability of X-type to confer benefits to the host when two threats are experienced simultaneously. Our aim is to explore how robust symbiont protection may be outside a benign laboratory environment. Aphids were subjected to heat shock either before or after attack by parasitoid wasps. Under a benign temperature regime, the aphids carrying X-type tended to be better protected from the parasitoid than those cured. When the aphids experienced a heat shock before being parasitized aphids carrying X-type were more susceptible than those cured. Regardless of infection with the symbiont, the aphids benefitted from being heat shocked after parasitization. The results demonstrate how resistance to parasitoid wasps can be strongly environment-dependent and that a beneficial phenotype conferred by a symbiont under controlled conditions in the laboratory does not necessarily equate to a consistently useful effect in natural populations.

  4. Evolution: Welcome to Symbiont Prison.

    Science.gov (United States)

    Kiers, E Toby; West, Stuart A

    2016-01-25

    Can egalitarian partnerships exist in nature? A new study demonstrates how protist hosts use and abuse their algal symbionts depending on their needs. While this relationship allows protists to survive in low nutrient conditions, it leaves little room for algal retaliation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Evolution: Welcome to Symbiont Prison

    NARCIS (Netherlands)

    Kiers, E.T.; West, S.A.

    2016-01-01

    Can egalitarian partnerships exist in nature? A new study demonstrates how protist hosts use and abuse their algal symbionts depending on their needs. While this relationship allows protists to survive in low nutrient conditions, it leaves little room for algal retaliation.

  6. Insect symbionts in food webs

    Czech Academy of Sciences Publication Activity Database

    McLean, A. H. C.; Parker, B. J.; Hrček, Jan; Henry, L. M.; Godfray, H. C. J.

    2016-01-01

    Roč. 371, č. 1702 (2016), article number 20150325 ISSN 0962-8436 Institutional support: RVO:60077344 Keywords : food web * symbiont * symbiosis Subject RIV: EE - Microbiology, Virology Impact factor: 5.846, year: 2016 http://rstb.royalsocietypublishing.org/content/371/1702/20150325

  7. Population density influences dispersal in female white-tailed deer

    Science.gov (United States)

    Lutz, Clayton L.; Diefenbach, Duane R.; Rosenberry, Christopher S.

    2015-01-01

    Dispersal behavior in white-tailed deer (Odocoileus virginianus) predominantly occurs in 1-year-old males; however, females of the same age also disperse. The timing of female dispersal during fawning season and low dispersal rates suggest that competition for mates and reduced inbreeding are not ultimate causes of female dispersal, as suggested for males. We proposed that female dispersal is the result of competition for space when pregnant females seek to isolate themselves before and after parturition. To test this hypothesis, we conducted a meta-analysis of female dispersal rates from 12 populations of white-tailed deer and predicted dispersal rate and distance were positively related to deer density. We found a positive relationship between dispersal rate and deer per forested km2 and between dispersal distance and deer per forested km2. These results are consistent with the hypothesis that female dispersal is density-dependent and caused by the exclusion of subordinate 1-year-olds as adult females seek isolation before and after parturition.

  8. 10 CFR 960.5-2-1 - Population density and distribution.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Population density and distribution. 960.5-2-1 Section 960... Population density and distribution. (a) Qualifying condition. The site shall be located such that, during... specified in § 960.5-1(a)(1). (b) Favorable conditions. (1) A low population density in the general region...

  9. Comparative metagenomics of Daphnia symbionts

    Directory of Open Access Journals (Sweden)

    Preston James F

    2009-04-01

    Full Text Available Abstract Background Shotgun sequences of DNA extracts from whole organisms allow a comprehensive assessment of possible symbionts. The current project makes use of four shotgun datasets from three species of the planktonic freshwater crustaceans Daphnia: one dataset from clones of D. pulex and D. pulicaria and two datasets from one clone of D. magna. We analyzed these datasets with three aims: First, we search for bacterial symbionts, which are present in all three species. Second, we search for evidence for Cyanobacteria and plastids, which had been suggested to occur as symbionts in a related Daphnia species. Third, we compare the metacommunities revealed by two different 454 pyrosequencing methods (GS 20 and GS FLX. Results In all datasets we found evidence for a large number of bacteria belonging to diverse taxa. The vast majority of these were Proteobacteria. Of those, most sequences were assigned to different genera of the Betaproteobacteria family Comamonadaceae. Other taxa represented in all datasets included the genera Flavobacterium, Rhodobacter, Chromobacterium, Methylibium, Bordetella, Burkholderia and Cupriavidus. A few taxa matched sequences only from the D. pulex and the D. pulicaria datasets: Aeromonas, Pseudomonas and Delftia. Taxa with many hits specific to a single dataset were rare. For most of the identified taxa earlier studies reported the finding of related taxa in aquatic environmental samples. We found no clear evidence for the presence of symbiotic Cyanobacteria or plastids. The apparent similarity of the symbiont communities of the three Daphnia species breaks down on a species and strain level. Communities have a similar composition at a higher taxonomic level, but the actual sequences found are divergent. The two Daphnia magna datasets obtained from two different pyrosequencing platforms revealed rather similar results. Conclusion Three clones from three species of the genus Daphnia were found to harbor a rich

  10. Superparasitism Drives Heritable Symbiont Epidemiology and Host Sex Ratio in a Wasp.

    Directory of Open Access Journals (Sweden)

    Steven R Parratt

    2016-06-01

    Full Text Available Heritable microbial symbionts have profound impacts upon the biology of their arthropod hosts. Whilst our current understanding of the dynamics of these symbionts is typically cast within a framework of vertical transmission only, horizontal transmission has been observed in a number of cases. For instance, several symbionts can transmit horizontally when their parasitoid hosts share oviposition patches with uninfected conspecifics, a phenomenon called superparasitism. Despite this, horizontal transmission, and the host contact structures that facilitates it, have not been considered in heritable symbiont epidemiology. Here, we tested for the importance of host contact, and resulting horizontal transmission, for the epidemiology of a male-killing heritable symbiont (Arsenophonus nasoniae in parasitoid wasp hosts. We observed that host contact through superparasitism is necessary for this symbiont's spread in populations of its primary host Nasonia vitripennis, such that when superparasitism rates are high, A. nasoniae almost reaches fixation, causes highly female biased population sex ratios and consequently causes local host extinction. We further tested if natural interspecific variation in superparasitism behaviours predicted symbiont dynamics among parasitoid species. We found that A. nasoniae was maintained in laboratory populations of a closely related set of Nasonia species, but declined in other, more distantly related pteromalid hosts. The natural proclivity of a species to superparasitise was the primary factor determining symbiont persistence. Our results thus indicate that host contact behaviour is a key factor for heritable microbe dynamics when horizontal transmission is possible, and that 'reproductive parasite' phenotypes, such as male-killing, may be of secondary importance in the dynamics of such symbiont infections.

  11. Population Density Modeling for Diverse Land Use Classes: Creating a National Dasymetric Worker Population Model

    Science.gov (United States)

    Trombley, N.; Weber, E.; Moehl, J.

    2017-12-01

    Many studies invoke dasymetric mapping to make more accurate depictions of population distribution by spatially restricting populations to inhabited/inhabitable portions of observational units (e.g., census blocks) and/or by varying population density among different land classes. LandScan USA uses this approach by restricting particular population components (such as residents or workers) to building area detected from remotely sensed imagery, but also goes a step further by classifying each cell of building area in accordance with ancillary land use information from national parcel data (CoreLogic, Inc.'s ParcelPoint database). Modeling population density according to land use is critical. For instance, office buildings would have a higher density of workers than warehouses even though the latter would likely have more cells of detection. This paper presents a modeling approach by which different land uses are assigned different densities to more accurately distribute populations within them. For parts of the country where the parcel data is insufficient, an alternate methodology is developed that uses National Land Cover Database (NLCD) data to define the land use type of building detection. Furthermore, LiDAR data is incorporated for many of the largest cities across the US, allowing the independent variables to be updated from two-dimensional building detection area to total building floor space. In the end, four different regression models are created to explain the effect of different land uses on worker distribution: A two-dimensional model using land use types from the parcel data A three-dimensional model using land use types from the parcel data A two-dimensional model using land use types from the NLCD data, and A three-dimensional model using land use types from the NLCD data. By and large, the resultant coefficients followed intuition, but importantly allow the relationships between different land uses to be quantified. For instance, in the model

  12. Antibiotics, primary symbionts and wing polyphenism in three aphid species.

    Science.gov (United States)

    Hardie, Jim; Leckstein, Peter

    2007-08-01

    The possible role of the primary Buchnera symbionts in wing polyphenism is examined in three aphid species. Presumptive winged aphids were fed on antibiotic-treated beans to destroy these symbionts. As previously reported, this leads to inhibited growth and low/zero fecundity. When such treatment is applied to the short-day-induced gynoparae (the winged autumn migrant) of the black bean aphid, Aphis fabae, it also causes many insects to develop as wingless or winged/wingless intermediate adult forms (apterisation). However, whilst antibiotic treatment of crowd-induced, long-day winged forms of the pea aphid, Acyrthosiphon pisum (a green and a pink clone) and the vetch aphid, Megoura viciae has similar effects on size and fecundity, it does not affect wing development. Food deprivation also promotes apterisation in A. fabae gynoparae but not in the crowd-induced winged morphs of the other two species. Thus, it appears that apterisation in A. fabae is not a direct effect of antibiotic treatment or a novel role for symbionts but is most likely related to impaired nutrition induced by the loss of the symbiont population.

  13. Cordia dichotoma G. Forst. : Bioecology and population density

    Science.gov (United States)

    Rahayu, E. S.; Martin, P.; Dewi, N. K.; Kurniawan, F. H.

    2017-04-01

    Kendal tree is declared as an identity flora of Kendal Regency, Central Java, Indonesia. It is predicted as a rare species; most of the local people do not know the existence of this tree. The study aimed to describe some aspects of bioecology and a population density of Kendal tree. An explorative study was conducted from March to July 2016, through interview, observation, and literature review. The respondents were determined by purposive and snowball sampling methods. The data were analysed descriptively. Results showed that there were very limited numbers (only five trees) of Kendal tree throughout Kendal Regency. The species was identified as Cordia dichotoma G. Forst. The tree is 3-15 m in height. The leaves are simple and arranged spirally, inflorescence dichotomous, bisexual, with five gamosepalous and gamopetalous. Generative reproduction occurred at a low rate. The tree grew optimally in a dusty, sandy loam soil, pH 6.0-6.5 with a temperature ranged from 27-34 °C, a light intensity of 450-1580 lux, and an altitude of about 10 meters above sea level. In conclusion, C. dichotoma is a rare plant in Kendal Regency. This plant needs an alternative method of propagation, regeneration and conservation using in vitro technique.

  14. Monitoring low density populations: a perspective on what level of population decline we can truly detect

    Directory of Open Access Journals (Sweden)

    Lurz, P. W. W.

    2008-06-01

    Full Text Available Monitoring of mammal species is an important part in detecting changes in their status. Efforts are based on a variety of direct and indirect methods and many low density populations are monitored through field signs. We present data on the endangered European red squirrel from Kidland Forest in the UK. We used cone transects to both record changes in seed availability and to monitor population trends. We examined the difficulty of accurately detecting population change when populations are low and field signs are patchily distributed. Current efforts would be sufficient to detect significant population declines of 50-75% in years with a modest squirrel population but not when they fall below one squirrel for every 20 ha of forest. The findings emphasise that monitoring aims have to be clearly defined with an awareness and understanding of what level of change the adopted methodological approach can reliably detect. We propose that mammal monitoring schemes need to be based on a pilot scheme to determine effect size and planned accordingly.

  15. Forage selection by mule deer: does niche breadth increase with population density.

    Science.gov (United States)

    M.C. Nicholson; R.T. Bowyer; J.G. Kie

    2006-01-01

    Effects of population density of mule deer Odocoileus hemionus on forage selection were investigated by comparing diet characteristics of two subpopulations of deer in southern California, USA, that differed in population density during winter. Quality of diet for deer, as indexed by faecal crude protein, was higher at the low-density site than at...

  16. Profound Effects of Population Density on Fitness-Related Traits in an Invasive Freshwater Snail

    Science.gov (United States)

    Zachar, Nicholas; Neiman, Maurine

    2013-01-01

    Population density can profoundly influence fitness-related traits and population dynamics, and density dependence plays a key role in many prominent ecological and evolutionary hypotheses. Here, we evaluated how individual-level changes in population density affect growth rate and embryo production early in reproductive maturity in two different asexual lineages of Potamopyrgus antipodarum, a New Zealand freshwater snail that is an important model system for ecotoxicology and the evolution of sexual reproduction as well as a potentially destructive worldwide invader. We showed that population density had a major influence on individual growth rate and early-maturity embryo production, effects that were often apparent even when comparing treatments that differed in population density by only one individual. While individual growth rate generally decreased as population density increased, we detected a hump-shaped relationship between embryo production and density, with females from intermediate-density treatments producing the most embryos and females from low- and high-density treatments producing the fewest embryos. The two lineages responded similarly to the treatments, indicating that these effects of population density might apply more broadly across P. antipodarum. These results indicate that there are profound and complex relationships between population density, growth rate, and early-maturity embryo production in at least two lineages of this important model system, with potential implications for the study of invasive populations, research on the maintenance of sex, and approaches used in ecotoxicology. PMID:24278240

  17. Profound effects of population density on fitness-related traits in an invasive freshwater snail.

    Directory of Open Access Journals (Sweden)

    Nicholas Zachar

    Full Text Available Population density can profoundly influence fitness-related traits and population dynamics, and density dependence plays a key role in many prominent ecological and evolutionary hypotheses. Here, we evaluated how individual-level changes in population density affect growth rate and embryo production early in reproductive maturity in two different asexual lineages of Potamopyrgus antipodarum, a New Zealand freshwater snail that is an important model system for ecotoxicology and the evolution of sexual reproduction as well as a potentially destructive worldwide invader. We showed that population density had a major influence on individual growth rate and early-maturity embryo production, effects that were often apparent even when comparing treatments that differed in population density by only one individual. While individual growth rate generally decreased as population density increased, we detected a hump-shaped relationship between embryo production and density, with females from intermediate-density treatments producing the most embryos and females from low- and high-density treatments producing the fewest embryos. The two lineages responded similarly to the treatments, indicating that these effects of population density might apply more broadly across P. antipodarum. These results indicate that there are profound and complex relationships between population density, growth rate, and early-maturity embryo production in at least two lineages of this important model system, with potential implications for the study of invasive populations, research on the maintenance of sex, and approaches used in ecotoxicology.

  18. Profound effects of population density on fitness-related traits in an invasive freshwater snail.

    Science.gov (United States)

    Zachar, Nicholas; Neiman, Maurine

    2013-01-01

    Population density can profoundly influence fitness-related traits and population dynamics, and density dependence plays a key role in many prominent ecological and evolutionary hypotheses. Here, we evaluated how individual-level changes in population density affect growth rate and embryo production early in reproductive maturity in two different asexual lineages of Potamopyrgus antipodarum, a New Zealand freshwater snail that is an important model system for ecotoxicology and the evolution of sexual reproduction as well as a potentially destructive worldwide invader. We showed that population density had a major influence on individual growth rate and early-maturity embryo production, effects that were often apparent even when comparing treatments that differed in population density by only one individual. While individual growth rate generally decreased as population density increased, we detected a hump-shaped relationship between embryo production and density, with females from intermediate-density treatments producing the most embryos and females from low- and high-density treatments producing the fewest embryos. The two lineages responded similarly to the treatments, indicating that these effects of population density might apply more broadly across P. antipodarum. These results indicate that there are profound and complex relationships between population density, growth rate, and early-maturity embryo production in at least two lineages of this important model system, with potential implications for the study of invasive populations, research on the maintenance of sex, and approaches used in ecotoxicology.

  19. Hierarchical spatial capture-recapture models: Modeling population density from stratified populations

    Science.gov (United States)

    Royle, J. Andrew; Converse, Sarah J.

    2014-01-01

    Capture–recapture studies are often conducted on populations that are stratified by space, time or other factors. In this paper, we develop a Bayesian spatial capture–recapture (SCR) modelling framework for stratified populations – when sampling occurs within multiple distinct spatial and temporal strata.We describe a hierarchical model that integrates distinct models for both the spatial encounter history data from capture–recapture sampling, and also for modelling variation in density among strata. We use an implementation of data augmentation to parameterize the model in terms of a latent categorical stratum or group membership variable, which provides a convenient implementation in popular BUGS software packages.We provide an example application to an experimental study involving small-mammal sampling on multiple trapping grids over multiple years, where the main interest is in modelling a treatment effect on population density among the trapping grids.Many capture–recapture studies involve some aspect of spatial or temporal replication that requires some attention to modelling variation among groups or strata. We propose a hierarchical model that allows explicit modelling of group or strata effects. Because the model is formulated for individual encounter histories and is easily implemented in the BUGS language and other free software, it also provides a general framework for modelling individual effects, such as are present in SCR models.

  20. High population density enhances recruitment and survival of a harvested coral reef fish.

    Science.gov (United States)

    Wormald, Clare L; Steele, Mark A; Forrester, Graham E

    2013-03-01

    A negative relationship between population growth and population density (direct density dependence) is necessary for population regulation and is assumed in most models of harvested populations. Experimental tests for density dependence are lacking for large-bodied, harvested fish because of the difficulty of manipulating population density over large areas. We studied a harvested coral reef fish, Lutjanus apodus (schoolmaster snapper), using eight large, isolated natural reefs (0.4-1.6 ha) in the Bahamas as replicates. An initial observational test for density dependence was followed by a manipulation of population density. The manipulation weakened an association between density and shelter-providing habitat features and revealed a positive effect of population density on recruitment and survival (inverse density dependence), but no effect of density on somatic growth. The snappers on an individual reef were organized into a few shoals, and we hypothesize that large shoals on high-density reefs were less vulnerable to large piscivores (groupers and barracudas) than the small shoals on low-density reefs. Reductions in predation risk for individuals in large social groups are well documented, but because snapper shoals occupied reefs the size of small marine reserves, these ecological interactions may influence the outcome of management actions.

  1. A novel bacterial symbiont association in the hispid beetle, Octodonta nipae (Coleoptera: Chrysomelidae), their dynamics and phylogeny.

    Science.gov (United States)

    Ali, Habib; Muhammad, Abrar; Islam, Saif Ul; Islam, Waqar; Hou, Youming

    2018-03-27

    The hispid leaf beetle, Octodonta nipae (Maulik), (Coleoptera: Chrysomelidae), is a devastating pest of palm cultivation worldwide. Endosymbiotic bacteria in the genus Wolbachia are arguably one of the most abundant bacterial group associated with arthropods. Owing to its critical effects on host reproduction, Wolbachia has garnered much attention as a prospective future tool for insect pest management. However, their association, infection dynamics, and functionality remain unknown in this insect pest. Here, we diagnosis for the first time, the infection prevalence, and occurrence of Wolbachia in O. nipae. Experimental evidence by the exploration of wsp gene vindicate that O. nipae is naturally infected with bacterial symbiont of genus Wolbachia, showing a complete maternal inheritance with shared a common Wolbachia strain (wNip). Moreover, MLST (gatB, fbpA, coxA, ftsZ, and hcpA) analysis enabled the detections of new sequence type (ST-484), suggesting a particular genotypic association of O. nipae and Wolbachia. Subsequently, quantitative real-time PCR (qPCR) assay demonstrated variable infection density across different life stages (eggs, larvae, pupae and adult male and female), body parts (head, thorax, abdomen), and tissues (ovaries, testes, and guts). Infection density was higher in egg and female adult stage, as well as abdomen and reproductive tissues as compared to other samples. Interestingly, Wolbachia harbored dominantly in a female than the male adult, while, no significant differences were observed between male and female body parts and tissues. Phylogeny of Wolbachia infection associated with O. nipae rectified from all tested life stages were unique and fall within the same monophyletic supergroup-A of Wolbachia clades. The infection density of symbiont is among the valuable tool to understand their biological influence on hosts, and this latest discovery would facilitate the future investigations to understand the host-symbiont complications and

  2. Population density of Beauveria bassiana in soil under the action of fungicides and native microbial populations

    Directory of Open Access Journals (Sweden)

    Flávia Barbosa Soares

    2017-08-01

    Full Text Available This study investigated whether populations of naturally-occurring soil bacteria, fungi and actinomycetes influence the effect of fungicides on the survival and growth of Beauveria bassiana. The toxicity of methyl thiophanate, pyraclostrobin, mancozeb and copper oxychloride at the recommended doses was analyzed in culture medium and in soil inoculated with fungus at various time points after addition of fungicides. All fungicides completely inhibited the growth and sporulation of B. bassiana in the culture medium. The fungicides were less toxic in soil, emphasizing the action of the microbial populations, which interfered with the toxic effects of these products to the fungus. Actinomycetes had the greatest influence on the entomopathogen, inhibiting it or degrading the fungicides to contribute to the survival and growth of B. bassiana in soil. Native populations of fungi and bacteria had a smaller influence on the population density of B. bassiana and the action of fungicides towards entomopathogen. The toxic effect of the fungicides was greater when added to the soil one hour before or after inoculation than at 48h after inoculation.

  3. Phylogenetic affinity of arbuscular mycorrhizal symbionts in Psilotum nudum.

    Science.gov (United States)

    Winther, Jennifer L; Friedman, William E

    2009-09-01

    Many lineages of land plants (from lycopsids to angiosperms) have non-photosynthetic life cycle phases that involve obligate mycoheterotrophic arbuscular mycorrhizal (AM) associations where the plant host gains organic carbon through glomalean symbionts. Our goal was to isolate and phylogenetically identify the AM fungi associated with both the autotrophic and underground mycoheterotrophic life cycle phases of Psilotum nudum. Phylogenetic analyses recovered 11 fungal phylotypes in four diverse clades of Glomus A that form AM associations with P. nudum mycoheterotrophic gametophytes and autotrophic sporophytes, and angiosperm roots found in the same greenhouse pots. The correspondence of identities of AM symbionts in P. nudum sporophytes, gametophytes and neighboring angiosperms provides compelling evidence that photosynthetic heterospecific and conspecific plants can serve as the ultimate sources of fixed carbon for mycoheterotrophic gametophytes of P. nudum, and that the transfer of carbon occurs via shared fungal networks. Moreover, broader phylogenetic analyses suggest greenhouse Psilotum populations, like field-surveyed populations of mycoheterotrophic plants, form AM associations with restricted clades of Glomus A. The phylogenetic affinities and distribution of Glomus A symbionts indicate that P. nudum greenhouse populations have the potential to be exploited as an experimental system to further study the physiology, ecology and evolution of mycoheterotrophic AM associations.

  4. Bone Mass Density in Normal Iranian Population - Shariati Hospital (1996

    Directory of Open Access Journals (Sweden)

    M Pajoohi

    2002-09-01

    Full Text Available Introduction: The bone mass density (BMD may vary in different countries due to different genetic and environmental factors. This study was performed to determine the BMD of the normal population in Iran. Methods and Materials: Subjects were selected randomly from different works and social classes in Tehran (from the lowest to the highest. For each decade and sexes, 20 normal subjects were selected (140 men and 140 women. BMD was measured with a Hologic 1000 plus machine by dual energy x-ray absorptiometry (DEXA method for the lumber spine (L1, L2, L3, L4, L1-L4 and the femoral neck (neck, trochanter, intertrochanter, ward, total. Data were treated by polynomial approximation (3 rd degree. The obtained curves were compared with the standard Hologic curves for Caucasians. Results: In female the peak bone mass (PBM was 1.019 g/cm² for the lumbar spine and 0.832 for the femoral neck. In male the peak bone mass (PBM was 0.987 g/cm² for the lumbar spine and 0.907 for the femoral neck. The BMD of both lumbar spine and femoral neck were lower than the Hologic standards. For the lumbar spine the mean difference was 6.5 percent (2 to 21 percent, CI=1 for women and 13.8 percent (2 to 36 percent, CI=1.45 for men. In femoral neck the mean difference was 5.4 percent (2 to 16 percent, CI=0.96 for women and 4.6 percent (1 to 14 percent, CI=0.96 for men. Conclusion: The BMD of the lumbar spine and the femoral neck was lower in Iranian compared to the Hologic standards for Caucasians. This was seen in all age groups and in both sexes. It was less pronounced for the PBM in spine was lower in men than woman. The lower BMD of the spine in men was also seen in a cohort of patients with different diseases (inflammatory and non-inflammatory.

  5. Novel bacteriocyte-associated pleomorphic symbiont of the grain pest beetleRhyzopertha dominica(Coleoptera: Bostrichidae).

    Science.gov (United States)

    Okude, Genta; Koga, Ryuichi; Hayashi, Toshinari; Nishide, Yudai; Meng, Xian-Ying; Nikoh, Naruo; Miyanoshita, Akihiro; Fukatsu, Takema

    2017-01-01

    The lesser grain borer Rhyzopertha dominica (Coleoptera: Bostrichidae) is a stored-product pest beetle. Early histological studies dating back to 1930s have reported that R. dominica and other bostrichid species possess a pair of oval symbiotic organs, called the bacteriomes, in which the cytoplasm is densely populated by pleomorphic symbiotic bacteria of peculiar rosette-like shape. However, the microbiological nature of the symbiont has remained elusive. Here we investigated the bacterial symbiont of R. dominica using modern molecular, histological, and microscopic techniques. Whole-mount fluorescence in situ hybridization specifically targeting symbiotic bacteria consistently detected paired bacteriomes, in which the cytoplasm was full of pleomorphic bacterial cells, in the abdomen of adults, pupae and larvae, confirming previous histological descriptions. Molecular phylogenetic analysis identified the symbiont as a member of the Bacteroidetes, in which the symbiont constituted a distinct bacterial lineage allied to a variety of insect-associated endosymbiont clades, including Uzinura of diaspidid scales, Walczuchella of giant scales, Brownia of root mealybugs, Sulcia of diverse hemipterans, and Blattabacterium of roaches. The symbiont gene exhibited markedly AT-biased nucleotide composition and significantly accelerated molecular evolution, suggesting degenerative evolution of the symbiont genome. The symbiotic bacteria were detected in oocytes and embryos, confirming continuous host-symbiont association and vertical symbiont transmission in the host life cycle. We demonstrate that the symbiont of R. dominica constitutes a novel bacterial lineage in the Bacteroidetes. We propose that reductive evolution of the symbiont genome may be relevant to the amorphous morphology of the bacterial cells via disruption of genes involved in cell wall synthesis and cell division. Genomic and functional aspects of the host-symbiont relationship deserve future studies.

  6. Density dependence and population dynamics of black rhinos (Diceros bicornis michaeli) in Kenya's rhino sanctuaries

    NARCIS (Netherlands)

    Ouma, B.O.; Amin, R.; Langevelde, van F.; Leader-Williams, N.

    2010-01-01

    Density-dependent feedback mechanisms provide insights into the population dynamics and interactions of large herbivores with their ecosystem. Sex ratio also has particularly important implications for growth rates of many large mammal populations through its influence on reproductive potential.

  7. Intracellular Oceanospirillales inhabit the gills of the hydrothermal vent snail Alviniconcha with chemosynthetic, γ-Proteobacterial symbionts.

    Science.gov (United States)

    Beinart, R A; Nyholm, S V; Dubilier, N; Girguis, P R

    2014-12-01

    Associations between bacteria from the γ-Proteobacterial order Oceanospirillales and marine invertebrates are quite common. Members of the Oceanospirillales exhibit a diversity of interactions with their various hosts, ranging from the catabolism of complex compounds that benefit host growth to attacking and bursting host nuclei. Here, we describe the association between a novel Oceanospirillales phylotype and the hydrothermal vent snail Alviniconcha. Alviniconcha typically harbour chemoautotrophic γ- or ε-Proteobacterial symbionts inside their gill cells. Via fluorescence in situ hybridization and transmission electron microscopy, we observed an Oceanospirillales phylotype (named AOP for ‘Alviniconcha Oceanospirillales phylotype’) in membrane-bound vacuoles that were separate from the known γ- or ε-Proteobacterial symbionts. Using quantitative polymerase chain reaction, we surveyed 181 Alviniconcha hosting γ-Proteobacterial symbionts and 102 hosting ε-Proteobacterial symbionts, and found that the population size of AOP was always minor relative to the canonical symbionts (median 0.53% of the total quantified 16S rRNA genes). Additionally, we detected AOP more frequently in Alviniconcha hosting γ-Proteobacterial symbionts than in those hosting ε-Proteobacterial symbionts (96% and 5% of individuals respectively). The high incidence of AOP in γ-Proteobacteria hosting Alviniconcha implies that it could play a significant ecological role either as a host parasite or as an additional symbiont with unknown physiological capacities.

  8. Relationships between human population density and burned area at continental and global scales.

    Science.gov (United States)

    Bistinas, Ioannis; Oom, Duarte; Sá, Ana C L; Harrison, Sandy P; Prentice, I Colin; Pereira, José M C

    2013-01-01

    We explore the large spatial variation in the relationship between population density and burned area, using continental-scale Geographically Weighted Regression (GWR) based on 13 years of satellite-derived burned area maps from the global fire emissions database (GFED) and the human population density from the gridded population of the world (GPW 2005). Significant relationships are observed over 51.5% of the global land area, and the area affected varies from continent to continent: population density has a significant impact on fire over most of Asia and Africa but is important in explaining fire over population density is associated with both increased and decreased in fire. The nature of the relationship depends on land-use: increasing population density is associated with increased burned are in rangelands but with decreased burned area in croplands. Overall, the relationship between population density and burned area is non-monotonic: burned area initially increases with population density and then decreases when population density exceeds a threshold. These thresholds vary regionally. Our study contributes to improved understanding of how human activities relate to burned area, and should contribute to a better estimate of atmospheric emissions from biomass burning.

  9. densities and biomasses of some ungulate populations in eastern

    African Journals Online (AJOL)

    some data on the sex and age structures of the populations of ungulates living in the Rwindi-. Rutshuru plain, south ... population succeeds in living all the year around at the ecotone between the Congo forest and the Kivu-West .... If one bears in mind the fact that the average annual kill per lion is estimated to range from 20 ...

  10. High urban population density of birds reflects their timing of urbanization.

    Science.gov (United States)

    Møller, Anders Pape; Diaz, Mario; Flensted-Jensen, Einar; Grim, Tomas; Ibáñez-Álamo, Juan Diego; Jokimäki, Jukka; Mänd, Raivo; Markó, Gábor; Tryjanowski, Piotr

    2012-11-01

    Living organisms generally occur at the highest population density in the most suitable habitat. Therefore, invasion of and adaptation to novel habitats imply a gradual increase in population density, from that at or below what was found in the ancestral habitat to a density that may reach higher levels in the novel habitat following adaptation to that habitat. We tested this prediction of invasion biology by analyzing data on population density of breeding birds in their ancestral rural habitats and in matched nearby urban habitats that have been colonized recently across a continental latitudinal gradient. We estimated population density in the two types of habitats using extensive point census bird counts, and we obtained information on the year of urbanization when population density in urban habitats reached levels higher than that of the ancestral rural habitat from published records and estimates by experienced ornithologists. Both the difference in population density between urban and rural habitats and the year of urbanization were significantly repeatable when analyzing multiple populations of the same species across Europe. Population density was on average 30 % higher in urban than in rural habitats, although density reached as much as 100-fold higher in urban habitats in some species. Invasive urban bird species that colonized urban environments over a long period achieved the largest increases in population density compared to their ancestral rural habitats. This was independent of whether species were anciently or recently urbanized, providing a unique cross-validation of timing of urban invasions. These results suggest that successful invasion of urban habitats was associated with gradual adaptation to these habitats as shown by a significant increase in population density in urban habitats over time.

  11. Population densities of wheat thrips, Haplothrips tritici Kurdjumov ...

    African Journals Online (AJOL)

    Jane

    2011-07-18

    Jul 18, 2011 ... studied in Kahramanmaraş, Turkey. In 2002, bread wheat cultivars, Bocro 4, Pehlivan and ... grains in Turkey is Haplothrips tritici (H. tritici) Kurdjumov from the Phlaeothripidae family (Tunç, 1978; ..... for average production and prices, the economic damage threshold was 17 larvae per spike. The density of ...

  12. effect of population density and dose of nitrogen and potassium ...

    African Journals Online (AJOL)

    A. Hussein

    2018-01-01

    Jan 1, 2018 ... while, nitrogen consumption increased dry weight resulting in increased plant yield (Hatami et al., 2009). Vorob (2000) ... of this study was to investigate the effect of plant density and dose of nitrogen and potassium on Green bean Cv. ..... biogeochem. cycle., 2008, 22(1), 1022-1041. [11] Moniruzzaman M ...

  13. The influence of population density and duration of breeding on ...

    African Journals Online (AJOL)

    USER

    2010-07-12

    Jul 12, 2010 ... density decreases the daily gain of broiler chickens and increased feed consumption per kilogram of gain. Similar statements were made by Dozier et al. (2005) who suggested that increased production of broiler meat per square meter from 30 to 45 kg negatively influences final body mass and food ...

  14. Population density and habitat preferences of forest duikers in ...

    African Journals Online (AJOL)

    The encounter rate for P. monticola and C. silvicultor did not vary significantly between the transects, while that of red duikers was higher in the primary forest than in the young secondary or gallery forest. The duiker densities in our study area are among the highest in the African rainforest. Our results indicate that quick ...

  15. Explaining density-dependent regulation in earthworm populations using life-history analysis

    NARCIS (Netherlands)

    Kammenga, J.E.; Spurgeon, D.J.; Svendsen, C.; Weeks, J.M.

    2003-01-01

    At present there is little knowledge about how density regulates population growth rate and to what extent this is determined by life-history patterns. We compared density dependent population consequences in the Nicholsonian sense based oil experimental observations and life-history modeling for

  16. Influence of Population Density on Offspring Number and Size in Burying Beetles

    Science.gov (United States)

    Rauter, Claudia M.

    2010-01-01

    This laboratory exercise investigates the influence of population density on offspring number and size in burying beetles. Students test the theoretical predictions that brood size declines and offspring size increases when competition over resources becomes stronger with increasing population density. Students design the experiment, collect and…

  17. Influence of larval diet and population density on pre-adult ...

    African Journals Online (AJOL)

    The influence of larval diet and population density on pre-adult developmental rate, adult population sizes, pre-adult survival and sex ratio was investigated. Mean developmental period varied significantly with low larval densities. Similarly, there were significant variations of developmental periods with different diets.

  18. Forms of density regulation and (quasi-) stationary distributions of population sizes in birds

    DEFF Research Database (Denmark)

    Sæther, Bernt-Erik; Engen, Steinar; Grøtan, Vidar

    2008-01-01

    The theta-logistic model of density regulation is an especially flexible class of density regulation models where different forms of non-linear density regulation can be expressed by only one parameter, u. Estimating the parameters of the thetalogistic model is, however, challenging. This is mainly...... due to the need for information concerning population growth at low densities as well as data on fluctuations around the carrying capacity K in order to estimate the strength of density regulation. Here we estimate parameters of the theta-logistic model for 28 populations of three species of birds...... that have grown from very small population sizes followed by a period of fluctuations around K. We then use these parameters to estimate the quasi-stationary distribution of population size. There were often large uncertainties in these parameters specifying the form of density regulation that were...

  19. Pika Population Density Is Associated with the Composition and Diversity of Gut Microbiota

    OpenAIRE

    Li, Huan; Qu, Jiapeng; Li, Tongtong; Li, Jiabao; Lin, Qiang; Li, Xiangzhen

    2016-01-01

    Host population density is positively associated with the strength of social interactions or the frequency of physical contacts, and thus potentially influences microbial transmission among individuals. However, the relationship between host density and gut microbiota remains unknown. Here, we characterized the gut microbiota of plateau pikas (Ochotona curzoniae) in wild experimental fields with different host population densities. The abundance of some gut microbes significantly correlated w...

  20. Pika population density is associated with composition and diversity of gut microbiota

    OpenAIRE

    Huan eLi; Jiapeng eQu; Tongtong eLi; Jiabao eLi; Qiang eLin; Xiangzhen eLi

    2016-01-01

    Host population density is positively associated with the strength of social interactions or the frequency of physical contacts, and thus potentially influences microbial transmission among individuals. However, the relationship between host density and gut microbiota remains unknown. Here, we characterized the gut microbiota of plateau pikas (Ochotona curzoniae) in wild experimental fields with different host population densities. The abundance of some gut microbes significantly correlated w...

  1. Measurement of bone density in the pediatric population.

    Science.gov (United States)

    Bogunovic, Ljiljana; Doyle, Shevaun M; Vogiatzi, Maria G

    2009-02-01

    The purpose of this review is to provide a comprehensive synopsis of pediatric bone density. Osteoporosis of the adult is a well established clinical problem, and algorithms to diagnose and treat this disease are recognized throughout the medical community. Osteoporosis or 'low bone mass' in pediatrics, on the other hand, is a rather new and evolving area, with certain unique diagnostic and clinical challenges. Recent findings in the literature include benefits and limitations of pediatric bone densitometry techniques, proper interpretation of the results of these various techniques, efforts to establish standards and guidelines for diagnosing low bone mass in children and adolescents, optimization of bone growth and mineral accrual for life, pediatric bone mineral density and fracture risk prediction, as well as a clearer awareness of bone fragility in children. Throughout the last decade, great strides have been made in our understanding of pediatric metabolic bone disease. These will be the focus of this review.

  2. Effects of population density on corticosterone levels of prairie voles in the field.

    Science.gov (United States)

    Blondel, Dimitri V; Wallace, Gerard N; Calderone, Stefanie; Gorinshteyn, Marija; St Mary, Colette M; Phelps, Steven M

    2016-01-01

    High population density is often associated with increased levels of stress-related hormones, such as corticosterone (CORT). Prairie voles (Microtus ochrogaster) are a socially monogamous species known for their large population density fluctuations in the wild. Although CORT influences the social behavior of prairie voles in the lab, the effect of population density on CORT has not previously been quantified in this species in the field. We validated a non-invasive hormone assay for measuring CORT metabolites in prairie vole feces. We then used semi-natural enclosures to experimentally manipulate population density, and measured density effects on male space use and fecal CORT levels. Our enclosures generated patterns of space use and social interaction that were consistent with previous prairie vole field studies. Contrary to the positive relationship between CORT and density typical of other taxa, we found that lower population densities (80 animals/ha) produced higher fecal CORT than higher densities (240/ha). Combined with prior work in the lab and field, the data suggest that high prairie vole population densities indicate favorable environments, perhaps through reduced predation risk. Lastly, we found that field animals had lower fecal CORT levels than laboratory-living animals. The data emphasize the usefulness of prairie voles as models for integrating ecological, evolutionary, and mechanistic questions in social behavior. Copyright © 2015 Elsevier Inc. All rights reserved.

  3. Effects of social organization, trap arrangement and density, sampling scale, and population density on bias in population size estimation using some common mark-recapture estimators.

    Directory of Open Access Journals (Sweden)

    Manan Gupta

    Full Text Available Mark-recapture estimators are commonly used for population size estimation, and typically yield unbiased estimates for most solitary species with low to moderate home range sizes. However, these methods assume independence of captures among individuals, an assumption that is clearly violated in social species that show fission-fusion dynamics, such as the Asian elephant. In the specific case of Asian elephants, doubts have been raised about the accuracy of population size estimates. More importantly, the potential problem for the use of mark-recapture methods posed by social organization in general has not been systematically addressed. We developed an individual-based simulation framework to systematically examine the potential effects of type of social organization, as well as other factors such as trap density and arrangement, spatial scale of sampling, and population density, on bias in population sizes estimated by POPAN, Robust Design, and Robust Design with detection heterogeneity. In the present study, we ran simulations with biological, demographic and ecological parameters relevant to Asian elephant populations, but the simulation framework is easily extended to address questions relevant to other social species. We collected capture history data from the simulations, and used those data to test for bias in population size estimation. Social organization significantly affected bias in most analyses, but the effect sizes were variable, depending on other factors. Social organization tended to introduce large bias when trap arrangement was uniform and sampling effort was low. POPAN clearly outperformed the two Robust Design models we tested, yielding close to zero bias if traps were arranged at random in the study area, and when population density and trap density were not too low. Social organization did not have a major effect on bias for these parameter combinations at which POPAN gave more or less unbiased population size estimates

  4. Effects of social organization, trap arrangement and density, sampling scale, and population density on bias in population size estimation using some common mark-recapture estimators.

    Science.gov (United States)

    Gupta, Manan; Joshi, Amitabh; Vidya, T N C

    2017-01-01

    Mark-recapture estimators are commonly used for population size estimation, and typically yield unbiased estimates for most solitary species with low to moderate home range sizes. However, these methods assume independence of captures among individuals, an assumption that is clearly violated in social species that show fission-fusion dynamics, such as the Asian elephant. In the specific case of Asian elephants, doubts have been raised about the accuracy of population size estimates. More importantly, the potential problem for the use of mark-recapture methods posed by social organization in general has not been systematically addressed. We developed an individual-based simulation framework to systematically examine the potential effects of type of social organization, as well as other factors such as trap density and arrangement, spatial scale of sampling, and population density, on bias in population sizes estimated by POPAN, Robust Design, and Robust Design with detection heterogeneity. In the present study, we ran simulations with biological, demographic and ecological parameters relevant to Asian elephant populations, but the simulation framework is easily extended to address questions relevant to other social species. We collected capture history data from the simulations, and used those data to test for bias in population size estimation. Social organization significantly affected bias in most analyses, but the effect sizes were variable, depending on other factors. Social organization tended to introduce large bias when trap arrangement was uniform and sampling effort was low. POPAN clearly outperformed the two Robust Design models we tested, yielding close to zero bias if traps were arranged at random in the study area, and when population density and trap density were not too low. Social organization did not have a major effect on bias for these parameter combinations at which POPAN gave more or less unbiased population size estimates. Therefore, the

  5. Population density predicts outcome from out-of-hospital cardiac arrest in Victoria, Australia.

    Science.gov (United States)

    Nehme, Ziad; Andrew, Emily; Cameron, Peter A; Bray, Janet E; Bernard, Stephen A; Meredith, Ian T; Smith, Karen

    2014-05-05

    To examine the impact of population density on incidence and outcome of out-of-hospital cardiac arrest (OHCA). Data were extracted from the Victorian Ambulance Cardiac Arrest Registry for all adult OHCA cases of presumed cardiac aetiology attended by the emergency medical service (EMS) between 1 January 2003 and 31 December 2011. Cases were allocated into one of five population density groups according to their statistical local area: very low density (≤ 10 people/km(2)), low density (11-200 people/km(2)), medium density (201-1000 people/km(2)), high density (1001-3000 people/km(2)), and very high density (> 3000 people/km(2)). Survival to hospital and survival to hospital discharge. The EMS attended 27 705 adult presumed cardiac OHCA cases across 204 Victorian regions. In 12 007 of these (43.3%), resuscitation was attempted by the EMS. Incidence was lower and arrest characteristics were consistently less favourable for lower population density groups. Survival outcomes, including return of spontaneous circulation, survival to hospital and survival to hospital discharge, were significantly poorer in less densely populated groups (P populations, the risk-adjusted odds ratios of surviving to hospital discharge were: low density, 1.88 (95% CI, 1.15-3.07); medium density, 2.49 (95% CI, 1.55-4.02); high density, 3.47 (95% CI, 2.20-5.48) and very high density, 4.32 (95% CI, 2.67-6.99). Population density is independently associated with survival after OHCA, and significant variation in the incidence and characteristics of these events are observed across the state.

  6. Immigration Rates during Population Density Reduction in a Coral Reef Fish

    Science.gov (United States)

    Turgeon, Katrine; Kramer, Donald L.

    2016-01-01

    Although the importance of density-dependent dispersal has been recognized in theory, few empirical studies have examined how immigration changes over a wide range of densities. In a replicated experiment using a novel approach allowing within-site comparison, we examined changes in immigration rate following the gradual removal of territorial damselfish from a limited area within a much larger patch of continuous habitat. In all sites, immigration occurred at intermediate densities but did not occur before the start of removals and only rarely as density approached zero. In the combined data and in 5 of 7 sites, the number of immigrants was a hump-shaped function of density. This is the first experimental evidence for hump-shaped, density-dependent immigration. This pattern may be more widespread than previously recognized because studies over more limited density ranges have identified positive density dependence at low densities and negative density dependence at high densities. Positive density dependence at low density can arise from limits to the number of potential immigrants and from behavioral preferences for settling near conspecifics. Negative density dependence at high density can arise from competition for resources, especially high quality territories. The potential for non-linear effects of local density on immigration needs to be recognized for robust predictions of conservation reserve function, harvest impacts, pest control, and the dynamics of fragmented populations. PMID:27271081

  7. The evolution of host-symbiont dependence

    NARCIS (Netherlands)

    Fisher, Roberta M.; Henry, Lee M.; Cornwallis, Charlie K.; Kiers, E. Toby; West, Stuart A.

    2017-01-01

    Organisms across the tree of life form symbiotic partnerships with microbes for metabolism, protection and resources. While some hosts evolve extreme dependence on their symbionts, others maintain facultative associations. Explaining this variation is fundamental to understanding when symbiosis can

  8. Effect of population density and dose of nitrogen and potassium ...

    African Journals Online (AJOL)

    This experiment was executed in a split randomized complete block design with three replications. Two plant densities (D), (D1; D2) equal to one plant and two plants per pot and seven fertilizers doses (F), (N0 K0; N1 K0; N1 K1; N2 K0; N2 K2; N0 K1; N0 K2) were investigated. N0, N11 and N2 equal to 0, 0.46, and 0.92 g ...

  9. Monitoring population density and fluctuations of Anisandrus dispar ...

    African Journals Online (AJOL)

    Bark and ambrosia beetles consist of two main ecological groups; bark beetles settle in the phloem, whereas ambrosia beetles bore in the xylem (sapwood). The latter are very detrimental ... in Samsun province. Key words: Hazelnut, population monitoring, Anisandrus dispar, Xyleborinus saxesenii, red winged sticky traps.

  10. Experimental evolution reveals differences between phenotypic and evolutionary responses to population density.

    Science.gov (United States)

    McNamara, K B; Simmons, L W

    2017-09-01

    Group living can select for increased immunity, given the heightened risk of parasite transmission. Yet, it also may select for increased male reproductive investment, given the elevated risk of female multiple mating. Trade-offs between immunity and reproduction are well documented. Phenotypically, population density mediates both reproductive investment and immune function in the Indian meal moth, Plodia interpunctella. However, the evolutionary response of populations to these traits is unknown. We created two replicated populations of P. interpunctella, reared and mated for 14 generations under high or low population densities. These population densities cause plastic responses in immunity and reproduction: at higher numbers, both sexes invest more in one index of immunity [phenoloxidase (PO) activity] and males invest more in sperm. Interestingly, our data revealed divergence in PO and reproduction in a different direction to previously reported phenotypic responses. Males evolving at low population densities transferred more sperm, and both males and females displayed higher PO than individuals at high population densities. These positively correlated responses to selection suggest no apparent evolutionary trade-off between immunity and reproduction. We speculate that the reduced PO activity and sperm investment when evolving under high population density may be due to the reduced population fitness predicted under increased sexual conflict and/or to trade-offs between pre- and post-copulatory traits. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

  11. Preferential allocation, physio-evolutionary feedbacks, and the stability and environmental patterns of mutualism between plants and their root symbionts.

    Science.gov (United States)

    Bever, James D

    2015-03-01

    The common occurrence of mutualistic interactions between plants and root symbionts is problematic. As the delivery of benefit to hosts involves costs to symbionts, symbionts that provide reduced benefit to their host are expected to increase in frequency. Plants have been shown to allocate preferentially to the most efficient symbiont and this preferential allocation may stabilize the mutualism. I construct a general model of the interactive feedbacks of host preferential allocation and the dynamics of root symbiont populations to evaluate the stability of nutritional mutualisms. Preferential allocation can promote the evolution of mutualism even when the cost to the symbiont is very large. Moreover, the physiological plasticity of preferential allocation likely leads to coexistence of beneficial and nonbeneficial symbionts. For arbuscular mycorrhizal fungi, which facilitate plant uptake of phosphorus (P), the model predicts greater P transfer from these fungi per unit carbon invested with decreasing concentrations of soil P and with increasing concentrations of atmospheric CO2 , patterns that have been observed in laboratory and field studies. This framework connects physiological plasticity in plant allocation to population processes that determine mutualism stability and, as such, represents a significant step in understanding the stability and environmental patterns in mutualism. © 2015 The Author. New Phytologist © 2015 New Phytologist Trust.

  12. Elucidating Cellular Population Dynamics by Molecular Density Function Perturbations

    Directory of Open Access Journals (Sweden)

    Thanneer Malai Perumal

    2018-01-01

    Full Text Available Studies performed at single-cell resolution have demonstrated the physiological significance of cell-to-cell variability. Various types of mathematical models and systems analyses of biological networks have further been used to gain a better understanding of the sources and regulatory mechanisms of such variability. In this work, we present a novel sensitivity analysis method, called molecular density function perturbation (MDFP, for the dynamical analysis of cellular heterogeneity. The proposed analysis is based on introducing perturbations to the density or distribution function of the cellular state variables at specific time points, and quantifying how such perturbations affect the state distribution at later time points. We applied the MDFP analysis to a model of a signal transduction pathway involving TRAIL (tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis in HeLa cells. The MDFP analysis shows that caspase-8 activation regulates the timing of the switch-like increase of cPARP (cleaved poly(ADP-ribose polymerase, an indicator of apoptosis. Meanwhile, the cell-to-cell variability in the commitment to apoptosis depends on mitochondrial outer membrane permeabilization (MOMP and events following MOMP, including the release of Smac (second mitochondria-derived activator of caspases and cytochrome c from mitochondria, the inhibition of XIAP (X-linked inhibitor of apoptosis by Smac, and the formation of the apoptosome.

  13. The demography of climate-driven and density-regulated population dynamics in a perennial plant

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Bengstsson, Karin; Ehrlén, Johan

    2016-01-01

    Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly...... important aspect of such forecasts. We examined the simultaneous impact of climate and intraspecific density on vital rates of the dwarf shrub Fumana procumbens over 20 yr, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models...... to be driven solely by the environment can overestimate extinction risks if there is density dependence. We conclude that density regulation can dampen effects of climate change on Fumana population size, and discuss the need to quantify density dependence in predictions of population responses...

  14. Local environment and density-dependent feedbacks determine population growth in a forest herb.

    Science.gov (United States)

    Dahlgren, Johan P; Ostergård, Hannah; Ehrlén, Johan

    2014-12-01

    Linking spatial variation in environmental factors to variation in demographic rates is essential for a mechanistic understanding of the dynamics of populations. However, we still know relatively little about such links, partly because feedbacks via intraspecific density make them difficult to observe in natural populations. We conducted a detailed field study and investigated simultaneous effects of environmental factors and the intraspecific density of individuals on the demography of the herb Lathyrus vernus. In regression models of vital rates we identified effects associated with spring shade on survival and growth, while density was negatively correlated with these vital rates. Density was also negatively correlated with average individual size in the study plots, which is consistent with self-thinning. In addition, average plant sizes were larger than predicted by density in plots that were less shaded by the tree canopy, indicating an environmentally determined carrying capacity. A size-structured integral projection model based on the vital rate regressions revealed that the identified effects of shade and density were strong enough to produce differences in stable population sizes similar to those observed in the field. The results illustrate how the local environment can determine dynamics of populations and that intraspecific density may have to be more carefully considered in studies of plant demography and population viability analyses of threatened species. We conclude that demographic approaches incorporating information about both density and key environmental factors are powerful tools for understanding the processes that interact to determine population dynamics and abundances.

  15. Stochastic density dependence in population size of a benthic clonal invertebrate: the regulating role of fission.

    Science.gov (United States)

    Tanner, Jason E

    2000-03-01

    The influence of environmental variation on the demography of clonal organisms has been poorly studied. I utilise a matrix model of the population dynamics of the intertidal zoanthid Palythoa caesia to examine how density dependence and temporal variation in demographic rates interact in regulating population size. The model produces realistic simulations of population size, with erratic fluctuations between soft lower and upper boundaries of approximately 55 and 90% cover. Cover never exceeds the maximum possible of 100%, and the population never goes to extinction. A sensitivity analysis indicates that the model's behaviour is driven by density dependence in the fission of large colonies to produce intermediate sized colonies. Importantly, there is no density-dependent mortality in the model, and density dependence in recruitment, while present, is unimportant. Thus it appears that the main demographic processes which are considered to regulate population size in aclonal organisms may not be important for clonal species.

  16. Productivity, biodiversity, and pathogens influence the global hunter-gatherer population density.

    Science.gov (United States)

    Tallavaara, Miikka; Eronen, Jussi T; Luoto, Miska

    2018-02-06

    The environmental drivers of species distributions and abundances are at the core of ecological research. However, the effects of these drivers on human abundance are not well-known. Here, we report how net primary productivity, biodiversity, and pathogen stress affect human population density using global ethnographic hunter-gatherer data. Our results show that productivity has significant effects on population density globally. The most important direct drivers, however, depend on environmental conditions: biodiversity influences population density exclusively in low-productivity regions, whereas pathogen stress does so in high-productivity regions. Our results also indicate that subtropical and temperate forest biomes provide the highest carrying capacity for hunter-gatherer populations. These findings document that environmental factors play a key role in shaping global population density patterns of preagricultural humans.

  17. Effect of population density on reproduction in Microtus fortis under laboratory conditions.

    Science.gov (United States)

    Han, Qunhua; Zhang, Meiwen; Guo, Cong; Shen, Guo; Wang, Yong; Li, Bo; Xu, Zhenggang

    2014-06-01

    Between December 2011 and March 2012, the reproductive characteristics of Microtus fortis reared in the laboratory at different population densities were assessed. In all, 258 male and female voles were randomly divided into 4 groups and reared at densities of 2, 4, 6, and 8 animals per cage (sex ratio: 1:1). The results showed that the pregnancy rate (χ2 = 21.671, df = 3, P population density groups, but the mean litter size (mean ± SD) was not (F = 2.669, df = 3, P > 0.05). In particular, the reproductive index and sex hormone levels showed a significant difference among the different density groups studied.

  18. Anatomical traits related to stress in high density populations of Typha angustifolia L. (Typhaceae

    Directory of Open Access Journals (Sweden)

    F. F. Corrêa

    Full Text Available Abstract Some macrophytes species show a high growth potential, colonizing large areas on aquatic environments. Cattail (Typha angustifolia L. uncontrolled growth causes several problems to human activities and local biodiversity, but this also may lead to competition and further problems for this species itself. Thus, the objective of this study was to investigate anatomical modifications on T. angustifolia plants from different population densities, once it can help to understand its biology. Roots and leaves were collected from natural populations growing under high and low densities. These plant materials were fixed and submitted to usual plant microtechnique procedures. Slides were observed and photographed under light microscopy and images were analyzed in the UTHSCSA-Imagetool software. The experimental design was completely randomized with two treatments and ten replicates, data were submitted to one-way ANOVA and Scott-Knott test at p<0.05. Leaves from low density populations showed higher stomatal density and index. These modifications on stomatal characteristics were more evident on the leaf abaxial surface. Plants from low density populations showed thicker mesophyll and higher proportion of aerenchymal area. Roots from low density populations showed a higher proportion of the vascular cylinder. Whereas, plants from higher density populations showed greater thickness of the endodermis, exodermis, phloem and root cortex. Higher density populations showed a higher proportion of aerenchymal gaps in the root cortex. Therefore, cattail plants from populations growing under high density population show anatomical traits typical of plants under stress, which promotes the development of less functional anatomical modifications to aquatic environments.

  19. Bayesian inference on the effect of density dependence and weather on a guanaco population from Chile

    DEFF Research Database (Denmark)

    Zubillaga, Maria; Skewes, Oscar; Soto, Nicolás

    2014-01-01

    on a time series of 36 years of population sampling of guanacos in Tierra del Fuego, Chile. The population density varied between 2.7 and 30.7 guanaco/km², with an apparent monotonic growth during the first 25 years; however, in the last 10 years the population has shown large fluctuations, suggesting...

  20. [Mating behavior in mutant strains of Drosophila melanogaster at different population densities].

    Science.gov (United States)

    Volkova, N E; Sheremet, O Iu; Vorobieva, L I

    2006-04-01

    The effects of mutations and genetic background on the mating activity of male and receptivity of female Drosophila melanogaster have been studied at different population densities. Population density, as well as its combinations with other factors, significantly affects mating behavior of D. melanogaster. There are two distinct trends in the effect of this factor on mating behavior: the maximum larval overpopulation may cause either a significant suppression of the behaviors studied or an increase in their expressivity. The mating behaviors of wa and cn mutants against a certain genetic background changed similarly in response to varying population density.

  1. Population density and phenotypic attributes influence the level of nematode parasitism in roe deer.

    Science.gov (United States)

    Body, Guillaume; Ferté, Hubert; Gaillard, Jean-Michel; Delorme, Daniel; Klein, François; Gilot-Fromont, Emmanuelle

    2011-11-01

    The impact of parasites on population dynamics is well documented, but less is known on how host population density affects parasite spread. This relationship is difficult to assess because of confounding effects of social structure, population density, and environmental conditions that lead to biased among-population comparisons. Here, we analyzed the infestation by two groups of nematodes (gastro-intestinal (GI) strongyles and Trichuris) in the roe deer (Capreolus capreolus) population of Trois Fontaines (France) between 1997 and 2007. During this period, we experimentally manipulated population density through changes in removals. Using measures collected on 297 individuals, we quantified the impact of density on parasite spread after taking into account possible influences of date, age, sex, body mass, and weather conditions. The prevalence and abundance of eggs of both parasites in females were positively related to roe deer density, except Trichuris in adult females. We also found a negative relationship between parasitism and body mass, and strong age and sex-dependent patterns of parasitism. Prime-age adults were less often parasitized and had lower fecal egg counts than fawns or old individuals, and males were more heavily and more often infected than females. Trichuris parasites were not affected by weather, whereas GI strongyles were less present after dry and hot summers. In the range of observed densities, the observed effect of density likely involves a variation of the exposure rate, as opposed to variation in host susceptibility.

  2. Floater dynamics can explain positive patterns of density-dependent fecundity in animal populations.

    Science.gov (United States)

    Penteriani, Vincenzo; Otalora, Fermín; Ferrer, Miguel

    2006-11-01

    After some 70 years of debate on density-dependent regulation of animal populations, there is still poor understanding of where spatial and temporal density dependence occurs. Clearly defining the portion of the population that shapes density-dependent patterns may help to solve some of the ambiguities that encircle density dependence and its patterns. In fact, individuals of the same species and population can show different dynamics and behaviors depending on their locations (e.g., breeding vs. dispersal areas). Considering this form of intrapopulation heterogeneity may improve our understanding of density dependence and population dynamics in general. We present the results of individual-based simulations on a metapopulation of the Spanish imperial eagle Aquila adalberti. Our results suggest that high rates of floater mortality within settlement areas can determine a shift in the classical relationship (from negative to positive) between the fecundity (i.e., fledglings per pair) and density (i.e., number of pairs) of the breeding population. Finally, we proved that different initial conditions affecting the breeder portion of the population can lead to the same values of fecundity. Our results can represent a starting point for new and more complex approaches studying the regulation of animal populations, where the forgotten and invisible component--the floater--is taken into account.

  3. Food for folivores: nutritional explanations linking diets to population density.

    Science.gov (United States)

    Wallis, Ian R; Edwards, Melanie J; Windley, Hannah; Krockenberger, Andrew K; Felton, Annika; Quenzer, Megan; Ganzhorn, Joerg U; Foley, William J

    2012-06-01

    Ecologists want to explain why populations of animals are not evenly distributed across landscapes and often turn to nutritional explanations. In seeking to link population attributes with food quality, they often contrast nutritionally positive traits, such as the concentration of nitrogen, against negative ones, such as fibre concentration, by using a ratio of these traits. This specific ratio has attracted attention because it sometimes correlates with the biomass of colobine primates across sites in Asia and Africa. Although empirically successful, we have identified problems with the ratio that may explain why it fails under some conditions to predict colobine biomass. First, available nitrogen, rather than total nitrogen, is nutritionally important, while the presence of tannins is the major factor reducing the availability of nitrogen in browse plant species. Second, tannin complexes inflate measures of fibre. Finally, simple ratios may be unsound statistically because they implicitly assume isometric relationships between variables. We used data on the chemical composition of plants from three continents to examine the relationships between the concentrations of nitrogen, available nitrogen, fibre and tannins in foliage and to evaluate the nitrogen to fibre ratio. Our results suggest that the ratio of the concentration of nitrogen to fibre in leaves does sometimes closely correlate with the concentration of available nitrogen. However, the ratio may give misleading results when leaves contain high concentrations of tannins. The concentration of available nitrogen, which incorporates measures of total nitrogen, dry matter digestibility and tannins, should give a better indication of the nutritional value of leaves for herbivorous mammals that can readily be extrapolated to habitats.

  4. Local environment and density-dependent feedbacks determine population growth in a forest herb

    DEFF Research Database (Denmark)

    Dahlgren, Johan Petter; Östergård, Hannah; Ehrlén, Johan

    2014-01-01

    Linking spatial variation in environmental factors to variation in demographic rates is essential for a mechanistic understanding of the dynamics of populations. However, we still know relatively little about such links, partly because feedbacks via intraspecific density make them difficult...... shade on survival and growth, while density was negatively correlated with these vital rates. Density was also negatively correlated with average individual size in the study plots, which is consistent with self-thinning. In addition, average plant sizes were larger than predicted by density in plots...... similar to those observed in the field. The results illustrate how the local environment can determine dynamics of populations and that intraspecific density may have to be more carefully considered in studies of plant demography and population viability analyses of threatened species. We conclude...

  5. Shifts of community composition and population density substantially affect ecosystem function despite invariant richness

    NARCIS (Netherlands)

    Spaak, Jurg W.; Baert, Jan M.; Baird, Donald J.; Eisenhauer, Nico; Maltby, Lorraine; Pomati, Francesco; Radchuk, Viktoriia; Rohr, Jason R.; Brink, van den Paul J.; Laender, De Frederik

    2017-01-01

    There has been considerable focus on the impacts of environmental change on ecosystem function arising from changes in species richness. However, environmental change may affect ecosystem function without affecting richness, most notably by affecting population densities and community

  6. Diversity and localization of bacterial symbionts in three whitefly species (Hemiptera: Aleyrodidae) from the east coast of the Adriatic Sea.

    Science.gov (United States)

    Skaljac, M; Zanić, K; Hrnčić, S; Radonjić, S; Perović, T; Ghanim, M

    2013-02-01

    Several whitefly species (Hemiptera: Aleyrodidae) are cosmopolitan phloem-feeders that cause serious damage in numerous agricultural crops. All whitefly species harbor a primary bacterial symbiont and a diverse array of secondary symbionts which may influence several aspects of the insect's biology. We surveyed infections by secondary symbionts in Bemisia tabaci (Gennadius), Trialeurodes vaporariorum (Westwood) and Siphoninus phillyreae (Haliday) from areas in the east cost of the Adriatic Sea. Both the Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) B. tabaci genetic groups were detected in Montenegro, whereas only the MED was confirmed in Croatia. Trialeurodes vaporariorum and S. phillyreae were found in all areas surveyed. MEAM1 and MED exhibited similarity to previously reported infections, while populations of T. vaporariorum from Montenegro harbored Rickettsia, Wolbachia and Cardinium in addition to previously reported Hamiltonella and Arsenopnohus. Siphoninus phillyreae harbored Hamiltonella, Wolbachia, Cardinium and Arsenophonus, with the latter appearing in two alleles. Multiple infections of all symbionts were common in the three insect species tested, with some reaching near fixation. Florescent in situ hybridization showed new localization patterns for Hamiltonella in S. phillyreae, and the morphology of the bacteriosome differed from that observed in other whitefly species. Our results show new infections with bacterial symbionts in the whitefly species studied. Infections with the same symbionts in reproductively isolated whitefly species confirm complex relationships between whiteflies and bacterial symbionts, and suggest possible horizontal transfer of some of these bacteria.

  7. Predation and physical environment structure the density and population size structure of zebra mussels

    OpenAIRE

    Naddafi, Rahmat; Pettersson, Kurt; Eklöv, Peter

    2010-01-01

    The zebra mussel (Dreissena polymorpha) provides one example of successful invaders in novel environments. However, little attention has been devoted to exploring the factors regulating zebra mussel density and population size structure at the local scale. We tested effects of physicochemical factors and fish predation on the density of zebra mussels at several sites and between years in a natural lake. Water depth and roach (Rutilus rutilus) density were the most important variables affectin...

  8. Population density of Lophodermium pinastri in living and fallen needles - Population analysis of a tree pathogen.

    OpenAIRE

    "畑 邦彦"

    2016-01-01

    2009-2013年度科学研究費助成事業(基盤研究(C))研究成果報告書 課題番号:21580185 研究代表者:畑邦彦(鹿児島大学・農学部・准教授) マツ葉ふるい病菌について生活史各時期における生息密度の指標を検討した結果、本菌はクローンレベルの体細胞不和合性を有しており、葉上では分離時のコロニー数をほぼクローン数とみなしうることが明らかになった。これに基づいて本菌の季節的、地理的変動を調査した結果、本菌の変動はかなり不規則であり、胞子飛散時期と感染時期が一致しないことや、同じ葉内に生息する他の菌との相互作用に強く影響されることが明らかになった。 "I examined what are proper indices of population density of Lophodermium pinastri. As a result, this fungus was proved to possess clone-level somatic incompatibility, which means that the numbers of colonies in i...

  9. Evidence-based control of canine rabies: a critical review of population density reduction.

    Science.gov (United States)

    Morters, Michelle K; Restif, Olivier; Hampson, Katie; Cleaveland, Sarah; Wood, James L N; Conlan, Andrew J K

    2013-01-01

    Control measures for canine rabies include vaccination and reducing population density through culling or sterilization. Despite the evidence that culling fails to control canine rabies, efforts to reduce canine population density continue in many parts of the world. The rationale for reducing population density is that rabies transmission is density-dependent, with disease incidence increasing directly with host density. This may be based, in part, on an incomplete interpretation of historical field data for wildlife, with important implications for disease control in dog populations. Here, we examine historical and more recent field data, in the context of host ecology and epidemic theory, to understand better the role of density in rabies transmission and the reasons why culling fails to control rabies. We conclude that the relationship between host density, disease incidence and other factors is complex and may differ between species. This highlights the difficulties of interpreting field data and the constraints of extrapolations between species, particularly in terms of control policies. We also propose that the complex interactions between dogs and people may render culling of free-roaming dogs ineffective irrespective of the relationship between host density and disease incidence. We conclude that vaccination is the most effective means to control rabies in all species. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

  10. Comparative analysis of methods of cartographic representation of population density in lithuania

    OpenAIRE

    Šturaitė, Aurelija

    2016-01-01

    Residents are one of conditions for state existance, therefore analysis of demographic characteristics is iportant not only in theoretical, but also practical aspect. Population density is one of the most important demographic characteristics which contains and also reflects economic, social, political and sometimes cultural meaning of region. Mapping of population density has dual objectives: on the one hand, representing quantity and distribution of residents in the analyzed area, on the ot...

  11. Correlations of Rotylenchulus reniformis Population Densities with 1,3-Dichloropropene Dosage Rate and Pineapple Yields

    OpenAIRE

    Schenck, Susan

    1990-01-01

    The relationships between Rotylenchulus reniformis population densities and pineapple growth and yield were studied in a small-plot field experiment. Increasing rates of handgun-injected 1,3-dichloropropene (1,3-D) preplant fumigant from 0 to 337 liters/ha resulted in greater nematode control, faster plant growth, and larger pineapple fruits. Rotylenchulus reniformis population densities at 2, 4, 6, and 8 months postplant were correlated with plant size and yield. The shorter the time period ...

  12. Population density-dependent hair cortisol concentrations in rhesus monkeys (Macaca mulatta).

    Science.gov (United States)

    Dettmer, A M; Novak, M A; Meyer, J S; Suomi, S J

    2014-04-01

    Population density is known to influence acute measures of hypothalamic-pituitary-adrenal (HPA) axis activity in a variety of species, including fish, deer, birds, and humans. However, the effects of population density on levels of chronic stress are unknown. Given the fact that exposure to chronically elevated levels of circulating glucocorticoids results in a host of health disparities in animals and humans alike, it is important to understand how population density may impact chronic stress. We assessed hair cortisol concentrations (HCCs), which are reliable indicators of chronic HPA axis activity, in rhesus monkeys (Macaca mulatta) to determine the influence of population density on these values. In Experiment 1, we compared HCCs of monkeys living in high-density (HD; 1 monkey/0.87m(2)) and low-density (LD; 1 monkey/63.37m(2)) environments (N=236 hair samples) and found that HD monkeys exhibited higher hair cortisol across all age categories (infant, juvenile, young adult, adult, and aged) except infancy and aged (F(5)=4.240, p=0.001), for which differences were nearly significant. HD monkeys also received more severe fight wounds than LD monkeys (χ(2)=26.053, ppopulation levels across 5 years in the adult LD monkeys (N=155 hair samples) and found that increased population density was significantly positively correlated with HCCs in this semi-naturalistic population (r(s)=0.975, p=0.005). These are the first findings to demonstrate that increased population density is associated with increased chronic, endogenous glucocorticoid exposure in a nonhuman primate species. We discuss the implications of these findings with respect to laboratory research, population ecology, and human epidemiology. Published by Elsevier Ltd.

  13. Determinants of pika population density vs. occupancy in the Southern Rocky Mountains.

    Science.gov (United States)

    Erb, Liesl P; Ray, Chris; Guralnick, Robert

    2014-04-01

    Species distributions are responding rapidly to global change. While correlative studies of local extinction have been vital to understanding the ecological impacts of global change, more mechanistic lines of inquiry are needed for enhanced forecasting. The current study assesses whether the predictors of local extinction also explain population density for a species apparently impacted by climate change. We tested a suite of climatic and habitat metrics as predictors of American pika (Ochotona princeps) relative population density in the Southern Rocky Mountains, USA. Population density was indexed as the density of pika latrine sites. Negative binomial regression and AICc showed that the best predictors of pika latrine density were patch area followed by two measures of vegetation quality: the diversity and relative cover of forbs. In contrast with previous studies of habitat occupancy in the Southern Rockies, climatic factors were not among the top predictors of latrine density. Populations may be buffered from decline and ultimately from extirpation at sites with high-quality vegetation. Conversely, populations at highest risk for declining density and extirpation are likely to be those in sites with poor-quality vegetation.

  14. Discontinuous Galerkin finite element method for solving population density functions of cortical pyramidal and thalamic neuronal populations.

    Science.gov (United States)

    Huang, Chih-Hsu; Lin, Chou-Ching K; Ju, Ming-Shaung

    2015-02-01

    Compared with the Monte Carlo method, the population density method is efficient for modeling collective dynamics of neuronal populations in human brain. In this method, a population density function describes the probabilistic distribution of states of all neurons in the population and it is governed by a hyperbolic partial differential equation. In the past, the problem was mainly solved by using the finite difference method. In a previous study, a continuous Galerkin finite element method was found better than the finite difference method for solving the hyperbolic partial differential equation; however, the population density function often has discontinuity and both methods suffer from a numerical stability problem. The goal of this study is to improve the numerical stability of the solution using discontinuous Galerkin finite element method. To test the performance of the new approach, interaction of a population of cortical pyramidal neurons and a population of thalamic neurons was simulated. The numerical results showed good agreement between results of discontinuous Galerkin finite element and Monte Carlo methods. The convergence and accuracy of the solutions are excellent. The numerical stability problem could be resolved using the discontinuous Galerkin finite element method which has total-variation-diminishing property. The efficient approach will be employed to simulate the electroencephalogram or dynamics of thalamocortical network which involves three populations, namely, thalamic reticular neurons, thalamocortical neurons and cortical pyramidal neurons. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Dietary Energy Density in the Australian Adult Population from National Nutrition Surveys 1995 to 2012.

    Science.gov (United States)

    Grech, Amanda Lee; Rangan, Anna; Allman-Farinelli, Margaret

    2017-12-01

    It is hypothesized that the observed proliferation of energy-dense, nutrient-poor foods globally is an important contributing factor to the development of the obesity epidemic. However, evidence that the population's dietary energy density has increased is sparse. The World Cancer Research Fund recommends that dietary energy density be energy density of the Australian population has changed between 1995 and 2012. A secondary analysis of two cross-sectional Australian national nutrition surveys from 1995 and 2011/2012 was conducted. Participants of the surveys included adults aged 18 years and older (1995 n=10,986 and 2011/2012 n=9,435) completing 24-hour dietary recalls, including a second recall for a subset of the population (10.4% in 1995 and 64.6% in 2011/2012). Outcome measures included the change in dietary energy density (calculated as energy/weight of food [kcal/g] for food only) between surveys. The National Cancer Institute method for "estimating ratios of two dietary components that are consumed nearly every day" was used to determine the usual distribution and the percentage of participants reporting energy density energy density was 1.59 (0.26) kcal/g and 1.64 (0.32) kcal/g (Penergy-density recommendations. For those aged 70 years and older, the percentage with energy density energy density energy density has increased between the two surveys and few people consumed low energy-dense diets in line with recommendations. The change was largely due to increased energy density of older adult's diets, while young adults had high dietary energy density at both time points. These data suggest efforts now focus on the evaluation of the role of modifying energy density of the diet to reduce the risk of weight gain in adults. Copyright © 2017 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

  16. Interaction between stocking density and settlement on population dynamics in suspended mussel culture

    Science.gov (United States)

    Cubillo, Alhambra M.; Fuentes-Santos, Isabel; Labarta, Uxío

    2015-01-01

    Population dynamics on mussels growing on suspended culture depend mainly on the balance of several processes: mortality and/or dislodgements from the ropes, recruitment and growth. The negative effect of overcrowding on mussel growth and survival has been widely studied. Other works have addressed the effect of population size on recruitment on bottom beds. This study aims to provide insight into the processes underlying population dynamics. To this purpose, we analyzed the effect of stocking density on mussel growth, survival and seed settlement, and the post-settlement interaction between adults and recruits in suspended culture. The temporal pattern of the variables involved in population dynamics was fitted by GAM models, which in contrast with parametric models does not assume any prior relationships between variables. Our results show that mussel growth and survival depend on a trade-off between competition for resources at high densities and the risk of great settlements in less crowded adult mussel populations. Intracohort competition increased with stocking density, while seed settlement, which increases the risk of mussel dislodgements and leads to intercohort competition, was higher at moderate stocking densities. Post-settlement competitive pressures were driven by total population density and size composition. Both intracohort competition in adults and asymmetric competition between adults and recruits increase with higher adult-recruit ratios. All these density-dependent processes should be considered in future management strategies and research experimental designs.

  17. Sexual minority population density and incidence of lung, colorectal and female breast cancer in California.

    Science.gov (United States)

    Boehmer, Ulrike; Miao, Xiaopeng; Maxwell, Nancy I; Ozonoff, Al

    2014-03-26

    Risk factors for breast, colorectal, and lung cancer are known to be more common among lesbian, gay, and bisexual (LGB) individuals, suggesting they may be more likely to develop these cancers. Our objective was to determine differences in cancer incidence by sexual orientation, using sexual orientation data aggregated at the county level. Data on cancer incidence were obtained from the California Cancer Registry and data on sexual orientation were obtained from the California Health Interview Survey, from which a measure of age-specific LGB population density by county was calculated. Using multivariable Poisson regression models, the association between the age-race-stratified incident rate of breast, lung and colorectal cancer in each county and LGB population density was examined, with race, age group and poverty as covariates. Among men, bisexual population density was associated with lower incidence of lung cancer and with higher incidence of colorectal cancer. Among women, lesbian population density was associated with lower incidence of lung and colorectal cancer and with higher incidence of breast cancer; bisexual population density was associated with higher incidence of lung and colorectal cancer and with lower incidence of breast cancer. These study findings clearly document links between county-level LGB population density and cancer incidence, illuminating an important public health disparity.

  18. Predicting Intra-Urban Population Densities in Africa using SAR and Optical Remote Sensing Data

    Science.gov (United States)

    Linard, C.; Steele, J.; Forget, Y.; Lopez, J.; Shimoni, M.

    2017-12-01

    The population of Africa is predicted to double over the next 40 years, driving profound social, environmental and epidemiological changes within rapidly growing cities. Estimations of within-city variations in population density must be improved in order to take urban heterogeneities into account and better help urban research and decision making, especially for vulnerability and health assessments. Satellite remote sensing offers an effective solution for mapping settlements and monitoring urbanization at different spatial and temporal scales. In Africa, the urban landscape is covered by slums and small houses, where the heterogeneity is high and where the man-made materials are natural. Innovative methods that combine optical and SAR data are therefore necessary for improving settlement mapping and population density predictions. An automatic method was developed to estimate built-up densities using recent and archived optical and SAR data and a multi-temporal database of built-up densities was produced for 48 African cities. Geo-statistical methods were then used to study the relationships between census-derived population densities and satellite-derived built-up attributes. Best predictors were combined in a Random Forest framework in order to predict intra-urban variations in population density in any large African city. Models show significant improvement of our spatial understanding of urbanization and urban population distribution in Africa in comparison to the state of the art.

  19. Disentangling the effects of climate, density dependence, and harvest on an iconic large herbivore's population dynamics

    DEFF Research Database (Denmark)

    Koons, David; Colchero, Fernando; Hersey, Kent

    2015-01-01

    Understanding the relative effects of climate, harvest, and density dependence on population dynamics is critical for guiding sound population management, especially for ungulates in arid and semi-arid environments experiencing climate change. To address these issues for bison in southern Utah, we...... spring temperature could have a greater ‘relative effect’ on equilibrium abundance than either harvest or the strength of density dependence. Our findings highlight the utility of incorporating elasticity analyses into state-space population models, and the need to include climatic processes in wildlife...... applied a Bayesian state-space model to a 72-year time series of abundance counts. While accounting for known harvest (as well as live removal) from the population, we found that the bison population in southern Utah exhibited strong potential to grow from low density (β0 = 0.26; Bayesian credible...

  20. Initial density affects biomass – density and allometric relationships in self-thinning populations of Fagopyrum esculentum

    DEFF Research Database (Denmark)

    Li, Lei; Weiner, Jacob; Zhou, Daowei

    2013-01-01

    and the biomass–density trajectory, we grew Fagopyrum esculentum populations at three high densities and measured shoot biomass, density and the height and diameter of individual plants at six harvests. * Initial density did not affect the slope of the log biomass–log density relationship, but there was a clear...... by the biomass density: the relationship between mass and volume. Initial density could affect this by altering allometric growth in a way that influences architectural compactness. An alternative hypothesis is that competition at higher initial density is more size symmetric, which has been shown to reduce...

  1. Pika Population Density Is Associated with the Composition and Diversity of Gut Microbiota

    Science.gov (United States)

    Li, Huan; Qu, Jiapeng; Li, Tongtong; Li, Jiabao; Lin, Qiang; Li, Xiangzhen

    2016-01-01

    Host population density is positively associated with the strength of social interactions or the frequency of physical contacts, and thus potentially influences microbial transmission among individuals. However, the relationship between host density and gut microbiota remains unknown. Here, we characterized the gut microbiota of plateau pikas (Ochotona curzoniae) in wild experimental fields with different host population densities. The abundance of some gut microbes significantly correlated with host density, such as Ruminococcaceae, Lachnospiraceae, and Staphylococcaceae. Intriguingly, host density was positively correlated with alpha diversity (Shannon diversity and observed species) of gut microbial communities. The inter-individual gut microbiota within high-density groups were more similar to each other than those of low-density groups. Host density significantly explained the variations in the gut microbiota, even after controlling sex, weight, diet and geographical locations. Based on the PICRUSt metagenome prediction, positive correlations were observed between host density and the relative abundances of 12 gene functions involved in cellular processes, environmental information processing and metabolism. These results indicate the importance of host density as a factor in shaping gut microbial composition and diversity in plateau pikas, and may further help us understand the social transmission of gut microbiota. PMID:27242770

  2. Pika Population Density Is Associated with the Composition and Diversity of Gut Microbiota.

    Science.gov (United States)

    Li, Huan; Qu, Jiapeng; Li, Tongtong; Li, Jiabao; Lin, Qiang; Li, Xiangzhen

    2016-01-01

    Host population density is positively associated with the strength of social interactions or the frequency of physical contacts, and thus potentially influences microbial transmission among individuals. However, the relationship between host density and gut microbiota remains unknown. Here, we characterized the gut microbiota of plateau pikas (Ochotona curzoniae) in wild experimental fields with different host population densities. The abundance of some gut microbes significantly correlated with host density, such as Ruminococcaceae, Lachnospiraceae, and Staphylococcaceae. Intriguingly, host density was positively correlated with alpha diversity (Shannon diversity and observed species) of gut microbial communities. The inter-individual gut microbiota within high-density groups were more similar to each other than those of low-density groups. Host density significantly explained the variations in the gut microbiota, even after controlling sex, weight, diet and geographical locations. Based on the PICRUSt metagenome prediction, positive correlations were observed between host density and the relative abundances of 12 gene functions involved in cellular processes, environmental information processing and metabolism. These results indicate the importance of host density as a factor in shaping gut microbial composition and diversity in plateau pikas, and may further help us understand the social transmission of gut microbiota.

  3. Disentangling the effects of climate, density dependence, and harvest on an iconic large herbivore's population dynamics.

    Science.gov (United States)

    Koons, David N; Colchero, Fernando; Hersey, Kent; Gimenez, Olivier

    2015-06-01

    Understanding the relative effects of climate, harvest, and density dependence on population dynamics is critical for guiding sound population management, especially for ungulates in arid and semiarid environments experiencing climate change. To address these issues for bison in southern Utah, USA, we applied a Bayesian state-space model to a 72-yr time series of abundance counts. While accounting for known harvest (as well as live removal) from the population, we found that the bison population in southern Utah exhibited a strong potential to grow from low density (β0 = 0.26; Bayesian credible interval based on 95% of the highest posterior density [BCI] = 0.19-0.33), and weak but statistically significant density dependence (β1 = -0.02, BCI = -0.04 to -0.004). Early spring temperatures also had strong positive effects on population growth (Pfat1 = 0.09, BCI = 0.04-0.14), much more so than precipitation and other temperature-related variables (model weight > three times more than that for other climate variables). Although we hypothesized that harvest is the primary driving force of bison population dynamics in southern Utah, our elasticity analysis indicated that changes in early spring temperature could have a greater relative effect on equilibrium abundance than either harvest or. the strength of density dependence. Our findings highlight the utility of incorporating elasticity analyses into state-space population models, and the need to include climatic processes in wildlife management policies and planning.

  4. The impact of urbanization and population density on childhood Plasmodium falciparum parasite prevalence rates in Africa.

    Science.gov (United States)

    Kabaria, Caroline W; Gilbert, Marius; Noor, Abdisalan M; Snow, Robert W; Linard, Catherine

    2017-01-26

    Although malaria has been traditionally regarded as less of a problem in urban areas compared to neighbouring rural areas, the risk of malaria infection continues to exist in densely populated, urban areas of Africa. Despite the recognition that urbanization influences the epidemiology of malaria, there is little consensus on urbanization relevant for malaria parasite mapping. Previous studies examining the relationship between urbanization and malaria transmission have used products defining urbanization at global/continental scales developed in the early 2000s, that overestimate actual urban extents while the population estimates are over 15 years old and estimated at administrative unit level. This study sought to discriminate an urbanization definition that is most relevant for malaria parasite mapping using individual level malaria infection data obtained from nationally representative household-based surveys. Boosted regression tree (BRT) modelling was used to determine the effect of urbanization on malaria transmission and if this effect varied with urbanization definition. In addition, the most recent high resolution population distribution data was used to determine whether population density had significant effect on malaria parasite prevalence and if so, could population density replace urban classifications in modelling malaria transmission patterns. The risk of malaria infection was shown to decline from rural areas through peri-urban settlements to urban central areas. Population density was found to be an important predictor of malaria risk. The final boosted regression trees (BRT) model with urbanization and population density gave the best model fit (Tukey test p value <0.05) compared to the models with urbanization only. Given the challenges in uniformly classifying urban areas across different countries, population density provides a reliable metric to adjust for the patterns of malaria risk in densely populated urban areas. Future malaria risk

  5. Density dependence in a recovering osprey population: demographic and behavioural processes.

    Science.gov (United States)

    Bretagnolle, V; Mougeot, F; Thibault, J-C

    2008-09-01

    1. Understanding how density-dependent and independent processes influence demographic parameters, and hence regulate population size, is fundamental within population ecology. We investigated density dependence in growth rate and fecundity in a recovering population of a semicolonial raptor, the osprey Pandion haliaetus [Linnaeus, 1758], using 31 years of count and demographic data in Corsica. 2. The study population increased from three pairs in 1974 to an average of 22 pairs in the late 1990s, with two distinct phases during the recovery (increase followed by stability) and contrasted trends in breeding parameters in each phase. 3. We show density dependence in population growth rate in the second phase, indicating that the stabilized population was regulated. We also show density dependence in productivity (fledging success between years and hatching success within years). 4. Using long-term data on behavioural interactions at nest sites, and on diet and fish provisioning rate, we evaluated two possible mechanisms of density dependence in productivity, food depletion and behavioural interference. 5. As density increased, both provisioning rate and the size of prey increased, contrary to predictions of a food-depletion mechanism. In the time series, a reduction in fledging success coincided with an increase in the number of non-breeders. Hatching success decreased with increasing local density and frequency of interactions with conspecifics, suggesting that behavioural interference was influencing hatching success. 6. Our study shows that, taking into account the role of non-breeders, in particular in species or populations where there are many floaters and where competition for nest sites is intense, can improve our understanding of density-dependent processes and help conservation actions.

  6. Population density of red langurs in Sabangau tropical peat-swamp forest, Central Kalimantan, Indonesia.

    Science.gov (United States)

    Ehlers Smith, David A; Ehlers Smith, Yvette C

    2013-08-01

    Because of the large-scale destruction of Borneo's rainforests on mineral soils, tropical peat-swamp forests (TPSFs) are increasingly essential for conserving remnant biodiversity, particularly in the lowlands where the majority of habitat conversion has occurred. Consequently, effective strategies for biodiversity conservation are required, which rely on accurate population density and distribution estimates as a baseline. We sought to establish the first population density estimates of the endemic red langur (Presbytis rubicunda) in Sabangau TPSF, the largest remaining contiguous lowland forest-block on Borneo. Using Distance sampling principles, we conducted line transect surveys in two of Sabangau's three principle habitat sub-classes and calculated group density at 2.52 groups km⁻² (95% CI 1.56-4.08) in the mixed-swamp forest sub-class. Based on an average recorded group size of 6.95 individuals, population density was 17.51 ind km⁻², the second highest density recorded in this species. The accessible area of the tall-interior forest, however, was too disturbed to yield density estimates representative of the entire sub-class, and P. rubicunda was absent from the low-pole forest, likely as a result of the low availability of the species' preferred foods. This absence in 30% of Sabangau's total area indicates the importance of in situ population surveys at the habitat-specific level for accurately informing conservation strategies. We highlight the conservation value of TPSFs for P. rubicunda given the high population density and large areas remaining, and recommend 1) quantifying the response of P. rubicunda to the logging and burning of its habitats; 2) surveying degraded TPSFs for viable populations, and 3) effectively delineating TPSF sub-class boundaries from remote imagery to facilitate population estimates across the wider peat landscape, given the stark contrast in densities found across the habitat sub-classes of Sabangau. © 2013 Wiley

  7. The role of weather and density dependence on population dynamics of Alpine-dwelling red deer.

    Science.gov (United States)

    Bonardi, Anna; Corlatti, Luca; Bragalanti, Natalia; Pedrotti, Luca

    2017-01-01

    The dynamics of red deer Cervus elaphus populations has been investigated across different environmental conditions, with the notable exception of the European Alps. Although the population dynamics of mountain-dwelling ungulates is typically influenced by the interaction between winter severity and density, the increase of temperatures and the reduction of snowpack occurring on the Alps since the 1980s may be expected to alter this pattern, especially in populations dwelling at medium - low elevations. Taking advantage of a 29-year time series of spring count data, we explored the role of weather stochasticity and density dependence on growth rate and vital rates (mortality and weaning success), and the density-dependent variation in body mass in a red deer population of the Italian Alps. The interaction between increasing values of density and snow depth exerted negative and positive effects on growth and mortality rates, respectively, while weaning success was negatively affected by increasing values of density, female-biased sex ratio and snow depth. Body mass of males and females of different age classes declined as population size increased. Our data support the role of winter severity and density dependence as key components of red deer population dynamics, and provide insight into the species' ecology on the European Alps. Despite the recent decline of snowpack on the Alpine Region, the negative impacts of winter severity and population abundance on growth rrate (possibly mediated by the density-dependent decline in body mass) confirms the importance of overwinter mortality in affecting the population dynamics of Alpine-dwelling red deer. © 2016 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

  8. Fitness Impact of Obligate Intranuclear Bacterial Symbionts Depends on Host Growth Phase.

    Science.gov (United States)

    Bella, Chiara; Koehler, Lars; Grosser, Katrin; Berendonk, Thomas U; Petroni, Giulio; Schrallhammer, Martina

    2016-01-01

    According to text book definition, parasites reduce the fitness of their hosts whereas mutualists provide benefits. But biotic and abiotic factors influence symbiotic interactions, thus under certain circumstances parasites can provide benefits and mutualists can harm their host. Here we addressed the question which intrinsic biotic factors shape a symbiosis and are crucial for the outcome of the interaction between the obligate intranuclear bacterium Holospora caryophila ( Alphaproteobacteria; Rickettsiales ) and its unicellular eukaryotic host Paramecium biaurelia (Alveolata; Ciliophora). The virulence of H. caryophila , i.e., the negative fitness effect on host division and cell number, was determined by growth assays of several P. biaurelia strains. The performances of genetically identical lines either infected with H. caryophila or symbiont-free were compared. Following factors were considered as potentially influencing the outcome of the interaction: (1) host strain, (2) parasite strain, and (3) growth phases of the host. All three factors revealed a strong effect on the symbiosis. In presence of H. caryophila , the Paramecium density in the stationary growth phase decreased. Conversely, a positive effect of the bacteria during the exponential phase was observed for several host × parasite combinations resulting in an increased growth rate of infected P. biaurelia . Furthermore, the fitness impact of the tested endosymbionts on different P. biaurelia lines was not only dependent on one of the two involved strains but distinct for the specific combination. Depending on the current host growth phase, the presence of H. caryophila can be harmful or advantageous for P. biaurelia . Thus, under the tested experimental conditions, the symbionts can switch from the provision of benefits to the exploitation of host resources within the same host population and a time-span of less than 6 days.

  9. An experimental field study of delayed density dependence in natural populations of Aedes albopictus.

    Directory of Open Access Journals (Sweden)

    Rachael K Walsh

    Full Text Available Aedes albopictus, a species known to transmit dengue and chikungunya viruses, is primarily a container-inhabiting mosquito. The potential for pathogen transmission by Ae. albopictus has increased our need to understand its ecology and population dynamics. Two parameters that we know little about are the impact of direct density-dependence and delayed density-dependence in the larval stage. The present study uses a manipulative experimental design, under field conditions, to understand the impact of delayed density dependence in a natural population of Ae. albopictus in Raleigh, North Carolina. Twenty liter buckets, divided in half prior to experimentation, placed in the field accumulated rainwater and detritus, providing oviposition and larval production sites for natural populations of Ae. albopictus. Two treatments, a larvae present and larvae absent treatment, were produced in each bucket. After five weeks all larvae were removed from both treatments and the buckets were covered with fine mesh cloth. Equal numbers of first instars were added to both treatments in every bucket. Pupae were collected daily and adults were frozen as they emerged. We found a significant impact of delayed density-dependence on larval survival, development time and adult body size in containers with high larval densities. Our results indicate that delayed density-dependence will have negative impacts on the mosquito population when larval densities are high enough to deplete accessible nutrients faster than the rate of natural food accumulation.

  10. Low larval densities in northern populations reinforce range expansion by a Mediterranean damselfly

    DEFF Research Database (Denmark)

    Therry, Lieven; Swaegers, Janne; Dinh, Khuong Van

    2016-01-01

    towards the very edge of the expansion front has been neglected. Density effects may, however, have a profound direct impact on traits involved in range expansion and influence range dynamics. 2. In this study, we contrast the effects of high conspecific larval density typical for established populations......1. Contemporary climate change triggers a poleward range shift in many species. A growing number of studies document evolutionary changes in traits accelerating range expansion (such as growth rate and dispersal-related traits). In contrast, the direct impact of decreasing conspecific densities...... and low larval density typical for newly founded populations at the edge of the expansion front on a set of larval traits that may affect the range dynamics in the poleward moving damselfly Coenagrion scitulum. We therefore ran an outdoor mesocosm experiment with a low- and high-density treatment close...

  11. Gridded Population of the World, Version 3 (GPWv3): Population Density Grid, Future Estimates

    Data.gov (United States)

    National Aeronautics and Space Administration — Gridded Population of the World, Version 3 (GPWv3), Future Estimates consists of estimates of human population for the years 2005, 2010, and 2015 by 2.5 arc-minute...

  12. Gridded Population of the World, Version 3 (GPWv3): Population Density Grid

    Data.gov (United States)

    National Aeronautics and Space Administration — Gridded Population of the World, Version 3 (GPWv3) consists of estimates of human population for the years 1990, 1995, and 2000 by 2.5 arc-minute grid cells and...

  13. Investment in constitutive immune function by North American elk experimentally maintained at two different population densities.

    Directory of Open Access Journals (Sweden)

    Cynthia J Downs

    Full Text Available Natural selection favors individuals that respond with effective and appropriate immune responses to macro or microparasites. Animals living in populations close to ecological carrying capacity experience increased intraspecific competition, and as a result are often in poor nutritional condition. Nutritional condition, in turn, affects the amount of endogenous resources that are available for investment in immune function. Our objective was to understand the relationship between immune function and density dependence mediated by trade-offs between immune function, nutritional condition, and reproduction. To determine how immune function relates to density-dependent processes, we quantified bacteria killing ability, hemolytic-complement activity, and nutritional condition of North American elk (Cervus elaphus from populations maintained at experimentally high- and low-population densities. When compared with elk from the low-density population, those from the high-density population had higher bacteria killing ability and hemolytic-complement activity despite their lower nutritional condition. Similarly, when compared with adults, yearlings had higher bacteria killing ability, higher hemolytic-complement activity, and lower nutritional condition. Pregnancy status and lactational status did not change either measure of constitutive immunity. Density-dependent processes affected both nutritional condition and investment in constitutive immune function. Although the mechanism for how density affects immunity is ambiguous, we hypothesize two possibilities: (i individuals in higher population densities and in poorer nutritional condition invested more into constitutive immune defenses, or (ii had higher parasite loads causing higher induced immune responses. Those explanations are not mutually exclusive, and might be synergistic, but overall our results provide stronger support for the hypothesis that animals in poorer nutritional condition invest

  14. Evidence of a high density population of harvested leopards in a montane environment.

    Science.gov (United States)

    Chase Grey, Julia N; Kent, Vivien T; Hill, Russell A

    2013-01-01

    Populations of large carnivores can persist in mountainous environments following extensive land use change and the conversion of suitable habitat for agriculture and human habitation in lower lying areas of their range. The significance of these populations is poorly understood, however, and little attention has focussed on why certain mountainous areas can hold high densities of large carnivores and what the conservation implications of such populations might be. Here we use the leopard (Panthera pardus) population in the western Soutpansberg Mountains, South Africa, as a model system and show that montane habitats can support high numbers of leopards. Spatially explicit capture-recapture (SECR) analysis recorded the highest density of leopards reported outside of state-protected areas in sub-Saharan Africa. This density represents a temporally high local abundance of leopards and we explore the explanations for this alongside some of the potential conservation implications.

  15. Evidence of a high density population of harvested leopards in a montane environment.

    Directory of Open Access Journals (Sweden)

    Julia N Chase Grey

    Full Text Available Populations of large carnivores can persist in mountainous environments following extensive land use change and the conversion of suitable habitat for agriculture and human habitation in lower lying areas of their range. The significance of these populations is poorly understood, however, and little attention has focussed on why certain mountainous areas can hold high densities of large carnivores and what the conservation implications of such populations might be. Here we use the leopard (Panthera pardus population in the western Soutpansberg Mountains, South Africa, as a model system and show that montane habitats can support high numbers of leopards. Spatially explicit capture-recapture (SECR analysis recorded the highest density of leopards reported outside of state-protected areas in sub-Saharan Africa. This density represents a temporally high local abundance of leopards and we explore the explanations for this alongside some of the potential conservation implications.

  16. Development of a spatially distributed model of fish population density for habitat assessment of rivers

    Science.gov (United States)

    Sui, Pengzhe; Iwasaki, Akito; Ryo, Masahiro; Saavedra, Oliver; Yoshimura, Chihiro

    2013-04-01

    Flow conditions play an important role in sustaining biodiversity of river ecosystem. However, their relations to freshwater fishes, especially to fish population density, have not been clearly described. This study, therefore, aimed to propose a new methodology to quantitatively link habitat conditions, including flow conditions and other physical conditions, to population density of fish species. We developed a basin-scale fish distribution model by integrating the concept of habitat suitability assessment with a distributed hydrological model (DHM) in order to estimate fish population density with particular attention to flow conditions. Generalized linear model (GLM) was employed to evaluate the relationship between population density of fish species and major environmental factors. The target basin was Sagami River in central Japan, where the river reach was divided into 10 sections by estuary, confluences of tributaries, and river-crossing structures (dams, weirs). The DHM was employed to simulate river discharge from 1998 to 2005, which was used to calculate 10 flow indices including mean discharge, 25th and 75th percentile discharge, duration of low and high flows, number of floods. In addition, 5 water quality parameters and 13 other physical conditions (such as basin area, river width, mean diameter of riverbed material, and number of river-crossing structures upstream and downstream) of each river section were considered as environmental variables. In case of Sagami River, 10 habitat variables among them were then selected based on their correlations to avoid multicollinearity. Finally, the best GLM was developed for each species based on Akaike's information criterion. As results, population densities of 16 fish species in Sagami River were modelled, and correlation coefficients between observed and calculated population densities for 10 species were more than 0.70. The key habitat factors for population density varied among fish species. Minimum

  17. Population densities of five migratory endoparasitic nematodes in carrot disk cultures.

    Science.gov (United States)

    Verdejo-Lucas, S; Pinochet, J

    1992-03-01

    Numbers of nematodes recovered per culture varied greatly among five species cultured on carrot disks. Radopholus similis and Pratylenchus vulnus showed the highest population densities, with 23,400-fold and 16,600-fold increases, respectively, in 90 days. Final populations of P. thornei and Zygotytenchus guevarai were similar but lower than those of R. similis and P. vulnus. The population of P. neglectus increased 74 times. Species with the greatest reproduction in this study reproduce sexually.

  18. Compensatory density feedback of Oncomelania hupensis populations in two different environmental settings in China.

    Science.gov (United States)

    Yang, Guo-Jing; Zhou, Xiao-Nong; Sun, Le-Ping; Wu, Feng; Zhong, Bo; Qiu, Dong-Chuan; Utzinger, Jürg; Bradshaw, Corey J A

    2011-07-13

    The most recent strategy for schistosomiasis control in the People's Republic of China aims to reduce the likelihood of environmental contamination of schistosome eggs. Despite considerable progress, it is believed that achievements would be further consolidated with additional intermediate host snail control measures. We provide an empirical framework for discerning the relative contribution of intrinsic effects (density feedback) from other extrinsic drivers of snail population dynamics. We set up experiments in two study locations to collect reproduction data of Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum. We applied a set of four population dynamic models that have been widely used to study phenomenological time-series data to examine the properties of demographic density feedback patterns from abundance data. We also contrasted the obtained results with the component feedback of density on survival rate to determine whether adult survival was the principal driver of the demographic feedback observed. Demographic density feedback models (Ricker- and Gompertz-logistic) accounted for > 99% of Akaike's information criterion model weight, with the Gompertz ranking highest in all O. hupensis population groups. We found some evidence for stronger compensatory feedback in the O. hupensis population from Sichuan compared to a Jiangsu population. Survival rates revealed strong component feedback, but the log-linear relationships (i.e. Gompertz) had less support in the demographic feedback analysis. Our findings indicate that integrated schistosomiasis control measures must continue to reduce parasite abundance further because intermediate host snail populations tend to grow exponentially at low densities, especially O. hupensis populations in mountainous regions. We conclude that density feedback in adult survival is the principal component contribution to the demographic phenomenon observed in the population fitness (r

  19. Compensatory density feedback of Oncomelania hupensis populations in two different environmental settings in China

    Science.gov (United States)

    2011-01-01

    Background The most recent strategy for schistosomiasis control in the People's Republic of China aims to reduce the likelihood of environmental contamination of schistosome eggs. Despite considerable progress, it is believed that achievements would be further consolidated with additional intermediate host snail control measures. We provide an empirical framework for discerning the relative contribution of intrinsic effects (density feedback) from other extrinsic drivers of snail population dynamics. Methods We set up experiments in two study locations to collect reproduction data of Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum. We applied a set of four population dynamic models that have been widely used to study phenomenological time-series data to examine the properties of demographic density feedback patterns from abundance data. We also contrasted the obtained results with the component feedback of density on survival rate to determine whether adult survival was the principal driver of the demographic feedback observed. Results Demographic density feedback models (Ricker- and Gompertz-logistic) accounted for > 99% of Akaike's information criterion model weight, with the Gompertz ranking highest in all O. hupensis population groups. We found some evidence for stronger compensatory feedback in the O. hupensis population from Sichuan compared to a Jiangsu population. Survival rates revealed strong component feedback, but the log-linear relationships (i.e. Gompertz) had less support in the demographic feedback analysis. Conclusions Our findings indicate that integrated schistosomiasis control measures must continue to reduce parasite abundance further because intermediate host snail populations tend to grow exponentially at low densities, especially O. hupensis populations in mountainous regions. We conclude that density feedback in adult survival is the principal component contribution to the demographic phenomenon observed in the

  20. Co-niche construction between hosts and symbionts

    Indian Academy of Sciences (India)

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

  1. Co-niche construction between hosts and symbionts: ideas and ...

    Indian Academy of Sciences (India)

    2017-07-05

    Jul 5, 2017 ... Symbiosis is a process that can generate evolutionary novelties and can extend the phenotypic niche space of organisms. Symbionts can act together with their hosts to co-construct host organs, within which symbionts are housed. Once established within hosts, symbionts can also influence various ...

  2. Allometric scaling of population variance with mean body size is predicted from Taylor's law and density-mass allometry.

    Science.gov (United States)

    Cohen, Joel E; Xu, Meng; Schuster, William S F

    2012-09-25

    Two widely tested empirical patterns in ecology are combined here to predict how the variation of population density relates to the average body size of organisms. Taylor's law (TL) asserts that the variance of the population density of a set of populations is a power-law function of the mean population density. Density-mass allometry (DMA) asserts that the mean population density of a set of populations is a power-law function of the mean individual body mass. Combined, DMA and TL predict that the variance of the population density is a power-law function of mean individual body mass. We call this relationship "variance-mass allometry" (VMA). We confirmed the theoretically predicted power-law form and the theoretically predicted parameters of VMA, using detailed data on individual oak trees (Quercus spp.) of Black Rock Forest, Cornwall, New York. These results connect the variability of population density to the mean body mass of individuals.

  3. Modeling the impact of the indigenous microbial population on the maximum population density of Salmonella on alfalfa

    NARCIS (Netherlands)

    Rijgersberg, H.; Nierop Groot, M.N.; Tromp, S.O.; Franz, E.

    2013-01-01

    Within a microbial risk assessment framework, modeling the maximum population density (MPD) of a pathogenic microorganism is important but often not considered. This paper describes a model predicting the MPD of Salmonella on alfalfa as a function of the initial contamination level, the total count

  4. Sexual conflict and the evolution of asexuality at low population densities

    Science.gov (United States)

    Kokko, Hanna

    2016-01-01

    Theories for the evolution of sex rarely include facultatively sexual reproduction. Sexual harassment by males is an underappreciated factor: it should at first sight increase the relative advantage of asexual reproduction by increasing the cost of sex. However, if the same females can perform either sexual or asexual life cycles, then females trying to reproduce asexually may not escape harassment. If resisting male harassment is costly, it might be beneficial for a female to accept a mating and undertake a sexual life cycle rather than ‘insist’ on an asexual one. We investigate the effects of sexual harassment on the maintenance of sex under different population densities. Our model shows that resisting matings pays off at low population densities, which leads to the complete extinction of males, and thus to the evolution of completely asexual populations. Facultative sex persists in a narrow range of slightly higher densities. At high densities, selection favours giving up resisting male mating attempts and thus sexual reproduction takes over. These interactions between the outcomes of sexual conflict and population density suggest an explanation for the rarity of facultative sex and also patterns of geographical parthenogenesis, where marginal environments with potentially low densities are associated with asexuality. PMID:27798298

  5. Social deprivation and population density are not associated with small area risk of amyotrophic lateral sclerosis.

    Science.gov (United States)

    Rooney, James P K; Tobin, Katy; Crampsie, Arlene; Vajda, Alice; Heverin, Mark; McLaughlin, Russell; Staines, Anthony; Hardiman, Orla

    2015-10-01

    Evidence of an association between areal ALS risk and population density has been previously reported. We aim to examine ALS spatial incidence in Ireland using small areas, to compare this analysis with our previous analysis of larger areas and to examine the associations between population density, social deprivation and ALS incidence. Residential area social deprivation has not been previously investigated as a risk factor for ALS. Using the Irish ALS register, we included all cases of ALS diagnosed in Ireland from 1995-2013. 2006 census data was used to calculate age and sex standardised expected cases per small area. Social deprivation was assessed using the pobalHP deprivation index. Bayesian smoothing was used to calculate small area relative risk for ALS, whilst cluster analysis was performed using SaTScan. The effects of population density and social deprivation were tested in two ways: (1) as covariates in the Bayesian spatial model; (2) via post-Bayesian regression. 1701 cases were included. Bayesian smoothed maps of relative risk at small area resolution matched closely to our previous analysis at a larger area resolution. Cluster analysis identified two areas of significant low risk. These areas did not correlate with population density or social deprivation indices. Two areas showing low frequency of ALS have been identified in the Republic of Ireland. These areas do not correlate with population density or residential area social deprivation, indicating that other reasons, such as genetic admixture may account for the observed findings. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Population density and racial differences in the performance of emergency medical services.

    Science.gov (United States)

    David, Guy; Harrington, Scott E

    2010-07-01

    This paper analyzes the existence and scope of possible racial differences/disparities in the provision of emergency medical services (EMS) response capability (time from dispatch to arrival at the scene and level of training of the responding team) using data on approximately 120,000 cardiac incidents in the state of Mississippi during 1995-2004. The conceptual framework and empirical analysis focus on the likely effects of population density on the efficient production of EMS as a local public good subject to congestion, and on the need to control adequately for population density to avoid bias in testing for racial differences. Models that control for aggregate population density at the county-level indicate "reverse" disparities: faster estimated response times for African-Americans than for whites. When a refined county-level measure of population density is used that incorporates differences in African-American and white population density by Census tract, the reverse disparity in response times disappears. There also is little or no evidence of race-related differences in the certification level of EMS responders. However, there is evidence that, controlling for response time, African-Americans on average were significantly more likely to be deceased than whites upon EMS arrival at the scene. The overall results are germane to the debate over the scope of conditioning variables that should be included when testing for racial disparities in health care.

  7. Sphingolipid Metabolism of a Sea Anemone Is Altered by the Presence of Dinoflagellate Symbionts.

    Science.gov (United States)

    Kitchen, Sheila A; Poole, Angela Z; Weis, Virginia M

    2017-12-01

    In host-microbe interactions, signaling lipids function in interpartner communication during both the establishment and maintenance of associations. Previous evidence suggests that sphingolipids play a role in the mutualistic cnidarian-Symbiodinium symbiosis. Exogenously applied sphingolipids have been shown to alter this partnership, though endogenous host regulation of sphingolipids by the sphingosine rheostat under different symbiotic conditions has not been characterized. The rheostat regulates levels of pro-survival sphingosine-1-phosphate (S1P) and pro-apoptotic sphingosine (Sph) through catalytic activities of sphingosine kinase (SPHK) and S1P phosphatase (SGPP). The role of the rheostat in recognition and establishment of cnidarian-Symbiodinium symbiosis was investigated in the sea anemone Aiptasia pallida by measuring gene expression, protein levels, and sphingolipid metabolites in symbiotic, aposymbiotic, and newly recolonized anemones. Comparison of two host populations showed that symbiotic animals from one population had lower SGPP gene expression and Sph lipid concentrations compared to aposymbiotic animals, while the other population had higher S1P concentrations than their aposymbiotic counterparts. In both populations, the host rheostat trended toward host cell survival in the presence of symbionts. Furthermore, upregulation of both rheostat enzymes on the first day of host recolonization by symbionts suggests a role for the rheostat in host-symbiont recognition during symbiosis onset. Collectively, these data suggest a regulatory role of sphingolipid signaling in cnidarian-Symbiodinium symbiosis and symbiont uptake.

  8. Sensitivity of condition indices to changing density in a white-tailed deer population

    Science.gov (United States)

    Sams, M.G.; Lochmiller, R.L.; Qualls, C.W.; Leslie, David M.

    1998-01-01

    The ways in which comprehensive condition profiles, incorporating morphometric, histologic, physiologic, and diet quality indices, responded to changes in density of a white-tailed deer (Odocoileus virginianus) population were examined. Changes in these condition indices were monitored in a northeastern Oklahoma deer herd as density declined from peaks of 80 and 72 deer/km2 in 1989 and 1990 (high-density) to lows of 39 and 41 deer/km2 in 1991 and 1992 (reduced-density), respectively. Compared to a reference population (6 deer/km2), deer sampled during high-density exhibited classic signs of nutritional stress such as low body and visceral organ masses (except elevated adrenal gland mass), low fecal nitrogen levels, reduced concentrations of serum albumin, elevated serum creatinine concentrations, and a high prevalence of parasitic infections. Although density declined by one half over the 4-yr study, gross indices of condition (in particular body mass and size) remained largely unchanged. However, selected organ masses, serum albumin and non-protein nitrogen constituents, and fecal nitrogen indices reflected improvements in nutritional status with reductions in density. Many commonly used indices of deer condition (fat reserves, hematocrit, total serum protein, and blood urea nitrogen) were not responsive to fluctuations in density. ?? Wildlife Disease Association 1998.

  9. Aphid thermal tolerance is governed by a point mutation in bacterial symbionts.

    Directory of Open Access Journals (Sweden)

    Helen E Dunbar

    2007-05-01

    Full Text Available Symbiosis is a ubiquitous phenomenon generating biological complexity, affecting adaptation, and expanding ecological capabilities. However, symbionts, which can be subject to genetic limitations such as clonality and genomic degradation, also impose constraints on hosts. A model of obligate symbiosis is that between aphids and the bacterium Buchnera aphidicola, which supplies essential nutrients. We report a mutation in Buchnera of the aphid Acyrthosiphon pisum that recurs in laboratory lines and occurs in field populations. This single nucleotide deletion affects a homopolymeric run within the heat-shock transcriptional promoter for ibpA, encoding a small heat-shock protein. This Buchnera mutation virtually eliminates the transcriptional response of ibpA to heat stress and lowers its expression even at cool or moderate temperatures. Furthermore, this symbiont mutation dramatically affects host fitness in a manner dependent on thermal environment. Following a short heat exposure as juveniles, aphids bearing short-allele symbionts produced few or no progeny and contained almost no Buchnera, in contrast to aphids bearing symbionts without the deletion. Conversely, under constant cool conditions, aphids containing symbionts with the short allele reproduced earlier and maintained higher reproductive rates. The short allele has appreciable frequencies in field populations (up to 20%, further supporting the view that lowering of ibpA expression improves host fitness under some conditions. This recurring Buchnera mutation governs thermal tolerance of aphid hosts. Other cases in which symbiont microevolution has a major effect on host ecological tolerance are likely to be widespread because of the high mutation rates of symbiotic bacteria and their crucial roles in host metabolism and development.

  10. Population density does not influence male gonadal investment in the Least Killifish, Heterandria formosa.

    Science.gov (United States)

    Schrader, Matthew; Apodaca, Joseph J; Macrae, Pamela S D; Travis, Joseph

    2012-12-01

    Comparative studies documenting a relationship between male gonadal investment and the degree of sperm competition (SC) have usually considered the association between these traits to be driven by qualitative differences in the mating system, such as whether spawning occurs in pairs or groups. However, ecological and demographic differences between conspecific populations may also generate variation in the importance of SC that can drive the evolution of male gonadal investment. In this study, we examined whether variation in population density, which is predicted to influence the level of SC in many animals, is correlated with male gonadal investment among populations of the least killifish, Heterandria formosa, a species with internal fertilization in which multiple mating is common. We complemented this field study by testing whether males respond plastically to experimentally increased levels of SC by increasing investment in testis. This experiment involved two treatments. In the first, we eliminated the potential for sperm competition (NSC) by housing a single male with a single female. In the second, we created a high risk of SC by housing five males with two females. In the field survey, we found significant differences among populations in density and relative testis mass. However, there was no evidence for a correlation between population density and relative testis mass. In our lab experiment, males did not adjust their gonadal investment in response to experiencing different levels of SC for 4 weeks. Our combined results indicate that gonadal investment in male H. formosa is not related to variation in population density.

  11. Age structure and growth of wild brown trout in relation to population density and habitat quality

    OpenAIRE

    Závorka, Libor

    2015-01-01

    Brown trout Salmo trutta L. is a fish species with high socio-economic value, which is favourable among anglers and a successful invader worldwide. The aim of this thesis is to explore environmental factors affecting body growth and survival of brown trout with emphasis on density dependent selection in juvenile life stages. This thesis is specifically focused on: (1) effect of population density on growth and survival with respect to a dynamic of a local group of individuals (papers I and II...

  12. Identification of the population density of a species model with nonlocal diffusion and nonlinear reaction

    Science.gov (United States)

    Tuan, Nguyen Huy; Van Au, Vo; Khoa, Vo Anh; Lesnic, Daniel

    2017-05-01

    The identification of the population density of a logistic equation backwards in time associated with nonlocal diffusion and nonlinear reaction, motivated by biology and ecology fields, is investigated. The diffusion depends on an integral average of the population density whilst the reaction term is a global or local Lipschitz function of the population density. After discussing the ill-posedness of the problem, we apply the quasi-reversibility method to construct stable approximation problems. It is shown that the regularized solutions stemming from such method not only depend continuously on the final data, but also strongly converge to the exact solution in L 2-norm. New error estimates together with stability results are obtained. Furthermore, numerical examples are provided to illustrate the theoretical results.

  13. Genetic Diversity and Population Structure of Ethiopian Sheep Populations Revealed by High-Density SNP Markers

    Directory of Open Access Journals (Sweden)

    Zewdu Edea

    2017-12-01

    Full Text Available Sheep in Ethiopia are adapted to a wide range of environments, including extreme habitats. Elucidating their genetic diversity is critical for improving breeding strategies and mapping quantitative trait loci associated with productivity. To this end, the present study investigated the genetic diversity and population structure of five Ethiopian sheep populations exhibiting distinct phenotypes and sampled from distinct production environments, including arid lowlands and highlands. To investigate the genetic relationships in greater detail and infer population structure of Ethiopian sheep breeds at the continental and global levels, we analyzed genotypic data of selected sheep breeds from the Ovine SNP50K HapMap dataset. All Ethiopian sheep samples were genotyped with Ovine Infinium HD SNP BeadChip (600K. Mean genetic diversity ranged from 0.29 in Arsi-Bale to 0.32 in Menz sheep, while estimates of genetic differentiation among populations ranged from 0.02 to 0.07, indicating low to moderate differentiation. An analysis of molecular variance revealed that 94.62 and 5.38% of the genetic variation was attributable to differences within and among populations, respectively. Our population structure analysis revealed clustering of five Ethiopian sheep populations according to tail phenotype and geographic origin—i.e., short fat-tailed (very cool high-altitude, long fat-tailed (mid to high-altitude, and fat-rumped (arid low-altitude, with clear evidence of admixture between long fat-tailed populations. North African sheep breeds showed higher levels of within-breed diversity, but were less differentiated than breeds from Eastern and Southern Africa. When African breeds were grouped according to geographic origin (North, South, and East, statistically significant differences were detected among groups (regions. A comparison of population structure between Ethiopian and global sheep breeds showed that fat-tailed breeds from Eastern and Southern Africa

  14. Genetic Variation and Phenotypic Response of 15 Sweet Corn (Zea mays L. Hybrids to Population Density

    Directory of Open Access Journals (Sweden)

    William F. Tracy

    2013-06-01

    Full Text Available Planting sweet corn at higher densities may increase the canopy cover, reducing light transmission to the understory and suppressing weed growth. High planting densities can also negatively impact the crop, however, by decreasing ear size and overall yield. The objective of this study was to determine the potential for increased density tolerance of 15 sweet corn hybrids by estimating the general combining ability (GCA and specific combining ability (SCA for traits of interest. In 2010 and 2011, a half-diallel of six historic sweet corn inbreds was evaluated in a split-block randomized complete block design in four Wisconsin environments, with four replicates in each environment. Hybrids were planted at a low density of 29,936 plants ha−1, a medium density of 63,615 plants ha−1, and a high density of 97,293 plants ha−1. Significant differences between hybrids were found for phenomorphological traits and ear characteristics. Inbreds C68, C40 and Ia5125 produced the progeny most tolerant of the highest population density. Among these genotypes, tolerance to high density is a heritable trait, indicating the feasibility of breeding sweet corn for density tolerance and potential weed competitiveness.

  15. Social insect symbionts: evolution in homeostatic fortresses

    DEFF Research Database (Denmark)

    Hughes, David P; Pierce, Naomi E; Boomsma, Jacobus J

    2008-01-01

    The massive environmentally buffered nests of some social insects can contain millions of individuals and a wide variety of parasites, commensals and mutualists. We suggest that the ways in which these homeostatic fortress environments affect the evolution of social insect symbionts are relevant ...

  16. Influence of microbial symbionts on insect pheromones.

    Science.gov (United States)

    Engl, Tobias; Kaltenpoth, Martin

    2018-03-22

    Covering: up to 2018Pheromones serve as chemical signals between individuals of the same species and play important roles for mate localization and mate choice as well as other social interactions in insects. A growing body of literature indicates that microbial symbionts can modulate their hosts' chemical profiles, mate choice decisions and social behavior. This modulation can occur by the direct biosynthesis of pheromone components or the provisioning of precursors, or through general changes in the metabolite pool of the host and its resource allocation into pheromone production. Here we review and discuss the contexts in which microbial modulation of intraspecific communication in insects occurs and emphasize cases in which microbes are known to affect the involved chemistry. The described examples for a symbiotic influence on mate attraction and mate choice, aggregation, nestmate and kin recognition highlight the context-dependent costs and benefits of these symbiotic interactions and the potential for conflict and manipulation among the interacting partners. However, despite the increasing number of studies reporting on symbiont-mediated effects on insect chemical communication, experimentally validated connections between the presence of specific symbionts, changes in the host's chemistry, and behavioral effects thereof, remain limited to very few systems, highlighting the need for increased collaborative efforts between symbiosis researchers and chemical ecologists to gain more comprehensive insights into the influence of microbial symbionts on insect pheromones.

  17. Potential applications of insect symbionts in biotechnology.

    Science.gov (United States)

    Berasategui, Aileen; Shukla, Shantanu; Salem, Hassan; Kaltenpoth, Martin

    2016-02-01

    Symbiotic interactions between insects and microorganisms are widespread in nature and are often the source of ecological innovations. In addition to supplementing their host with essential nutrients, microbial symbionts can produce enzymes that help degrade their food source as well as small molecules that defend against pathogens, parasites, and predators. As such, the study of insect ecology and symbiosis represents an important source of chemical compounds and enzymes with potential biotechnological value. In addition, the knowledge on insect symbiosis can provide novel avenues for the control of agricultural pest insects and vectors of human diseases, through targeted manipulation of the symbionts or the host-symbiont associations. Here, we discuss different insect-microbe interactions that can be exploited for insect pest and human disease control, as well as in human medicine and industrial processes. Our aim is to raise awareness that insect symbionts can be interesting sources of biotechnological applications and that knowledge on insect ecology can guide targeted efforts to discover microorganisms of applied value.

  18. Density and population viability of coastal marten: a rare and geographically isolated small carnivore.

    Science.gov (United States)

    Linnell, Mark A; Moriarty, Katie; Green, David S; Levi, Taal

    2018-01-01

    Pacific martens ( Martes caurina humboldtensis ) in coastal forests of Oregon and northern California in the United States are rare and geographically isolated, prompting a petition for listing under the Endangered Species Act. If listed, regulations have the potential to influence land-use decisions on public and private lands, but no estimates of population size, density, or viability of remnant marten populations are available for evaluating their conservation status. We used GPS and VHF telemetry and spatial mark-resight to estimate home ranges, density, and population size of Pacific martens in the Oregon Dunes National Recreation Area, central coast Oregon, USA. We then estimated population viability at differing levels of human-caused mortality (e.g., vehicle mortality). Marten home ranges were small on average (females = 0.8 km 2 , males 1.5 km 2 ) and density (1.13 martens/1 km 2 ) was the highest reported for North American populations ( M. caurina , M. americana ). We estimated 71 adult martens (95% CRI [41-87]) across two subpopulations separated by a large barrier (Umpqua River). Using population viability analysis, extinction risk for a subpopulation of 30 martens, approximately the size of the subpopulation south of the Umpqua River, ranged from 32% to 99% with two or three annual human-caused mortalities within 30 years. Absent population expansion, limiting human-caused mortalities will likely have the greatest conservation impact.

  19. Local environment and density-dependent feedbacks determine population growth in a forest herb

    DEFF Research Database (Denmark)

    Dahlgren, Johan Petter; Östergård, Hannah; Ehrlén, Johan

    2014-01-01

    to observe in natural populations. We conducted a detailed field study and investigated simultaneous effects of environmental factors and the intraspecific density of individuals on the demography of the herb Lathyrus vernus. In regression models of vital rates we identified effects associated with spring...... that were less shaded by the tree canopy, indicating an environmentally determined carrying capacity. A size-structured integral projection model based on the vital rate regressions revealed that the identified effects of shade and density were strong enough to produce differences in stable population sizes...

  20. Switching from negative to positive density-dependence among populations of a cobble beach plant.

    Science.gov (United States)

    Goldenheim, William M; Irving, Andrew D; Bertness, Mark D

    2008-12-01

    Interactions among species occur across a continuum from negative to positive and can have a critical role in shaping population and community dynamics. Growing evidence suggests that inter- and intra-specific interactions can vary in strength or even switch direction (i.e., negative to positive) depending on environmental conditions, consumer pressure, and also among life-history stages. We tested the hypothesis that seedlings and adults of the intertidal annual forb Suaeda linearis growing on New England shores exhibit positive density-dependence under physically stressful conditions high on the shore (i.e., greater temperatures, evaporative stress), but negative density-dependence under physically milder conditions low on the shore. Among experimental treatments of plant density (dense versus sparse) at each shore height, plant biomass, length, and number of leaves/branches were greater in dense stands high on the shore (positive density-dependence), but greater in sparse stands low on the shore (negative density-dependence). Such responses were consistent among life-history stages and generally consistent between sites. As a more direct measure of fitness, per capita seed production was also positively density-dependent high on the shore, but negatively density-dependent low on the shore. These results support the current theory predicting an increase in the frequency of positive interactions with increasing environmental stress and further emphasize the previously understated role of positive interactions in shaping and maintaining populations and communities.

  1. Effects of demographic structure on key properties of stochastic density-independent population dynamics.

    Science.gov (United States)

    Vindenes, Yngvild; Sæther, Bernt-Erik; Engen, Steinar

    2012-12-01

    The development of stochastic demography has largely been based on age structured populations, although other types of demographic structure, especially permanent and dynamic heterogeneity, are likely common in natural populations. The combination of stochasticity and demographic structure is a challenge for analyses of population dynamics and extinction risk, because the population structure will fluctuate around the stable structure and the population size shows transient fluctuations. However, by using a diffusion approximation for the total reproductive value, density-independent dynamics of structured populations can be described with only three population parameters: the expected population growth rate, the environmental variance and the demographic variance. These parameters depend on population structure via the state-specific vital rates and transition rates. Once they are found, the diffusion approximation represents a substantial reduction in model complexity. Here, we review and compare the key population parameters across a wide range of demographic structure, from the case of no structure to the most general case of dynamic heterogeneity, and for both discrete and continuous types. We focus on the demographic variance, but also show how environmental stochasticity can be included. This study brings together results from recent models, each considering a specific type of population structure, and places them in a general framework for structured populations. Comparison across different types of demographic structure reveals that the reproductive value is an essential concept for understanding how population structure affects stochastic dynamics and extinction risk. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. Population model of hippocampal pyramidal neurons, linking a refractory density approach to conductance-based neurons

    Science.gov (United States)

    Chizhov, Anton V.; Graham, Lyle J.

    2007-01-01

    We propose a macroscopic approach toward realistic simulations of the population activity of hippocampal pyramidal neurons, based on the known refractory density equation with a different hazard function and on a different single-neuron threshold model. The threshold model is a conductance-based model taking into account adaptation-providing currents, which is reduced by omitting the fast sodium current and instead using an explicit threshold criterion for action potential events. Compared to the full pyramidal neuron model, the threshold model well approximates spike-time moments, postspike refractory states, and postsynaptic current integration. The dynamics of a neural population continuum are described by a set of one-dimensional partial differential equations in terms of the distributions of the refractory density (where the refractory state is defined by the time elapsed since the last action potential), the membrane potential, and the gating variables of the voltage-dependent channels, across the entire population. As the source term in the density equation, the probability density of firing, or hazard function, is derived from the Fokker-Planck (FP) equation, assuming that a single neuron is governed by a deterministic average-across-population input and a noise term. A self-similar solution of the FP equation in the subthreshold regime is obtained. Responses of the ensemble to stimulation by a current step and oscillating current are simulated and compared with individual neuron simulations. An example of interictal-like activity of a population of all-to-all connected excitatory neurons is presented.

  3. Population density models of integrate-and-fire neurons with jumps: well-posedness.

    Science.gov (United States)

    Dumont, Grégory; Henry, Jacques

    2013-09-01

    In this paper we study the well-posedness of different models of population of leaky integrate-and-fire neurons with a population density approach. The synaptic interaction between neurons is modeled by a potential jump at the reception of a spike. We study populations that are self excitatory or self inhibitory. We distinguish the cases where this interaction is instantaneous from the one where there is a repartition of conduction delays. In the case of a bounded density of delays both excitatory and inhibitory population models are shown to be well-posed. But without conduction delay the solution of the model of self excitatory neurons may blow up. We analyze the different behaviours of the model with jumps compared to its diffusion approximation.

  4. [On the relation between encounter rate and population density: Are classical models of population dynamics justified?].

    Science.gov (United States)

    Nedorezov, L V

    2015-01-01

    A stochastic model of migrations on a lattice and with discrete time is considered. It is assumed that space is homogenous with respect to its properties and during one time step every individual (independently of local population numbers) can migrate to nearest nodes of lattice with equal probabilities. It is also assumed that population size remains constant during certain time interval of computer experiments. The following variants of estimation of encounter rate between individuals are considered: when for the fixed time moments every individual in every node of lattice interacts with all other individuals in the node; when individuals can stay in nodes independently, or can be involved in groups in two, three or four individuals. For each variant of interactions between individuals, average value (with respect to space and time) is computed for various values of population size. The samples obtained were compared with respective functions of classic models of isolated population dynamics: Verhulst model, Gompertz model, Svirezhev model, and theta-logistic model. Parameters of functions were calculated with least square method. Analyses of deviations were performed using Kolmogorov-Smirnov test, Lilliefors test, Shapiro-Wilk test, and other statistical tests. It is shown that from traditional point of view there are no correspondence between the encounter rate and functions describing effects of self-regulatory mechanisms on population dynamics. Best fitting of samples was obtained with Verhulst and theta-logistic models when using the dataset resulted from the situation when every individual in the node interacts with all other individuals.

  5. Spontaneous mutation rate is a plastic trait associated with population density across domains of life.

    Science.gov (United States)

    Krašovec, Rok; Richards, Huw; Gifford, Danna R; Hatcher, Charlie; Faulkner, Katy J; Belavkin, Roman V; Channon, Alastair; Aston, Elizabeth; McBain, Andrew J; Knight, Christopher G

    2017-08-01

    Rates of random, spontaneous mutation can vary plastically, dependent upon the environment. Such plasticity affects evolutionary trajectories and may be adaptive. We recently identified an inverse plastic association between mutation rate and population density at 1 locus in 1 species of bacterium. It is unknown how widespread this association is, whether it varies among organisms, and what molecular mechanisms of mutagenesis or repair are required for this mutation-rate plasticity. Here, we address all 3 questions. We identify a strong negative association between mutation rate and population density across 70 years of published literature, comprising hundreds of mutation rates estimated using phenotypic markers of mutation (fluctuation tests) from all domains of life and viruses. We test this relationship experimentally, determining that there is indeed density-associated mutation-rate plasticity (DAMP) at multiple loci in both eukaryotes and bacteria, with up to 23-fold lower mutation rates at higher population densities. We find that the degree of plasticity varies, even among closely related organisms. Nonetheless, in each domain tested, DAMP requires proteins scavenging the mutagenic oxidised nucleotide 8-oxo-dGTP. This implies that phenotypic markers give a more precise view of mutation rate than previously believed: having accounted for other known factors affecting mutation rate, controlling for population density can reduce variation in mutation-rate estimates by 93%. Widespread DAMP, which we manipulate genetically in disparate organisms, also provides a novel trait to use in the fight against the evolution of antimicrobial resistance. Such a prevalent environmental association and conserved mechanism suggest that mutation has varied plastically with population density since the early origins of life.

  6. Estimation of the population density of the sweetpotato weevils on the Mariana Islands

    Directory of Open Access Journals (Sweden)

    Gadi V.P. Reddy

    2012-05-01

    Full Text Available The sweetpotato Ipomoea batatas L. (Convolvulaceae has been one of the most important foods for Pacific islanders for centuries. However, the yield levels have been declining in the recent past due to the presence of sweetpotato weevils Cylas formicarius (Fabricius (Coleoptera, Brentidae, Euscepes postfasciatus (Fairmaire and Daealus tuberosus (Zimmer man (Coleoptera, Curculionidae. Therefore, urgent management or eradication methods are sought in the Mariana Islands (Guam, Rota, Saipan, and Tinian. However, the management or eradication of these weevil pests requires accurate assessments of the target pest density. Currently, no advice is provided to growers on the best method for sampling sweetpotato for weevil pests, although pheromone-based traps or chemicals are being used. This study defines the results of field counts designed to adjust relative sampling techniques for three sweetpotato weevil pests by inspecting plants visually and at random in the field with an absolute measure of population density. Significant relationships were detected between the relative four sampling sites between the three weevil pests. In the dry and wet season, 90% and 35.5%, respectively, of population density of C. formicarius was noticed in Rota. This density of the population levels of this species is significantly lower in Saipan, Guam and Tinian. No incidence of E. postfasciatus and D. tuberosus was observed on Guam. However, E. postfasciatus is identified as the second most destructive pest in Rota, Tinian and Saipan in both the dry and wet seasons. Likewise, D. tuberosus is the third major pest as the recorded population density ranged from 12.5% to 2.5%. Also, it is evident from the sampling study that the population densities of all three weevils are significantly higher in the dry season than the wet season.

  7. Spontaneous mutation rate is a plastic trait associated with population density across domains of life.

    Directory of Open Access Journals (Sweden)

    Rok Krašovec

    2017-08-01

    Full Text Available Rates of random, spontaneous mutation can vary plastically, dependent upon the environment. Such plasticity affects evolutionary trajectories and may be adaptive. We recently identified an inverse plastic association between mutation rate and population density at 1 locus in 1 species of bacterium. It is unknown how widespread this association is, whether it varies among organisms, and what molecular mechanisms of mutagenesis or repair are required for this mutation-rate plasticity. Here, we address all 3 questions. We identify a strong negative association between mutation rate and population density across 70 years of published literature, comprising hundreds of mutation rates estimated using phenotypic markers of mutation (fluctuation tests from all domains of life and viruses. We test this relationship experimentally, determining that there is indeed density-associated mutation-rate plasticity (DAMP at multiple loci in both eukaryotes and bacteria, with up to 23-fold lower mutation rates at higher population densities. We find that the degree of plasticity varies, even among closely related organisms. Nonetheless, in each domain tested, DAMP requires proteins scavenging the mutagenic oxidised nucleotide 8-oxo-dGTP. This implies that phenotypic markers give a more precise view of mutation rate than previously believed: having accounted for other known factors affecting mutation rate, controlling for population density can reduce variation in mutation-rate estimates by 93%. Widespread DAMP, which we manipulate genetically in disparate organisms, also provides a novel trait to use in the fight against the evolution of antimicrobial resistance. Such a prevalent environmental association and conserved mechanism suggest that mutation has varied plastically with population density since the early origins of life.

  8. Effects of the distant population density on spatial patterns of demographic dynamics

    Science.gov (United States)

    Tamura, Kohei; Masuda, Naoki

    2017-08-01

    Spatio-temporal patterns of population changes within and across countries have various implications. Different geographical, demographic and econo-societal factors seem to contribute to migratory decisions made by individual inhabitants. Focusing on internal (i.e. domestic) migration, we ask whether individuals may take into account the information on the population density in distant locations to make migratory decisions. We analyse population census data in Japan recorded with a high spatial resolution (i.e. cells of size 500×500 m) for the entirety of the country, and simulate demographic dynamics induced by the gravity model and its variants. We show that, in the census data, the population growth rate in a cell is positively correlated with the population density in nearby cells up to a distance of 20 km as well as that of the focal cell. The ordinary gravity model does not capture this empirical observation. We then show that the empirical observation is better accounted for by extensions of the gravity model such that individuals are assumed to perceive the attractiveness, approximated by the population density, of the source or destination cell of migration as the spatial average over a circle of radius ≈1 km.

  9. Effects of the distant population density on spatial patterns of demographic dynamics.

    Science.gov (United States)

    Tamura, Kohei; Masuda, Naoki

    2017-08-01

    Spatio-temporal patterns of population changes within and across countries have various implications. Different geographical, demographic and econo-societal factors seem to contribute to migratory decisions made by individual inhabitants. Focusing on internal (i.e. domestic) migration, we ask whether individuals may take into account the information on the population density in distant locations to make migratory decisions. We analyse population census data in Japan recorded with a high spatial resolution (i.e. cells of size 500×500  m ) for the entirety of the country, and simulate demographic dynamics induced by the gravity model and its variants. We show that, in the census data, the population growth rate in a cell is positively correlated with the population density in nearby cells up to a distance of 20 km as well as that of the focal cell. The ordinary gravity model does not capture this empirical observation. We then show that the empirical observation is better accounted for by extensions of the gravity model such that individuals are assumed to perceive the attractiveness, approximated by the population density, of the source or destination cell of migration as the spatial average over a circle of radius ≈1 km.

  10. Conservation implications of brown hyaena (Parahyaena brunnea population densities and distribution across landscapes in Botswana

    Directory of Open Access Journals (Sweden)

    Christiaan W. Winterbach

    2017-05-01

    Full Text Available The brown hyaena (Parahyaena brunnea is endemic to southern Africa. The largest population of this near-threatened species occurs in Botswana, but limited data were available to assess distribution and density. Our objectives were to use a stratified approach to collate available data and to collect more data to assess brown hyaena distribution and density across land uses in Botswana. We conducted surveys using track counts, camera traps and questionnaires and collated our results and available data to estimate the brown hyaena population based on the stratification of Botswana for large carnivores. Brown hyaenas occur over 533 050 km² (92% of Botswana. Our density estimates ranged from 0 brown hyaenas/100 km² in strata of northern Botswana to 2.94 (2.16–3.71 brown hyaenas/100 km² in the southern stratum of the Central Kalahari Game Reserve. We made assumptions regarding densities in strata that lacked data, using the best references available. We estimated the brown hyaena population in Botswana as 4642 (3133–5993 animals, with 6.8% of the population in the Northern Conservation Zone, 73.1% in the Southern Conservation Zone, 2.0% in the smaller conservation zones and 18.1% in the agricultural zones. The similar densities of brown hyaenas in the Central Kalahari Game Reserve and the Ghanzi farms highlight the potential of agricultural areas in Botswana to conserve this species. The conservation of brown hyaenas in the agricultural landscape of Botswana is critical for the long-term conservation of the species; these areas provide important links between populations in South Africa, Namibia and Zimbabwe. Conservation implications: Botswana contains the core of the brown hyaena population in southern Africa, and conflict mitigation on agricultural land is crucial to maintaining connectivity among the range countries.

  11. Estimating population density and connectivity of American mink using spatial capture-recapture

    Science.gov (United States)

    Fuller, Angela K.; Sutherland, Christopher S.; Royle, Andy; Hare, Matthew P.

    2016-01-01

    Estimating the abundance or density of populations is fundamental to the conservation and management of species, and as landscapes become more fragmented, maintaining landscape connectivity has become one of the most important challenges for biodiversity conservation. Yet these two issues have never been formally integrated together in a model that simultaneously models abundance while accounting for connectivity of a landscape. We demonstrate an application of using capture–recapture to develop a model of animal density using a least-cost path model for individual encounter probability that accounts for non-Euclidean connectivity in a highly structured network. We utilized scat detection dogs (Canis lupus familiaris) as a means of collecting non-invasive genetic samples of American mink (Neovison vison) individuals and used spatial capture–recapture models (SCR) to gain inferences about mink population density and connectivity. Density of mink was not constant across the landscape, but rather increased with increasing distance from city, town, or village centers, and mink activity was associated with water. The SCR model allowed us to estimate the density and spatial distribution of individuals across a 388 km2 area. The model was used to investigate patterns of space usage and to evaluate covariate effects on encounter probabilities, including differences between sexes. This study provides an application of capture–recapture models based on ecological distance, allowing us to directly estimate landscape connectivity. This approach should be widely applicable to provide simultaneous direct estimates of density, space usage, and landscape connectivity for many species.

  12. Using ecology to inform physiology studies: implications of high population density in the laboratory.

    Science.gov (United States)

    Newman, Amy E M; Edmunds, Nicholas B; Ferraro, Shannon; Heffell, Quentin; Merritt, Gillian M; Pakkala, Jesse J; Schilling, Cory R; Schorno, Sarah

    2015-03-15

    Conspecific density is widely recognized as an important ecological factor across the animal kingdom; however, the physiological impacts are less thoroughly described. In fact, population density is rarely mentioned as a factor in physiological studies on captive animals and, when it is infrequently addressed, the animals used are reared and housed at densities far above those in nature, making the translation of results from the laboratory to natural systems difficult. We survey the literature to highlight this important ecophysiological gap and bring attention to the possibility that conspecific density prior to experimentation may be a critical factor influencing results. Across three taxa: mammals, birds, and fish, we present evidence from ecology that density influences glucocorticoid levels, immune function, and body condition with the intention of stimulating discussion and increasing consideration of population density in physiology studies. We conclude with several directives to improve the applicability of insights gained in the laboratory to organisms in the natural environment. Copyright © 2015 the American Physiological Society.

  13. A dynamic urban air pollution population exposure assessment study using model and population density data derived by mobile phone traffic

    Science.gov (United States)

    Gariazzo, Claudio; Pelliccioni, Armando; Bolignano, Andrea

    2016-04-01

    A dynamic city-wide air pollution exposure assessment study has been carried out for the urban population of Rome, Italy, by using time resolved population distribution maps, derived by mobile phone traffic data, and modelled air pollutants (NO2, O3 and PM2.5) concentrations obtained by an integrated air dispersion modelling system. More than a million of persons were tracked during two months (March and April 2015) for their position within the city and its surroundings areas, with a time resolution of 15 min and mapped over an irregular grid system with a minimum resolution of 0.26 × 0.34 Km2. In addition, demographics information (as gender and age ranges) were available in a separated dataset not connected with the total population one. Such BigData were matched in time and space with air pollution model results and then used to produce hourly and daily resolved cumulative population exposures during the studied period. A significant mobility of population was identified with higher population densities in downtown areas during daytime increasing of up to 1000 people/Km2 with respect to nigh-time one, likely produced by commuters, tourists and working age population. Strong variability (up to ±50% for NO2) of population exposures were detected as an effect of both mobility and time/spatial changing in pollutants concentrations. A comparison with the correspondent stationary approach based on National Census data, allows detecting the inability of latter in estimating the actual variability of population exposure. Significant underestimations of the amount of population exposed to daily PM2.5 WHO guideline was identified for the Census approach. Very small differences (up to a few μg/m3) on exposure were detected for gender and age ranges population classes.

  14. International Consortium on Mammographic Density : Methodology and population diversity captured across 22 countries

    NARCIS (Netherlands)

    McCormack, Valerie A; Burton, Anya; Dos-Santos-Silva, Isabel; Hipwell, John H; Dickens, Caroline; Salem, Dorria; Kamal, Rasha; Hartman, Mikael; Lee, Charmaine Pei Ling; Chia, Kee-Seng; Ozmen, Vahit; Aribal, Mustafa Erkin; Flugelman, Anath Arzee; Lajous, Martín; Lopez-Riduara, Ruy; Rice, Megan; Romieu, Isabelle; Ursin, Giske; Qureshi, Samera; Ma, Huiyan; Lee, Eunjung; van Gils, Carla H; Wanders, Johanna O P; Vinayak, Sudhir; Ndumia, Rose; Allen, Steve; Vinnicombe, Sarah; Moss, Sue; Won Lee, Jong; Kim, Jisun; Pereira, Ana; Garmendia, Maria Luisa; Sirous, Reza; Sirous, Mehri; Peplonska, Beata; Bukowska, Agnieszka; Tamimi, Rulla M; Bertrand, Kimberly; Nagata, Chisato; Kwong, Ava; Vachon, Celine; Scott, Christopher; Perez-Gomez, Beatriz; Pollan, Marina; Maskarinec, Gertraud; Giles, Graham; Hopper, John; Stone, Jennifer; Rajaram, Nadia; Teo, Soo-Hwang; Mariapun, Shivaani; Yaffe, Martin J; Schüz, Joachim; Chiarelli, Anna M; Linton, Linda; Boyd, Norman F

    2015-01-01

    Mammographic density (MD) is a quantitative trait, measurable in all women, and is among the strongest markers of breast cancer risk. The population-based epidemiology of MD has revealed genetic, lifestyle and societal/environmental determinants, but studies have largely been conducted in women with

  15. DNA-based population density estimation of black bear at northern ...

    African Journals Online (AJOL)

    The analysis of deoxyribonucleic acid (DNA) microsatellites from hair samples obtained by the non-invasive method of traps was used to estimate the population density of black bears (Ursus americanus eremicus) in a mountain located at the county of Lampazos, Nuevo Leon, Mexico. The genotyping of bears was ...

  16. Modelling the effect of intersections in linear habitat on spatial distribution and local population density

    NARCIS (Netherlands)

    Langevelde, van F.; Grashof-Bokdam, C.J.

    2011-01-01

    Many species in human-dominated landscapes find their habitat in linear elements, such as road verges, hedgerows and ditches. Local concentrations of species have been observed in the intersections of linear elements, but their spatial distribution and local population density in this linear habitat

  17. High population density of Little Owl (Athene noctua) in Hortobagy National Park, Hungary, Central Europe

    Czech Academy of Sciences Publication Activity Database

    Šálek, Martin; Chrenková, M.; Kipson, M.

    2013-01-01

    Roč. 61, č. 1 (2013), s. 165-169 ISSN 1505-2249 Institutional support: RVO:68081766 Keywords : Little Owl * population density * distribution * breeding places * Hortobagy National Park * Hungary Subject RIV: EH - Ecology, Behaviour Impact factor: 0.554, year: 2013

  18. Effects of population density on the growth and egg-laying capacity ...

    African Journals Online (AJOL)

    The effects of the population density of adult African giant land snail, Archachatina marginata on the egg-laying capacity and the growth of the brooders and hatchlings were investigated for 9 months. Ten culture pens were stocked with snails at 20%, 40%, 60%, 80% and 100% capacity with each group in 2 replicates.

  19. Place and Child Health: The Interaction of Population Density and Sanitation in Developing Countries.

    Science.gov (United States)

    Hathi, Payal; Haque, Sabrina; Pant, Lovey; Coffey, Diane; Spears, Dean

    2017-02-01

    A long literature in demography has debated the importance of place for health, especially children's health. In this study, we assess whether the importance of dense settlement for infant mortality and child height is moderated by exposure to local sanitation behavior. Is open defecation (i.e., without a toilet or latrine) worse for infant mortality and child height where population density is greater? Is poor sanitation is an important mechanism by which population density influences child health outcomes? We present two complementary analyses using newly assembled data sets, which represent two points in a trade-off between external and internal validity. First, we concentrate on external validity by studying infant mortality and child height in a large, international child-level data set of 172 Demographic and Health Surveys, matched to census population density data for 1,800 subnational regions. Second, we concentrate on internal validity by studying child height in Bangladeshi districts, using a new data set constructed with GIS techniques that allows us to control for fixed effects at a high level of geographic resolution. We find a statistically robust and quantitatively comparable interaction between sanitation and population density with both approaches: open defecation externalities are more important for child health outcomes where people live more closely together.

  20. Performance in wild ungulates: measuring population density and condition of individuals

    Science.gov (United States)

    John G. Kie

    1988-01-01

    Measures of performance in wild ungulates can include characteristics indicative of condition and health such as body weights, fat reserves, blood values, reproductive rates, and parasite loads. Performance may also be inferred from habitat-related factors, such as diet and nutritional intake. However, these parameters interact with population density to form a...

  1. Effects of habitat size and quality on equilibrium density and extinction time of Sorex araneus populations

    NARCIS (Netherlands)

    Klok, C.; Roos, de A.M.

    1998-01-01

    1. The effects of changes in habitat size and quality on the expected population density and the expected time to extinction of Sorex araneus are studied by means of mathematical models that incorporate demographic stochasticity. 2. Habitat size is characterized by the number of territories, while

  2. Population-based reference values for bone mineral density in young men

    DEFF Research Database (Denmark)

    Høiberg, M; Nielsen, T L; Wraae, Kristian

    2007-01-01

    Population-based reference values for peak bone mass density in Danish men. BMD of total hip (1.078 +/- 0,14 g/cm2) differed significantly from values from National Health and Nutrition Examination Survey III and of total lumbar spine ((1.073 +/- 0.125 g/cm2) differed significantly from Hologic...

  3. The ideal free distribution as an evolutionarily stable state in density-dependent population games

    Czech Academy of Sciences Publication Activity Database

    Cressman, R.; Křivan, Vlastimil

    2010-01-01

    Roč. 119, č. 8 (2010), s. 1231-1242 ISSN 0030-1299 R&D Projects: GA AV ČR IAA100070601 Institutional research plan: CEZ:AV0Z50070508 Keywords : density-dependent population games Subject RIV: EH - Ecology, Behaviour Impact factor: 3.393, year: 2010

  4. DNA-based population density estimation of black bear at northern ...

    African Journals Online (AJOL)

    UANL

    Studies performed in this place from 1991 to. 1994 indicate that the subspecies eremicus is very abundant and the estimated population density was as high as 0.72 bears /km2, although other studies using a different methodology calculated this value in 0.31 bears/km2 (Doan-Crider, 1995; Doan-Crider and Hewitt, ...

  5. Item Response Theory with Estimation of the Latent Population Distribution Using Spline-Based Densities

    Science.gov (United States)

    Woods, Carol M.; Thissen, David

    2006-01-01

    The purpose of this paper is to introduce a new method for fitting item response theory models with the latent population distribution estimated from the data using splines. A spline-based density estimation system provides a flexible alternative to existing procedures that use a normal distribution, or a different functional form, for the…

  6. Estimating group size and population density of Eurasian badgers Meles meles by quantifying latrine use

    NARCIS (Netherlands)

    Tuyttens, F.A.M.; Long, B.; Fawcett, T.W.; Skinner, A.; Brown, J.A.; Cheeseman, C.L.; Roddam, A.W.; MacDonald, D.W.

    2001-01-01

    1. Conservation issues and a potential role in disease transmission generate the continued need to census Eurasian badgers Meles metes, but direct counts and sett counts present difficulties. The feasibility of estimating social group size and population density of badgers by quantifying their use

  7. Spatial relationship between human population density, land use intensity and biodiversity in the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Vačkář, David; Chobot, K.; Orlitová, E.

    2012-01-01

    Roč. 27, č. 9 (2012), s. 1279-1290 ISSN 0921-2973 Institutional support: RVO:67179843 Keywords : species richness * landscape diversity * human population density * human appropriation of net primary production * Czech Republic Subject RIV: EH - Ecology, Behaviour Impact factor: 2.897, year: 2012

  8. Characterization of a newly discovered symbiont of the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae).

    Science.gov (United States)

    Bing, Xiao-Li; Yang, Jiao; Zchori-Fein, Einat; Wang, Xiao-Wei; Liu, Shu-Sheng

    2013-01-01

    Bemisia tabaci (Hemiptera: Aleyrodidae) is a species complex containing >28 cryptic species, some of which are important crop pests worldwide. Like many other sap-sucking insects, whiteflies harbor an obligatory symbiont, "Candidatus Portiera aleyrodidarum," and a number of secondary symbionts. So far, six genera of secondary symbionts have been identified in B. tabaci. In this study, we report and describe the finding of an additional bacterium in the indigenous B. tabaci cryptic species China 1 (formerly known as B. tabaci biotype ZHJ3). Phylogenetic analysis based on the 16S rRNA and gltA genes showed that the bacterium belongs to the Alphaproteobacteria subdivision of the Proteobacteria and has a close relationship with human pathogens of the genus Orientia. Consequently, we temporarily named it Orientia-like organism (OLO). OLO was found in six of eight wild populations of B. tabaci China 1, with the infection rate ranging from 46.2% to 76.8%. Fluorescence in situ hybridization (FISH) of B. tabaci China 1 in nymphs and adults revealed that OLOs are confined to the bacteriome and co-occur with "Ca. Portiera aleyrodidarum." The vertical transmission of OLO was demonstrated by detection of OLO at the anterior pole end of the oocytes through FISH. Quantitative PCR analysis of population dynamics suggested a complex interaction between "Ca. Portiera aleyrodidarum" and OLO. Based on these results, we propose "Candidatus Hemipteriphilus asiaticus" for the classification of this symbiont from B. tabaci.

  9. Earthworm Population Density in Sugarcane Cropping System Applied with Various Quality of Organic Matter

    Directory of Open Access Journals (Sweden)

    Nurhidayati Nurhidayati

    2012-12-01

    Full Text Available Earthworms population in the soil are greatly impacted by agricultural management, yet little is known about how the quality and quantity of organic matter addition interact in sugarcane cropping system to earthworm population. This study describes the effect of various organic matter and application rates on earthworms in sugarcane cropping system. Earthworms were collected in April, July and December from 48 experimental plots under five kinds of organic matter application : (1 cattle manure, (2 filter cake of sugar mill, (3 sugarcane trash, (4 mixture of cattle manure+filter cake, and (5 mixture of cattle manure+sugarcane trash. There were three application rates of the organic matter (5, 10, and 15 ton ha-1. The treatments were arranged in factorial block randomize design with three replications and one treatment as a control (no organic input. Earthworms were collected using monolith sampling methods and hand-sorted from each plot, and measured its density (D (indiv.m-2, biomass (B (g m-2 and B/D ratio (g/indiv.. All the plots receiving organic matter input had higher earthworm density, biomass, and B/D ratio than the control. The highest earthworm population density was found in the plot receiving application of sugarcane trash (78 indiv.m-2 and the mixture of cattle manure+sugarcane trash (84 indiv.m-2. The increase in application rates of organic matter could increase the earthworm density and biomass. Earthworm population density also appeared to be strongly influenced by the quality of organic matter, such as the C-organic, N, C/N ratio, lignin, polyphenols, and cellulose content. Earthworm preferred low quality organic matter. It was caused by the higher energy of low quality organic matter than high quality organic matter. Our findings suggest that the input of low quality organic matter with application rate as 10 ton ha-1 is important for maintaining earthworm population and soil health in sugarcane land.

  10. Grain yield of corn at different population densities and intercropped with forages

    Directory of Open Access Journals (Sweden)

    José M. do Nascimento

    2015-12-01

    Full Text Available ABSTRACT The no-tillage system optimizes agricultural areas, maintaining the supply of straw and promoting crop rotation and soil conservation. The aim of the present study was to evaluate sowing quality and grain yield of corn intercropped with three forage species of the Urochloa genus associated with two corn population densities. The experiment was conducted at the São Paulo State University (UNESP, in Jaboticabal-SP, Brazil. The experimental design was randomized blocks in a 2 x 3 factorial scheme with four replicates. The treatments consisted of two corn densities (55,000 and 75,000 plants ha-1 intercropped with three forages (Urochloa brizantha, Urochloa decumbens and Urochloa ruziziensis sown between rows of corn in the V4 stage. The following corn variables were analysed: mean number of days for emergence, longitudinal distribution, grain yield, initial population and final population. There were differences between corn populations (p < 0.1 and the intercropping of corn with the species U. brizantha and U. ruziziensis promoted the best results, which permitted concluding that the cultivation of corn at the population density of 75,000 plants ha-1 intercropped U. brizantha and U. ruziziensis promoted better sowing quality and, consequently, higher grain yields.

  11. Correlations between U.S. county annual cancer incidence and population density.

    Science.gov (United States)

    Vares, David Ae; St-Pierre, Linda S; Persinger, Michael A

    2015-01-01

    Population density implicitly involves specific distances between living individuals who exhibit biophysical forces and energies. Objective was to investigate major data bases of cancer incidence and population data to help understand the emergent properties of diseases that become apparent only when large populations and areas are considered. Correlation analyses of the annual incidence (years 2007 to 2011) of cancer in counties (2,885) of the U.S. and population densities were convergent with these quantitative predictions and suggested an inflection threshold around 50 people per square mile. The potential role of subtle or even "non-local" factors coupled to averaged population density in the viability and mortality of the human species may serve as alternative explanations to the attribution of malignancy to "chance" factors. Calculations indicated average distances between the electric force dipole of the brains or bodies of human beings generate forces known to affect DNA extension and when distributed over the Compton wavelength of the electron could produce energies sufficient to affect the binding of base nucleotides. An inclusive science of human ecology might benefit from considering subtle forces and energies associated with the individual members within the habitat that could determine the probability of cellular anomalies.

  12. Gridded Population of the World, Version 4 (GPWv4): Population Density Adjusted to Match 2015 Revision UN WPP Country Totals, Revision 10

    Data.gov (United States)

    National Aeronautics and Space Administration — Gridded Population of the World, Version 4 (GPWv4) Population Density Adjusted to Match 2015 Revision of UN WPP Country Totals, Revision 10 consists of estimates of...

  13. The Calyptogena magnifica chemoautotrophic symbiont genome

    Energy Technology Data Exchange (ETDEWEB)

    Newton, I.L.; Woyke, T.; Auchtung, T.A.; Dilly, G.F.; Dutton,R.J.; Fisher, M.C.; Fontanez, K.M.; Lau, E.; Stewart, F.J.; Richardson,P.M.; Barry, K.W.; Saunders, E.; Detter, J.C.; Wu, D.; Eisen, J.A.; Cavanaugh, C.M.

    2007-03-01

    Chemoautotrophic endosymbionts are the metabolic cornerstone of hydrothermal vent communities, providing invertebrate hosts with nearly all of their nutrition. The Calyptogena magnifica (Bivalvia: Vesicomyidae) symbiont, Candidatus Ruthia magnifica, is the first intracellular sulfur-oxidizing endosymbiont to have its genome sequenced, revealing a suite of metabolic capabilities. The genome encodes major chemoautotrophic pathways as well as pathways for biosynthesis of vitamins, cofactors, and all 20 amino acids required by the clam.

  14. Potential applications of insect symbionts in biotechnology

    OpenAIRE

    Berasategui, A.; Shukla, S.; Salem, H.; Kaltenpoth, M.

    2016-01-01

    Symbiotic interactions between insects and microorganisms are widespread in nature and are often the source of ecological innovations. In addition to supplementing their host with essential nutrients, microbial symbionts can produce enzymes that help degrade their food source as well as small molecules that defend against pathogens, parasites, and predators. As such, the study of insect ecology and symbiosis represents an important source of chemical compounds and enzymes with potential biote...

  15. Role of prey and intraspecific density dependence on the population growth of an avian top predator

    Science.gov (United States)

    Fernandez-de-Simon, Javier; Díaz-Ruiz, Francisco; Cirilli, Francesca; Tortosa, Francisco S.; Villafuerte, Rafael; Ferreras, Pablo

    2014-10-01

    Exploring predator-prey systems in diverse ecosystems increases our knowledge about ecological processes. Predator population growth may be positive when conspecific density is low but predators also need areas with prey availability, associated with competition, which increases the risk of suffering losses but stabilises populations. We studied relationships between European rabbits Oryctolagus cuniculus (prey) and adult eagle owls Bubo bubo (predators) in south-western Europe. We assessed models explaining the predator population growth and stability. We estimated the abundance of rabbits and adult eagle owls during three years in eight localities of central-southern Spain. We explored models including rabbit and adult eagle owl abundance, accounting for yearly variations and including the locality as a random variable. We found that population growth of adult eagle owls was positive in situations with low conspecific abundance and tended to be negative but approaching equilibrium in situations of higher conspecific abundance. Population growth was also positively related to previous summer rabbit density when taking into account eagle owl conspecific abundance, possibly indicating that rabbits may support recruitment. Furthermore, abundance stability of adult eagle owls was positively related to previous winter-spring rabbit density, which could suggest predator population stabilisation through quick territory occupation in high-quality areas. These results exemplify the trade-off between prey availability and abundance of adult predators related to population growth and abundance stability in the eagle owl-rabbit system in south-western Europe. Despite rabbits have greatly declined during the last decades and eagle owls locally specialise on them, eagle owls currently have a favourable conservation status. As eagle owls are the only nocturnal raptor with such dependence on rabbits, this could point out that predators may overcome prey decreases in areas with

  16. Estimation of Large Regional Urban and Rural Population Density Based on the Differences of Population Distribution between Urban and Rural: Take Shandong Province as Example

    OpenAIRE

    LU Nan; ZHANG Weiwei; CHEN Lijun; LI Zhilin; CHEN Jun; LI Ran; CHEN Xuehong; ZHANG Yushuo; LIU Jiyu

    2015-01-01

    Existing methods for large regional population density estimation, which are mostly concentrated in the kilometer scale and only reflect the macro distribution characteristics of the urban and rural population, are difficult to describe details of urban and rural population spatial distribution accurately. In order to resolve the problem above, an estimation method of large regional urban and rural population density, which is based on the first 30 m global land cover dataset(GlobeLand30) is ...

  17. Sociodemographic Factors, Population Density, and Bicycling for Transportation in the United States.

    Science.gov (United States)

    Nehme, Eileen K; Pérez, Adriana; Ranjit, Nalini; Amick, Benjamin C; Kohl, Harold W

    2016-01-01

    Transportation bicycling is a behavior with demonstrated health benefits. Population-representative studies of transportation bicycling in United States are lacking. This study examined associations between sociodemographic factors, population density, and transportation bicycling and described transportation bicyclists by trip purposes, using a US-representative sample. This cross-sectional study used 2009 National Household Travel Survey datasets. Associations among study variables were assessed using weighted multivariable logistic regression. On a typical day in 2009, 1% of Americans older than 5 years of age reported a transportation bicycling trip. Transportation cycling was inversely associated with age and directly with being male, with being white, and with population density (≥ 10,000 vs transportation. Twenty-one percent of transportation bicyclists reported trips to work, whereas 67% reported trips to social or other activities. Transportation bicycling in the United States is associated with sociodemographic characteristics and population density. Bicycles are used for a variety of trip purposes, which has implications for transportation bicycling research based on commuter data and for developing interventions to promote this behavior.

  18. Relationship of cancer incidence to terrestrial radiation and population density in Connecticut, 1935-1974

    International Nuclear Information System (INIS)

    Walter, S.D.; Meigs, J.W.; Heston, J.F.

    1986-01-01

    The relationship of cancer incidence to terrestrial radiation and population density was investigated. Cancer incidence was obtained using 40 years of age-standardized data from the Connecticut Tumor Registry, and environmental radiation was estimated using data from an airborne gamma radiation survey of the entire state. These variables were examined ecologically, using the 169 towns of the state as the analytic units in a weighted regression analysis. The study design involves a large population base in a state having relatively high terrestrial radiation exposure levels overall and reasonable variation in exposure between towns. For all cancer combined, only one of the eight sex-specific analyses by decade yielded a significant radiation regression coefficient, and this was negative. In the sex- and site-specific analyses, almost all the coefficients for radiation were not significantly different from zero. In contrast, significant positive relationships of cancer incidence with population density were found for all cancer, for cancer of the lung for both sexes, for stomach, colonic, and prostatic cancer for males, and for lymphomas, thyroid, breast, and ovarian cancer for females. Both the radiation and population density relationships were adjusted for socioeconomic status. Socioeconomic status was significantly negatively associated with stomach and lung cancer in males and with cervical cancer in females; it was also positively associated with lymphomas and breast cancer in females. A power calculation revealed that, despite the relatively large size of this study, there was only a small probability of detecting a radiation effect of the strength anticipated from previous estimates

  19. Evaluation of sweet sorghum (Sorghum bicolor L. [Moench]) on several population density for bioethanol production

    Science.gov (United States)

    Suwarti; Efendi, R.; Massinai, R.; Pabendon, M. B.

    2018-03-01

    Sweet sorghum (Sorghum bicolor L. [Moench]) crop management that is use for raw source of bioethanol for industrial purpose in Indonesia is less developed. The aim of this research was to evaluated sweet sorghum variety at several population to determine optimum density for juice production. Experiment design was set on split-plot design with three replications, conducted on August to December 2016 at the Indonesian Cereals Research Institute Research Station, Maros South Sulawesi. Main plot were six variation of plant row, and sub plot were three sweet sorghum varieties. Result of the study showed that plant population was high significanty affect to stalk weight, total biomass yield, leaf weight, and also significantly affect bagass weight and juice volume. Varieties were high significantly different in plant height, juice volume, and number of nodes. Super 1 variety on population at 166,667 plants/ha (P1) was obtained the highest juice volume (19,445 lHa-1), meanwhile the highest brix value obtained from Numbu at the same plants population. Furthermore juice volume had significant correlation with biomass weight at the r=0.73. Based on ethanol production, Super 2 and Numbu had the highest volume at 83.333 plants/ha density (P3) and Super 1 at 166.667 plants/ha density with the ethanol volume were 827.68 l Ha-1, 1116.50 l/ha and 993.62 l Ha-1 respectively.

  20. Occurrence of Density-Dependent Height Repression within Jack Pine and Black Spruce Populations

    Directory of Open Access Journals (Sweden)

    Peter F. Newton

    2015-07-01

    Full Text Available The objective of this study was to investigate the occurrence of density-dependent height relationships in jack pine (Pinus banksiana Lamb. and black spruce (Picea mariana (Mill. B.S.P. populations. After assessing and ruling out the presence of consequential spatial correlation effects, the analysis consisted of analyzing the relationship between mean dominant height and initial planting density within 28 Nelder plots located in the central portion of the Canadian Boreal Forest Region. Employing remeasurement data obtained at periodic intervals (16, 20 and 40–41 years post-establishment across a stand density gradient ranging from a minimum of 1425 stems/ha to a maximum of 28,621 stems/ha, graphical and simple linear regression analyses were used to quantify the stand height–density relationship by species, plot and measurement year. The results indicated the presence of density-dependent effects on height development for both species: 65% of the 83 jack pine relationships and 89% of the 27 black spruce relationships had significant (p ≤ 0.05 and negative slope values. In regards to jack pine for which the data permitted, the occurrence and magnitude of the observed height repression effect increased over time. The asymptotic height repression effect for jack pine was 24% greater than that for black spruce. The results are discussed within the context of the applicability of the density-independent height growth assumption and potential implications for site quality estimation and thinning response modeling.

  1. Parasitoid gene expression changes after adaptation to symbiont-protected hosts.

    Science.gov (United States)

    Dennis, Alice B; Patel, Vilas; Oliver, Kerry M; Vorburger, Christoph

    2017-11-01

    Reciprocal selection between aphids, their protective endosymbionts, and the parasitoid wasps that prey upon them offers an opportunity to study the basis of their coevolution. We investigated adaptation to symbiont-conferred defense by rearing the parasitoid wasp Lysiphlebus fabarum on aphids (Aphis fabae) possessing different defensive symbiont strains (Hamiltonella defensa). After ten generations of experimental evolution, wasps showed increased abilities to parasitize aphids possessing the H. defensa strain they evolved with, but not aphids possessing the other strain. We show that the two symbiont strains encode different toxins, potentially creating different targets for counter-adaptation. Phenotypic and behavioral comparisons suggest that neither life-history traits nor oviposition behavior differed among evolved parasitoid lineages. In contrast, comparative transcriptomics of adult female wasps identified a suite of differentially expressed genes among lineages, even when reared in a common, symbiont-free, aphid host. In concurrence with the specificity of each parasitoid lineages' infectivity, most differentially expressed parasitoid transcripts were also lineage-specific. These transcripts are enriched with putative venom toxins and contain highly expressed, potentially defensive viral particles. Together, these results suggest that wild populations of L. fabarum employ a complicated offensive arsenal with sufficient genetic variation for wasps to adapt rapidly and specifically to their hosts' microbial defenses. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  2. Population Density Modulates Drug Inhibition and Gives Rise to Potential Bistability of Treatment Outcomes for Bacterial Infections.

    Directory of Open Access Journals (Sweden)

    Jason Karslake

    2016-10-01

    Full Text Available The inoculum effect (IE is an increase in the minimum inhibitory concentration (MIC of an antibiotic as a function of the initial size of a microbial population. The IE has been observed in a wide range of bacteria, implying that antibiotic efficacy may depend on population density. Such density dependence could have dramatic effects on bacterial population dynamics and potential treatment strategies, but explicit measures of per capita growth as a function of density are generally not available. Instead, the IE measures MIC as a function of initial population size, and population density changes by many orders of magnitude on the timescale of the experiment. Therefore, the functional relationship between population density and antibiotic inhibition is generally not known, leaving many questions about the impact of the IE on different treatment strategies unanswered. To address these questions, here we directly measured real-time per capita growth of Enterococcus faecalis populations exposed to antibiotic at fixed population densities using multiplexed computer-automated culture devices. We show that density-dependent growth inhibition is pervasive for commonly used antibiotics, with some drugs showing increased inhibition and others decreased inhibition at high densities. For several drugs, the density dependence is mediated by changes in extracellular pH, a community-level phenomenon not previously linked with the IE. Using a simple mathematical model, we demonstrate how this density dependence can modulate population dynamics in constant drug environments. Then, we illustrate how time-dependent dosing strategies can mitigate the negative effects of density-dependence. Finally, we show that these density effects lead to bistable treatment outcomes for a wide range of antibiotic concentrations in a pharmacological model of antibiotic treatment. As a result, infections exceeding a critical density often survive otherwise effective treatments.

  3. Patterns of bone density evaluation in a community population treated with aromatase inhibitors.

    Science.gov (United States)

    Ligibel, Jennifer A; O'Malley, A James; Fisher, Maxine; Daniel, Gregory W; Winer, Eric P; Keating, Nancy L

    2012-08-01

    Aromatase inhibitors (AIs) increase the risk of bone loss and fracture. Guidelines recommend routine bone density screening for women on AIs, but there are few data regarding the incorporation of these guidelines into clinical practice. We assessed bone density testing in a community-based cohort of breast cancer patients treated with AIs. By means of encounter and pharmacy data from WellPoint plans in the HealthCore Integrated Research Database, we assessed bone density testing among 9,138 women aged ≥50 years with breast cancer who were treated with AIs between 2002 and 2008. We used multivariable logistic regression to identify factors associated with baseline bone density testing in women initiating an AI, and among a subset of 2,086 women treated with AIs for at least 2 years, with testing during the first 2 years of therapy. Only 41.6 % of women underwent bone density testing when initiating AI therapy. Rates of bone density testing increased over time, but were lower for women who were older, lived in the Northeast (vs. other regions), had been treated with prior proton pump inhibitor or tamoxifen therapy, lived in areas with lower educational attainment, or were enrolled in a health maintenance organization (vs. other insurance types) (all P < 0.05). Among women treated with AIs for at least 2 years, 59.9 % of women underwent bone density testing during the first 2 years of AI therapy. Rates of testing were lower for women living in the Midwest or West (vs. Northeast), living in areas with lower education levels, enrolled in health maintenance organizations (vs. other insurance types), and with prior tamoxifen use. In conclusion, most women initiating AI therapy, and 40 % of those on long-term therapy, did not undergo recommended bone density evaluation in this community-based population. Attention is needed to insure that unnecessary fractures are avoided in breast cancer patients taking AIs.

  4. Contrasting physiological plasticity in response to environmental stress within different cnidarians and their respective symbionts

    Science.gov (United States)

    Hoadley, Kenneth D.; Pettay, Daniel. T.; Dodge, Danielle; Warner, Mark E.

    2016-06-01

    Given concerns surrounding coral bleaching and ocean acidification, there is renewed interest in characterizing the physiological differences across the multiple host-algal symbiont combinations commonly found on coral reefs. Elevated temperature and CO2 were used to compare physiological responses within the scleractinian corals Montipora hirsuta ( Symbiodinium C15) and Pocillopora damicornis ( Symbiodinium D1), as well as the corallimorph (a non-calcifying anthozoan closely related to scleractinians) Discosoma nummiforme ( Symbiodinium C3). Several physiological proxies were affected more by temperature than CO2, including photochemistry, algal number and cellular chlorophyll a. Marked differences in symbiont number, chlorophyll and volume contributed to distinctive patterns of chlorophyll absorption among these animals. In contrast, carbon fixation either did not change or increased under elevated temperature. Also, the rate of photosynthetically fixed carbon translocated to each host did not change, and the percent of carbon translocated to the host increased in the corallimorph. Comparing all data revealed a significant negative correlation between photosynthetic rate and symbiont density that corroborates previous hypotheses about carbon limitation in these symbioses. The ratio of symbiont-normalized photosynthetic rate relative to the rate of symbiont-normalized carbon translocation (P:T) was compared in these organisms as well as the anemone, Exaiptasia pallida hosting Symbiodinium minutum, and revealed a P:T close to unity ( D. nummiforme) to a range of 2.0-4.5, with the lowest carbon translocation in the sea anemone. Major differences in the thermal responses across these organisms provide further evidence of a range of acclimation potential and physiological plasticity that highlights the need for continued study of these symbioses across a larger group of host taxa.

  5. Nutritional correlates of koala persistence in a low-density population.

    Directory of Open Access Journals (Sweden)

    Eleanor Stalenberg

    Full Text Available It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence.

  6. Nutritional correlates of koala persistence in a low-density population.

    Science.gov (United States)

    Stalenberg, Eleanor; Wallis, Ian R; Cunningham, Ross B; Allen, Chris; Foley, William J

    2014-01-01

    It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus) populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts) compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence.

  7. Rock partridge (Alectoris graeca graeca population density and trends in central Greece

    Directory of Open Access Journals (Sweden)

    Bontzorlos, V. A.

    2012-01-01

    Full Text Available The rock partridge is an emblematic species of the Greek avifauna and one of the most important game species in the country. The present study, which combined long term in–situ counts with distance sampling methodology in central Greece, indicated that the species’ population in Greece is the highest within its European distribution, in contrast to all prior considerations. Inter–annual trends suggested a stable rock partridge population both within hunting areas and wildlife refuges, whereas during summer, the species presented significantly higher densities in altitudes of more than 1,000 m, most probably due to the effect of predation at lower zones. The similarity of population structure between wildlife refuges and hunting zones along with the stable population trends demonstrate that rock partridge harvest in the country is sustainable.

  8. Tiller size/population density compensation in grazed Coastcross bermudagrass swards

    Directory of Open Access Journals (Sweden)

    Sbrissia André Fischer

    2001-01-01

    Full Text Available Several compensatory mechanisms in pastures do not allow optimisation of responses from the processes of herbage production and utilisation. Compensation due to tiller size/density relationships is one of these mechanisms. This experiment evaluated this process for Coastcross bermudagrass and compared the responses to those reported for temperate forages. Treatments were "steady state" sward surface heights of 5, 10, 15, and 20 cm that were maintained from August, 1998, through July, 1999 by sheep grazing. The experimental design was a randomised complete block, replicated four times. Pasture responses were evaluated on four separate dates (15/12/1998, 25/01/1999, 07/04/1999 and 04/07/1999 with respect to: tiller population density, tiller weight, leaf mass and leaf area per tiller and herbage mass (biomass. Tiller volume, leaf area index (LAI, tiller leaf:stem ratio and tiller leaf area:volume ratio (R were calculated. Simple regression analyses between tiller population density and tiller weight were also performed. Coastcross swards showed a tiller size/density compensation mechanism where high tiller population densities were associated with small tillers and vice-versa; except on the last evaluation. However, regression analysis revealed linear coefficients of -3.83 to -2.05, which are lower than the theoretical expectation of -3/2. The lower R values observed, when compared to those reported for perennial ryegrass, suggest that Coastcross swards optimised their LAI via clonal integration among tillers in contrast with tillers of cool-season grasses that respond more as individuals. However, this hypothesis has yet to be experimentally verified.

  9. Population-based reference values for bone mineral density in young men

    DEFF Research Database (Denmark)

    Høiberg, M; Nielsen, Torben Leo; Wraae, K

    2007-01-01

    SUMMARY: Population-based reference values for peak bone mass density in Danish men. BMD of total hip (1.078 +/- 0,14 g/cm2) differed significantly from values from National Health and Nutrition Examination Survey III and of total lumbar spine ((1.073 +/- 0.125 g/cm2) differed significantly from...... Hologic values. INTRODUCTION: Geographic, ethnic, and socio-economic factors are known to affect bone mineral density (BMD) and peak bone mass significantly. Reference values for male peak bone mass are scarce, and the diagnosis of male osteoporosis often relies on values provided by producers of dual......-energy X-ray absorptiometry (DXA) equipment. METHODS: The aim of the present study was 1) to establish population-based reference values for BMD in young men and 2) to study subgroups based on variables with suspected impact on bone metabolism. We included 783 young Caucasian men aged 20 to 30 years...

  10. Population dynamics of three songbird species in a nestbox population in Central Europe show effects of density, climate and competitive interactions

    NARCIS (Netherlands)

    Smallegange, I.M.; van der Meer, J.; Fiedler, W.

    2011-01-01

    Unravelling the contributions of density-dependent and density-independent factors in determining species population dynamics is a challenge, especially if the two factors interact. One approach is to apply stochastic population models to long-term data, yet few studies have included interactions

  11. Horizontal Transmission of Intracellular Insect Symbionts via Plants

    Directory of Open Access Journals (Sweden)

    Ewa Chrostek

    2017-11-01

    Full Text Available Experimental evidence is accumulating that endosymbionts of phytophagous insects may transmit horizontally via plants. Intracellular symbionts known for manipulating insect reproduction and altering fitness (Rickettsia, Cardinium, Wolbachia, and bacterial parasite of the leafhopper Euscelidius variegatus have been found to travel from infected insects into plants. Other insects, either of the same or different species can acquire the symbiont from the plant through feeding, and in some cases transfer it to their progeny. These reports prompt many questions regarding how intracellular insect symbionts are delivered to plants and how they affect them. Are symbionts passively transported along the insect-plant-insect path, or do they actively participate in the process? How widespread are these interactions? How does symbiont presence influence the plant? And what conditions are required for the new infection to establish in an insect? From an ecological, evolutionary, and applied perspective, this mode of horizontal transmission could have profound implications if occurring frequently enough or if new stable symbiont infections are established. Transmission of symbionts through plants likely represents an underappreciated means of infection, both in terms of symbiont epidemiology and the movement of symbionts to new host species.

  12. Horizontal Transmission of Intracellular Insect Symbionts via Plants.

    Science.gov (United States)

    Chrostek, Ewa; Pelz-Stelinski, Kirsten; Hurst, Gregory D D; Hughes, Grant L

    2017-01-01

    Experimental evidence is accumulating that endosymbionts of phytophagous insects may transmit horizontally via plants. Intracellular symbionts known for manipulating insect reproduction and altering fitness ( Rickettsia, Cardinium, Wolbachia , and bacterial parasite of the leafhopper Euscelidius variegatus ) have been found to travel from infected insects into plants. Other insects, either of the same or different species can acquire the symbiont from the plant through feeding, and in some cases transfer it to their progeny. These reports prompt many questions regarding how intracellular insect symbionts are delivered to plants and how they affect them. Are symbionts passively transported along the insect-plant-insect path, or do they actively participate in the process? How widespread are these interactions? How does symbiont presence influence the plant? And what conditions are required for the new infection to establish in an insect? From an ecological, evolutionary, and applied perspective, this mode of horizontal transmission could have profound implications if occurring frequently enough or if new stable symbiont infections are established. Transmission of symbionts through plants likely represents an underappreciated means of infection, both in terms of symbiont epidemiology and the movement of symbionts to new host species.

  13. Ethnic density, urbanicity and psychosis risk for migrant groups - A population cohort study.

    Science.gov (United States)

    Schofield, Peter; Thygesen, Malene; Das-Munshi, Jay; Becares, Laia; Cantor-Graae, Elizabeth; Pedersen, Carsten; Agerbo, Esben

    2017-12-01

    Rates of psychotic disorder are raised for many migrant groups. Understanding the role played by the social context in which they live may help explain why. This study investigates the effect of both neighbourhood ethnic density and urbanicity on the incidence of non-affective psychosis for migrant groups. Population based cohort of all those born 1965 or later followed from their 15th birthday (2,224,464 people) to 1st July 2013 (37,335,812 person years). Neighbourhood exposures were measured at age 15. For all groups incidence of non-affective psychosis was greater in lower ethnic density neighbourhoods. For migrants of African origin there was a 1.94-fold increase (95% CI, 1.17-3.23) comparing lowest and highest density quintiles; with similar effects for migrants from Europe (excluding Scandinavia): incidence rate ratio (IRR) 1.99 (95% CI, 1.56-2.54); Asia: IRR 1.63 (95% CI, 1.02-2.59); and the Middle East: IRR 1.68 (95% CI, 1.19-2.38). This initial analysis found no evidence for an urbanicity effect for migrant groups. Adjusting for ethnic density revealed a positive association between level of urbanicity and psychosis for two groups, with a statistically significant linear trend (average effect of a one quintile increase) for migrants from Europe: IRR 1.09 (95% CI, 1.02-1.16) and the Middle East: IRR 1.12 (95% CI, 1.01-1.23). In this first nationwide population-based study of ethnic density, urbanicity and psychosis we show that lower ethnic density is associated with increased incidence of non-affective psychosis for different migrant groups; masking urban/rural differences in psychosis for some groups. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  14. A consumer-resource approach to the density-dependent population dynamics of mutualism

    Science.gov (United States)

    Holland, J. Nathaniel; DeAngelis, Donald L.

    2010-01-01

    Like predation and competition, mutualism is now recognized as a consumer resource (C-R) interaction, including, in particular, bi-directional (e.g., coral, plant- mycorrhizae) and uni-directional (e.g., ant-plant defense, plant-pollinator) C-R mutualisms. Here, we develop general theory for the density-dependent population dynamics of mutualism based on the C-R mechanism of interspecific interaction. To test the influence of C-R interactions on the dynamics and stability of bi- and uni-directional C-R mutualisms, we developed simple models that link consumer functional response of one mutualistic species with the resources supplied by another. Phase-plane analyses show that the ecological dynamics of C-R mutualisms are stable in general. Most transient behavior leads to an equilibrium of mutualistic coexistence, at which both species densities are greater than in the absence of interactions. However, due to the basic nature of C-R interactions, certain density-dependent conditions can lead to C-R dynamics characteristic of predator-prey interactions, in which one species overexploits and causes the other to go extinct. Consistent with empirical phenomena, these results suggest that the C-R interaction can provide a broad mechanism for understanding density-dependent population dynamics of mutualism. By unifying predation, competition, and mutualism under the common ecological framework of consumer-resource theory, we may also gain a better understanding of the universal features of interspecific interactions in general.

  15. Musk Deer (Moschus moschiferus ) Population Density Based on Pellet Group Count Method in Sikhote-Alin

    OpenAIRE

    Maksimova, Dariya; Seryodkin, Ivan; Zaitsev, Vitaliy

    2017-01-01

    As a component of a complex program studying musk deer ecology in the Sikhote-Alin Biosphere Reserve, a survey of the musk deer population density, based on pellet group count method, was carried out at stationary posts from 2012 to 2014. The use of this method in the snowless season provides a means of surveying the most hard-to-reach areas of the musk deer habitat.

  16. Subwavelength population density gratings in resonant medium created by few-cycle pulses

    Science.gov (United States)

    Arkhipov, R. M.; Arkhipov, M. V.; Pakhomov, A. V.; Babushkin, I.; Demircan, A.; Morgner, U.; Rosanov, N. N.

    2017-11-01

    We consider theoretically recently proposed a new possibility of creation, erasing and ultrafast control of population density grating. Such grating can be created in resonant medium when ultrashort pulses with duration smaller than relaxation times in the resonant medium (coherent light matter interactions) propagate without overlapping in this medium. Possible applications in the ultrafast optics such as optical switcher and laser beam deflector are discussed.

  17. Population density, sexual reproduction and diapause in monogonont rotifers: new data for Brachionus and a review

    Directory of Open Access Journals (Sweden)

    John J. GILBERT

    2004-09-01

    Full Text Available Diapausing, fertilized eggs in monogonont rotifers typically are formed after an environmental signal induces amictic females to produce mictic daughters. Mictic females lay haploid eggs that may develop parthenogenetically into males, or that may be fertilized and develop into diapausing, female embryos called resting eggs. Laboratory experiments demonstrate that crowding is the signal for production of mictic females in strains of Brachionus calyciflorus from Texas, Spain and Germany, and in a strain of Brachionus variabilis from Spain. In these experiments, newborn amictic females were cultured singly in large and small volumes to give lowand high-density treatments. Therefore, the induction of mictic females is due exclusively to population density and cannot be attributed to a grouping effect involving some interaction among individuals. B. variabilis is very sensitive to population density; females had to be cultured in 30 ml to prevent appreciable production of mictic daughters. Crowding is now known to be the signal for initiation of sexuality and diapause in four species of Brachionus, two species of Epiphanes, and Rhinoglena frontalis. The chemical that mediates this response somehow influences oocytes in the maternal body cavity to differentiate into mictic females. Aggregation of individuals in natural systems may facilitate the production of mictic females. In some of these rotifers, the response to crowding is suppressed in early generations from the resting egg, assuring that clonal populations will attain higher population densities before committing to sexual reproduction. Fitness benefits of the mictic-female response to crowding, and to other environmental signals in other rotifers (dietary tocopherol, long photoperiod, are discussed.

  18. A new approach on seismic mortality estimations based on average population density

    Science.gov (United States)

    Zhu, Xiaoxin; Sun, Baiqing; Jin, Zhanyong

    2016-12-01

    This study examines a new methodology to predict the final seismic mortality from earthquakes in China. Most studies established the association between mortality estimation and seismic intensity without considering the population density. In China, however, the data are not always available, especially when it comes to the very urgent relief situation in the disaster. And the population density varies greatly from region to region. This motivates the development of empirical models that use historical death data to provide the path to analyze the death tolls for earthquakes. The present paper employs the average population density to predict the final death tolls in earthquakes using a case-based reasoning model from realistic perspective. To validate the forecasting results, historical data from 18 large-scale earthquakes occurred in China are used to estimate the seismic morality of each case. And a typical earthquake case occurred in the northwest of Sichuan Province is employed to demonstrate the estimation of final death toll. The strength of this paper is that it provides scientific methods with overall forecast errors lower than 20 %, and opens the door for conducting final death forecasts with a qualitative and quantitative approach. Limitations and future research are also analyzed and discussed in the conclusion.

  19. A nonnative and a native fungal plant pathogen similarly stimulate ectomycorrhizal development but are perceived differently by a fungal symbiont.

    Science.gov (United States)

    Zampieri, Elisa; Giordano, Luana; Lione, Guglielmo; Vizzini, Alfredo; Sillo, Fabiano; Balestrini, Raffaella; Gonthier, Paolo

    2017-03-01

    The effects of plant symbionts on host defence responses against pathogens have been extensively documented, but little is known about the impact of pathogens on the symbiosis and if such an impact may differ for nonnative and native pathogens. Here, this issue was addressed in a study of the model system comprising Pinus pinea, its ectomycorrhizal symbiont Tuber borchii, and the nonnative and native pathogens Heterobasidion irregulare and Heterobasidion annosum, respectively. In a 6-month inoculation experiment and using both in planta and gene expression analyses, we tested the hypothesis that H. irregulare has greater effects on the symbiosis than H. annosum. Although the two pathogens induced the same morphological reaction in the plant-symbiont complex, with mycorrhizal density increasing exponentially with pathogen colonization of the host, the number of target genes regulated in T. borchii in plants inoculated with the native pathogen (i.e. 67% of tested genes) was more than twice that in plants inoculated with the nonnative pathogen (i.e. 27% of genes). Although the two fungal pathogens did not differentially affect the amount of ectomycorrhizas, the fungal symbiont perceived their presence differently. The results may suggest that the symbiont has the ability to recognize a self/native and a nonself/nonnative pathogen, probably through host plant-mediated signal transduction. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  20. Cytogenetic and symbiont analysis of five members of the B. dorsalis complex (Diptera, Tephritidae): no evidence of chromosomal or symbiont-based speciation events.

    Science.gov (United States)

    Augustinos, Antonios A; Drosopoulou, Elena; Gariou-Papalexiou, Aggeliki; Asimakis, Elias D; Cáceres, Carlos; Tsiamis, George; Bourtzis, Kostas; Penelope Mavragani-Tsipidou; Zacharopoulou, Antigone

    2015-01-01

    The Bactrocera dorsalis species complex, currently comprising about 90 entities has received much attention. During the last decades, considerable effort has been devoted to delimiting the species of the complex. This information is of great importance for agriculture and world trade, since the complex harbours several pest species of major economic importance and other species that could evolve into global threats. Speciation in Diptera is usually accompanied by chromosomal rearrangements, particularly inversions that are assumed to reduce/eliminate gene flow. Other candidates currently receiving much attention regarding their possible involvement in speciation are reproductive symbionts, such as Wolbachia, Spiroplasma, Arsenophonus, Rickettsia and Cardinium. Such symbionts tend to spread quickly through natural populations and can cause a variety of phenotypes that promote pre-mating and/or post-mating isolation and, in addition, can affect the biology, physiology, ecology and evolution of their insect hosts in various ways. Considering all these aspects, we present: (a) a summary of the recently gained knowledge on the cytogenetics of five members of the Bactrocera dorsalis complex, namely Bactrocera dorsalis s.s., Bactrocera invadens, Bactrocera philippinensis, Bactrocera papayae and Bactrocera carambolae, supplemented by additional data from a Bactrocera dorsalis s.s. colony from China, as well as by a cytogenetic comparison between the dorsalis complex and the genetically close species, Bactrocera tryoni, and, (b) a reproductive symbiont screening of 18 different colonized populations of these five taxa. Our analysis did not reveal any chromosomal rearrangements that could differentiate among them. Moreover, screening for reproductive symbionts was negative for all colonies derived from different geographic origins and/or hosts. There are many different factors that can lead to speciation, and our data do not support chromosomal and/or symbiotic

  1. Deer presence rather than abundance determines the population density of the sheep tick, Ixodes ricinus, in Dutch forests

    NARCIS (Netherlands)

    Hofmeester, Tim R.; Sprong, Hein; Jansen, Patrick A.; Prins, Herbert H.T.; Wieren, Van Sipke E.

    2017-01-01

    Background: Understanding which factors drive population densities of disease vectors is an important step in assessing disease risk. We tested the hypothesis that the density of ticks from the Ixodes ricinus complex, which are important vectors for tick-borne diseases, is determined by the density

  2. Deer presence rather than abundance determines the population density of the sheep tick, Ixodes ricinus, in Dutch forests.

    NARCIS (Netherlands)

    Hofmeester, Tim R; Sprong, Hein; Jansen, Patrick A; Prins, Herbert H T; van Wieren, Sipke E

    2017-01-01

    Understanding which factors drive population densities of disease vectors is an important step in assessing disease risk. We tested the hypothesis that the density of ticks from the Ixodes ricinus complex, which are important vectors for tick-borne diseases, is determined by the density of deer, as

  3. Sex differences in fingerprint ridge density in the Mataco-Mataguayo population.

    Science.gov (United States)

    Gutiérrez-Redomero, E; Alonso, M C; Dipierri, J E

    2011-12-01

    Ridge density (RD), the number of digital ridges per unit area, varies according to sex, age, and population origin. The main objective of this study was to determine the extent of sexual dimorphism in RD and to set the age at which it appears, in an Amerindian sample from the Mataco-Mataguayo population. The sample studied for this research consisted of 99 males and 110 females, between 6 and 25 years old, which amounts to a total of 2090 fingerprints. Ridge count was carried out on distal radial and distal ulnar and on proximal regions of each finger to explore the RD patterns in order to identify similarities and differences among samples, areas, age groups, and sexes. RD decreased with age and, at all ages, RD was higher on the distal (radial and ulnar) areas, followed by the proximal sides. Females were found to have higher RD than males when older than 12 years, but not when younger. In the radial area, the Mataco-Mataguayo population, in both sexes, presented the RD similar to Spanish samples, but higher than all other populations analysed to date using this method. Variations in RD in the Amerindian population based on sex, age, and topology were confirmed in this work, and it is postulated that these variations are due to developmental differences among individuals and populations. A comparison between the Mataco-Mataguayo and Spanish populations is presented. Copyright © 2011 Elsevier GmbH. All rights reserved.

  4. Vitamin D status and bone mineral density in the Chinese population: a review.

    Science.gov (United States)

    Man, P W; van der Meer, I M; Lips, P; Middelkoop, B J C

    2016-01-01

    Low vitamin D status is associated with low bone mass which, in turn, is an important predictor of fracture. However, data on this relationship in non-Caucasian populations are scarce. This review shows such an association in the Chinese population in five of the 11 included studies. In the elderly population, the serum 25-hydroxyvitamin D [25(OH)D] concentration is often inadequate. This may cause a lower bone mineral density (BMD), which is an important predictor of fracture. It is estimated that by 2050 more than half of all hip fractures worldwide will occur in Asia. However, data on the relationship between vitamin D status and BMD in a non-Caucasian population are scarce. Therefore, this study reviews the literature on the relationship between serum 25(OH)D and BMD in the Chinese population. A search was made in PubMed, EMBASE, Web of Science and Cochrane Library (up to December 2014) to identify relevant studies using the terms vitamin D status, bone mineral density, and Chinese. Of the 293 studies identified, 11 fulfilled the inclusion and exclusion criteria and were analyzed. Mean serum 25(OH)D concentrations ranged from 29-82 nmol/L. In 5 of the 11 studies, an association was found between vitamin D status and BMD in the Chinese population. The evidence for a relationship between the serum 25(OH)D concentration and BMD in the middle-aged and elderly Chinese population living in Asia appears to be limited and inconsistent.

  5. Larval Population Density Alters Adult Sleep in Wild-Type Drosophila melanogaster but Not in Amnesiac Mutant Flies

    Directory of Open Access Journals (Sweden)

    Michael W. Chi

    2014-08-01

    Full Text Available Sleep has many important biological functions, but how sleep is regulated remains poorly understood. In humans, social isolation and other stressors early in life can disrupt adult sleep. In fruit flies housed at different population densities during early adulthood, social enrichment was shown to increase subsequent sleep, but it is unknown if population density during early development can also influence adult sleep. To answer this question, we maintained Drosophila larvae at a range of population densities throughout larval development, kept them isolated during early adulthood, and then tested their sleep patterns. Our findings reveal that flies that had been isolated as larvae had more fragmented sleep than those that had been raised at higher population densities. This effect was more prominent in females than in males. Larval population density did not affect sleep in female flies that were mutant for amnesiac, which has been shown to be required for normal memory consolidation, adult sleep regulation, and brain development. In contrast, larval population density effects on sleep persisted in female flies lacking the olfactory receptor or83b, suggesting that olfactory signals are not required for the effects of larval population density on adult sleep. These findings show that population density during early development can alter sleep behavior in adulthood, suggesting that genetic and/or structural changes are induced by this developmental manipulation that persist through metamorphosis.

  6. Larval Population Density Alters Adult Sleep in Wild-Type Drosophila melanogaster but Not in Amnesiac Mutant Flies

    Science.gov (United States)

    Chi, Michael W.; Griffith, Leslie C.; Vecsey, Christopher G.

    2014-01-01

    Sleep has many important biological functions, but how sleep is regulated remains poorly understood. In humans, social isolation and other stressors early in life can disrupt adult sleep. In fruit flies housed at different population densities during early adulthood, social enrichment was shown to increase subsequent sleep, but it is unknown if population density during early development can also influence adult sleep. To answer this question, we maintained Drosophila larvae at a range of population densities throughout larval development, kept them isolated during early adulthood, and then tested their sleep patterns. Our findings reveal that flies that had been isolated as larvae had more fragmented sleep than those that had been raised at higher population densities. This effect was more prominent in females than in males. Larval population density did not affect sleep in female flies that were mutant for amnesiac, which has been shown to be required for normal memory consolidation, adult sleep regulation, and brain development. In contrast, larval population density effects on sleep persisted in female flies lacking the olfactory receptor or83b, suggesting that olfactory signals are not required for the effects of larval population density on adult sleep. These findings show that population density during early development can alter sleep behavior in adulthood, suggesting that genetic and/or structural changes are induced by this developmental manipulation that persist through metamorphosis. PMID:25116571

  7. Unique Features of High-Density Lipoproteins in the Japanese: In Population and in Genetic Factors

    Directory of Open Access Journals (Sweden)

    Shinji Yokoyama

    2015-04-01

    Full Text Available Despite its gradual increase in the past several decades, the prevalence of atherosclerotic vascular disease is low in Japan. This is largely attributed to difference in lifestyle, especially food and dietary habits, and it may be reflected in certain clinical parameters. Plasma high-density lipoprotein (HDL levels, a strong counter risk for atherosclerosis, are indeed high among the Japanese. Accordingly, lower HDL seems to contribute more to the development of coronary heart disease (CHD than an increase in non-HDL lipoproteins at a population level in Japan. Interestingly, average HDL levels in Japan have increased further in the past two decades, and are markedly higher than in Western populations. The reasons and consequences for public health of this increase are still unknown. Simulation for the efficacy of raising HDL cholesterol predicts a decrease in CHD of 70% in Japan, greater than the extent by reducing low-density lipoprotein cholesterol predicted by simulation or achieved in a statin trial. On the other hand, a substantial portion of hyperalphalipoproteinemic population in Japan is accounted for by genetic deficiency of cholesteryl ester transfer protein (CETP, which is also commonly unique in East Asian populations. It is still controversial whether CETP mutations are antiatherogenic. Hepatic Schistosomiasis is proposed as a potential screening factor for historic accumulation of CETP deficiency in East Asia.

  8. The integrative effects of population density, photoperiod, temperature, and host plant on the induction of alate aphids in Schizaphis graminum.

    Science.gov (United States)

    An, Chunju; Fei, Xiaodong; Chen, Wenfeng; Zhao, Zhangwu

    2012-04-01

    The wheat aphid Schizaphis graminum (Rondani) displays wing dimorphism with both winged and wingless adult morphs. The winged morph is an adaptive microevolutionary response to undesirable environmental conditions, including undesirable population density, photoperiod, temperature, and host plant. Here we studied the integrative effects of population density, photoperiod, temperature, and host plant on the induction of alate aphids in S. graminum. The present results show that these four factors all play roles in inducing alate aphids in S. graminum but population density is the most important under almost all circumstances. In importance, population density is followed by photoperiod, host plant, and temperature, in that order. These results indicate that ambient environmental factors are highly important to stimulation of alate aphids in S. graminum, especially when population density reaches 64 individuals per leaf. © 2012 Wiley Periodicals, Inc.

  9. Adaptive landscapes and density-dependent selection in declining salmonid populations: going beyond numerical responses to human disturbance

    OpenAIRE

    Einum, Sigurd; Robertsen, Grethe; Fleming, Ian A

    2008-01-01

    Theory suggests an important role for population density in shaping adaptive landscapes through density-dependent selection. Here, we identify five methodological approaches for studying such selection, review the existing empirical evidence for it, and ask whether current declines in abundance can be expected to trigger evolutionary responses in salmonid fishes. Across taxa we find substantial amounts of evidence for population density influencing the location of adaptive peaks for a range o...

  10. Mechanisms regulating amphipod population density within macroalgal communities with low predator impact

    Directory of Open Access Journals (Sweden)

    Hartvig Christie

    2004-04-01

    Full Text Available In eight mesocosms (land based basins macroalgae communities with associated fauna were transplanted from the sea and established during two years. Then, different doses of nutrients (N and P were added to the basins throughout the following three years. During the period of nutrient addition, macroinvertebrate grazers showed seasonal fluctuations with densities usually between 500,000 and 1 million individuals per mesocosm during summer and to a level of about 100,000 during winter. The macroinvertebrate grazers mainly consisted of about 10 species of amphipods and isopods, among which the amphipod Gammarus locusta dominated strongly by biomass. Although the number of predators was very low, the grazer populations never reached a density where considerable grazing impact could be found on the macroalgae. No increase in grazer density was found in the basins with improved nutrient conditions. Thus food quality may be insufficient for further population growth, or density dependant regulation mechanisms may have prevented the grazers from flourishing and overgrazing the system. In aquarium experiments we showed that G. locusta could grow and reproduce on Fucus serratus, Ulva lactuca, periphyton and detritus, and that cannibalism by adult G. locusta on juveniles may have great impact on the population growth. The basins were run with a water flow through system. Nets were placed in front of the inflow and outflow tubes to measure immigration and emigration. Only few individuals (and no Gammarus sp. were recorded in the inflowing water, while high numbers of both amphipods and isopods were found in the outflowing water. Emigration reached peak values during night-time, and it was then two to three times as high as during day-time. Emigration of mobile grazers from the basins amounted to 1-2% of the standing stock daily. These mechanisms that regulate grazers do contribute to maintenance of the seaweed dominance and thus the stability of the seaweed

  11. Escape from the competence state in Streptococcus mutans is governed by the bacterial population density.

    Science.gov (United States)

    Dufour, D; Villemin, C; Perry, J A; Lévesque, C M

    2016-12-01

    Horizontal gene transfer through natural DNA transformation is an important evolutionary mechanism among bacteria. Transformation requires that the bacteria are physiologically competent to take and incorporate free DNA directly from the environment. Although natural genetic transformation is a remarkable feature of many naturally competent bacteria, the process is energetically expensive for the cells. Consequently, a tight control of the competence state is necessary. The objective of the present work was to help decipher the molecular mechanisms regulating the escape from the competence state in Streptococcus mutans, the principal etiological agent responsible for tooth decay in humans. Our results showed that the cessation of competence in S. mutans was abrupt, and did not involve the accumulation of a competence inhibitor nor the depletion of a competence activator in the extracellular environment. The competence state was repressed at high cell population density via concomitant repression of sigX gene encoding the master regulator of the competence regulon. Co-culture experiments performed with oral and non-oral bacteria showed that S. mutans assesses its own population density and also the microbial density of its surroundings to regulate its competence escape. Interestingly, neither the intra-species and extra-species quorum-sensing systems nor the other 13 two-component regulatory systems identified in S. mutans were involved in the cell-density-dependent escape of the competence state. Altogether, our results suggest a complex mechanism regulating the competence shut-off involving cell-density-dependent repression of sigX through an as yet undefined system, and possibly SigX protein stability. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  12. Population density of mediterranean fruit fly (Ceratitis capitata) on fruit orchards in south Baghdad

    International Nuclear Information System (INIS)

    Khalaf, M. Z.; Shbar, A. K.; Naher, F. H.; Jabo, N. F.; Abdulhamza, B. H.; Abod, R. S.

    2012-12-01

    In the recent years the mediterranean fruit fly, Ceratitis capitata distributed in the orchards of central Iraq and caused highly economic losses. This study was conducted in orchards in South Baghdad during 2009 and 2010 and made field survey of the insect in four types of orchards (Citrus, Apricot, Figs and Citrus and A mixture of fruit trees) and used for this purpose tephri traps supplied with Q-Lure and dimethyl dichlorovinyl phosphate (DDVP). The present preliminary study has shown that the Mediterranean fruit fly C.capitata has a year round presence in fruit orchards in central Iraq and reached its highest numerical density of the pest in citrus orchards during November and December were 345 and 363 insect / Trap per month in citrus orchards and the least numerical density during of January and February while the highest numerical density of the insect in orchards of orchards of apricot in Mrch 2010, Figs and Citrus in August 2009 and a Mixture of fruit trees in November 2009 were 45, 116, 311 Insect/ trap per month respectively. The population density of the pest was highest beginning 2010 compared with 2009 , but the high temperature degree (46 - o 5 2) in August 2010 caused a decrease in population density of this pest. C.capitata caused highly economic losses in citrus reaching 68, 71, 82% of the Mandarin, Kaki, Apricot fruits respectively. Currently in Iraq no control method to reduce the economic losses caused by this pest except the use of pesticides GF-120. Therefore, results of this study could be of benefit for orcharch owners when applying an integrated program for controlling fruit fly pests. (Author)

  13. Application of Semiparametric Spline Regression Model in Analyzing Factors that In uence Population Density in Central Java

    Science.gov (United States)

    Sumantari, Y. D.; Slamet, I.; Sugiyanto

    2017-06-01

    Semiparametric regression is a statistical analysis method that consists of parametric and nonparametric regression. There are various approach techniques in nonparametric regression. One of the approach techniques is spline. Central Java is one of the most densely populated province in Indonesia. Population density in this province can be modeled by semiparametric regression because it consists of parametric and nonparametric component. Therefore, the purpose of this paper is to determine the factors that in uence population density in Central Java using the semiparametric spline regression model. The result shows that the factors which in uence population density in Central Java is Family Planning (FP) active participants and district minimum wage.

  14. Delivery of a functional anti-trypanosome Nanobody in different tsetse fly tissues via a bacterial symbiont, Sodalis glossinidius.

    Science.gov (United States)

    De Vooght, Linda; Caljon, Guy; De Ridder, Karin; Van Den Abbeele, Jan

    2014-11-07

    Sodalis glossinidius, a vertically transmitted microbial symbiont of the tsetse fly, is currently considered as a potential delivery system for anti-trypanosomal components that reduce or eliminate the capability of the tsetse fly host to transmit parasitic trypanosomes, an approach also known as paratransgenesis. An essential step in developing paratransgenic tsetse is the stable colonization of adult flies and their progeny with recombinant Sodalis bacteria, expressing trypanocidal effector molecules in tissues where the parasite resides. In this study, Sodalis was tested for its ability to deliver functional anti-trypanosome nanobodies (Nbs) in Glossina morsitans morsitans. We characterized the in vitro and in vivo stability of recombinant Sodalis (recSodalis) expressing a potent trypanolytic nanobody, i.e. Nb_An46. We show that recSodalis is competitive with WT Sodalis in in vivo conditions and that tsetse flies transiently cleared of their endogenous WT Sodalis population can be successfully repopulated with recSodalis at high densities. In addition, vertical transmission to the offspring was observed. Finally, we demonstrated that recSodalis expressed significant levels (ng range) of functional Nb_An46 in different tsetse fly tissues, including the midgut where an important developmental stage of the trypanosome parasite occurs. We demonstrated the proof-of-concept that the Sodalis symbiont can be genetically engineered to express and release significant amounts of functional anti-trypanosome Nbs in different tissues of the tsetse fly. The application of this innovative concept of using pathogen-targeting nanobodies delivered by insect symbiotic bacteria could be extended to other vector-pathogen systems.

  15. The applicability of camera trapping to estimate population density of chamois in Biokovo Nature Park

    Directory of Open Access Journals (Sweden)

    Nikica Šprem

    2012-01-01

    Full Text Available Chamois (Rupicapra rupicapra L. with the Biokovo Nature Park is one of the largest and most stable populations of chamois in Croatia. Reintroduced in year 1964, and present estimated population size is estimated at 350 to 400 individuals. Estimate of population size is very important, since the animals inhabit and are often distributed across forest habitats, it is sometimes difficult and/or very expensive. Therefore, our objective was use of sensor cameras to estimate population density and population structure of chamois on the Biokovo mountain. The study was conducted in summer 2011th year, with three sensor cameras in three different localities. The cameras have recorded a total of 1003 JPEG images. During monitoring, we recorded 164 different individuals of chamois, of which there are 119 female and 45 male specimens. Daily dynamics of arriving was the highest in two periods, morning between 06:00 and 08:00, and in the evening between 18:00 and 20:00. The results of sensor cameras can be considered valid, and are extremely technical aid for the better management and protection of animal species, because we have data on the structure of the population.

  16. Rhizobium laguerreae is the main nitrogen-fixing symbiont of cultivated lentil (Lens culinaris) in Morocco.

    Science.gov (United States)

    Taha, Kaoutar; Berraho, El Bekkay; El Attar, Imane; Dekkiche, Samia; Aurag, Jamal; Béna, Gilles

    2018-03-01

    Genetic diversity and population structure of 268 Lens culinaris symbiotic rhizobia collected from 40 cultivated fields in the main lentil production regions in Morocco were estimated. Three chromosomal housekeeping genes (recA, glnII and atpD) and one common symbiotic gene (nodC) were sequenced and analyzed in order to identify the local symbionts of lentil. The molecular phylogeny of the concatenated housekeeping genes clustered more than 95% of the isolates in one main clade together with Rhizobium laguerreae species. R. laguerreae represents the main symbiont of cultivated lentil in Morocco and, for the first time, a large sample of individuals is obtained for this species. There is a significant and high genetic differentiation of bacterial populations among the four regions for their symbiotic gene, and much lower for their housekeeping genes. The reasons why R. laguerreae is so frequently recovered in our study is discussed. Copyright © 2018 Elsevier GmbH. All rights reserved.

  17. Density estimation in a wolverine population using spatial capture-recapture models

    Science.gov (United States)

    Royle, J. Andrew; Magoun, Audrey J.; Gardner, Beth; Valkenbury, Patrick; Lowell, Richard E.; McKelvey, Kevin

    2011-01-01

    Classical closed-population capture-recapture models do not accommodate the spatial information inherent in encounter history data obtained from camera-trapping studies. As a result, individual heterogeneity in encounter probability is induced, and it is not possible to estimate density objectively because trap arrays do not have a well-defined sample area. We applied newly-developed, capture-recapture models that accommodate the spatial attribute inherent in capture-recapture data to a population of wolverines (Gulo gulo) in Southeast Alaska in 2008. We used camera-trapping data collected from 37 cameras in a 2,140-km2 area of forested and open habitats largely enclosed by ocean and glacial icefields. We detected 21 unique individuals 115 times. Wolverines exhibited a strong positive trap response, with an increased tendency to revisit previously visited traps. Under the trap-response model, we estimated wolverine density at 9.7 individuals/1,000-km2(95% Bayesian CI: 5.9-15.0). Our model provides a formal statistical framework for estimating density from wolverine camera-trapping studies that accounts for a behavioral response due to baited traps. Further, our model-based estimator does not have strict requirements about the spatial configuration of traps or length of trapping sessions, providing considerable operational flexibility in the development of field studies.

  18. Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality

    Science.gov (United States)

    Bruggeman, Jason E.; Swem, Ted; Andersen, David E.; Kennedy, Patricia L.; Nigro, Debora A.

    2015-01-01

    Intrinsic and extrinsic factors affect vital rates and population-level processes, and understanding these factors is paramount to devising successful management plans for wildlife species. For example, birds time migration in response, in part, to local and broadscale climate fluctuations to initiate breeding upon arrival to nesting territories, and prolonged inclement weather early in the breeding season can inhibit egg-laying and reduce productivity. Also, density-dependent regulation occurs in raptor populations, as territory size is related to resource availability. Arctic Peregrine Falcons (Falco peregrinus tundrius; hereafter Arctic peregrine) have a limited and northern breeding distribution, including the Colville River Special Area (CRSA) in the National Petroleum Reserve–Alaska, USA. We quantified influences of climate, topography, nest productivity, prey habitat, density dependence, and interspecific competition affecting Arctic peregrines in the CRSA by applying the Dail-Madsen model to estimate abundance and vital rates of adults on nesting cliffs from 1981 through 2002. Arctic peregrine abundance increased throughout the 1980s, which spanned the population's recovery from DDT-induced reproductive failure, until exhibiting a stationary trend in the 1990s. Apparent survival rate (i.e., emigration; death) was negatively correlated with the number of adult Arctic peregrines on the cliff the previous year, suggesting effects of density-dependent population regulation. Apparent survival and arrival rates (i.e., immigration; recruitment) were higher during years with earlier snowmelt and milder winters, and apparent survival was positively correlated with nesting season maximum daily temperature. Arrival rate was positively correlated with average Arctic peregrine productivity along a cliff segment from the previous year and initial abundance was positively correlated with cliff height. Higher cliffs with documented higher productivity (presumably

  19. Experimental evolution of parasitoid infectivity on symbiont-protected hosts leads to the emergence of genotype specificity.

    Science.gov (United States)

    Rouchet, Romain; Vorburger, Christoph

    2014-06-01

    Host-parasitoid interactions may lead to strong reciprocal selection for traits involved in host defense and parasitoid counterdefense. In aphids, individuals harboring the facultative bacterial endosymbiont, Hamiltonella defensa, exhibit enhanced resistance to parasitoid wasps. We used an experimental evolution approach to investigate the ability of the parasitoid wasp, Lysiphlebus fabarum, to adapt to the presence of H. defensa in its aphid host Aphis fabae. Sexual populations of the parasitoid were exposed for 11 generations to a single clone of A. fabae, either free of H. defensa or harboring artificial infections with three different isolates of H. defensa. Parasitoids adapted rapidly to the presence of H. defensa in their hosts, but this adaptation was in part specific to the symbiont isolate they were evolving against and did not result in an improved infectivity on all symbiont-protected hosts. Comparisons of life-history traits among the evolved lines of parasitoids did not reveal any evidence for costs of adaptation to H. defensa in terms of correlated responses that could constrain such adaptation. These results show that parasitoids readily evolve counter-adaptations to heritable defensive symbionts of their hosts, but that different symbiont strains impose different evolutionary challenges. The symbionts thus mediate the host-parasite interaction by inducing line-by-line genetic specificity. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

  20. Model-based estimators of density and connectivity to inform conservation of spatially structured populations

    Science.gov (United States)

    Morin, Dana J.; Fuller, Angela K.; Royle, J. Andrew; Sutherland, Chris

    2017-01-01

    Conservation and management of spatially structured populations is challenging because solutions must consider where individuals are located, but also differential individual space use as a result of landscape heterogeneity. A recent extension of spatial capture–recapture (SCR) models, the ecological distance model, uses spatial encounter histories of individuals (e.g., a record of where individuals are detected across space, often sequenced over multiple sampling occasions), to estimate the relationship between space use and characteristics of a landscape, allowing simultaneous estimation of both local densities of individuals across space and connectivity at the scale of individual movement. We developed two model-based estimators derived from the SCR ecological distance model to quantify connectivity over a continuous surface: (1) potential connectivity—a metric of the connectivity of areas based on resistance to individual movement; and (2) density-weighted connectivity (DWC)—potential connectivity weighted by estimated density. Estimates of potential connectivity and DWC can provide spatial representations of areas that are most important for the conservation of threatened species, or management of abundant populations (i.e., areas with high density and landscape connectivity), and thus generate predictions that have great potential to inform conservation and management actions. We used a simulation study with a stationary trap design across a range of landscape resistance scenarios to evaluate how well our model estimates resistance, potential connectivity, and DWC. Correlation between true and estimated potential connectivity was high, and there was positive correlation and high spatial accuracy between estimated DWC and true DWC. We applied our approach to data collected from a population of black bears in New York, and found that forested areas represented low levels of resistance for black bears. We demonstrate that formal inference about measures

  1. Estimating cetacean population density using fixed passive acoustic sensors: an example with Blainville's beaked whales.

    Science.gov (United States)

    Marques, Tiago A; Thomas, Len; Ward, Jessica; DiMarzio, Nancy; Tyack, Peter L

    2009-04-01

    Methods are developed for estimating the size/density of cetacean populations using data from a set of fixed passive acoustic sensors. The methods convert the number of detected acoustic cues into animal density by accounting for (i) the probability of detecting cues, (ii) the rate at which animals produce cues, and (iii) the proportion of false positive detections. Additional information is often required for estimation of these quantities, for example, from an acoustic tag applied to a sample of animals. Methods are illustrated with a case study: estimation of Blainville's beaked whale density over a 6 day period in spring 2005, using an 82 hydrophone wide-baseline array located in the Tongue of the Ocean, Bahamas. To estimate the required quantities, additional data are used from digital acoustic tags, attached to five whales over 21 deep dives, where cues recorded on some of the dives are associated with those received on the fixed hydrophones. Estimated density was 25.3 or 22.5 animals/1000 km(2), depending on assumptions about false positive detections, with 95% confidence intervals 17.3-36.9 and 15.4-32.9. These methods are potentially applicable to a wide variety of marine and terrestrial species that are hard to survey using conventional visual methods.

  2. Comparative genomics of vesicomyid clam (Bivalvia: Mollusca chemosynthetic symbionts

    Directory of Open Access Journals (Sweden)

    Girguis Peter R

    2008-12-01

    Full Text Available Abstract Background The Vesicomyidae (Bivalvia: Mollusca are a family of clams that form symbioses with chemosynthetic gamma-proteobacteria. They exist in environments such as hydrothermal vents and cold seeps and have a reduced gut and feeding groove, indicating a large dependence on their endosymbionts for nutrition. Recently, two vesicomyid symbiont genomes were sequenced, illuminating the possible nutritional contributions of the symbiont to the host and making genome-wide evolutionary analyses possible. Results To examine the genomic evolution of the vesicomyid symbionts, a comparative genomics framework, including the existing genomic data combined with heterologous microarray hybridization results, was used to analyze conserved gene content in four vesicomyid symbiont genomes. These four symbionts were chosen to include a broad phylogenetic sampling of the vesicomyid symbionts and represent distinct chemosynthetic environments: cold seeps and hydrothermal vents. Conclusion The results of this comparative genomics analysis emphasize the importance of the symbionts' chemoautotrophic metabolism within their hosts. The fact that these symbionts appear to be metabolically capable autotrophs underscores the extent to which the host depends on them for nutrition and reveals the key to invertebrate colonization of these challenging environments.

  3. Standard methods for research on apis mellifera gut symbionts

    Science.gov (United States)

    Gut microbes can play an important role in digestion, disease resistance, and the general health of animals, but little is known about the biology of gut symbionts in Apis mellifera. This paper is part of a series on honey bee research methods, providing protocols for studying gut symbionts. We desc...

  4. Standard methods for research on Apis mellifera gut symbionts

    Science.gov (United States)

    Gut microbes can play an important role in digestion, disease resistance, and the general health of animals, but little is known about the biology of gut symbionts in Apis mellifera. This paper is part of a series on honey bee research methods, providing protocols for studying gut symbionts. We desc...

  5. Functional Convergence in Reduced Genomes of Bacterial Symbionts Spanning 200 My of Evolution

    OpenAIRE

    McCutcheon, John P.; Moran, Nancy A.

    2010-01-01

    The main genomic changes in the evolution of host-restricted microbial symbionts are ongoing inactivation and loss of genes combined with rapid sequence evolution and extreme structural stability; these changes reflect high levels of genetic drift due to small population sizes and strict clonality. This genomic erosion includes irreversible loss of genes in many functional categories and can include genes that underlie the nutritional contributions to hosts that are the basis of the symbiotic...

  6. Population density, call-response interval, and survival of out-of-hospital cardiac arrest

    Science.gov (United States)

    2011-01-01

    Background Little is known about the effects of geographic variation on outcomes of out-of-hospital cardiac arrest (OHCA). The present study investigated the relationship between population density, time between emergency call and ambulance arrival, and survival of OHCA, using the All-Japan Utstein-style registry database, coupled with geographic information system (GIS) data. Methods We examined data from 101,287 bystander-witnessed OHCA patients who received emergency medical services (EMS) through 4,729 ambulatory centers in Japan between 2005 and 2007. Latitudes and longitudes of each center were determined with address-match geocoding, and linked with the Population Census data using GIS. The endpoints were 1-month survival and neurologically favorable 1-month survival defined as Glasgow-Pittsburgh cerebral performance categories 1 or 2. Results Overall 1-month survival was 7.8%. Neurologically favorable 1-month survival was 3.6%. In very low-density (population size may lead to inequality in health outcomes between urban and rural areas. PMID:21489299

  7. International Consortium on Mammographic Density: Methodology and Population Diversity captured across 22 Countries

    Science.gov (United States)

    McCormack, Valerie A.; Burton, Anya; dos-Santos-Silva, Isabel; Hipwell, John H.; Dickens, Caroline; Salem, Dorria; Kamal, Rasha; Hartman, Mikael; Ling Lee, Charmaine Pei; Chia, Kee-Seng; Ozmen, Vahit; Aribal, Mustafa Erkin; Flugelman, Anath Arzee; Lajous, Martín; Lopez-Riduara, Ruy; Rice, Megan; Romieu, Isabelle; Ursin, Giske; Qureshi, Samera; Ma, Huiyan; Lee, Eunjung; van Gils, Carla H.; Wanders, Johanna O.P.; Vinayak, Sudhir; Ndumia, Rose; Allen, Steve; Vinnicombe, Sarah; Moss, Sue; Lee, Jong Won; Kim, Jisun; Pereira, Ana; Garmendia, Maria Luisa; Sirous, Reza; Sirous, Mehri; Peplonska, Beata; Bukowska, Agnieszka; Tamimi, Rulla M.; Bertrand, Kimberly; Nagata, Chisato; Kwong, Ava; Vachon, Celine; Scott, Christopher; Perez-Gomez, Beatriz; Pollan, Marina; Maskarinec, Gertraud; Giles, Graham; Hopper, John; Stone, Jennifer; Rajaram, Nadia; Teo, Soo-Hwang; Mariapun, Shivaani; Yaffe, Martin J.; Schüz, Joachim; Chiarelli, Anna; Linton, Linda; Boyd, Norman F.

    2015-01-01

    Mammographic density (MD) is a quantitative trait, measurable in all women, and is among the strongest markers of breast cancer risk. The population-based epidemiology of MD has revealed genetic, lifestyle and societal/environmental determinants, but studies have largely been conducted in women with similar westernized lifestyles living in countries with high breast cancer incidence rates. To benefit from the heterogeneity in risk factors and their combinations worldwide, we created an International Consortium on Mammographic Density (ICMD) to pool individual-level epidemiological and MD data from general population studies worldwide. ICMD aims to characterize determinants of MD more precisely, and to evaluate whether they are consistent across populations worldwide. We included 11755 women, from 27 studies in 22 countries, on whom individual-level risk factor data were pooled and original mammographic images were re-read for ICMD by a core team to obtain standardized comparable MD data. In the present article, we present (i) the rationale for this consortium; (ii) characteristics of the studies and women included; and (iii) study methodology to obtain comparable MD data from original re-read films. We also highlight the risk factor heterogeneity captured by such an effort and, thus, the unique insight the pooled study promises to offer through wider exposure ranges, different confounding structures and enhanced power for sub-group analyses. PMID:26724463

  8. Estimating Population Density of the San Martin Titi Monkey (Callicebus oenanthe) in Peru Using Vocalisations.

    Science.gov (United States)

    van Kuijk, Silvy M; García-Suikkanen, Carolina; Tello-Alvarado, Julio C; Vermeer, Jan; Hill, Catherine M

    2015-01-01

    We calculated the population density of the critically endangered Callicebus oenanthe in the Ojos de Agua Conservation Concession, a dry forest area in the department of San Martin, Peru. Results showed significant differences (p < 0.01) in group densities between forest boundaries (16.5 groups/km2, IQR = 21.1-11.0) and forest interior (4.0 groups/km2, IQR = 5.0-0.0), suggesting the 2,550-ha area harbours roughly 1,150 titi monkeys. This makes Ojos de Agua an important cornerstone in the conservation of the species, because it is one of the largest protected areas where the species occurs. © 2016 S. Karger AG, Basel.

  9. Mammals in the areas adjacent to Forsmark and Oskarshamn. Population density, ecological data and carbon budget

    Energy Technology Data Exchange (ETDEWEB)

    Truve, Johan; Cederlund, Goeran [Svensk Naturfoervaltning AB, Ramsberg (Sweden)

    2005-06-01

    The Swedish Nuclear Fuel and Waste Management Co is in the process of selecting a safe and environmentally acceptable location for the deep-level repository of radioactive waste. SKB has expressed the importance of monitoring mammal species that are of interest both in biodiversity issues and for local hunting and recreational purposes. Two of the major goals are to: 1) monitor dynamics of population density over several years; 2) obtain information that is essential for modelling of energy/carbon flows in the biosphere and ultimately calculations of the risks of exposure to radionuclides. This report contributes to the major goals by presenting: Results from surveys of mammal abundance in the study sites near Forsmark and Oskarshamn, and a comparison with data from other surveys. A summary of traits associated to demography, resource selection and spatial distribution. A model framework that can be used to model the future development of populations. A plausible future scenario for mammal species. Mammal contribution to fluxes of energy and material in the ecosystem. Estimated harvest rates of mammals in the study sites. General conclusions that can be drawn from the survey are that population densities of the most common species are in the same range as many other populations. Lynx, wild boar, red deer and fallow deer are expanding in the areas. Marine mammals have not been surveyed but at least grey seals are important top consumers in the coastal ecosystem. Red listed species resident in the areas are Lynx, Otter, Whiskered bat, Natterer's bat, Nathusius' pipistrelle and Harbour seal. Annual production of the mammal species that were surveyed was 40-50 mg carbon/m2 and year. Hunters harvest nearly half of the production each year. Future developments for the populations are briefly discussed and a model framework that can be used to make better quantitative predictions is presented.

  10. Mammals in the areas adjacent to Forsmark and Oskarshamn. Population density, ecological data and carbon budget

    International Nuclear Information System (INIS)

    Truve, Johan; Cederlund, Goeran

    2005-06-01

    The Swedish Nuclear Fuel and Waste Management Co is in the process of selecting a safe and environmentally acceptable location for the deep-level repository of radioactive waste. SKB has expressed the importance of monitoring mammal species that are of interest both in biodiversity issues and for local hunting and recreational purposes. Two of the major goals are to: 1) monitor dynamics of population density over several years; 2) obtain information that is essential for modelling of energy/carbon flows in the biosphere and ultimately calculations of the risks of exposure to radionuclides. This report contributes to the major goals by presenting: Results from surveys of mammal abundance in the study sites near Forsmark and Oskarshamn, and a comparison with data from other surveys. A summary of traits associated to demography, resource selection and spatial distribution. A model framework that can be used to model the future development of populations. A plausible future scenario for mammal species. Mammal contribution to fluxes of energy and material in the ecosystem. Estimated harvest rates of mammals in the study sites. General conclusions that can be drawn from the survey are that population densities of the most common species are in the same range as many other populations. Lynx, wild boar, red deer and fallow deer are expanding in the areas. Marine mammals have not been surveyed but at least grey seals are important top consumers in the coastal ecosystem. Red listed species resident in the areas are Lynx, Otter, Whiskered bat, Natterer's bat, Nathusius' pipistrelle and Harbour seal. Annual production of the mammal species that were surveyed was 40-50 mg carbon/m2 and year. Hunters harvest nearly half of the production each year. Future developments for the populations are briefly discussed and a model framework that can be used to make better quantitative predictions is presented

  11. Extrapolating cetacean densities to quantitatively assess human impacts on populations in the high seas.

    Science.gov (United States)

    Mannocci, Laura; Roberts, Jason J; Miller, David L; Halpin, Patrick N

    2017-06-01

    As human activities expand beyond national jurisdictions to the high seas, there is an increasing need to consider anthropogenic impacts to species inhabiting these waters. The current scarcity of scientific observations of cetaceans in the high seas impedes the assessment of population-level impacts of these activities. We developed plausible density estimates to facilitate a quantitative assessment of anthropogenic impacts on cetacean populations in these waters. Our study region extended from a well-surveyed region within the U.S. Exclusive Economic Zone into a large region of the western North Atlantic sparsely surveyed for cetaceans. We modeled densities of 15 cetacean taxa with available line transect survey data and habitat covariates and extrapolated predictions to sparsely surveyed regions. We formulated models to reduce the extent of extrapolation beyond covariate ranges, and constrained them to model simple and generalizable relationships. To evaluate confidence in the predictions, we mapped where predictions were made outside sampled covariate ranges, examined alternate models, and compared predicted densities with maps of sightings from sources that could not be integrated into our models. Confidence levels in model results depended on the taxon and geographic area and highlighted the need for additional surveying in environmentally distinct areas. With application of necessary caution, our density estimates can inform management needs in the high seas, such as the quantification of potential cetacean interactions with military training exercises, shipping, fisheries, and deep-sea mining and be used to delineate areas of special biological significance in international waters. Our approach is generally applicable to other marine taxa and geographic regions for which management will be implemented but data are sparse. © 2016 The Authors. Conservation Biology published by Wiley Periodicals, Inc. on behalf of Society for Conservation Biology.

  12. Quantifying Nearshore Sea Turtle Densities: Applications of Unmanned Aerial Systems for Population Assessments.

    Science.gov (United States)

    Sykora-Bodie, Seth T; Bezy, Vanessa; Johnston, David W; Newton, Everette; Lohmann, Kenneth J

    2017-12-18

    Although sea turtles face significant pressure from human activities, some populations are recovering due to conservation programs, bans on the trade of turtle products, and reductions in bycatch. While these trends are encouraging, the status of many populations remains unknown and scientific monitoring is needed to inform conservation and management decisions. To address these gaps, this study presents methods for using unmanned aerial systems (UAS) to conduct population assessments. Using a fixed-wing UAS and a modified strip-transect method, we conducted aerial surveys along a three-kilometer track line at Ostional, Costa Rica during a mass-nesting event of olive ridley turtles (Lepidochelys olivacea). We visually assessed images collected during six transects for sea turtle presence, resulting in 682 certain detections. A cumulative total of 1091 certain and probable turtles were detected in the collected imagery. Using these data, we calculate estimates of sea turtle density (km -2 ) in nearshore waters. After adjusting for both availability and perception biases, we developed a low-end estimate of 1299 ± 458 and a high-end estimate of 2086 ± 803 turtles per km -2 . This pilot study illustrates how UAS can be used to conduct robust, safe, and cost-effective population assessments of sea turtle populations in coastal marine ecosystems.

  13. Change in alcohol outlet density and alcohol-related harm to population health (CHALICE

    Directory of Open Access Journals (Sweden)

    Fone David

    2012-06-01

    Full Text Available Abstract Background Excess alcohol consumption has serious adverse effects on health and violence-related harm. In the UK around 37% of men and 29% of women drink to excess and 20% and 13% report binge drinking. The potential impact on population health from a reduction in consumption is considerable. One proposed method to reduce consumption is to reduce availability through controls on alcohol outlet density. In this study we investigate the impact of a change in the density of alcohol outlets on alcohol consumption and alcohol-related harms to health in the community. Methods/Design A natural experiment of the effect of change in outlet density between 2005–09, in Wales, UK; population 2.4 million aged 16 years and over. Data on outlets are held by the 22 local authorities in Wales under The Licensing Act 2003. The study outcomes are change in (1 alcohol consumption using data from annual Welsh Health Surveys, (2 alcohol-related hospital admissions using the Patient Episode Database for Wales, (3 Accident & Emergency department attendances between midnight–6am, and (4 alcohol-related violent crime against the person, using Police data. The data will be anonymously record-linked within the Secure Anonymised Information Linkage Databank at individual and 2001 Census Lower Super Output Area levels. New methods of network analysis will be used to estimate outlet density. Longitudinal statistical analysis will use (1 multilevel ordinal models of consumption and logistic models of admissions and Accident & Emergency attendance as a function of change in individual outlet exposure, adjusting for confounding variables, and (2 spatial models of the change in counts/rates of each outcome measure and outlet density. We will assess the impact on health inequalities and will correct for population migration. Discussion This inter-disciplinary study requires expertise in epidemiology and public health, health informatics, medical statistics

  14. Change in alcohol outlet density and alcohol-related harm to population health (CHALICE)

    Science.gov (United States)

    2012-01-01

    Background Excess alcohol consumption has serious adverse effects on health and violence-related harm. In the UK around 37% of men and 29% of women drink to excess and 20% and 13% report binge drinking. The potential impact on population health from a reduction in consumption is considerable. One proposed method to reduce consumption is to reduce availability through controls on alcohol outlet density. In this study we investigate the impact of a change in the density of alcohol outlets on alcohol consumption and alcohol-related harms to health in the community. Methods/Design A natural experiment of the effect of change in outlet density between 2005–09, in Wales, UK; population 2.4 million aged 16 years and over. Data on outlets are held by the 22 local authorities in Wales under The Licensing Act 2003. The study outcomes are change in (1) alcohol consumption using data from annual Welsh Health Surveys, (2) alcohol-related hospital admissions using the Patient Episode Database for Wales, (3) Accident & Emergency department attendances between midnight–6am, and (4) alcohol-related violent crime against the person, using Police data. The data will be anonymously record-linked within the Secure Anonymised Information Linkage Databank at individual and 2001 Census Lower Super Output Area levels. New methods of network analysis will be used to estimate outlet density. Longitudinal statistical analysis will use (1) multilevel ordinal models of consumption and logistic models of admissions and Accident & Emergency attendance as a function of change in individual outlet exposure, adjusting for confounding variables, and (2) spatial models of the change in counts/rates of each outcome measure and outlet density. We will assess the impact on health inequalities and will correct for population migration. Discussion This inter-disciplinary study requires expertise in epidemiology and public health, health informatics, medical statistics, geographical information science

  15. Effect of mechanical fragmentation of sphagnum on population density and structure of micromycete communities

    Science.gov (United States)

    Semenova, T. A.; Golovchenko, A. V.

    2017-07-01

    The population density and taxonomic structure of micromycetes were monitored for six months in a model experiment with natural and mechanically fragmented (fine and coarse) samples of sphagnum. Sphagnum fragmentation favored an increase in the number of micromycetes only during the first week of the experiment. On the average, the number of micromycetes in fine-fragmented samples was two times greater than that in the coarse-fragmented samples. The diversity of micromycetes increased in the fragmented samples of sphagnum owing to the activation of some species, which remained in the inactive state as spores in the peat before fragmentation.

  16. Population density of Sotalia guianensis (Cetacea: Delphinidae in the Cananéia region, Southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Liisa Havukainen

    2011-09-01

    Full Text Available Population density in cetaceans can be estimated through photo-identification, mark-recapture, land-based observations and visual estimative. We the aim to contribute with conservation strategies, we used line transects (distance method to estimate the population density of the river dolphin, S. guianensis, in the estuarine region of Cananéia, Southeastern Brazil. The study, developed from May 2003 until April 2004, during dry and rainy seasons and different times of the day, included a sampling area divided into three sectors according to their proximity to the open sea: Sector I (the closest to the open sea; Sector II (with a large flow of fresh water and a salient declivity; and Sector III (with a large flow of fresh water and non salient declivity. Onboard random sampling was carried out in all three sectors, and dolphins seen from the bow to 90° on both port and starboard sides, were registered along with their position and distance from the boat. The total density found was 12.41ind/km² (CV=25.53% with an average of 2.2 individuals per group for both periods of the day, morning and afternoon. Densities also varied between dry and rainy seasons, being lower in the first with 5.77ind/km² (CV=27.87% than in the second 20.28ind/km² (CV=31.95%, respectively. Regarding the three sectors, a non-causal heterogeneous distribution was found: Sector I was the most populated (D=33.10ind/km², CV=13.34%, followed by Sector II (D=7.8ind/km², CV=21.07% and Sector III (D=3.04ind/km², CV=34.04%. The aforementioned area, due to its proximity to the open sea, has the highest salinity level and therefore has the greatest chance of holding most of the marine fish schools which can be cornered by dolphins on high declivity areas during fishing activities. This suggests that food availability may be the most important factor on the river dolphin’s distribution in the estuary. Similar studies will contribute to a better understanding of these populations

  17. Population density of Sotalia guianensis (Cetacea: Delphinidae) in the Cananéia region, Southeastern Brazil.

    Science.gov (United States)

    Havukainen, Liisa; Monteiro, Emygdio Leite de Araujo Fiho; Filla, Gislaine de Fatima

    2011-09-01

    Population density in cetaceans can be estimated through photo-identification, mark-recapture, land-based observations and visual estimative. We the aim to contribute with conservation strategies, we used line transects (distance method) to estimate the population density of the river dolphin, S. guianensis, in the estuarine region of Cananéia, Southeastern Brazil. The study, developed from May 2003 until April 2004, during dry and rainy seasons and different times of the day, included a sampling area divided into three sectors according to their proximity to the open sea: Sector I (the closest to the open sea); Sector II (with a large flow of fresh water and a salient declivity); and Sector III (with a large flow of fresh water and non salient declivity). Onboard random sampling was carried out in all three sectors, and dolphins seen from the bow to 90 degrees on both port and starboard sides, were registered along with their position and distance from the boat. The total density found was 12.41 ind/km2 (CV = 25.53%) with an average of 2.2 individuals per group for both periods of the day, morning and afternoon. Densities also varied between dry and rainy seasons, being lower in the first with 5.77 ind/km2 (CV = 27.87%) than in the second 20.28 ind/km2 (CV = 31.95%), respectively. Regarding the three sectors, a non-causal heterogeneous distribution was found: Sector I was the most populated (D = 33.10 ind/km2, CV = 13.34%), followed by Sector II (D = 7.8 ind/km2, CV = 21.07%) and Sector III (D = 3.04 ind/km2, CV = 34.04%). The aforementioned area, due to its proximity to the open sea, has the highest salinity level and therefore has the greatest chance of holding most of the marine fish schools which can be cornered by dolphins on high declivity areas during fishing activities. This suggests that food availability may be the most important factor on the river dolphin's distribution in the estuary. Similar studies will contribute to a better understanding of these

  18. Stochastic population growth in spatially heterogeneous environments: the density-dependent case.

    Science.gov (United States)

    Hening, Alexandru; Nguyen, Dang H; Yin, George

    2018-02-01

    This work is devoted to studying the dynamics of a structured population that is subject to the combined effects of environmental stochasticity, competition for resources, spatio-temporal heterogeneity and dispersal. The population is spread throughout n patches whose population abundances are modeled as the solutions of a system of nonlinear stochastic differential equations living on [Formula: see text]. We prove that r, the stochastic growth rate of the total population in the absence of competition, determines the long-term behaviour of the population. The parameter r can be expressed as the Lyapunov exponent of an associated linearized system of stochastic differential equations. Detailed analysis shows that if [Formula: see text], the population abundances converge polynomially fast to a unique invariant probability measure on [Formula: see text], while when [Formula: see text], the population abundances of the patches converge almost surely to 0 exponentially fast. This generalizes and extends the results of Evans et al. (J Math Biol 66(3):423-476, 2013) and proves one of their conjectures. Compared to recent developments, our model incorporates very general density-dependent growth rates and competition terms. Furthermore, we prove that persistence is robust to small, possibly density dependent, perturbations of the growth rates, dispersal matrix and covariance matrix of the environmental noise. We also show that the stochastic growth rate depends continuously on the coefficients. Our work allows the environmental noise driving our system to be degenerate. This is relevant from a biological point of view since, for example, the environments of the different patches can be perfectly correlated. We show how one can adapt the nondegenerate results to the degenerate setting. As an example we fully analyze the two-patch case, [Formula: see text], and show that the stochastic growth rate is a decreasing function of the dispersion rate. In particular, coupling two

  19. Population density and development potential in rural Zimbabwe: an assessment based on the 1969 and 1982 censuses.

    Science.gov (United States)

    Davies, D H

    1991-01-01

    "Based on 1969 and 1982 census data, this paper examines the spatial association between high rural population density and development potential in Zimbabwe and its significance for national development policy. A 1982 grid cell density map was compiled on the same geographical frame as an existing 1969 density map, yielding an intercensal density change map. A land classification map and a composite map of development constraints were rasterized on the same spatial framework and subjected to computer analysis. Areas of critically high (and generally increasing) densities showed strong spatial associations with areas of severe development constraints...." excerpt

  20. Evaluation of Quantra Hologic Volumetric Computerized Breast Density Software in Comparison With Manual Interpretation in a Diverse Population.

    Science.gov (United States)

    Richard-Davis, Gloria; Whittemore, Brianna; Disher, Anthony; Rice, Valerie Montgomery; Lenin, Rathinasamy B; Dollins, Camille; Siegel, Eric R; Eswaran, Hari

    2018-01-01

    Increased mammographic breast density is a well-established risk factor for breast cancer development, regardless of age or ethnic background. The current gold standard for categorizing breast density consists of a radiologist estimation of percent density according to the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) criteria. This study compares paired qualitative interpretations of breast density on digital mammograms with quantitative measurement of density using Hologic's Food and Drug Administration-approved R2 Quantra volumetric breast density assessment tool. Our goal was to find the best cutoff value of Quantra-calculated breast density for stratifying patients accurately into high-risk and low-risk breast density categories. Screening digital mammograms from 385 subjects, aged 18 to 64 years, were evaluated. These mammograms were interpreted by a radiologist using the ACR's BI-RADS density method, and had quantitative density measured using the R2 Quantra breast density assessment tool. The appropriate cutoff for breast density-based risk stratification using Quantra software was calculated using manually determined BI-RADS scores as a gold standard, in which scores of D3/D4 denoted high-risk densities and D1/D2 denoted low-risk densities. The best cutoff value for risk stratification using Quantra-calculated breast density was found to be 14.0%, yielding a sensitivity of 65%, specificity of 77%, and positive and negative predictive values of 75% and 69%, respectively. Under bootstrap analysis, the best cutoff value had a mean ± SD of 13.70% ± 0.89%. Our study is the first to publish on a North American population that assesses the accuracy of the R2 Quantra system at breast density stratification. Quantitative breast density measures will improve accuracy and reliability of density determination, assisting future researchers to accurately calculate breast cancer risks associated with density increase.

  1. Geographic variation in racial disparities in child maltreatment: The influence of county poverty and population density.

    Science.gov (United States)

    Maguire-Jack, Kathryn; Lanier, Paul; Johnson-Motoyama, Michelle; Welch, Hannah; Dineen, Michael

    2015-09-01

    There are documented disparities in the rates at which black children come into contact with the child welfare system in the United States compared to white children. A great deal of research has proliferated aimed at understanding whether systematic biases or differential rates of risk among different groups drive these disparities (Drake et al., 2011). In the current study, county rates of maltreatment disparity are compared across the United States and examined in relation to rates of poverty disparity as well as population density. Specifically, using hierarchical linear modeling with a spatially lagged dependent variable, the current study examined data from the National Child Abuse and Neglect Data System (NCANDS) and found that poverty disparities were associated with rates of maltreatment disparities, and densely populated metropolitan counties tended to have the greatest levels of maltreatment disparity for both black and Hispanic children. A significant curvilinear relationship was also observed between these variables, such that in addition to the most densely populated counties, the most sparsely populated counties also tended to have higher rates of maltreatment disparity for black and Hispanic children. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Fingerprint ridge density in the Argentinean population and its application to sex inference: A comparative study.

    Science.gov (United States)

    Rivaldería, Noemí; Sánchez-Andrés, Ángeles; Alonso-Rodríguez, Concepción; Dipierri, José E; Gutiérrez-Redomero, Esperanza

    2016-02-01

    Fingerprint ridge density (RD) is known to vary according to sex and population, and such variation can be used for forensic purposes. The aim of this study was to analyze the fingerprint RD of two samples of the Argentinean population in order to assess their topological, digital, bilateral, sexual, and population differences for subsequent application in the inference of sex. Data were collected from the fingerprints of 172 individuals from the Buenos Aires province and 163 from the Chubut province. RD was assessed for three different count areas for all 10 fingers of each individual. In both sexes and both samples, significant differences among areas were obtained, so that radial-RD>ulnar-RD>proximal-RD. Females presented greater RD than males in all areas and on all fingers. Regarding population differences, no significant differences were found between the Buenos Aires and Chubut samples (except for proximal RD in males). However, both samples showed RD significantly different from that of the Jujuy province. The application of Bayes' theorem allowed for the identification of an RD threshold for discrimination of sexes in these Argentinean samples. In conclusion females consistently exhibit narrower epidermal ridges than males, which may evidence a universal pattern of sexual dimorphism in this trait that can be useful in forensics in the identification of individuals. Copyright © 2015 Elsevier GmbH. All rights reserved.

  3. Modelling the broadband propagation of marine mammal echolocation clicks for click-based population density estimates.

    Science.gov (United States)

    von Benda-Beckmann, Alexander M; Thomas, Len; Tyack, Peter L; Ainslie, Michael A

    2018-02-01

    Passive acoustic monitoring with widely-dispersed hydrophones has been suggested as a cost-effective method to monitor population densities of echolocating marine mammals. This requires an estimate of the area around each receiver over which vocalizations are detected-the "effective detection area" (EDA). In the absence of auxiliary measurements enabling estimation of the EDA, it can be modelled instead. Common simplifying model assumptions include approximating the spectrum of clicks by flat energy spectra, and neglecting the frequency-dependence of sound absorption within the click bandwidth (narrowband assumption), rendering the problem amenable to solution using the sonar equation. Here, it is investigated how these approximations affect the estimated EDA and their potential for biasing the estimated density. EDA was estimated using the passive sonar equation, and by applying detectors to simulated clicks injected into measurements of background noise. By comparing model predictions made using these two approaches for different spectral energy distributions of echolocation clicks, but identical click source energy level and detector settings, EDA differed by up to a factor of 2 for Blainville's beaked whales. Both methods predicted relative density bias due to narrowband assumptions ranged from 5% to more than 100%, depending on the species, detector settings, and noise conditions.

  4. Preferential enrichment of large-sized very low density lipoprotein populations with transferred cholesteryl esters

    International Nuclear Information System (INIS)

    Eisenberg, S.

    1985-01-01

    The effect of lipid transfer proteins on the exchange and transfer of cholesteryl esters from rat plasma HDL2 to human very low (VLDL) and low density (LDL) lipoprotein populations was studied. The use of a combination of radiochemical and chemical methods allowed separate assessment of [ 3 H]cholesteryl ester exchange and of cholesteryl ester transfer. VLDL-I was the preferred acceptor for transferred cholesteryl esters, followed by VLDL-II and VLDL-III. LDL did not acquire cholesteryl esters. The contribution of exchange of [ 3 H]cholesteryl esters to total transfer was highest for LDL and decreased in reverse order along the VLDL density range. Inactivation of lecithin: cholesterol acyltransferase (LCAT) and heating the HDL2 for 60 min at 56 degrees C accelerated transfer and exchange of [ 3 H]cholesteryl esters. Addition of lipid transfer proteins increased cholesterol esterification in all systems. The data demonstrate that large-sized, triglyceride-rich VLDL particles are preferred acceptors for transferred cholesteryl esters. It is suggested that enrichment of very low density lipoproteins with cholesteryl esters reflects the triglyceride content of the particles

  5. Population density and sex do not influence fine-scale natal dispersal in roe deer

    Science.gov (United States)

    Gaillard, J.-M; Hewison, A.J.M; Kjellander, P; Pettorelli, N; Bonenfant, C; Van Moorter, B; Liberg, O; Andren, H; Van Laere, G; Klein, F; Angibault, J.-M; Coulon, A; Vanpé, C

    2008-01-01

    It is commonly assumed that the propensity to disperse and the dispersal distance of mammals should increase with increasing density and be greater among males than among females. However, most empirical evidence, especially on large mammals, has focused on highly polygynous and dimorphic species displaying female-defence mating tactics. We tested these predictions on roe deer, a weakly polygynous species of large herbivore exhibiting a resource-defence mating tactic at a fine spatial scale. Using three long-term studies of populations that were subject to the experimental manipulation of size, we did not find any support for either prediction, whether in terms of dispersal probability or dispersal distance. Our findings of similar dispersal patterns in both sexes of roe deer suggest that the underlying cause of natal dispersal is not related to inbreeding avoidance in this species. The absence of positive density dependence in fine-scale dispersal behaviour suggests that roe deer natal dispersal is a pre-saturation process that is shaped by heterogeneities in habitat quality rather than by density per se. PMID:18505718

  6. Population density estimated from locations of individuals on a passive detector array

    Science.gov (United States)

    Efford, Murray G.; Dawson, Deanna K.; Borchers, David L.

    2009-01-01

    The density of a closed population of animals occupying stable home ranges may be estimated from detections of individuals on an array of detectors, using newly developed methods for spatially explicit capture–recapture. Likelihood-based methods provide estimates for data from multi-catch traps or from devices that record presence without restricting animal movement ("proximity" detectors such as camera traps and hair snags). As originally proposed, these methods require multiple sampling intervals. We show that equally precise and unbiased estimates may be obtained from a single sampling interval, using only the spatial pattern of detections. This considerably extends the range of possible applications, and we illustrate the potential by estimating density from simulated detections of bird vocalizations on a microphone array. Acoustic detection can be defined as occurring when received signal strength exceeds a threshold. We suggest detection models for binary acoustic data, and for continuous data comprising measurements of all signals above the threshold. While binary data are often sufficient for density estimation, modeling signal strength improves precision when the microphone array is small.

  7. Spacing, population density and nitrogen fertilization in corn grown in an Oxisoil

    Directory of Open Access Journals (Sweden)

    Maria do Carmo Lana

    2014-06-01

    Full Text Available The objective of this study was to evaluate yield components, leaf nitrogen content and grain yield in corn as affected by row spacing, plant density and nitrogen topdressing. The experiment was conducted with the single-cross hybrid AG 8021, in the municipality of Toledo-PR, in an Oxisoil under no-tillage system, in the crop year 2005/ 2006. The experiment was arranged in a randomized block design and treatments in split-split-plots, with four replications. The two row spacings (0.45 and 0.90 m were allocated in the main plots, the two plant densities (60,000 and 80,000 plants ha-1 were allocated in the subplots and the three nitrogen rates (80, 100, 120 and 140 kg ha-1 N were allocated in the sub-subplots. Topdress nitrogen was applied using urea as N source. The rise of the plant population from 60,000 to 80,000 plants ha-1 and the application of topdress nitrogen resulted in increased production components. The application of topdress fertilization provided increase in leaf N content and grain yield for the spacings 0.45 m and 0.90 m. Yield was higher in the spacing 0.45 m than 0.90 m. Yield was higher with 60,000 plants than with 80,000 plants at 0.90 m, while at 0.45 m there was no difference in relation to the plant density.

  8. Population density and structure drive differential investment in pre- and postmating sexual traits in frogs.

    Science.gov (United States)

    Lüpold, Stefan; Jin, Long; Liao, Wen Bo

    2017-06-01

    Sexual selection theory predicts a trade-off between premating (ornaments and armaments) and postmating (testes and ejaculates) sexual traits, assuming that growing and maintaining these traits is costly and that total reproductive investments are limited. The number of males in competition, the reproductive gains from investing in premating sexual traits, and the level of sperm competition are all predicted to influence how males allocate their finite resources to these traits. Yet, empirical examination of these predictions is currently scarce. Here, we studied relative expenditure on pre- and postmating sexual traits among frog species varying in their population density, operational sex ratio, and the number of competing males for each clutch of eggs. We found that the intensifying struggle to monopolize fertilizations as more and more males clasp the same female to fertilize her eggs shifts male reproductive investment toward sperm production and away from male weaponry. This shift, which is mediated by population density and the associated level of male-male competition, likely also explains the trade-off between pre- and postmating sexual traits in our much broader sample of anuran species. Our results highlight the power of such a multilevel approach in resolving the evolution of traits and allocation trade-offs. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  9. A perfect storm: the combined effects on population fluctuations of autocorrelated environmental noise, age structure, and density dependence.

    Science.gov (United States)

    Wilmers, Christopher C; Post, Eric; Hastings, Alan

    2007-05-01

    While it is widely appreciated that climate can affect the population dynamics of various species, a mechanistic understanding of how climate interacts with life-history traits to influence population fluctuations requires development. Here we build a general density-dependent age-structured model that accounts for differential responses in life-history traits to increasing population density. We show that as the temporal frequency of favorable environmental conditions increases, population fluctuations also increase provided that unfavorable environmental conditions still occur. As good years accumulate and the number of individuals in a population increases, successive life-history traits become vulnerable to density dependence once a return to unfavorable conditions prevails. The stronger this ratcheting of density dependence in life-history traits by autocorrelated climatic conditions, the larger the population fluctuations become. Highly fecund species, and those in which density dependence occurs in juvenile and adult vital rates at similar densities, are most sensitive to increases in the frequency of favorable conditions. Understanding the influence of global warming on temporal correlation in regional environmental conditions will be important in identifying those species liable to exhibit increased population fluctuations that could lead to their extinction.

  10. Facultative symbiont Hamiltonella confers benefits to Bemisia tabaci (Hemiptera: Aleyrodidae), an invasive agricultural pest worldwide.

    Science.gov (United States)

    Su, Qi; Oliver, Kerry M; Pan, Huipeng; Jiao, Xiaoguo; Liu, Baiming; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Xu, Baoyun; White, Jennifer A; Zhou, Xuguo; Zhang, Youjun

    2013-12-01

    Bacterial symbionts infect most insect species, including important pests such as whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), and often exert important effects on host ecology. The facultative symbiont Hamiltonella is found at high frequencies in the B. tabaci MED (type: Mediterranean-MED) in China. The prevalence of this symbiont in natural populations suggests beneficial effects of infection or manipulation of host reproduction. To date, however, no empirical studies on the biological role of Hamiltonella on the host B. tabaci have been reported. Here, we investigated the effects of Hamiltonella infection on the sex ratio and several fitness parameters in B. tabaci MED by comparing Hamiltonella-infected whiteflies with Hamiltonella-free ones. We found that Hamiltonella-infected whiteflies produced significantly more eggs, exhibited significantly higher nymphal survival, faster development times, and larger adult body size in comparison with Hamiltonella-free whiteflies, while no evidence of reproductive manipulation by Hamiltonella were found in B. tabaci MED. In conclusion, Hamiltonella infection substantially enhanced B. tabaci MED performance. This beneficial role may, at least partially, explain the high prevalence of Hamiltonella in B. tabaci MED populations and may also contribute to their effectiveness in spread of the plant pathogens tomato yellow leaf curl virus.

  11. A study of sex differences in fingerprint ridge density in a North Indian young adult population.

    Science.gov (United States)

    Krishan, Kewal; Kanchan, Tanuj; Ngangom, Chitrabala

    2013-05-01

    Fingerprints have considerable value in morphological, biological, anthropological and forensic studies. Fingerprints collected from the crime scene and from the items of evidence of crime have been successfully used to identify suspects, victims or any other person who had touched the surface in question. The thickness of epidermal ridges varies between individuals; females are supposed to have finer ridges than males and therefore a greater ridge density. The present research is an attempt to distinguish sex from fingerprint ridge density in the radial, ulnar and lower areas of a fingerprint in a North Indian population. A total of 194 individuals (97 males and 97 females) aged between 18 and 25 years were included in the study and fingerprints were collected from each finger of the participants. Thus, a total of 1940 fingerprints were obtained and epidermal ridges were counted in the radial, ulnar, and lower areas of each fingerprint. The radial and ulnar areas are the 5 mm × 5 mm areas on the radial and ulnar side of the central core respectively while the lower area is designated as 5 mm × 5 mm area adjoining the flexion crease of the terminal phalanx on a fingerprint. The fingerprint ridge density in radial, ulnar and lower areas and between sexes was compared statistically using t-test. The results indicate that the females tend to have a significantly higher ridge density than males in the three areas analyzed in the study. The fingerprint ridge density in the ulnar and radial areas of the fingerprints is significantly higher than the lower area. The present study suggests that the fingerprint ridge density can be a relevant and useful morphological parameter in distinguishing sex of a latent fingerprint of unknown origin from the scene of crime. The findings can also be useful in identification of mutilated remains when a dismembered hand is brought for medico-legal examination. Copyright © 2012 Elsevier Ltd and Faculty of Forensic and Legal

  12. Evaluation of Quantra Hologic Volumetric Computerized Breast Density Software in Comparison With Manual Interpretation in a Diverse Population

    Science.gov (United States)

    Richard-Davis, Gloria; Whittemore, Brianna; Disher, Anthony; Rice, Valerie Montgomery; Lenin, Rathinasamy B; Dollins, Camille; Siegel, Eric R; Eswaran, Hari

    2018-01-01

    Objective: Increased mammographic breast density is a well-established risk factor for breast cancer development, regardless of age or ethnic background. The current gold standard for categorizing breast density consists of a radiologist estimation of percent density according to the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) criteria. This study compares paired qualitative interpretations of breast density on digital mammograms with quantitative measurement of density using Hologic’s Food and Drug Administration–approved R2 Quantra volumetric breast density assessment tool. Our goal was to find the best cutoff value of Quantra-calculated breast density for stratifying patients accurately into high-risk and low-risk breast density categories. Methods: Screening digital mammograms from 385 subjects, aged 18 to 64 years, were evaluated. These mammograms were interpreted by a radiologist using the ACR’s BI-RADS density method, and had quantitative density measured using the R2 Quantra breast density assessment tool. The appropriate cutoff for breast density–based risk stratification using Quantra software was calculated using manually determined BI-RADS scores as a gold standard, in which scores of D3/D4 denoted high-risk densities and D1/D2 denoted low-risk densities. Results: The best cutoff value for risk stratification using Quantra-calculated breast density was found to be 14.0%, yielding a sensitivity of 65%, specificity of 77%, and positive and negative predictive values of 75% and 69%, respectively. Under bootstrap analysis, the best cutoff value had a mean ± SD of 13.70% ± 0.89%. Conclusions: Our study is the first to publish on a North American population that assesses the accuracy of the R2 Quantra system at breast density stratification. Quantitative breast density measures will improve accuracy and reliability of density determination, assisting future researchers to accurately calculate

  13. Whitebark pine, population density, and home-range size of grizzly bears in the greater yellowstone ecosystem.

    Directory of Open Access Journals (Sweden)

    Daniel D Bjornlie

    Full Text Available Changes in life history traits of species can be an important indicator of potential factors influencing populations. For grizzly bears (Ursus arctos in the Greater Yellowstone Ecosystem (GYE, recent decline of whitebark pine (WBP; Pinus albicaulis, an important fall food resource, has been paired with a slowing of population growth following two decades of robust population increase. These observations have raised questions whether resource decline or density-dependent processes may be associated with changes in population growth. Distinguishing these effects based on changes in demographic rates can be difficult. However, unlike the parallel demographic responses expected from both decreasing food availability and increasing population density, we hypothesized opposing behavioral responses of grizzly bears with regard to changes in home-range size. We used the dynamic changes in food resources and population density of grizzly bears as a natural experiment to examine hypotheses regarding these potentially competing influences on grizzly bear home-range size. We found that home-range size did not increase during the period of whitebark pine decline and was not related to proportion of whitebark pine in home ranges. However, female home-range size was negatively associated with an index of population density. Our data indicate that home-range size of grizzly bears in the GYE is not associated with availability of WBP, and, for female grizzly bears, increasing population density may constrain home-range size.

  14. Whitebark pine, population density, and home-range size of grizzly bears in the greater yellowstone ecosystem.

    Science.gov (United States)

    Bjornlie, Daniel D; Van Manen, Frank T; Ebinger, Michael R; Haroldson, Mark A; Thompson, Daniel J; Costello, Cecily M

    2014-01-01

    Changes in life history traits of species can be an important indicator of potential factors influencing populations. For grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem (GYE), recent decline of whitebark pine (WBP; Pinus albicaulis), an important fall food resource, has been paired with a slowing of population growth following two decades of robust population increase. These observations have raised questions whether resource decline or density-dependent processes may be associated with changes in population growth. Distinguishing these effects based on changes in demographic rates can be difficult. However, unlike the parallel demographic responses expected from both decreasing food availability and increasing population density, we hypothesized opposing behavioral responses of grizzly bears with regard to changes in home-range size. We used the dynamic changes in food resources and population density of grizzly bears as a natural experiment to examine hypotheses regarding these potentially competing influences on grizzly bear home-range size. We found that home-range size did not increase during the period of whitebark pine decline and was not related to proportion of whitebark pine in home ranges. However, female home-range size was negatively associated with an index of population density. Our data indicate that home-range size of grizzly bears in the GYE is not associated with availability of WBP, and, for female grizzly bears, increasing population density may constrain home-range size.

  15. Rapid evolution of symbiont-mediated resistance compromises biological control of aphids by parasitoids.

    Science.gov (United States)

    Käch, Heidi; Mathé-Hubert, Hugo; Dennis, Alice B; Vorburger, Christoph

    2018-02-01

    There is growing interest in biological control as a sustainable and environmentally friendly way to control pest insects. Aphids are among the most detrimental agricultural pests worldwide, and parasitoid wasps are frequently employed for their control. The use of asexual parasitoids may improve the effectiveness of biological control because only females kill hosts and because asexual populations have a higher growth rate than sexuals. However, asexuals may have a reduced capacity to track evolutionary change in their host populations. We used a factorial experiment to compare the ability of sexual and asexual populations of the parasitoid Lysiphlebus fabarum to control caged populations of black bean aphids ( Aphis fabae ) of high and low clonal diversity. The aphids came from a natural population, and one-third of the aphid clones harbored Hamiltonella defensa , a heritable bacterial endosymbiont that increases resistance to parasitoids. We followed aphid and parasitoid population dynamics for 3 months but found no evidence that the reproductive mode of parasitoids affected their effectiveness as biocontrol agents, independent of host clonal diversity. Parasitoids failed to control aphids in most cases, because their introduction resulted in strong selection for clones protected by H. defensa . The increasingly resistant aphid populations escaped control by parasitoids, and we even observed parasitoid extinctions in many cages. The rapid evolution of symbiont-conferred resistance in turn imposed selection on parasitoids. In cages where asexual parasitoids persisted until the end of the experiment, they became dominated by a single genotype able to overcome the protection provided by H. defensa . Thus, there was evidence for parasitoid counteradaptation, but it was generally too slow for parasitoids to regain control over aphid populations. It appears that when pest aphids possess defensive symbionts, the presence of parasitoid genotypes able to overcome

  16. Neighbourhood density and genetic relatedness interact to determine fruit set and abortion rates in a continuous tropical tree population

    OpenAIRE

    Jones, F.A; Comita, L.S

    2008-01-01

    Tropical trees may show positive density dependence in fruit set and maturation due to pollen limitation in low-density populations. However, pollen from closely related individuals in the local neighbourhood might reduce fruit set or increase fruit abortion in self-incompatible tree species. We investigated the role of neighbourhood density and genetic relatedness on individual fruit set and abortion in the neotropical tree Jacaranda copaia in a large forest plot in central Panama. Using nes...

  17. Effects of salmon-derived nutrients and habitat characteristics on population densities of stream-resident sculpins.

    Directory of Open Access Journals (Sweden)

    Noel R Swain

    Full Text Available Movement of nutrients across ecosystem boundaries can have important effects on food webs and population dynamics. An example from the North Pacific Rim is the connection between productive marine ecosystems and freshwaters driven by annual spawning migrations of Pacific salmon (Oncorhynchus spp. While a growing body of research has highlighted the importance of both pulsed nutrient subsidies and disturbance by spawning salmon, their effects on population densities of vertebrate consumers have rarely been tested, especially across streams spanning a wide range of natural variation in salmon densities and habitat characteristics. We studied resident freshwater prickly (Cottus asper, and coastrange sculpins (C. aleuticus in coastal salmon spawning streams to test whether their population densities are affected by spawning densities of pink and chum salmon (O. gorbuscha and O. keta, as well as habitat characteristics. Coastrange sculpins occurred in the highest densities in streams with high densities of spawning pink and chum salmon. They also were more dense in streams with high pH, large watersheds, less area covered by pools, and lower gradients. In contrast, prickly sculpin densities were higher in streams with more large wood and pools, and less canopy cover, but their densities were not correlated with salmon. These results for coastrange sculpins provide evidence of a numerical population response by freshwater fish to increased availability of salmon subsidies in streams. These results demonstrate complex and context-dependent relationships between spawning Pacific salmon and coastal ecosystems and can inform an ecosystem-based approach to their management and conservation.

  18. A minimum stochastic model evaluating the interplay between population density and drift for species coexistence

    Science.gov (United States)

    Guariento, Rafael Dettogni; Caliman, Adriano

    2017-02-01

    Despite the general acknowledgment of the role of niche and stochastic process in community dynamics, the role of species relative abundances according to both perspectives may have different effects regarding coexistence patterns. In this study, we explore a minimum probabilistic stochastic model to determine the relationship of populations relative and total abundances with species chances to outcompete each other and their persistence in time (i.e., unstable coexistence). Our model is focused on the effects drift (i.e., random sampling of recruitment) under different scenarios of selection (i.e., fitness differences between species). Our results show that taking into account the stochasticity in demographic properties and conservation of individuals in closed communities (zero-sum assumption), initial population abundance can strongly influence species chances to outcompete each other, despite fitness inequalities between populations, and also, influence the period of coexistence of these species in a particular time interval. Systems carrying capacity can have an important role in species coexistence by exacerbating fitness inequalities and affecting the size of the period of coexistence. Overall, the simple stochastic formulation used in this study demonstrated that populations initial abundances could act as an equalizing mechanism, reducing fitness inequalities, which can favor species coexistence and even make less fitted species to be more likely to outcompete better-fitted species, and thus to dominate ecological communities in the absence of niche mechanisms. Although our model is restricted to a pair of interacting species, and overall conclusions are already predicted by the Neutral Theory of Biodiversity, our main objective was to derive a model that can explicitly show the functional relationship between population densities and community mono-dominance odds. Overall, our study provides a straightforward understanding of how a stochastic process (i

  19. Impact of land cover and population density on land surface temperature: case study in Wuhan, China

    Science.gov (United States)

    Li, Lin; Tan, Yongbin; Ying, Shen; Yu, Zhonghai; Li, Zhen; Lan, Honghao

    2014-01-01

    With the rapid development of urbanization, the standard of living has improved, but changes to the city thermal environment have become more serious. Population urbanization is a driving force of residential expansion, which predominantly influences the land surface temperature (LST). We obtained the land covers and LST maps of Wuhan from Landsat-5 images in 2000, 2002, 2005, and 2009, and discussed the distribution of land use/cover change and LST variation, and we analyzed the correlation between population distribution and LST values in residential regions. The results indicated massive variation of land cover types, which was shown as a reduction in cultivatable land and the expansion of building regions. High-LST regions concentrated on the residential and industrial areas with low vegetation coverage. In the residential region, the population density (PD) had effects on the LST values. Although the area or variation of residential regions was close, lower PD was associated with lower mean LST or LST variation. Thus, decreasing the high-LST regions concentration by reducing the PD may alleviate the urban heat island effect on the residential area. Taken together, these results can provide supports for urban planning projects and studies on city ecological environments.

  20. Acetic Acid Bacteria as Symbionts of Insects

    KAUST Repository

    Crotti, Elena

    2016-06-14

    Acetic acid bacteria (AAB) are being increasingly described as associating with different insect species that rely on sugar-based diets. AAB have been found in several insect orders, among them Diptera, Hemiptera, and Hymenoptera, including several vectors of plant, animal, and human diseases. AAB have been shown to associate with the epithelia of different organs of the host, they are able to move within the insect’s body and to be transmitted horizontally and vertically. Here, we review the ecology of AAB and examine their relationships with different insect models including mosquitoes, leafhoppers, and honey bees. We also discuss the potential use of AAB in symbiont-based control strategies, such as “Trojan-horse” agents, to block the transmission of vector-borne diseases.

  1. Saprotrophic fungal mycorrhizal symbionts in achlorophyllous orchids

    Science.gov (United States)

    Martos, Florent; Perry, Brian A; Padamsee, Mahajabeen; Roy, Mélanie; Pailler, Thierry

    2010-01-01

    Mycoheterotrophic plants are achlorophyllous plants that obtain carbon from their mycorrhizal fungi. They are usually considered to associate with fungi that are (1) specific of each mycoheterotrophic species and (2) mycorrhizal on surrounding green plants, which are the ultimate carbon source of the entire system. Here we review recent works revealing that some mycoheterotrophic plants are not fungal-specific, and that some mycoheterotrophic orchids associate with saprophytic fungi. A re-examination of earlier data suggests that lower specificity may be less rare than supposed in mycoheterotrophic plants. Association between mycoheterotrophic orchids and saprophytic fungi arose several times in the evolution of the two partners. We speculate that this indirectly illustrates why transition from saprotrophy to mycorrhizal status is common in fungal evolution. Moreover, some unexpected fungi occasionally encountered in plant roots should not be discounted as ‘molecular scraps’, since these facultatively biotrophic encounters may evolve into mycorrhizal symbionts in some other plants. PMID:20061806

  2. Symbiont-mediated RNA interference in insects

    Science.gov (United States)

    Whitten, Miranda M. A.; Facey, Paul D.; Del Sol, Ricardo; Fernández-Martínez, Lorena T.; Evans, Meirwyn C.; Mitchell, Jacob J.; Bodger, Owen G.

    2016-01-01

    RNA interference (RNAi) methods for insects are often limited by problems with double-stranded (ds) RNA delivery, which restricts reverse genetics studies and the development of RNAi-based biocides. We therefore delegated to insect symbiotic bacteria the task of: (i) constitutive dsRNA synthesis and (ii) trauma-free delivery. RNaseIII-deficient, dsRNA-expressing bacterial strains were created from the symbionts of two very diverse pest species: a long-lived blood-sucking bug, Rhodnius prolixus, and a short-lived globally invasive polyphagous agricultural pest, western flower thrips (Frankliniella occidentalis). When ingested, the manipulated bacteria colonized the insects, successfully competed with the wild-type microflora, and sustainably mediated systemic knockdown phenotypes that were horizontally transmissible. This represents a significant advance in the ability to deliver RNAi, potentially to a large range of non-model insects. PMID:26911963

  3. The role of population density on the impact of urbaniza-tion on GHG emissions in China

    Science.gov (United States)

    Liu, Yonghong; Gao, Chaochao; Lu, Yingying

    2017-04-01

    Urbanization directly drives rural to urban population migration and indirectly causes west to east migration in China, two phenomena that may significantly impact China's greenhouse gas emissions given its huge population and vast difference between the western rural and eastern urban areas. These two phenomena were analyzed by using emissions as a per capita term, and extending the impact from the traditional urbanization rate effect to include population density effect. The results show that population density has actually been the dominant demographic player in changing per capita emissions for the past two decades in China, and its elasticity changed from positive in economically less-developed provinces to negative for the developed provinces. This study provides a new perspective in the study of the relationship between urbanization and greenhouse gas emissions, and the results indicate that population density change should be taken into account to accurately assess the impact of urbanization.

  4. Topological variability of fingerprint ridge density in a sub-Saharan population sample for application in personal identification.

    Science.gov (United States)

    Gutiérrez-Redomero, Esperanza; Quirós, Juan A; Rivaldería, Noemí; Alonso, María C

    2013-05-01

    Variability in ridge density in a sub-Saharan population sample was studied by counting ridges in three fingerprint areas (two distal regions, radial and ulnar, and one proximal region) on the epidermal surface of the distal phalanx. Study material was obtained from the fingerprint impressions of 100 male sub-Saharan subjects aged between 18- and 48-years old. The results were compared with those obtained from a Spanish population sample. Sub-Saharan males presented lower ridge density than Spanish males in the distal regions (radial and ulnar) of all fingers, whereas differences in the proximal region were only observed on some fingers. Using the differences observed between these populations, the likelihood ratio for inferring membership of one of the populations from a fingerprint of unknown origin was calculated; therefore, a ridge density of 14 or less for both areas (ulnar and radial), support an origin sub-Saharan versus Spanish population. © 2013 American Academy of Forensic Sciences.

  5. Linking individual phenotype to density-dependent population growth: the influence of body size on the population dynamics of malaria vectors

    NARCIS (Netherlands)

    Russell, T.L.; Lwetoijera, D.W.; Knols, B.G.J.; Takken, W.; Killeen, G.F.; Ferguson, H.M.

    2011-01-01

    Understanding the endogenous factors that drive the population dynamics of malaria mosquitoes will facilitate more accurate predictions about vector control effectiveness and our ability to destabilize the growth of either low- or high-density insect populations. We assessed whether variation in

  6. Linking individual phenotype to density-dependent population growth: the influence of body size on the population dynamics of malaria vectors

    NARCIS (Netherlands)

    Russell, T.L.; Lwetoijera, D.W.; Knols, B.G.J.; Takken, W.; Killeen, G.F.; Ferguson, H.M.

    2011-01-01

    Understanding the endogenous factors that drive the population dynamics of malaria mosquitoes will facilitate more accurate predictions about vector control effectiveness and our ability to destabilize the growth of either low-or high-density insect populations. We assessed whether variation in

  7. Association between population density and reported incidence, characteristics and outcome after out-of-hospital cardiac arrest in Sweden.

    Science.gov (United States)

    Strömsöe, A; Svensson, L; Claesson, A; Lindkvist, J; Lundström, A; Herlitz, J

    2011-10-01

    To describe the reported incidence of out of hospital cardiac arrest (OHCA) and the characteristics and outcome after OHCA in relation to population density in Sweden. All patients participating in the Swedish Cardiac Arrest Register between 2008 and 2009 in (a) 20 of 21 regions (n=6457) and in (b) 165 of 292 municipalities (n=3522) in Sweden, took part in the survey. The regional population density varied between 3 and 310 inhabitants per km(2) in 2009. In 2008-2009, the number of reported cardiac arrests varied between 13 and 52 per 100,000 inhabitants and year. Survival to 1 month varied between 2% and 14% during the same period in different regions. With regard to population density, based on municipalities, bystander CPR (p=0.04) as well as cardiac etiology (p=0.002) were more frequent in less populated areas. Ambulance response time was longer in less populated areas (ppopulation density and survival to 1 month after OHCA or incidence (adjusted for age and gender) of OHCA. There was no significant association between population density and survival to 1 month after OHCA or incidence (adjusted for age and gender) of OHCA. However, bystander CPR, cardiac etiology and longer response times were more frequent in less populated areas. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  8. Estimating the influence of population density and dispersal behavior on the ability to detect and monitor Agrilus planipennis (Coleoptera: Buprestidae) populations.

    Science.gov (United States)

    Mercader, R J; Siegert, N W; McCullough, D G

    2012-02-01

    Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), a phloem-feeding pest of ash (Fraxinus spp.) trees native to Asia, was first discovered in North America in 2002. Since then, A. planipennis has been found in 15 states and two Canadian provinces and has killed tens of millions of ash trees. Understanding the probability of detecting and accurately delineating low density populations of A. planipennis is a key component of effective management strategies. Here we approach this issue by 1) quantifying the efficiency of sampling nongirdled ash trees to detect new infestations of A. planipennis under varying population densities and 2) evaluating the likelihood of accurately determining the localized spread of discrete A. planipennis infestations. To estimate the probability a sampled tree would be detected as infested across a gradient of A. planipennis densities, we used A. planipennis larval density estimates collected during intensive surveys conducted in three recently infested sites with known origins. Results indicated the probability of detecting low density populations by sampling nongirdled trees was very low, even when detection tools were assumed to have three-fold higher detection probabilities than nongirdled trees. Using these results and an A. planipennis spread model, we explored the expected accuracy with which the spatial extent of an A. planipennis population could be determined. Model simulations indicated a poor ability to delineate the extent of the distribution of localized A. planipennis populations, particularly when a small proportion of the population was assumed to have a higher propensity for dispersal.

  9. Variability in body mass and sexual dimorphism in Danish red foxes (Vulpes vulpes) in relation to population density

    DEFF Research Database (Denmark)

    Pagh, Sussie; Hansen, Mette Sif; Jensen, Birger

    2018-01-01

    /2016. During the first and the third periods, the fox population was below the carrying capacity due to hunting pressure and canine distemper, respectively. Adult males were significantly (p density, i.e. 1965......–1977 and compared to 2015/2016, compared to 2012–2014, when population density was high (the mean weight: 6.8 kg). However, no significant differences were found in the weight of females. Hence, sexual dimorphism ranged from 7.6 to 3.6 in adult foxes in low and high-density periods, respectively. During the winters...

  10. Distribution and ecology of Frankliniella occidentalis (Thysanoptera: Thripidae) bacterial symbionts.

    Science.gov (United States)

    Chanbusarakum, Lisa J; Ullman, Diane E

    2009-08-01

    Bacterial populations in Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) collected in diverse California environments consisted of two bacterial symbionts: BFo-1 and BFo-2 (B = bacteria, Fo = Frankliniella occidentalis, numbers reflect different types). Dual infections of BFo-1 and BFo-2 were found in 50% of the thrips, 18% had neither bacterium, and 24 and 8% were infected solely with BFo-1 and BFo-2, respectively. No other bacteria consistently infected F. occidentalis. Dual infections occurred more often in male thrips and in thrips of both sexes from southern mountain and valley sites. As average collection year or month minimum temperature decreased, infections of BFo-1, alone or in dual infections, increased significantly. As yearly precipitation increased, infection with BFo-1 alone also increased. F. occidentalis color morphology did not affect bacterial infection. BFo-1 created weak biofilms at 25 and 32 degrees C; BFo-2 made strong biofilms at 25 degrees C and no biofilms at 32 degrees C. When the bacteria were grown in culture together, weak biofilms formed at both temperatures studied, although there was no way to determine what each bacterium contributed to the biofilm. BFo-1 and BFo-2 grew at similar rates at 25 and 30 degrees C. Our data show BFo-1 and BFo-2 occur in natural populations of F. occidentalis and support the hypothesis BFo have a symbiotic relationship with F. occidentalis. Regional differences in bacterial prevalence suggest bacterial infection is associated with environmental conditions, and altitude, temperature, and precipitation may be important factors.

  11. Shifts of community composition and population density substantially affect ecosystem function despite invariant richness.

    Science.gov (United States)

    Spaak, Jurg W; Baert, Jan M; Baird, Donald J; Eisenhauer, Nico; Maltby, Lorraine; Pomati, Francesco; Radchuk, Viktoriia; Rohr, Jason R; Van den Brink, Paul J; De Laender, Frederik

    2017-10-01

    There has been considerable focus on the impacts of environmental change on ecosystem function arising from changes in species richness. However, environmental change may affect ecosystem function without affecting richness, most notably by affecting population densities and community composition. Using a theoretical model, we find that, despite invariant richness, (1) small environmental effects may already lead to a collapse of function; (2) competitive strength may be a less important determinant of ecosystem function change than the selectivity of the environmental change driver and (3) effects on ecosystem function increase when effects on composition are larger. We also present a complementary statistical analysis of 13 data sets of phytoplankton and periphyton communities exposed to chemical stressors and show that effects on primary production under invariant richness ranged from -75% to +10%. We conclude that environmental protection goals relying on measures of richness could underestimate ecological impacts of environmental change. © 2017 The Authors Ecology Letters published by CNRS and John Wiley & Sons Ltd.

  12. Population density of Sotalia guianensis (Cetacea: Delphinidae in the Cananéia region, Southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Liisa Havukainen

    2011-09-01

    Full Text Available Population density in cetaceans can be estimated through photo-identification, mark-recapture, land-based observations and visual estimative. We the aim to contribute with conservation strategies, we used line transects (distance method to estimate the population density of the river dolphin, S. guianensis, in the estuarine region of Cananéia, Southeastern Brazil. The study, developed from May 2003 until April 2004, during dry and rainy seasons and different times of the day, included a sampling area divided into three sectors according to their proximity to the open sea: Sector I (the closest to the open sea; Sector II (with a large flow of fresh water and a salient declivity; and Sector III (with a large flow of fresh water and non salient declivity. Onboard random sampling was carried out in all three sectors, and dolphins seen from the bow to 90° on both port and starboard sides, were registered along with their position and distance from the boat. The total density found was 12.41ind/km² (CV=25.53% with an average of 2.2 individuals per group for both periods of the day, morning and afternoon. Densities also varied between dry and rainy seasons, being lower in the first with 5.77ind/km² (CV=27.87% than in the second 20.28ind/km² (CV=31.95%, respectively. Regarding the three sectors, a non-causal heterogeneous distribution was found: Sector I was the most populated (D=33.10ind/km², CV=13.34%, followed by Sector II (D=7.8ind/km², CV=21.07% and Sector III (D=3.04ind/km², CV=34.04%. The aforementioned area, due to its proximity to the open sea, has the highest salinity level and therefore has the greatest chance of holding most of the marine fish schools which can be cornered by dolphins on high declivity areas during fishing activities. This suggests that food availability may be the most important factor on the river dolphin’s distribution in the estuary. Similar studies will contribute to a better understanding of these populations

  13. Adaptive landscapes and density-dependent selection in declining salmonid populations: going beyond numerical responses to human disturbance.

    Science.gov (United States)

    Einum, Sigurd; Robertsen, Grethe; Fleming, Ian A

    2008-05-01

    Theory suggests an important role for population density in shaping adaptive landscapes through density-dependent selection. Here, we identify five methodological approaches for studying such selection, review the existing empirical evidence for it, and ask whether current declines in abundance can be expected to trigger evolutionary responses in salmonid fishes. Across taxa we find substantial amounts of evidence for population density influencing the location of adaptive peaks for a range of traits, and, in the presence of frequency dependence, changing the shape of selection (stabilizing versus disruptive). For salmonids, biological and theoretical considerations suggest that the optimal value of a number of traits associated with juvenile competitive ability (e.g. egg size, timing of emergence from nests, dominance ability), may depend on population density. For adults, more direct experimental and comparative evidence suggest that secondary sexual traits can be subject to density-dependent selection. There is also evidence that density affects the frequency-dependent selection likely responsible for the expression of alternative male reproductive phenotypes in salmon. Less is known however about the role of density in maintaining genetic variation among juveniles. Further efforts are required to elucidate the indirect evolutionary effects of declining population abundances, both in salmonids and in other anthropogenically challenged organisms.

  14. Population Density and Seasonality Effects on Sin Nombre Virus Transmission in North American Deermice (Peromyscus maniculatus) in Outdoor Enclosures

    Science.gov (United States)

    Bagamian, Karoun H.; Douglass, Richard J.; Alvarado, Arlene; Kuenzi, Amy J.; Amman, Brian R.; Waller, Lance A.; Mills, James N.

    2012-01-01

    Surveys of wildlife host-pathogen systems often document clear seasonal variation in transmission; conclusions concerning the relationship between host population density and transmission vary. In the field, effects of seasonality and population density on natural disease cycles are challenging to measure independently, but laboratory experiments may poorly reflect what happens in nature. Outdoor manipulative experiments are an alternative that controls for some variables in a relatively natural environment. Using outdoor enclosures, we tested effects of North American deermouse (Peromyscus maniculatus) population density and season on transmission dynamics of Sin Nombre hantavirus. In early summer, mid-summer, late summer, and fall 2007–2008, predetermined numbers of infected and uninfected adult wild deermice were released into enclosures and trapped weekly or bi-weekly. We documented 18 transmission events and observed significant seasonal effects on transmission, wounding frequency, and host breeding condition. Apparent differences in transmission incidence or wounding frequency between high- and low-density treatments were not statistically significant. However, high host density was associated with a lower proportion of males with scrotal testes. Seasonality may have a stronger influence on disease transmission dynamics than host population density, and density effects cannot be considered independent of seasonality. PMID:22768034

  15. Remote sensing and spatial statistical techniques for modelling Ommatissus lybicus (Hemiptera: Tropiduchidae habitat and population densities

    Directory of Open Access Journals (Sweden)

    Khalifa M. Al-Kindi

    2017-08-01

    Full Text Available In order to understand the distribution and prevalence of Ommatissus lybicus (Hemiptera: Tropiduchidae as well as analyse their current biographical patterns and predict their future spread, comprehensive and detailed information on the environmental, climatic, and agricultural practices are essential. The spatial analytical techniques such as Remote Sensing and Spatial Statistics Tools, can help detect and model spatial links and correlations between the presence, absence and density of O. lybicus in response to climatic, environmental, and human factors. The main objective of this paper is to review remote sensing and relevant analytical techniques that can be applied in mapping and modelling the habitat and population density of O. lybicus. An exhaustive search of related literature revealed that there are very limited studies linking location-based infestation levels of pests like the O. lybicus with climatic, environmental, and human practice related variables. This review also highlights the accumulated knowledge and addresses the gaps in this area of research. Furthermore, it makes recommendations for future studies, and gives suggestions on monitoring and surveillance methods in designing both local and regional level integrated pest management strategies of palm tree and other affected cultivated crops.

  16. Habitats, population densities, and social structure of capybaras (Hydrochaeris Hydrochaeris, Rodentia in the Pantanal, Brazil

    Directory of Open Access Journals (Sweden)

    Cleber J.R. Alho

    1987-01-01

    Full Text Available (1 The Pantanal is the central portion of a sunken flat plain bordering the upper Paraguay river, with an area of 140,000 km². Seasonal floods begin in January and end in April. From May to October the land dries out and campos (grassland formations and scattered pools appear. (2 Typical capybara habitat in the Pantanal is composed of three components: the water, a patch of forest, and a grass field for foraging. Highest densities of capybaras (14 individuals/km² were found during the rainy season when the available space for capybaras was reduced due to the flooding. Areas without ponds or creeks presented low densities (from 0.38 to 0.84 capybaras/km². Group sizes ranged from 2 to 49 individuals (x = 9.48. (3 Reproduction occurred year-round and young of different ages were seen throughout the year. However, the principal recruitment of young to the population was observed in July-August. While the females took turns in caring for young of different ages, probably the offspring of mothers who are sisters in the same social groups, the males competed intensively with each other for access to breeding females. The male's reproductive success appears to be limited to the number of breeding females that males have access to in the social group.

  17. Crater density differences: Exploring regional resurfacing, secondary crater populations, and crater saturation equilibrium on the moon

    Science.gov (United States)

    Povilaitis, R Z; Robinson, M S; van der Bogert, C H; Hiesinger, Harald; Meyer, H M; Ostrach, Lillian

    2017-01-01

    The global population of lunar craters >20 km in diameter was analyzed by Head et al., (2010) to correlate crater distribution with resurfacing events and multiple impactor populations. The work presented here extends the global crater distribution analysis to smaller craters (5–20 km diameters, n = 22,746). Smaller craters form at a higher rate than larger craters and thus add granularity to age estimates of larger units and can reveal smaller and younger areas of resurfacing. An areal density difference map generated by comparing the new dataset with that of Head et al., (2010) shows local deficiencies of 5–20 km diameter craters, which we interpret to be caused by a combination of resurfacing by the Orientale basin, infilling of intercrater plains within the nearside highlands, and partial mare flooding of the Australe region. Chains of 5–30 km diameter secondaries northwest of Orientale and possible 8–22 km diameter basin secondaries within the farside highlands are also distinguishable. Analysis of the new database indicates that craters 57–160 km in diameter across much of the lunar highlands are at or exceed relative crater densities of R = 0.3 or 10% geometric saturation, but nonetheless appear to fit the lunar production function. Combined with the observation that small craters on old surfaces can reach saturation equilibrium at 1% geometric saturation (Xiao and Werner, 2015), this suggests that saturation equilibrium is a size-dependent process, where large craters persist because of their resistance to destruction, degradation, and resurfacing.

  18. Increased population density of neurosurgeons associated with decreased risk of death from motor vehicle accidents in the United States.

    Science.gov (United States)

    Desai, Atman; Bekelis, Kimon; Zhao, Wenyan; Ball, Perry A

    2012-09-01

    Motor vehicle accidents (MVAs) are a leading cause of death and disability in young people. Given that a major cause of death from MVAs is traumatic brain injury, and neurosurgeons hold special expertise in this area relative to other members of a trauma team, the authors hypothesized that neurosurgeon population density would be related to reduced mortality from MVAs across US counties. The Area Resource File (2009-2010), a national health resource information database, was retrospectively analyzed. The primary outcome variable was the 3-year (2004-2006) average in MVA deaths per million population for each county. The primary independent variable was the density of neurosurgeons per million population in the year 2006. Multiple regression analysis was performed, adjusting for population density of general practitioners, urbanicity of the county, and socioeconomic status of the county. The median number of annual MVA deaths per million population, in the 3141 counties analyzed, was 226 (interquartile range [IQR] 151-323). The median number of neurosurgeons per million population was 0 (IQR 0-0), while the median number of general practitioners per million population was 274 (IQR 175-410). Using an unadjusted analysis, each increase of 1 neurosurgeon per million population was associated with 1.90 fewer MVA deaths per million population (p population was associated with 1.01 fewer MVA deaths per million population (p population for an increase in 1 general practitioner (p = 0.007). Rural location, persistent poverty, and low educational level were all associated with significant increases in the rate of MVA deaths. A higher population density of neurosurgeons is associated with a significant reduction in deaths from MVAs, a major cause of death nationally. This suggests that the availability of local neurosurgeons is an important factor in the overall likelihood of survival from an MVA, and therefore indicates the importance of promoting neurosurgical education and

  19. Impacts of Antibiotic and Bacteriophage Treatments on the Gut-Symbiont-Associated Blissus insularis (Hemiptera: Blissidae

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    Yao Xu

    2016-11-01

    Full Text Available The Southern chinch bug, Blissus insularis, possesses specialized midgut crypts that harbor dense populations of the exocellular symbiont Burkholderia. Oral administration of antibiotics suppressed the gut symbionts in B. insularis and negatively impacted insect host fitness, as reflected by retarded development, smaller body size, and higher susceptibility to an insecticide, bifenthrin. Considering that the antibiotics probably had non-lethal but toxic effects on host fitness, attempts were conducted to reduce gut symbionts using bacteriophage treatment. Soil-lytic phages active against the cultures of specific Burkholderia ribotypes were successfully isolated using a soil enrichment protocol. Characterization of the BiBurk16MC_R phage determined its specificity to the Bi16MC_R_vitro ribotype and placed it within the family Podoviridae. Oral administration of phages to fifth-instar B. insularis, inoculated with Bi16MC_R_vitro as neonates had no deleterious effects on host fitness. However, the ingested phages failed to impact the crypt-associated Burkholderia. The observed inactivity of the phage was likely due to the blockage of the connection between the anterior and posterior midgut regions. These findings suggest that the initial colonization by Burkholderia programs the ontogeny of the midgut, providing a sheltered residence protected from microbial antagonists.

  20. The distribution of intra-genomically variable dinoflagellate symbionts at Lord Howe Island, Australia

    Science.gov (United States)

    Wilkinson, Shaun P.; Pontasch, Stefanie; Fisher, Paul L.; Davy, Simon K.

    2016-06-01

    The symbiotic dinoflagellates of corals and other marine invertebrates ( Symbiodinium) are essential to the development of shallow-water coral reefs. This genus contains considerable genetic diversity and a corresponding range of physiological and ecological traits. Most genetic variation arises through the accumulation of somatic mutations that arise during asexual reproduction. Yet growing evidence suggests that occasional sexual reproductive events also occur within, and perhaps between, Symbiodinium lineages, further contributing to the pool of genetic variation available for evolutionary adaptation. Intra-genomic variation can therefore arise from both sexual and asexual reproductive processes, making it difficult to discern its underlying causes and consequences. We used quantitative PCR targeting the ITS2 locus to estimate proportions of genetically homogeneous symbionts and intra-genomically variable Symbiodinium (IGV Symbiodinium) in the reef-building coral Pocillopora damicornis at Lord Howe Island, Australia. We then sampled colonies through time and at a variety of spatial scales to find out whether the distribution of these symbionts followed patterns consistent with niche partitioning. Estimated ratios of homogeneous to IGV Symbiodinium varied between colonies within sites (metres to tens of metres) and between sites separated by hundreds to thousands of metres, but remained stable within colonies through time. Symbiont ratios followed a temperature gradient, with the local thermal maximum emerging as a negative predictor for the estimated proportional abundance of IGV Symbiodinium. While this pattern may result from fine-scale spatial population structure, it is consistent with an increased susceptibility to thermal stress, suggesting that the evolutionary processes that generate IGV (such as inter-lineage recombination and the accumulation of somatic mutations at the ITS2 locus) may have important implications for the fitness of the symbiont and

  1. Aphid symbionts and endogenous resistance traits mediate competition between rival parasitoids.

    Science.gov (United States)

    Kraft, Laura J; Kopco, James; Harmon, Jason P; Oliver, Kerry M

    2017-01-01

    Insects use endogenous mechanisms and infection with protective symbionts to thwart attacks from natural enemies. Defenses that target specific enemies, however, potentially mediate competition between rivals and thereby impact community composition. Following its introduction to North America to control pea aphids (Acyrthosiphon pisum), the parasitoid Aphidius ervi competitively displaced other parasitoids, except for the native Praon pequodorum. The pea aphid exhibits tremendous clonal variation in resistance to A. ervi, primarily through infection with the heritable bacterial symbiont Hamiltonella defensa, although some symbiont-free aphid genotypes encode endogenous resistance. Interestingly, H. defensa strains and aphid genotypes that protect against A. ervi, provide no protection against the closely related, P. pequodorum. Given the specificity of aphid defenses, we hypothesized that aphid resistance traits may contribute to the continued persistence of P. pequodorum. We conducted multiparasitism assays to determine whether aphid resistance traits mediate internal competition between these two solitary parasitoid species, but found this was not the case; P. pequodorum was the successful internal competitor across lines varying in susceptibility to A. ervi. Next, to determine whether resistance traits influence competitive interactions resulting in the stable persistence of P. pequodorum, we established replicated cages varying in the proportion of resistant aphids and recorded successful parasitism for each wasp species over time. As expected, A. ervi outcompeted P. pequodorum in cages containing only susceptible aphids. However, P. pequodorum not only persisted, but was the superior competitor in populations containing any proportion (20-100%) of resistant aphids (20-100%). Smaller scale, better replicated competition cage studies corroborated this finding, and no-competition and behavioral assays provide insight into the processes mediating competition

  2. Population densities and diurnal activity pattern of the Indian Roller Coracias benghalensis (Aves: Coraciiformes in Nagapattinam District, Tamil Nadu, India

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    S. Asokan

    2010-09-01

    Full Text Available Population densities and diurnal activity pattern of the Indian Roller were studied in Nagapattinam District over three years in different habitats. The agricultural lands supported the highest populations (41km-2, followed by river banks (36km-2 and social forests (32km-2; populations showed yearly variations in numbers and density in all habitats. On average, birds were observed to spend most of the day scanning (57%, with the remainder divided among feeding (16%, flying, (12%, preening (10% and resting (5%. Some variations in activity breakdown were observed between time blocks, seasons and habitats.

  3. Low crop plant population densities promote pollen-mediated gene flow in spring wheat (Triticum aestivum L.).

    Science.gov (United States)

    Willenborg, Christian J; Brûlé-Babel, Anita L; Van Acker, Rene C

    2009-12-01

    Transgenic wheat is currently being field tested with the intent of eventual commercialization. The development of wheat genotypes with novel traits has raised concerns regarding the presence of volunteer wheat populations and the role they may play in facilitating transgene movement. Here, we report the results of a field experiment that investigated the potential of spring wheat plant population density and crop height to minimize gene flow from a herbicide-resistant (HR) volunteer population to a non-HR crop. Pollen-mediated gene flow (PMGF) between the HR volunteer wheat population and four conventional spring wheat genotypes varying in height was assessed over a range of plant population densities. Natural hybridization events between the two cultivars were detected by phenotypically scoring plants in F(1) populations followed by verification with Mendelian segregation ratios in the F(1:2) families. PMGF was strongly associated with crop yield components, but showed no association with flowering synchrony. Maximum observed PMGF was always less than 0.6%, regardless of crop height and density. The frequency of PMGF in spring wheat decreased exponentially with increasing plant population density, but showed no dependence on either crop genotype or height. However, increasing plant densities beyond the recommended planting rate of 300 cropped wheat plants m(-2) provided no obvious benefit to reducing PMGF. Nevertheless, our results demonstrate a critical plant density of 175-200 cropped wheat plants m(-2) below which PMGF frequencies rise exponentially with decreasing plant density. These results will be useful in the development of mechanistic models and best management practices that collectively facilitate the coexistence of transgenic and nontransgenic wheat crops.

  4. Consistent individual differences and population plasticity in network-derived sociality: An experimental manipulation of density in a gregarious ungulate.

    Science.gov (United States)

    O'Brien, Paul P; Webber, Quinn M R; Vander Wal, Eric

    2018-01-01

    In many taxa, individual social traits appear to be consistent across time and context, thus meeting the criteria for animal personality. How these differences are maintained in response to changes in population density is unknown, particularly in large mammals, such as ungulates. Using a behavioral reaction norm (BRN) framework, we examined how among- and within-individual variation in social connectedness, measured using social network analyses, change as a function of population density. We studied a captive herd of elk (Cervus canadensis) separated into a group of male elk and a group of female elk. Males and females were exposed to three different density treatments and we recorded social associations between individuals with proximity-detecting radio-collars fitted to elk. We constructed social networks using dyadic association data and calculated three social network metrics reflective of social connectedness: eigenvector centrality, graph strength, and degree. Elk exhibited consistent individual differences in social connectedness across densities; however, they showed little individual variation in their response to changes in density, i.e., individuals oftentimes responded plastically, but in the same manner to changes in density. Female elk had highest connectedness at an intermediate density. In contrast, male elk increased connectedness with increasing density. Whereas this may suggest that the benefits of social connectedness outweigh the costs of increased competition at higher density for males, females appear to exhibit a threshold in social benefits (e.g. predator detection and forage information). Our study illustrates the importance of viewing social connectedness as a density-dependent trait, particularly in the context of plasticity. Moreover, we highlight the need to revisit our understanding of density dependence as a population-level phenomenon by accounting for consistent individual differences not only in social connectedness, but likely

  5. Artificially constructed quorum-sensing circuits are used for subtle control of bacterial population density.

    Directory of Open Access Journals (Sweden)

    Zhaoshou Wang

    Full Text Available Vibrio fischeri is a typical quorum-sensing bacterium for which lux box, luxR, and luxI have been identified as the key elements involved in quorum sensing. To decode the quorum-sensing mechanism, an artificially constructed cell-cell communication system has been built. In brief, the system expresses several programmed cell-death BioBricks and quorum-sensing genes driven by the promoters lux pR and PlacO-1 in Escherichia coli cells. Their transformation and expression was confirmed by gel electrophoresis and sequencing. To evaluate its performance, viable cell numbers at various time periods were investigated. Our results showed that bacteria expressing killer proteins corresponding to ribosome binding site efficiency of 0.07, 0.3, 0.6, or 1.0 successfully sensed each other in a population-dependent manner and communicated with each other to subtly control their population density. This was also validated using a proposed simple mathematical model.

  6. Parasitic wasp responses to symbiont-based defense in aphids

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    Oliver Kerry M

    2012-02-01

    Full Text Available Abstract Background Recent findings indicate that several insect lineages receive protection against particular natural enemies through infection with heritable symbionts, but little is yet known about whether enemies are able to discriminate and respond to symbiont-based defense. The pea aphid, Acyrthosiphon pisum, receives protection against the parasitic wasp, Aphidius ervi, when infected with the bacterial symbiont Hamiltonella defensa and its associated bacteriophage APSE (Acyrthosiphon pisum secondary endosymbiont. Internally developing parasitoid wasps, such as A. ervi, use maternal and embryonic factors to create an environment suitable for developing wasps. If more than one parasitoid egg is deposited into a single aphid host (superparasitism, then additional complements of these factors may contribute to the successful development of the single parasitoid that emerges. Results We performed experiments to determine if superparasitism is a tactic allowing wasps to overcome symbiont-mediated defense. We found that the deposition of two eggs into symbiont-protected aphids significantly increased rates of successful parasitism relative to singly parasitized aphids. We then conducted behavioral assays to determine whether A. ervi selectively superparasitizes H. defensa-infected aphids. In choice tests, we found that A. ervi tends to deposit a single egg in uninfected aphids, but two or more eggs in H. defensa-infected aphids, indicating that oviposition choices may be largely determined by infection status. Finally, we identified differences in the quantity of the trans-β-farnesene, the major component of aphid alarm pheromone, between H. defensa-infected and uninfected aphids, which may form the basis for discrimination. Conclusions Here we show that the parasitic wasp A. ervi discriminates among symbiont-infected and uninfected aphids, and changes its oviposition behavior in a way that increases the likelihood of overcoming symbiont

  7. Tracking transmission of apicomplexan symbionts in diverse Caribbean corals.

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    Nathan L Kirk

    Full Text Available Symbionts in each generation are transmitted to new host individuals either vertically (parent to offspring, horizontally (from exogenous sources, or a combination of both. Scleractinian corals make an excellent study system for understanding patterns of symbiont transmission since they harbor diverse symbionts and possess distinct reproductive modes of either internal brooding or external broadcast spawning that generally correlate with vertical or horizontal transmission, respectively. Here, we focused on the under-recognized, but apparently widespread, coral-associated apicomplexans (Protista: Alveolata to determine if symbiont transmission depends on host reproductive mode. Specifically, a PCR-based assay was utilized towards identifying whether planula larvae and reproductive adults from brooding and broadcast spawning scleractinian coral species in Florida and Belize harbored apicomplexan DNA. Nearly all (85.5%; n = 85/89 examined planulae of five brooding species (Porites astreoides, Agaricia tenuifolia, Agaricia agaricites, Favia fragum, Mycetophyllia ferox and adults of P. astreoides were positive for apicomplexan DNA. In contrast, no (n = 0/10 apicomplexan DNA was detected from planulae of four broadcast spawning species (Acropora cervicornis, Acropora palmata, Pseudodiploria strigosa, and Orbicella faveolata and rarely in gametes (8.9%; n = 5/56 of these species sampled from the same geographical range as the brooding species. In contrast, tissue samples from nearly all (92.0%; n = 81/88 adults of the broadcast spawning species A. cervicornis, A. palmata and O. faveolata harbored apicomplexan DNA, including colonies whose gametes and planulae tested negative for these symbionts. Taken together, these data suggest apicomplexans are transmitted vertically in these brooding scleractinian coral species while the broadcast spawning scleractinian species examined here acquire these symbionts horizontally. Notably, these transmission

  8. Tracking transmission of apicomplexan symbionts in diverse Caribbean corals.

    Science.gov (United States)

    Kirk, Nathan L; Ritson-Williams, Raphael; Coffroth, Mary Alice; Miller, Margaret W; Fogarty, Nicole D; Santos, Scott R

    2013-01-01

    Symbionts in each generation are transmitted to new host individuals either vertically (parent to offspring), horizontally (from exogenous sources), or a combination of both. Scleractinian corals make an excellent study system for understanding patterns of symbiont transmission since they harbor diverse symbionts and possess distinct reproductive modes of either internal brooding or external broadcast spawning that generally correlate with vertical or horizontal transmission, respectively. Here, we focused on the under-recognized, but apparently widespread, coral-associated apicomplexans (Protista: Alveolata) to determine if symbiont transmission depends on host reproductive mode. Specifically, a PCR-based assay was utilized towards identifying whether planula larvae and reproductive adults from brooding and broadcast spawning scleractinian coral species in Florida and Belize harbored apicomplexan DNA. Nearly all (85.5%; n = 85/89) examined planulae of five brooding species (Porites astreoides, Agaricia tenuifolia, Agaricia agaricites, Favia fragum, Mycetophyllia ferox) and adults of P. astreoides were positive for apicomplexan DNA. In contrast, no (n = 0/10) apicomplexan DNA was detected from planulae of four broadcast spawning species (Acropora cervicornis, Acropora palmata, Pseudodiploria strigosa, and Orbicella faveolata) and rarely in gametes (8.9%; n = 5/56) of these species sampled from the same geographical range as the brooding species. In contrast, tissue samples from nearly all (92.0%; n = 81/88) adults of the broadcast spawning species A. cervicornis, A. palmata and O. faveolata harbored apicomplexan DNA, including colonies whose gametes and planulae tested negative for these symbionts. Taken together, these data suggest apicomplexans are transmitted vertically in these brooding scleractinian coral species while the broadcast spawning scleractinian species examined here acquire these symbionts horizontally. Notably, these transmission patterns are

  9. Symbiont modulates expression of specific gene categories in Angomonas deanei

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    Luciana Loureiro Penha

    Full Text Available Trypanosomatids are parasites that cause disease in humans, animals, and plants. Most are non-pathogenic and some harbor a symbiotic bacterium. Endosymbiosis is part of the evolutionary process of vital cell functions such as respiration and photosynthesis. Angomonas deanei is an example of a symbiont-containing trypanosomatid. In this paper, we sought to investigate how symbionts influence host cells by characterising and comparing the transcriptomes of the symbiont-containing A. deanei (wild type and the symbiont-free aposymbiotic strains. The comparison revealed that the presence of the symbiont modulates several differentially expressed genes. Empirical analysis of differential gene expression showed that 216 of the 7625 modulated genes were significantly changed. Finally, gene set enrichment analysis revealed that the largest categories of genes that downregulated in the absence of the symbiont were those involved in oxidation-reduction process, ATP hydrolysis coupled proton transport and glycolysis. In contrast, among the upregulated gene categories were those involved in proteolysis, microtubule-based movement, and cellular metabolic process. Our results provide valuable information for dissecting the mechanism of endosymbiosis in A. deanei.

  10. High population density of black-handed spider monkeys (Ateles geoffroyi) in Costa Rican lowland wet forest.

    Science.gov (United States)

    Weghorst, Jennifer A

    2007-04-01

    The main objective of this study was to estimate the population density and demographic structure of spider monkeys living in wet forest in the vicinity of Sirena Biological Station, Corcovado National Park, Costa Rica. Results of a 14-month line-transect survey showed that spider monkeys of Sirena have one of the highest population densities ever recorded for this genus. Density estimates varied, however, depending on the method chosen to estimate transect width. Data from behavioral monitoring were available to compare density estimates derived from the survey, providing a check of the survey's accuracy. A combination of factors has most probably contributed to the high density of Ateles, including habitat protection within a national park and high diversity of trees of the fig family, Moraceae. Although natural densities of spider monkeys at Sirena are substantially higher than those recorded at most other sites and in previous studies at this site, mean subgroup size and age ratios were similar to those determined in previous studies. Sex ratios were similar to those of other sites with high productivity. Although high densities of preferred fruit trees in the wet, productive forests of Sirena may support a dense population of spider monkeys, other demographic traits recorded at Sirena fall well within the range of values recorded elsewhere for the species.

  11. Are aphid parasitoids locally adapted to the prevalence of defensive symbionts in their hosts?

    Science.gov (United States)

    Vorburger, Christoph; Rouchet, Romain

    2016-12-12

    Insect parasitoids are under strong selection to overcome their hosts' defences. In aphids, resistance to parasitoids is largely determined by the presence or absence of protective endosymbionts such as Hamiltonella defensa. Hence, parasitoids may become locally adapted to the prevalence of this endosymbiont in their host populations. To address this, we collected isofemale lines of the aphid parasitoid Lysiphlebus fabarum from 17 sites in Switzerland and France, at which we also estimated the frequency of infection with H. defensa as well as other bacterial endosymbionts in five important aphid host species. The parasitoids' ability to overcome H. defensa-mediated resistance was then quantified by estimating their parasitism success on a single aphid clone (Aphis fabae fabae) that was either uninfected or experimentally infected with one of three different isolates of H. defensa. The five aphid species (Aphis fabae fabae, A. f. cirsiiacanthoides, A. hederae, A. ruborum, A. urticata) differed strongly in the relative frequencies of infection with different bacterial endosymbionts, but there was also geographic variation in symbiont prevalence. Specifically, the frequency of infection with H. defensa ranged from 22 to 47 % when averaged across species. Parasitoids from sites with a high prevalence of H. defensa tended to be more infective on aphids possessing H. defensa, but this relationship was not significant, thus providing no conclusive evidence that L. fabarum is locally adapted to the occurrence of H. defensa. On the other hand, we observed a strong interaction between parasitoid line and H. defensa isolate on parasitism success, indicative of a high specificity of symbiont-conferred resistance. This study is the first, to our knowledge, to test for local adaptation of parasitoids to the frequency of defensive symbionts in their hosts. While it yielded useful information on the occurrence of facultative endosymbionts in several important host species of L

  12. A journey into the wild of the cnidarian model system Aiptasia and its symbionts

    KAUST Repository

    Voolstra, Christian R.

    2013-08-27

    The existence of coral reef ecosystems relies critically on the mutualistic relationship between calcifying cnidarians and photosynthetic, dinoflagellate endosymbionts in the genus Symbiodinium. Reef-corals have declined globally due to anthropogenic stressors, for example, rising sea-surface temperatures and pollution that often disrupt these symbiotic relationships (known as coral bleaching), exacerbating mass mortality and the spread of disease. This threatens one of the most biodiverse marine ecosystems providing habitats to millions of species and supporting an estimated 500 million people globally (Hoegh-Guldberg et al. 2007). Our understanding of cnidarian-dinoflagellate symbioses has improved notably with the recent application of genomic and transcriptomic tools (e.g. Voolstra et al. 2009; Bayer et al. 2012; Davy et al. 2012), but a model system that allows for easy manipulation in a laboratory environment is needed to decipher underlying cellular mechanisms important to the functioning of these symbioses. To this end, the sea anemone Aiptasia, otherwise known as a \\'pest\\' to aquarium hobbyists, is emerging as such a model system (Schoenberg & Trench 1980; Sunagawa et al. 2009; Lehnert et al. 2012). Aiptasia is easy to grow in culture and, in contrast to its stony relatives, can be maintained aposymbiotically (i.e. dinoflagellate free) with regular feeding. However, we lack basic information on the natural distribution and genetic diversity of these anemones and their endosymbiotic dinoflagellates. These data are essential for placing the significance of this model system into an ecological context. In this issue of Molecular Ecology, Thornhill et al. (2013) are the first to present genetic evidence on the global distribution, diversity and population structure of Aiptasia and its associated Symbiodinium spp. By integrating analyses of the host and symbiont, this research concludes that the current Aitpasia taxonomy probably needs revision and that two

  13. Impact of population density on collision rates in a rapidly developing rural, exurban area of Los Angeles County.

    Science.gov (United States)

    Fischer, Kelly; Sternfeld, Isabelle; Melnick, Douglas Sloan

    2013-04-01

    To determine if the commonly acknowledged relationships between population density and traffic collisions are found at the subcounty level and to describe how collision characteristics may vary substantially at a local level, with a particular emphasis on exurban areas. Los Angeles County collision data were obtained from the California Highway Patrol and the census tract and service planning area (SPA) for each collision were determined. The correlation between population density and collision rates by census tract was calculated within each SPA and for the entire county. Primary collision factors were compared for geographic areas of different population densities within one exurban SPA in Los Angeles County. An inverse relationship was found between collision rates and population density within Los Angeles County. Primary collisions factors were different in areas of the county with different population densities, with driving or biking under the influence particularly common in the most rural area. Subcounty analyses are very important to the study of traffic collisions. Traffic problems in rapidly developing exurban areas may be quite different from those in older, more established areas.

  14. Resolving the interactions between population density and air pollution emissions controls in the San Joaquin Valley, USA.

    Science.gov (United States)

    Hixson, Mark; Mahmud, Abdullah; Hu, Jianlin; Kleeman, Michael J

    2012-05-01

    The effectiveness of emissions control programs designed to reduce concentrations of airborne particulate matter with an aerodynamic diameter transportation, area source, and point source emissions. The ambient PM2.5 response to each combination of population density and emissions control was evaluated using a regional chemical transport model over a 3-week winter stagnation episode. Comparisons between scenarios were based on regional average and population-weighted PM2.5 concentrations. In the absence of any emissions control program, population-weighted concentrations of PM2.5 in the future San Joaquin Valley are lowest undergrowth scenarios that emphasize low population density. A complete ban on wood burning and a 90% reduction in emissions from food cooking operations and diesel engines must occur before medium- to high-density growth scenarios result in lower population-weighted concentrations of PM2.5. These trends partly reflect the fact that existing downtown urban cores that naturally act as anchor points for new high-density growth in the San Joaquin Valley are located close to major transportation corridors for goods movement. Adding growth buffers around transportation corridors had little impact in the current analysis, since the 8-km resolution of the chemical transport model already provided an artificial buffer around major emissions sources. Assuming that future emissions controls will greatly reduce or eliminate emissions from residential wood burning, food cooking, and diesel engines, the 2030 growth scenario using "as-planned" (medium) population density achieves the lowest population-weighted average PM2.5 concentration in the future San Joaquin Valley during a severe winter stagnation event. The San Joaquin Valley is one of the most heavily polluted air basins in the United States that are projected to experience strong population growth in the coming decades. The best plan to improve air quality in the region combines medium- or high-density

  15. Neighbourhood density and genetic relatedness interact to determine fruit set and abortion rates in a continuous tropical tree population.

    Science.gov (United States)

    Jones, F A; Comita, L S

    2008-12-07

    Tropical trees may show positive density dependence in fruit set and maturation due to pollen limitation in low-density populations. However, pollen from closely related individuals in the local neighbourhood might reduce fruit set or increase fruit abortion in self-incompatible tree species. We investigated the role of neighbourhood density and genetic relatedness on individual fruit set and abortion in the neotropical tree Jacaranda copaia in a large forest plot in central Panama. Using nested neighbourhood models, we found a strong positive effect of increased conspecific density on fruit set and maturation. However, high neighbourhood genetic relatedness interacted with density to reduce total fruit set and increase the proportion of aborted fruit. Our results imply a fitness advantage for individuals growing in high densities as measured by fruit set, but realized fruit set is lowered by increased neighbourhood relatedness. We hypothesize that the mechanism involved is increased visitation by density-dependent invertebrate pollinators in high-density populations, which increases pollen quantity and carry-over and increases fruit set and maturation, coupled with self-incompatibility at early and late stages due to biparental inbreeding that lowers fruit set and increases fruit abortion. Implications for the reproductive ecology and conservation of tropical tree communities in continuous and fragmented habitats are discussed.

  16. Population density, water supply, and the risk of dengue fever in Vietnam: cohort study and spatial analysis.

    Directory of Open Access Journals (Sweden)

    Wolf-Peter Schmidt

    2011-08-01

    Full Text Available Aedes aegypti, the major vector of dengue viruses, often breeds in water storage containers used by households without tap water supply, and occurs in high numbers even in dense urban areas. We analysed the interaction between human population density and lack of tap water as a cause of dengue fever outbreaks with the aim of identifying geographic areas at highest risk.We conducted an individual-level cohort study in a population of 75,000 geo-referenced households in Vietnam over the course of two epidemics, on the basis of dengue hospital admissions (n = 3,013. We applied space-time scan statistics and mathematical models to confirm the findings. We identified a surprisingly narrow range of critical human population densities between around 3,000 to 7,000 people/km² prone to dengue outbreaks. In the study area, this population density was typical of villages and some peri-urban areas. Scan statistics showed that areas with a high population density or adequate water supply did not experience severe outbreaks. The risk of dengue was higher in rural than in urban areas, largely explained by lack of piped water supply, and in human population densities more often falling within the critical range. Mathematical modeling suggests that simple assumptions regarding area-level vector/host ratios may explain the occurrence of outbreaks.Rural areas may contribute at least as much to the dissemination of dengue fever as cities. Improving water supply and vector control in areas with a human population density critical for dengue transmission could increase the efficiency of control efforts. Please see later in the article for the Editors' Summary.

  17. Population density, water supply, and the risk of dengue fever in Vietnam: cohort study and spatial analysis.

    Science.gov (United States)

    Schmidt, Wolf-Peter; Suzuki, Motoi; Thiem, Vu Dinh; White, Richard G; Tsuzuki, Ataru; Yoshida, Lay-Myint; Yanai, Hideki; Haque, Ubydul; Tho, Le Huu; Anh, Dang Duc; Ariyoshi, Koya

    2011-08-01

    Aedes aegypti, the major vector of dengue viruses, often breeds in water storage containers used by households without tap water supply, and occurs in high numbers even in dense urban areas. We analysed the interaction between human population density and lack of tap water as a cause of dengue fever outbreaks with the aim of identifying geographic areas at highest risk. We conducted an individual-level cohort study in a population of 75,000 geo-referenced households in Vietnam over the course of two epidemics, on the basis of dengue hospital admissions (n = 3,013). We applied space-time scan statistics and mathematical models to confirm the findings. We identified a surprisingly narrow range of critical human population densities between around 3,000 to 7,000 people/km² prone to dengue outbreaks. In the study area, this population density was typical of villages and some peri-urban areas. Scan statistics showed that areas with a high population density or adequate water supply did not experience severe outbreaks. The risk of dengue was higher in rural than in urban areas, largely explained by lack of piped water supply, and in human population densities more often falling within the critical range. Mathematical modeling suggests that simple assumptions regarding area-level vector/host ratios may explain the occurrence of outbreaks. Rural areas may contribute at least as much to the dissemination of dengue fever as cities. Improving water supply and vector control in areas with a human population density critical for dengue transmission could increase the efficiency of control efforts. Please see later in the article for the Editors' Summary.

  18. Population Density, Water Supply, and the Risk of Dengue Fever in Vietnam: Cohort Study and Spatial Analysis

    Science.gov (United States)

    Schmidt, Wolf-Peter; Suzuki, Motoi; Dinh Thiem, Vu; White, Richard G.; Tsuzuki, Ataru; Yoshida, Lay-Myint; Yanai, Hideki; Haque, Ubydul; Huu Tho, Le; Anh, Dang Duc; Ariyoshi, Koya

    2011-01-01

    Background Aedes aegypti, the major vector of dengue viruses, often breeds in water storage containers used by households without tap water supply, and occurs in high numbers even in dense urban areas. We analysed the interaction between human population density and lack of tap water as a cause of dengue fever outbreaks with the aim of identifying geographic areas at highest risk. Methods and Findings We conducted an individual-level cohort study in a population of 75,000 geo-referenced households in Vietnam over the course of two epidemics, on the basis of dengue hospital admissions (n = 3,013). We applied space-time scan statistics and mathematical models to confirm the findings. We identified a surprisingly narrow range of critical human population densities between around 3,000 to 7,000 people/km2 prone to dengue outbreaks. In the study area, this population density was typical of villages and some peri-urban areas. Scan statistics showed that areas with a high population density or adequate water supply did not experience severe outbreaks. The risk of dengue was higher in rural than in urban areas, largely explained by lack of piped water supply, and in human population densities more often falling within the critical range. Mathematical modeling suggests that simple assumptions regarding area-level vector/host ratios may explain the occurrence of outbreaks. Conclusions Rural areas may contribute at least as much to the dissemination of dengue fever as cities. Improving water supply and vector control in areas with a human population density critical for dengue transmission could increase the efficiency of control efforts. Please see later in the article for the Editors' Summary PMID:21918642

  19. Comparison of trap types and colors for capturing emerald ash borer adults at different population densities.

    Science.gov (United States)

    Poland, Therese M; Mccullough, Deborah G

    2014-02-01

    Results of numerous trials to evaluate artificial trap designs and lures for detection of Agrilus planipennis Fairmaire, the emerald ash borer, have yielded inconsistent results, possibly because of different A. planipennis population densities in the field sites. In 2010 and 2011, we compared 1) green canopy traps, 2) purple canopy traps, 3) green double-decker traps, and 4) purple double-decker traps in sites representing a range of A. planipennis infestation levels. Traps were baited with cis-3-hexenol in both years, plus an 80:20 mixture of Manuka and Phoebe oil (2010) or Manuka oil alone (2011). Condition of trees bearing canopy traps, A. planipennis infestation level of trees in the vicinity of traps, and number of A. planipennis captured per trap differed among sites in both years. Overall in both years, more females, males, and beetles of both sexes were captured on double-decker traps than canopy traps, and more beetles of both sexes (2010) or females (2011) were captured on purple traps than green traps. In 2010, detection rates were higher for purple (100%) and green double-decker traps (100%) than for purple (82%) or green canopy traps (64%) at sites with very low to low A. planipennis infestation levels. Captures of A. planipennis on canopy traps consistently increased with the infestation level of the canopy trap-bearing trees. Differences among trap types were most pronounced at sites with low A. planipennis densities, where more beetles were captured on purple double-decker traps than on green canopy traps in both years.

  20. Effects of population density on growth and production of Tilapia in monoculture

    Directory of Open Access Journals (Sweden)

    TH Majumder

    2017-12-01

    Full Text Available The experiment was conducted to determine the effect of population density on growth and production of Tilapia (monosex GIFT tilapia in monoculture system for a period of 110 days. The experiment was carried out in six earthen ponds, which were situated in the Bangladesh Agricultural University Campus, Mymensingh. The experiment was carried out under three treatments each with two replications. Fish population density was 200 fish per decimal under treatment-I, 400 fish per decimal under treatment-II and 600 fish per decimal under treatment-III. In the ponds supplementary feed of wheat bran and rice bran mixture were used daily at the rate of 46 g, 92 g and 136 g per decimal under treatment-I, II, and III, respectively. The average initial length and weight of tilapia were 4.63 cm and 2.82 g respectively. The ponds were fertilized fortnightly with urea and TSP at the rates of 60 g and 90 g, respectively. During experimental period, the ranges of water temperature (25.82 to 29.80 ºC, transparency (28.00 to 38.00 cm, dissolved oxygen (5.50 to 8.30 mg/L, pH (7.00 to 7.90, total alkalinity (130.00 to 200.00 mg/L, free CO2 (2.00 to 6.00 mg/L, phosphate-phosphorus (1.20 to 2.30 mg/L, and nitrate-nitrogen (3.20 to 4.00 mg/L were within the productive range and more or less similar in all the ponds under three treatments. There were 25 genera of phytoplankton under five major groups and 10 genera of zooplankton under three major groups in the experimental ponds. Mean survival rate of fish under treatment-I, treatment-II, and treatment-III were 82.75%, 77.12% and 74.33% respectively. The calculated net fish production under treatment-I was 6.75 ton/ha/yr and that of the ponds under treatment-II was 10.26 ton/ha/yr and that of the ponds under treatment-III was 12.15 ton/ha/yr. The net fish production under treatment-II and treatment-III were 152% and 180% higher than that of treatment-I, taking net fish production under treatment-I for 100%. According to

  1. Effects of social organization, trap arrangement and density, sampling scale, and population density on bias in population size estimation using some common mark-recapture estimators

    OpenAIRE

    Gupta, Manan; Joshi, Amitabh; Vidya, T. N. C.

    2017-01-01

    Mark-recapture estimators are commonly used for population size estimation, and typically yield unbiased estimates for most solitary species with low to moderate home range sizes. However, these methods assume independence of captures among individuals, an assumption that is clearly violated in social species that show fission-fusion dynamics, such as the Asian elephant. In the specific case of Asian elephants, doubts have been raised about the accuracy of population size estimates. More impo...

  2. Combined thermal and herbicide stress in functionally diverse coral symbionts.

    Science.gov (United States)

    van Dam, J W; Uthicke, S; Beltran, V H; Mueller, J F; Negri, A P

    2015-09-01

    Most reef building corals rely on symbiotic microalgae (genus Symbiodinium) to supply a substantial proportion of their energy requirements. Functional diversity of different Symbiodinium genotypes, endorsing the host with physiological advantages, has been widely reported. Yet, the influence of genotypic specificity on the symbiont's susceptibility to contaminants or cumulative stressors is unknown. Cultured Symbiodinium of presumed thermal-tolerant clade D tested especially vulnerable to the widespread herbicide diuron, suggesting important free-living populations may be at risk in areas subjected to terrestrial runoff. Co-exposure experiments where cultured Symbiodinium were exposed to diuron over a thermal stress gradient demonstrated how fast-growing clade C1 better maintained photosynthetic capability than clade D. The mixture toxicity model of Independent Action, considering combined thermal stress and herbicide contamination, revealed response additivity for inhibition of photosynthetic yield in both tested cultures, emphasizing the need to account for cumulative stressor impacts in ecological risk assessment and resource management. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  3. Combined thermal and herbicide stress in functionally diverse coral symbionts

    International Nuclear Information System (INIS)

    Dam, J.W. van; Uthicke, S.; Beltran, V.H.; Mueller, J.F.; Negri, A.P.

    2015-01-01

    Most reef building corals rely on symbiotic microalgae (genus Symbiodinium) to supply a substantial proportion of their energy requirements. Functional diversity of different Symbiodinium genotypes, endorsing the host with physiological advantages, has been widely reported. Yet, the influence of genotypic specificity on the symbiont's susceptibility to contaminants or cumulative stressors is unknown. Cultured Symbiodinium of presumed thermal-tolerant clade D tested especially vulnerable to the widespread herbicide diuron, suggesting important free-living populations may be at risk in areas subjected to terrestrial runoff. Co-exposure experiments where cultured Symbiodinium were exposed to diuron over a thermal stress gradient demonstrated how fast-growing clade C1 better maintained photosynthetic capability than clade D. The mixture toxicity model of Independent Action, considering combined thermal stress and herbicide contamination, revealed response additivity for inhibition of photosynthetic yield in both tested cultures, emphasizing the need to account for cumulative stressor impacts in ecological risk assessment and resource management. - Highlights: • Water quality influences thermal stress thresholds in different Symbiodinium types. • Photosystem of clade D tested more sensitive than C1 to a common herbicide. • Increased thermal tolerance quickly countered in presence of herbicide. • Mixture toxicity approach demonstrated response additivity for combined stressors. • Symbiotic partnership may be compromised in areas subjected to terrestrial runoff. - Thermal-tolerant Symbiodinium type D tested especially vulnerable to a common herbicide, emphasizing the significance of cumulative stressors in ecological risk management

  4. Methods for estimating population density in data-limited areas: evaluating regression and tree-based models in Peru.

    Science.gov (United States)

    Anderson, Weston; Guikema, Seth; Zaitchik, Ben; Pan, William

    2014-01-01

    Obtaining accurate small area estimates of population is essential for policy and health planning but is often difficult in countries with limited data. In lieu of available population data, small area estimate models draw information from previous time periods or from similar areas. This study focuses on model-based methods for estimating population when no direct samples are available in the area of interest. To explore the efficacy of tree-based models for estimating population density, we compare six different model structures including Random Forest and Bayesian Additive Regression Trees. Results demonstrate that without information from prior time periods, non-parametric tree-based models produced more accurate predictions than did conventional regression methods. Improving estimates of population density in non-sampled areas is important for regions with incomplete census data and has implications for economic, health and development policies.

  5. Metropolitan expansion and population density patterns in third world supercities as indicated by integration of space and ground data

    Science.gov (United States)

    Eyre, L. A.

    Monitoring of the urbanization process in the less developed countries of the world is limited by the inadequacy of ground data such as censuses and by their explosive rates of population growth and spatial expansion. By integrating Landsat satellite imagery and available population data, more accurate analyses are possible than by using either medium alone. Using this technique, built-up area, population and patterns of population density for the year 1978 are quantified for six Third World supercities with population in excess of six million: Calcutta, Shanghai, Cairo, Mexico City, Sao Paulo and Rio de Janeiro. Significant differences in density patterns between these cities appear to be related to economic level and culture.

  6. Population dynamics models based on cumulative density dependent feedback: A link to the logistic growth curve and a test for symmetry using aphid data

    NARCIS (Netherlands)

    Matis, J.H.; Kiffe, T.R.; Werf, van der W.; Costamagna, A.C.; Matis, T.I.; Grant, W.E.

    2009-01-01

    Density dependent feedback, based on cumulative population size, has been advocated to explain and mathematically characterize “boom and bust” population dynamics. Such feedback results in a bell-shaped population trajectory of the population density. Here, we note that this trajectory is

  7. Attributes for NHDplus Catchments (Version 1.1) for the Conterminous United States: Population Density, 2000

    Science.gov (United States)

    Wieczorek, Michael; LaMottem, Andrew E.

    2010-01-01

    This data set represents the average population density, in number of people per square kilometer multiplied by 10 for the year 2000, compiled for every catchment of NHDPlus for the conterminous United States. The source data set is the 2000 Population Density by Block Group for the Conterminous United States (Hitt, 2003). The NHDPlus Version 1.1 is an integrated suite of application-ready geospatial datasets that incorporates many of the best features of the National Hydrography Dataset (NHD) and the National Elevation Dataset (NED). The NHDPlus includes a stream network (based on the 1:100,00-scale NHD), improved networking, naming, and value-added attributes (VAAs). NHDPlus also includes elevation-derived catchments (drainage areas) produced using a drainage enforcement technique first widely used in New England, and thus referred to as "the New England Method." This technique involves "burning in" the 1:100,000-scale NHD and when available building "walls" using the National Watershed Boundary Dataset (WBD). The resulting modified digital elevation model (HydroDEM) is used to produce hydrologic derivatives that agree with the NHD and WBD. Over the past two years, an interdisciplinary team from the U.S. Geological Survey (USGS), and the U.S. Environmental Protection Agency (USEPA), and contractors, found that this method produces the best quality NHD catchments using an automated process (USEPA, 2007). The NHDPlus dataset is organized by 18 Production Units that cover the conterminous United States. The NHDPlus version 1.1 data are grouped by the U.S. Geologic Survey's Major River Basins (MRBs, Crawford and others, 2006). MRB1, covering the New England and Mid-Atlantic River basins, contains NHDPlus Production Units 1 and 2. MRB2, covering the South Atlantic-Gulf and Tennessee River basins, contains NHDPlus Production Units 3 and 6. MRB3, covering the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins, contains NHDPlus Production Units 4, 5

  8. Determination of a new uniform thorax density representative of the living population from 3D external body shape modeling.

    Science.gov (United States)

    Amabile, Celia; Choisne, Julie; Nérot, Agathe; Pillet, Hélène; Skalli, Wafa

    2016-05-03

    Body segment parameters (BSP) for each body׳s segment are needed for biomechanical analysis. To provide population-specific BSP, precise estimation of body׳s segments volume and density are needed. Widely used uniform densities, provided by cadavers׳ studies, did not consider the air present in the lungs when determining the thorax density. The purpose of this study was to propose a new uniform thorax density representative of the living population from 3D external body shape modeling. Bi-planar X-ray radiographies were acquired on 58 participants allowing 3D reconstructions of the spine, rib cage and human body shape. Three methods of computing the thorax mass were compared for 48 subjects: (1) the Dempster Uniform Density Method, currently in use for BSPs calculation, using Dempster density data, (2) the Personalized Method using full-description of the thorax based on 3D reconstruction of the rib cage and spine and (3) the Improved Uniform Density Method using a uniform thorax density resulting from the Personalized Method. For 10 participants, comparison was made between the body mass obtained from a force-plate and the body mass computed with each of the three methods. The Dempster Uniform Density Method presented a mean error of 4.8% in the total body mass compared to the force-plate vs 0.2% for the Personalized Method and 0.4% for the Improved Uniform Density Method. The adjusted thorax density found from the 3D reconstruction was 0.74g/cm(3) for men and 0.73g/cm(3) for women instead of the one provided by Dempster (0.92g/cm(3)), leading to a better estimate of the thorax mass and body mass. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Characterizing the host and symbiont proteomes in the association between the Bobtail squid, Euprymna scolopes, and the bacterium, Vibrio fischeri.

    Directory of Open Access Journals (Sweden)

    Tyler R Schleicher

    Full Text Available The beneficial symbiosis between the Hawaiian bobtail squid, Euprymna scolopes, and the bioluminescent bacterium, Vibrio fischeri, provides a unique opportunity to study host/microbe interactions within a natural microenvironment. Colonization of the squid light organ by V. fischeri begins a lifelong association with a regulated daily rhythm. Each morning the host expels an exudate from the light organ consisting of 95% of the symbiont population in addition to host hemocytes and shed epithelial cells. We analyzed the host and symbiont proteomes of adult squid exudate and surrounding light organ epithelial tissue using 1D- and 2D-polyacrylamide gel electrophoresis and multidimensional protein identification technology (MudPIT in an effort to understand the contribution of both partners to the maintenance of this association. These proteomic analyses putatively identified 1581 unique proteins, 870 proteins originating from the symbiont and 711 from the host. Identified host proteins indicate a role of the innate immune system and reactive oxygen species (ROS in regulating the symbiosis. Symbiont proteins detected enhance our understanding of the role of quorum sensing, two-component signaling, motility, and detoxification of ROS and reactive nitrogen species (RNS inside the light organ. This study offers the first proteomic analysis of the symbiotic microenvironment of the adult light organ and provides the identification of proteins important to the regulation of this beneficial association.

  10. Molecular evidence for Lessepsian invasion of soritids (larger symbiont bearing benthic foraminifera.

    Directory of Open Access Journals (Sweden)

    Gily Merkado

    Full Text Available The Mediterranean Sea is considered as one of the hotspots of marine bioinvasions, largely due to the influx of tropical species migrating through the Suez Canal, so-called Lessepsian migrants. Several cases of Lessepsian migration have been documented recently, however, little is known about the ecological characteristics of the migrating species and their aptitude to colonize the new areas. This study focused on Red Sea soritids, larger symbiont-bearing benthic foraminifera (LBF that are indicative of tropical and subtropical environments and were recently found in the Israeli coast of the Eastern Mediterranean. We combined molecular phylogenetic analyses of soritids and their algal symbionts as well as network analysis of Sorites orbiculus Forskål to compare populations from the Gulf of Elat (northern Red Sea and from a known hotspot in Shikmona (northern Israel that consists of a single population of S. orbiculus. Our phylogenetic analyses show that all specimens found in Shikmona are genetically identical to a population of S. orbiculus living on a similar shallow water pebbles habitat in the Gulf of Elat. Our analyses also show that the symbionts found in Shikmona and Elat soritids belong to the Symbiodinium clade F5, which is common in the Red Sea and also present in the Indian Ocean and Caribbean Sea. Our study therefore provides the first genetic and ecological evidences that indicate that modern population of soritids found on the Mediterranean coast of Israel is probably Lessepsian, and is less likely the descendant of a native ancient Mediterranean species.

  11. Country roads, take me home… to my friends: How intelligence, population density, and friendship affect modern happiness.

    Science.gov (United States)

    Li, Norman P; Kanazawa, Satoshi

    2016-11-01

    We propose the savanna theory of happiness, which suggests that it is not only the current consequences of a given situation but also its ancestral consequences that affect individuals' life satisfaction and explains why such influences of ancestral consequences might interact with intelligence. We choose two varied factors that characterize basic differences between ancestral and modern life - population density and frequency of socialization with friends - as empirical test cases. As predicted by the theory, population density is negatively, and frequency of socialization with friends is positively, associated with life satisfaction. More importantly, the main associations of life satisfaction with population density and socialization with friends significantly interact with intelligence, and, in the latter case, the main association is reversed among the extremely intelligent. More intelligent individuals experience lower life satisfaction with more frequent socialization with friends. This study highlights the utility of incorporating evolutionary perspectives in the study of subjective well-being. © 2016 The British Psychological Society.

  12. Trends and population dynamics of a Velvet Scoter (Melanitta fusca) population: influence of density dependence and winter climate

    NARCIS (Netherlands)

    Hartman, G.; Kölzsch, A.; Larsson, K.; Nordberg, M.; Höglund, J.

    2013-01-01

    As many seaduck populations around the world have been reported to be in decline, there is an increasing demand for knowledge about intrinsic and extrinsic factors determining population dynamics of these species. In this study, we analyzed long-term dynamics of the summer population of Velvet

  13. Population density of oil palm pollinator weevil Elaeidobius kamerunicus based on seasonal effect and age of oil palm

    Science.gov (United States)

    Daud, Syarifah Nadiah Syed Mat; Ghani, Idris Abd.

    2016-11-01

    The pollinating weevil, Elaedobius kamerunicus (EK) has been known to be the most efficient insect pollinator of oil palm, and has successfully improved the oil palm pollination and increased the yield. Its introduction has greatly reduced the need for assisted pollination. The purpose of this study was to identify the population density of oil palm pollinator weevil EK using the concept of pollinator force and to relate the population density with the seasonal effect and the age of oil palm at Lekir Oil Palm Plantation Batu 14, Perak, Peninsular Malaysia. The pollinator force of the weevil was sustained at a range between 3095.2 to 19126.1 weevils per ha. The overall mean of weevil per spikelet shows that the range of weevil was between 13.51 and 54.06 per spikelet. There was no correlation between rainfall and population density of EK. However, positive correlation was obtained between weevil density and the number of anthesising female inflorescence of oil palm (r= 0.938, p< 0.05). Results of t-test show that the 6-year old oil palm stands had significantly different population density than that of a 8-year old oil palm stand. The information of this study should be useful as a baseline data to investigate why there is such a wide range of weevils per ha or spikelet. Further study should also be done to relate the number pollinator force per spikelete and the Fresh fruit Bunch (FFB), fruit set or fruit to bunch ratio.

  14. Semivariogram models for estimating fig fly population density throughout the year

    Directory of Open Access Journals (Sweden)

    Mauricio Paulo Batistella Pasini

    2014-07-01

    Full Text Available The objective of this work was to select semivariogram models to estimate the population density of fig fly (Zaprionus indianus; Diptera: Drosophilidae throughout the year, using ordinary kriging. Nineteen monitoring sites were demarcated in an area of 8,200 m2, cropped with six fruit tree species: persimmon, citrus, fig, guava, apple, and peach. During a 24 month period, 106 weekly evaluations were done in these sites. The average number of adult fig flies captured weekly per trap, during each month, was subjected to the circular, spherical, pentaspherical, exponential, Gaussian, rational quadratic, hole effect, K-Bessel, J-Bessel, and stable semivariogram models, using ordinary kriging interpolation. The models with the best fit were selected by cross-validation. Each data set (months has a particular spatial dependence structure, which makes it necessary to define specific models of semivariograms in order to enhance the adjustment to the experimental semivariogram. Therefore, it was not possible to determine a standard semivariogram model; instead, six theoretical models were selected: circular, Gaussian, hole effect, K-Bessel, J-Bessel, and stable.

  15. Background matching and camouflage efficiency predict population density in four-eyed turtle (Sacalia quadriocellata).

    Science.gov (United States)

    Xiao, Fanrong; Yang, Canchao; Shi, Haitao; Wang, Jichao; Sun, Liang; Lin, Liu

    2016-10-01

    Background matching is an important way to camouflage and is widespread among animals. In the field, however, few studies have addressed background matching, and there has been no reported camouflage efficiency in freshwater turtles. Background matching and camouflage efficiency of the four-eyed turtle, Sacalia quadriocellata, among three microhabitat sections of Hezonggou stream were investigated by measuring carapace components of CIE L*a*b* (International Commission on Illumination; lightness, red/green and yellow/blue) color space, and scoring camouflage efficiency through the use of humans as predators. The results showed that the color difference (ΔE), lightness difference (ΔL(*)), and chroma difference (Δa(*)b(*)) between carapace and the substrate background in midstream were significantly lower than that upstream and downstream, indicating that the four-eyed turtle carapace color most closely matched the substrate of midstream. In line with these findings, the camouflage efficiency was the best for the turtles that inhabit midstream. These results suggest that the four-eyed turtles may enhance camouflage efficiency by selecting microhabitat that best match their carapace color. This finding may explain the high population density of the four-eyed turtle in the midstream section of Hezonggou stream. To the best of our knowledge, this study is among the first to quantify camouflage of freshwater turtles in the wild, laying the groundwork to further study the function and mechanisms of turtle camouflage. Copyright © 2016. Published by Elsevier B.V.

  16. Mating system parameters in a high density population of andirobas in the Amazon forest

    Directory of Open Access Journals (Sweden)

    Tatiana de Campos

    2013-05-01

    Full Text Available The objective of this work was to estimate the mating system parameters of a andiroba (Carapa guianensis population using microsatellite markers and the mixed and correlated mating models. Twelve open‑pollinated progeny arrays of 15 individuals were sampled in an area with C. guianensis estimated density of 25.7 trees per hectare. Overall, the species has a mixed reproductive system, with a predominance of outcrossing. The multilocus outcrossing rate (t m = 0.862 was significantly lower than the unity, indicating that self‑pollination occurred. The rate of biparental inbreeding was substantial (t m ‑ t s = 0.134 and significantly different from zero. The correlation of selfing within progenies was high (r s = 0.635, indicating variation in the individual outcrossing rate. Consistent with this result, the estimate of the individual outcrossing rate ranged from 0.598 to 0.978. The multilocus correlation of paternity was low (r p(m = 0.081, but significantly different from zero, suggesting that the progenies contain full‑sibs. The coancestry within progenies (Θ = 0.185 was higher and the variance effective size (Ne(v = 2.7 was lower than expected for true half‑sib progenies (Θ = 0.125; Ne(v = 4. These results suggest that, in order to maintain a minimum effective size of 150 individuals for breeding, genetic conservation, and environmental reforestation programs, seeds from at least 56 trees must be collected.

  17. A candidate gene association study of bone mineral density in an Iranian population.

    Directory of Open Access Journals (Sweden)

    Seyed Alireza Dastgheib

    2016-10-01

    Full Text Available The genetic epidemiology of variation in bone mineral density (BMD and osteoporosis is not well studied in Iranian populations and needs more research. We report a candidate gene association study of BMD variation in a healthy cross sectional study of 501 males and females sampled from the IMOS study Shiraz, Iran. We selected to study the association with 21 SNPs located in the 7 candidate genes LRP5, RANK, RANKL, OPG, P2RX7, VDR and ESR1. BMD was measured at the three sites L2-L4, neck of femur and total hip. Association between BMD and each SNP was assessed using multiple linear regression assuming an allele dose (additive effect on BMD (adjusted for age and sex. Statistically significant (at the unadjusted 5% level associations were seen with 7 SNPs in 5 of the candidate genes. Two SNPs showed statistically significant association with more than one BMD site. Significant association was seen between BMD at all three sites with the VDR SNP rs731246 (L2-L4 p=0.038; neck of femur p=0.001 and total hip p<0.001. The T allele was consistently associated with lower BMD than the C allele. Significant association was also seen for the P2RX7 SNP rs3751143 where the G allele was consistently associated with lower BMD than the T allele, (L2-L4 p=0.069; neck of femur p=0.024, total hip p=0.045.

  18. Vitamin D receptor alleles and bone mineral density in a normal premenopausal Brazilian female population

    Directory of Open Access Journals (Sweden)

    Lazaretti-Castro M.

    1997-01-01

    Full Text Available Studies on the association between vitamin D receptor (VDR polymorphism and bone mineral density (BMD in different populations have produced conflicting results probably due to ethnic differences in the populations studied. The Brazilian population is characterized by a very broad genetic background and a high degree of miscegenation. Of an initial group of 164, we studied 127 women from the city of São Paulo, aged 20 to 47 years (median, 31 years, with normal menses, a normal diet and no history of diseases or use of any medication that could alter BMD. VDR genotype was assessed by PCR amplification followed by BsmI digestion of DNA isolated from peripheral leukocytes. BMD was measured using dual energy X-ray absorptiometry (Lunar DPX at the lumbar site (L2-L4 and femoral neck. Most of the women (77.6% were considered to be of predominantly European ancestry (20.6% of them reported also native American ancestry, 12.8% were of African-Brazilian ancestry and 9.6% of Asian ancestry, 41.0% (52 were classified as bb, 48.8% (62 as Bb and 10.2% (13 as BB. The BB, Bb and bb groups did not differ in age, height, weight, body mass index or age at menarche. Lumbar spine BMD was significantly higher in the bb group (1.22 ± 0.16 g/cm² than in the BB group (1.08 ± 0.14; P<0.05, and the Bb group presented an intermediate value (1.17 ± 0.15. Femoral neck BMD was higher in the bb group (0.99 ± 0.11 g/cm² compared to Bb (0.93 ± 0.12 and BB (0.90 ± 0.09 (P<0.05. These data indicate that there is a significant correlation between the VDR BsmI genotype and BMD in healthy Brazilian premenopausal females.

  19. Agricultural irrigation mediates climatic effects and density dependence in population dynamics of Chinese striped hamster in North China Plain.

    Science.gov (United States)

    Yan, Chuan; Xu, Lei; Xu, Tongqin; Cao, Xiaoping; Wang, Fusheng; Wang, Shuqing; Hao, Shoushen; Yang, Hefang; Zhang, Zhibin

    2013-03-01

    Several studies show that climatic (extrinsic) factors can interact with density-dependent (intrinsic) factors to alter long-term population dynamics, yet there is a surprising lack of investigations of how anthropogenic disturbance modifies such dynamics. Such interactions could be especially important in agricultural systems subject to climate change. We investigated the effects of density dependence, climate, recurrent disturbance from flood irrigation and their interactions on the population dynamics of an important rodent pest, the Chinese striped hamster (Cricetulus barabensis), over 27 years in the croplands of the North China Plain. Strong density-dependent feedbacks occurred at both annual and seasonal scales. While warmer weather increased population sizes in nonbreeding seasons, this effect was counteracted by the negative effect of flood irrigation in breeding seasons. Precipitation showed significant positive effects in nonbreeding seasons, but negative effects in breeding seasons. There were important interactions between intrinsic dynamics, extrinsic dynamics and disturbance. Low temperature significantly increased the strength of density dependence in nonbreeding seasons, whereas intensification of flood irrigation area significantly increased the strength of density dependence but reduced the effect of summer precipitation in breeding seasons. Overall climate change is expected to increase population levels, but anthropogenic disturbance from flood irrigation will help prevent long-term population increases. The interactions between anthropogenic disturbance and both intrinsic and extrinsic (weather-driven) population dynamics caution that we need to consider anthropogenic disturbance as an integral component of population responses to climate change. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

  20. Increase in Population Density and Aggravation of Social and Psychological Problems in Areas with High-Rise Construction

    Science.gov (United States)

    Romanova, Elena

    2018-03-01

    High-rise apartment houses have technical and economic advantages in areas with dense population. Their placement in the central part of the city allows increasing the number of living space in the limited territory, to bring population to the place of employment and reduce pendular migration. But increase in population density leads to psychological problems: level of a stress, fatigue increases, the number of phobias grows, infectious diseases extend quicker. These problems can be solved at resettlement of inhabitants to the suburb. However such decision leads to aggravation of a transport problem and the pulsing increase in population density in the downtown and on its suburb. To solve a transport problem, it is necessary not to increase the square of the cities. Therefore in the suburbs is also used high-rise construction. But high-rise residential districts on the suburb of the city get own social problems which are capable to destroy all advantages of high-rise construction.

  1. Protection from Cardiovascular Disease Due to Increased High-Density Lipoprotein Cholesterol in African Black Populations: Myth or Reality?

    Science.gov (United States)

    Woudberg, Nicholas J; Goedecke, Julia H; Lecour, Sandrine

    2016-10-20

    The burden of cardiovascular disease (CVD) in sub-Saharan Africa has increased over the last decade. Despite this, African Black populations present with relatively low incidences of coronary heart disease and ischemic heart disease, which may be attributed to their lower total cholesterol, triglycerides and low-density lipoprotein cholesterol concentrations, compared with White populations. Commensurate with these lower lipid levels, it was believed that high-density lipoprotein cholesterol (HDL-C) concentrations would be higher in Black populations compared with their White counterparts. This is based on data from previous studies of African and African American populations; however, recent studies conducted in Africa found similar or lower HDL-C concentrations in Black compared with White individuals. Current research, therefore, suggests that HDL-C may not be a good indicator of cardiovascular risk and future research should focus on HDL quality (vs quantity), by measuring HDL functionality and subclass.

  2. Rural to Urban Population Density Scaling of Crime and Property Transactions in English and Welsh Parliamentary Constituencies.

    Science.gov (United States)

    Hanley, Quentin S; Lewis, Dan; Ribeiro, Haroldo V

    2016-01-01

    Urban population scaling of resource use, creativity metrics, and human behaviors has been widely studied. These studies have not looked in detail at the full range of human environments which represent a continuum from the most rural to heavily urban. We examined monthly police crime reports and property transaction values across all 573 Parliamentary Constituencies in England and Wales, finding that scaling models based on population density provided a far superior framework to traditional population scaling. We found four types of scaling: i) non-urban scaling in which a single power law explained the relationship between the metrics and population density from the most rural to heavily urban environments, ii) accelerated scaling in which high population density was associated with an increase in the power-law exponent, iii) inhibited scaling where the urban environment resulted in a reduction in the power-law exponent but remained positive, and iv) collapsed scaling where transition to the high density environment resulted in a negative scaling exponent. Urban scaling transitions, when observed, took place universally between 10 and 70 people per hectare. This study significantly refines our understanding of urban scaling, making clear that some of what has been previously ascribed to urban environments may simply be the high density portion of non-urban scaling. It also makes clear that some metrics undergo specific transitions in urban environments and these transitions can include negative scaling exponents indicative of collapse. This study gives promise of far more sophisticated scale adjusted metrics and indicates that studies of urban scaling represent a high density subsection of overall scaling relationships which continue into rural environments.

  3. Maternal effects on male weaponry: female dung beetles produce major sons with longer horns when they perceive higher population density.

    Science.gov (United States)

    Buzatto, Bruno A; Tomkins, Joseph L; Simmons, Leigh W

    2012-07-23

    Maternal effects are environmental influences on the phenotype of one individual that are due to the expression of genes in its mother, and are expected to evolve whenever females are better capable of assessing the environmental conditions that their offspring will experience than the offspring themselves. In the dung beetle Onthophagus taurus, conditional male dimorphism is associated with alternative reproductive tactics: majors fight and guard females whereas minors sneak copulations. Furthermore, variation in dung beetle population density has different fitness consequences for each male morph, and theory predicts that higher population density might select for a higher frequency of minors and/or greater expenditure on weaponry in majors. Because adult dung beetles provide offspring with all the nutritional resources for their development, maternal effects strongly influence male phenotype. Here we tested whether female O. taurus are capable of perceiving population density, and responding by changing the phenotype of their offspring. We found that mothers who were reared with other conspecifics in their pre-mating period produced major offspring that had longer horns across a wider range of body sizes than the major offspring of females that were reared in isolation in their pre-mating period. Moreover, our results indicate that this maternal effect on male weaponry does not operate through the amount of dung provided by females to their offspring, but is rather transmitted through egg or brood mass composition. Finally, although theory predicts that females experiencing higher density might produce more minor males, we found no support for this, rather the best fitting models were equivocal as to whether fewer or the same proportions of minors were produced. Our study describes a new type of maternal effect in dung beetles, which probably allows females to respond to population density adaptively, preparing at least their major offspring for the sexual

  4. The effects of hair density of beef cattle on Haematobia irritans horn fly populations.

    Science.gov (United States)

    Steelman, C D; Brown, M A; Gbur, E E; Tolley, G

    1997-07-01

    We show the relationships that exist between the amount of hair and quantity of sebum on cattle skin and the population density of the horn fly, Haematobia irritans. Brahman and Chianina steers had means of 2390 and 1587 hairs per cm2, respectively, significantly more than the mean number of hairs on Angus, Brahman x Angus Crossbred, Charolais, and Red Poll steers. The Chianina steers had > 30% more sebum present on their skin and hair (0.58g/929 cm2) than the Angus, Charolais, and Red Poll steers at the Beef Cattle Research Station Savoy, Arkansas. The Brahman steers had a significantly greater amount of sebum present on the skin (1.51 g/929 cm2) than the Crossbred and purebred Angus steers (0.55 and 0.25 g/929 cm2, respectively) at the South Central Family Farms Research Centre Booneville, Arkansas. The Brahman and Chianina steers had means of 61.9 and 17.0 horn flies per steer, respectively, during the fly season, whereas the Angus, Crossbred, Charolais and Red Poll steers had fly season means that ranged from 76.9 to 265.8 flies per steer. Regression analysis showed that an increase of 100 hairs per cm2, was associated with a reduction of 11 horn flies in the Angus II, 5 in Angus I, 20 in Charolais, 37 in Red Poll, and 0.4 in Chianina steers at the Savoy Station and a reduction of 6.6 horn flies for the Angus, Brahman, and Crossbred steers at the Booneville Centre. Regardless of cattle breed, an increase of 1.0 g of sebum per 929 cm2 output by the steer was associated with 478.5 additional hairs per cm2 on the animal. Each increase of 0.25 g of sebum per 929 cm2 resulted in a decrease of 9.2 horn flies per steer. We conclude that some of the factors responsible for fly-resistance in cattle are hair density and the corresponding amount of sebum present on cattle skin and hair.

  5. Effect of a Terminated Cover Crop and Aldicarb on Cotton Yield and Meloidogyne incognita Population Density.

    Science.gov (United States)

    Wheeler, T A; Leser, J F; Keeling, J W; Mullinix, B

    2008-06-01

    Terminated small grain cover crops are valuable in light textured soils to reduce wind and rain erosion and for protection of young cotton seedlings. A three-year study was conducted to determine the impact of terminated small grain winter cover crops, which are hosts for Meloidogyne incognita, on cotton yield, root galling and nematode midseason population density. The small plot test consisted of the cover treatment as the main plots (winter fallow, oats, rye and wheat) and rate of aldicarb applied in-furrow at-plant (0, 0.59 and 0.84 kg a.i./ha) as subplots in a split-plot design with eight replications, arranged in a randomized complete block design. Roots of 10 cotton plants per plot were examined at approximately 35 days after planting. Root galling was affected by aldicarb rate (9.1, 3.8 and 3.4 galls/root system for 0, 0.59 and 0.84 kg aldicarb/ha), but not by cover crop. Soil samples were collected in mid-July and assayed for nematodes. The winter fallow plots had a lower density of M. incognita second-stage juveniles (J2) (transformed to Log(10) (J2 + 1)/500 cm(3) soil) than any of the cover crops (0.88, 1.58, 1.67 and 1.75 Log(10)(J2 + 1)/500 cm(3) soil for winter fallow, oats, rye and wheat, respectively). There were also fewer M. incognita eggs at midseason in the winter fallow (3,512, 7,953, 8,262 and 11,392 eggs/500 cm(3) soil for winter fallow, oats, rye and wheat, respectively). Yield (kg lint per ha) was increased by application of aldicarb (1,544, 1,710 and 1,697 for 0, 0.59 and 0.84 kg aldicarb/ha), but not by any cover crop treatments. These results were consistent over three years. The soil temperature at 15 cm depth, from when soils reached 18 degrees C to termination of the grass cover crop, averaged 9,588, 7,274 and 1,639 centigrade hours (with a minimum threshold of 10 degrees C), in 2005, 2006 and 2007, respectively. Under these conditions, potential reproduction of M. incognita on the cover crop did not result in a yield penalty.

  6. Effects of population density and chemical environment on the behavior of Escherichia coli in shallow temperature gradients

    International Nuclear Information System (INIS)

    Demir, Mahmut; Yoney, Anna; Salman, Hanna; Douarche, Carine; Libchaber, Albert

    2011-01-01

    In shallow temperature gradients, changes in temperature that bacteria experience occur over long time scales. Therefore, slow processes such as adaptation, metabolism, chemical secretion and even gene expression become important. Since these are cellular processes, the cell density is an important parameter that affects the bacteria's response. We find that there are four density regimes with distinct behaviors. At low cell density, bacteria do not cause changes in their chemical environment; however, their response to the temperature gradient is strongly influenced by it. In the intermediate cell-density regime, the consumption of nutrients becomes significant and induces a gradient of nutrients opposing the temperature gradient due to higher consumption rate at the high temperature. This causes the bacteria to drift toward low temperature. In the high cell-density regime, interactions among bacteria due to secretion of an attractant lead to a strong local accumulation of bacteria. This together with the gradient of nutrients, resulted from the differential consumption rate, creates a fast propagating pulse of bacterial density. These observations are a result of classical nonlinear population dynamics. At extremely high cell density, a change in the physiological state of the bacteria is observed. The bacteria, at the individual level, become cold seeking. This appears initially as a result of a change in the methylation level of the two most abundant sensing receptors, Tsr and Tar. It is further enforced at an even higher cell density by a change in the expression level of these receptors. (perspective)

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

    Science.gov (United States)

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

    2017-09-05

    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, " Candidatus Epulopiscium" and related giant bacteria. These symbionts lack cellulases but encode a distinctive and lineage-specific array of mostly intracellular carbohydrases concurrent with the unique and tractable dietary resources of their hosts. Importantly, enzymes initiating the breakdown of the abundant and complex algal polysaccharides also originate from these symbionts. These are also highly transcribed and peak according to the diel lifestyle of their host, further supporting their importance and host-symbiont cospeciation. Because of their distinctive genomic blueprint, we propose the classification of these giant bacteria into three candidate genera. Collectively, our findings show that the acquisition of metabolically distinct " Epulopiscium " symbionts in hosts feeding on compositionally varied algal diets is a key niche-partitioning driver in the nutritional ecology of herbivorous surgeonfishes.

  8. Host-Symbiont Interactions for Potentially Managing Heteropteran Pests

    Directory of Open Access Journals (Sweden)

    Simone Souza Prado

    2012-01-01

    Full Text Available Insects in the suborder Heteroptera, the so-called true bugs, include over 40,000 species worldwide. This insect group includes many important agricultural pests and disease vectors, which often have bacterial symbionts associated with them. Some symbionts have coevolved with their hosts to the extent that host fitness is compromised with the removal or alteration of their symbiont. The first bug/microbial interactions were discovered over 50 years ago. Only recently, mainly due to advances in molecular techniques, has the nature of these associations become clearer. Some researchers have pursued the genetic modification (paratransgenesis of symbionts for disease control or pest management. With the increasing interest and understanding of the bug/symbiont associations and their ecological and physiological features, it will only be a matter of time before pest/vector control programs utilize this information and technique. This paper will focus on recent discoveries of the major symbiotic systems in Heteroptera, highlighting how the understanding of the evolutionary and biological aspects of these relationships may lead to the development of alternative techniques for efficient heteropteran pest control and suppression of diseases vectored by Heteroptera.

  9. Observations on Neotricula aperta (Gastropoda: Pomatiopsidae) population densities in Thailand and central Laos: implications for the spread of Mekong schistosomiasis.

    Science.gov (United States)

    Attwood, Stephen W; Upatham, E Suchart

    2012-06-21

    The snail Neotricula aperta transmits Mekong schistosomiasis in southern Laos and Cambodia, with about 1.5 million people at risk of infection. Plans are under consideration for at least 12 hydroelectric power dams on the lower Mekong river and much controversy surrounds predictions of their environmental impacts. Unfortunately, there are almost no ecological data (such as long-term population trend studies) available for N. aperta which could be used in impact assessment. Predictions currently assume that the impacts will be the same as those observed in Africa (i.e., a worsening of the schistosomiasis problem); however, marked ecological differences between the snails involved suggest that region specific models are required. The present study was performed as an initial step in providing data, which could be useful in the planning of water resource development in the Mekong. Snail population density records were analyzed for populations close to, and far downstream of, the Nam Theun 2 (NT2) project in Laos in order to detect any changes that might be attributable to impoundment. The population immediately downstream of NT2 and that sampled 400 km downstream in Thailand both showed a long-term trend of slow growth from 1992 to 2005; however, both populations showed a marked decline in density between 2005 and 2011. The decline in Thailand was to a value significantly lower than that predicted by a linear mixed model for the data, whilst the population density close to NT2 fell to undetectable levels in 2011 from densities of over 5000 m(-2) in 2005. The NT2 dam began operation in 2010. The impact of the NT2 dam on N. aperta population density could be more complex than first thought and may reflect the strict ecological requirements of this snail. There was no indication that responses of N. aperta populations to dam construction are similar to those observed with Bulinus and Schistosoma haematobium in Africa, for example. In view of the present findings

  10. Observations on Neotricula aperta (Gastropoda: Pomatiopsidae population densities in Thailand and central Laos: implications for the spread of Mekong schistosomiasis

    Directory of Open Access Journals (Sweden)

    Attwood Stephen W

    2012-06-01

    Full Text Available Abstract Background The snail Neotricula aperta transmits Mekong schistosomiasis in southern Laos and Cambodia, with about 1.5 million people at risk of infection. Plans are under consideration for at least 12 hydroelectric power dams on the lower Mekong river and much controversy surrounds predictions of their environmental impacts. Unfortunately, there are almost no ecological data (such as long term population trend studies available for N. aperta which could be used in impact assessment. Predictions currently assume that the impacts will be the same as those observed in Africa (i.e., a worsening of the schistosomiasis problem; however, marked ecological differences between the snails involved suggest that region specific models are required. The present study was performed as an initial step in providing data, which could be useful in the planning of water resource development in the Mekong. Snail population density records were analyzed for populations close to, and far downstream of, the Nam Theun 2 (NT2 project in Laos in order to detect any changes that might be attributable to impoundment. Results The population immediately downstream of NT2 and that sampled 400 km downstream in Thailand both showed a long term trend of slow growth from 1992 to 2005; however, both populations showed a marked decline in density between 2005 and 2011. The decline in Thailand was to a value significantly lower than that predicted by a linear mixed model for the data, whilst the population density close to NT2 fell to undetectable levels in 2011 from densities of over 5000 m-2 in 2005. The NT2 dam began operation in 2010. Conclusions The impact of the NT2 dam on N. aperta population density could be more complex than first thought and may reflect the strict ecological requirements of this snail. There was no indication that responses of N. aperta populations to dam construction are similar to those observed with Bulinus and Schistosoma haematobium in

  11. The relationship between serum 25-hydroxy vitamin D, parathormone and bone mineral density in Indian population.

    Science.gov (United States)

    Garg, M K; Tandon, N; Marwaha, R K; Menon, A S; Mahalle, N

    2014-01-01

    Vitamin D deficiency (VDD) is a global problem. Not all patients with VDD have clinical manifestations or secondary hyperparathyroidism. We studied the interaction between serum 25-hydroxy vitamin D (25OHD), parathormone (PTH) and bone mineral density (BMD) in Indian adolescents and adults. Population survey. A total of 1829 adolescents and 1346 adults aged 50 years and above were analysed in this study. Serum biochemistry, 25OHD, PTH and BMD were estimated. Subjects were grouped according to quartiles of serum PTH. VDD was defined as severe (25OHD ≤ 5 ng/ml), moderate (25OHD ≤ 10 ng/ml) and mild (25OHD ≤ 20 ng/ml) and secondary hyperparathyroidism (SHPT) when serum PTH levels >65 pg/ml. Only 30-40% of subjects with moderate and severe VDD, respectively, had SHPT. BMD decreased from Quartile 1 to Quartile 4 of PTH at all sites among adolescents and adults, with only a marginal decline in serum 25OHD levels between these quartiles. Further, within each PTH quartile, there was no difference in BMD according to categories of VDD. Analysing BMD in the different PTH quartiles, the PTH cut-offs beyond which BMD showed a significant decline, was 35 pg/ml in adolescents and 53 pg/ml in adults. Less than half of the subjects with VDD have SHPT. BMD levels start to decline at PTH values currently considered to be normal. These data suggest the need to redefine SHPT in different age groups keeping in mind the relationship between PTH and BMD. This may also influence the decision to supplement subjects with VDD. © 2013 John Wiley & Sons Ltd.

  12. The effects of selection for size in cattle on horn fly population density.

    Science.gov (United States)

    Steelman, C D; Brown, C J; McNew, R W; Gbur, E E; Brown, M A; Tolley, G

    1996-04-01

    Statistically significant differences were observed in the population density of the horn fly, Haematobia irritans irritans L., on Angus cows having significantly different frame sizes. Angus cows, averaging horn flies than Angus cows that measured 112.5-117.5 cm, 117.5-120 cm, 120-126 cm and > 126 cm in height at the hip. The Angus I cows ( 126 cm). The estimated heritability (h2) of horn fly resistance was 0.43 +/- 0.07 and 0.95 +/- 0.31 for 1989 and 1990, respectively. Horn fly counts on the Angus I herd ( horn flies per cow (PBV = 26.9 flies per cow in 1989) and from 75.9 (PBV = -29.1) to 134.5 (PBV = 29.5) flies per cow in 1990. Angus I bulls had PBV = -23.7 to 13.4 and from -26.5 to 14.75 in 1989 and 1990, respectively. The Angus II cows had horn fly counts that ranged from 159.6 (PBV of -23.5) to 208.1 (PBV of 25) per cow in 1989 and from 232.3 (PBV of -56.2) to 378.7 (PBV of 90) per cow in 1990. Angus II bulls had PBVs that ranged from -17.1 to 18.9 in 1989 and from -28.1 to 48.8 in 1990. The Angus I cows had significantly (P horn flies (mean of 63.8 horn flies per m2) than the small, medium or large Angus II cows (mean of 129.4, 149.6 and 145.5 horn flies per m2, respectively). The data indicated that some specific factor(s) associated with cow size contribute(s) to innate resistance of cattle to the horn fly.

  13. Genetic Variation and Phenotypic Response of 15 Sweet Corn (Zea mays L.) Hybrids to Population Density

    OpenAIRE

    Shelton, Adrienne; Tracy, William

    2013-01-01

    Planting sweet corn at higher densities may increase the canopy cover, reducing light transmission to the understory and suppressing weed growth. High planting densities can also negatively impact the crop, however, by decreasing ear size and overall yield. The objective of this study was to determine the potential for increased density tolerance of 15 sweet corn hybrids by estimating the general combining ability (GCA) and specific combining ability (SCA) for traits of interest. In 2010 and ...

  14. Changes in home range sizes and population densities of carnivore species along the natural to urban habitat gradient

    Czech Academy of Sciences Publication Activity Database

    Šálek, Martin; Drahníková, L.; Tkadlec, Emil

    2015-01-01

    Roč. 45, č. 1 (2015), s. 1-14 ISSN 0305-1838 Institutional support: RVO:68081766 Keywords : Carnivores * home range size * natural–urban gradient * population density * review Subject RIV: EG - Zoology Impact factor: 4.116, year: 2015

  15. Spatial distribution of U.S. household carbon footprints reveals suburbanization undermines greenhouse gas benefits of urban population density.

    Science.gov (United States)

    Jones, Christopher; Kammen, Daniel M

    2014-01-21

    Which municipalities and locations within the United States contribute the most to household greenhouse gas emissions, and what is the effect of population density and suburbanization on emissions? Using national household surveys, we developed econometric models of demand for energy, transportation, food, goods, and services that were used to derive average household carbon footprints (HCF) for U.S. zip codes, cities, counties, and metropolitan areas. We find consistently lower HCF in urban core cities (∼ 40 tCO2e) and higher carbon footprints in outlying suburbs (∼ 50 tCO2e), with a range from ∼ 25 to >80 tCO2e in the 50 largest metropolitan areas. Population density exhibits a weak but positive correlation with HCF until a density threshold is met, after which range, mean, and standard deviation of HCF decline. While population density contributes to relatively low HCF in the central cities of large metropolitan areas, the more extensive suburbanization in these regions contributes to an overall net increase in HCF compared to smaller metropolitan areas. Suburbs alone account for ∼ 50% of total U.S. HCF. Differences in the size, composition, and location of household carbon footprints suggest the need for tailoring of greenhouse gas mitigation efforts to different populations.

  16. Browsing patterns of white-tailed deer following increased timber harvest and a decline in population density

    Science.gov (United States)

    Shawn M. Crimmins; John W. Edwards; W. Mark Ford; Patrick D. Keyser; James M. Crum

    2010-01-01

    We examined browsing patterns of white-tailed deer (Odocoileus virginianus) on a site in the central Appalachians that experienced a substantial (>50%) reduction in deer population density and an increase in the amount of timber harvest since 2001. We sampled woody browse in and immediately adjacent to 12 clearcuts ranging in age from 0-5 years...

  17. Microflora of Meloidogyne egg masses: species composition, population density and effect on the biocontrol agent Verticillium chlamudosporium (Goddard)

    NARCIS (Netherlands)

    Kok, C.J.; Papert, A.; Hok-A-Hin, C.H.

    2001-01-01

    Egg masses of Meloidogyne fallax from tomato and potato growing in soil from a nematode suppressive and a nonsuppressive field sustained bacterial population densities two to three orders of magnitude higher than those of the rhizosphere soil. BIOLOG metabolic profiling identified 16 bacterial

  18. Population densities and habitat use of the golden jackal (Canis aureus) in farmlands across the Balkan Peninsula

    Czech Academy of Sciences Publication Activity Database

    Šálek, Martin; Červinka, J.; Banea, O. C.; Krofel, M.; Ćirović, D.; Selanec, I.; Penezić, A.; Grill, S.; Riegert, J.

    2014-01-01

    Roč. 60, č. 2 (2014), s. 193-200 ISSN 1612-4642 Institutional support: RVO:68081766 Keywords : Golden jackal * Acoustic monitoring * Population density * Habitat use * GIS * Farmland * Balkan Peninsula Subject RIV: EG - Zoology Impact factor: 1.634, year: 2014

  19. Some remarks on the methods of assessing the population density of higher plants in cases of aggregated spatial structure

    Directory of Open Access Journals (Sweden)

    Anna Justyna Kwiatkowska

    2015-01-01

    Full Text Available This paper presents a comparative analysis of the methods used for. assessing the density of higher plants. The analysis was carried out on natural population (Vaccinium myrtillus L. characterized by aggregated spatial structure. Attention has been paid to the surface methods with high (0.25 m2 and low

  20. Survival After HIV Infection Stage 3 (AIDS) Diagnosis, by Population Density Areas, United States, 2005-2010.

    Science.gov (United States)

    Bosh, Karin A; Shi, Jing; Chen, Mi

    We examined the survival rates after diagnosis of HIV infection stage 3 (AIDS) in the United States by population density area of residence at diagnosis. We used data from the National HIV Surveillance System to calculate survival rates among people aged ≥13 with HIV infection stage 3 (AIDS) diagnosed from 2005 through 2010. We determined survival rates for more than 12, 24, and 36 months after diagnosis; overall and by demographic characteristics; and across 3 population density area categories (large metropolitan statistical areas [MSAs, ≥500 000 people], small-to-medium MSAs [50 000 to 499 999 people], and nonmetropolitan areas [population density area categories (estimated annual percentage change: large MSAs [0.88; 95% confidence interval (CI), 0.56-1.20]; small-to-medium MSAs [0.94; 95% CI, 0.06-1.83]; and nonmetropolitan areas [1.26; 95% CI, 0.07-2.46]). Although survival rates for those with HIV infection stage 3 (AIDS) improved in all 3 population density area categories, efforts to remove barriers to care and promote treatment adherence in nonmetropolitan areas will be necessary to eliminate survival disparities.

  1. Scalable population estimates using spatial-stream-network (SSN) models, fish density surveys, and national geospatial database frameworks for streams

    Science.gov (United States)

    Daniel J. Isaak; Jay M. Ver Hoef; Erin E. Peterson; Dona L. Horan; David E. Nagel

    2017-01-01

    Population size estimates for stream fishes are important for conservation and management, but sampling costs limit the extent of most estimates to small portions of river networks that encompass 100s–10 000s of linear kilometres. However, the advent of large fish density data sets, spatial-stream-network (SSN) models that benefit from nonindependence among samples,...

  2. Growth of Trichomycterus punctulatus “Life” in three population densities in intensive culture system with recirculation

    Directory of Open Access Journals (Sweden)

    Segundo Juan López Cubas

    2013-09-01

    Full Text Available The present research was conducted in order to determine the effect of population density on the growth of Trichomycterus punctulatus, in an intensive culture system with recirculation, to which was applied Increasing Stimulus Experimental Design with three treatments without repetition: 2.21 lifes / liter, 2.94 lifes / liter and 3.68 lifes / liter. The fish were fed a diet of 32% protein and were sampled monthly growth as well as physical and chemical parameters of the water. We applied ANOVA and Duncan test. Growth of T. punctulatus was affected by population density in direct, with a higher density of 3.68 lifes / liter: 90.90 mm and 5.95 g; also the overall production per cubic meter and observed the same trend. The physicochemical parameters of the water were similar among treatments and were within the ranges of good development for fish.

  3. Metagenomic Analysis of Microbial Symbionts in a Gutless Worm

    Energy Technology Data Exchange (ETDEWEB)

    Woyke, Tanja; Teeling, Hanno; Ivanova, Natalia N.; Hunteman, Marcel; Richter, Michael; Gloeckner, Frank Oliver; Boeffelli, Dario; Barry, Kerrie W.; Shapiro, Harris J.; Anderson, Iain J.; Szeto, Ernest; Kyrpides, Nikos C.; Mussmann, Marc; Amann, Rudolf; Bergin, Claudia; Ruehland, Caroline; Rubin, Edward M.; Dubilier, Nicole

    2006-05-01

    Symbioses between bacteria and eukaryotes are ubiquitous, yet our understanding of the interactions driving these associations is hampered by our inability to cultivate most host-associated microbes. Here we use a metagenomic approach to describe four co-occurring symbionts from the marine oligochaete Olavius algarvensis, a worm lacking a mouth, gut and nephridia. Shotgun sequencing and metabolic pathway reconstruction revealed that the symbionts are sulphur-oxidizing and sulphate-reducing bacteria, all of which are capable of carbon fixation, thus providing the host with multiple sources of nutrition. Molecular evidence for the uptake and recycling of worm waste products by the symbionts suggests how the worm could eliminate its excretory system, an adaptation unique among annelid worms. We propose a model that describes how the versatile metabolism within this symbiotic consortium provides the host with an optimal energy supply as it shuttles between the upper oxic and lower anoxic coastal sediments that it inhabits.

  4. Effect of Physicochemical Characteristics of Soil on Population Density of Arbuscular Mycorrhizal Fungi in the Roots of Grapevine in Urmia

    Directory of Open Access Journals (Sweden)

    A. Mahdavi Bileh Savar

    2015-01-01

    Full Text Available Relationship of is one of the most useful interactions in terrestrial ecosystems that its positive effects on growth, physiology and ecology of different plants has been documented. This study investigated the relationship between important physicochemical characteristics of soils such as pH, electrical conductivity (EC, soil texture, organic carbon percentage, soil potassium percentage and the amount of accessible phosphorus with population of mycorrhizal fungi. After dividing the study region into four areas, 43 samples of soil were collected. The results of statistical analysis on physico-chemical characteristics of soil and their relation with population density of spores of arbuscular mycorrhizal fungi showed that there was a negative correlation between electrical conductivity (EC, pH, clay percent, and percent of soil available phosphorus, potassium percent, and percentage of organic carbon with the mean number of fungi. There were positive correlations between silt and sand percentages and mean number of spores present in the soil. Based on the coefficien of determination and based on study conditions, the best model for the rhizosphere was found tobe the one in wich available phosphorus percent of soil was the independent variable, and mean population of fungi as the dependant variable. The correlation between available phosphorus percent in soil samples with average fungi population density negative (P<0/05, but there was not a meaningful correlation between other traits and population density of fungi

  5. A crab swarm at an ecological hotspot: patchiness and population density from AUV observations at a coastal, tropical seamount

    Directory of Open Access Journals (Sweden)

    Jesús Pineda

    2016-04-01

    Full Text Available A research cruise to Hannibal Bank, a seamount and an ecological hotspot in the coastal eastern tropical Pacific Ocean off Panama, explored the zonation, biodiversity, and the ecological processes that contribute to the seamount’s elevated biomass. Here we describe the spatial structure of a benthic anomuran red crab population, using submarine video and autonomous underwater vehicle (AUV photographs. High density aggregations and a swarm of red crabs were associated with a dense turbid layer 4–10 m above the bottom. The high density aggregations were constrained to 355–385 m water depth over the Northwest flank of the seamount, although the crabs also occurred at lower densities in shallower waters (∼280 m and in another location of the seamount. The crab aggregations occurred in hypoxic water, with oxygen levels of 0.04 ml/l. Barcoding of Hannibal red crabs, and pelagic red crabs sampled in a mass stranding event in 2015 at a beach in San Diego, California, USA, revealed that the Panamanian and the Californian crabs are likely the same species, Pleuroncodes planipes, and these findings represent an extension of the southern endrange of this species. Measurements along a 1.6 km transect revealed three high density aggregations, with the highest density up to 78 crabs/m2, and that the crabs were patchily distributed. Crab density peaked in the middle of the patch, a density structure similar to that of swarming insects.

  6. Stochastic seasonality and nonlinear density-dependent factors regulate population size in an African rodent

    DEFF Research Database (Denmark)

    Leirs, Herwig; Steneth, Nils Chr.; Nichols, James D.

    1997-01-01

    no information on actual demographic rates(9,10). Here we report on both density-dependent and density-independent effects in a murid rodent pest species, the multimammute rat Mastomys natalensis (Smith, 1834), using statistical capture-recapture models, Both effects occur simultaneously, but we also demonstrate...

  7. Effects of plant density on forage production in five populations of ...

    African Journals Online (AJOL)

    Kleingrass (Panicum coloratum L.) forage yield evaluation plots are often established at a density of 6.0 plants m-2 to accommodate mechanical transplanting and harvesting equipment. However, forage crops are usually established from seed at higher plant densities. Experiments were conducted to determine if ...

  8. Effect of plant population density on the growth and yield of sorghum ...

    African Journals Online (AJOL)

    Improvement of resource use efficiency and yields is probably possible through the use of appropriate plant densities. Field trials were therefore conducted to study the effects of four plant densities, varying from 2.0 to 12.5 plants m-2 on water and radiation use and performance of two Masakwa sorghum varieties grown on ...

  9. Almost there: transmission routes of bacterial symbionts between trophic levels.

    Directory of Open Access Journals (Sweden)

    Elad Chiel

    Full Text Available Many intracellular microbial symbionts of arthropods are strictly vertically transmitted and manipulate their host's reproduction in ways that enhance their own transmission. Rare horizontal transmission events are nonetheless necessary for symbiont spread to novel host lineages. Horizontal transmission has been mostly inferred from phylogenetic studies but the mechanisms of spread are still largely a mystery. Here, we investigated transmission of two distantly related bacterial symbionts--Rickettsia and Hamiltonella--from their host, the sweet potato whitefly, Bemisia tabaci, to three species of whitefly parasitoids: Eretmocerus emiratus, Eretmocerus eremicus and Encarsia pergandiella. We also examined the potential for vertical transmission of these whitefly symbionts between parasitoid generations. Using florescence in situ hybridization (FISH and transmission electron microscopy we found that Rickettsia invades Eretmocerus larvae during development in a Rickettsia-infected host, persists in adults and in females, reaches the ovaries. However, Rickettsia does not appear to penetrate the oocytes, but instead is localized in the follicular epithelial cells only. Consequently, Rickettsia is not vertically transmitted in Eretmocerus wasps, a result supported by diagnostic polymerase chain reaction (PCR. In contrast, Rickettsia proved to be merely transient in the digestive tract of Encarsia and was excreted with the meconia before wasp pupation. Adults of all three parasitoid species frequently acquired Rickettsia via contact with infected whiteflies, most likely by feeding on the host hemolymph (host feeding, but the rate of infection declined sharply within a few days of wasps being removed from infected whiteflies. In contrast with Rickettsia, Hamiltonella did not establish in any of the parasitoids tested, and none of the parasitoids acquired Hamiltonella by host feeding. This study demonstrates potential routes and barriers to horizontal

  10. Browsing Patterns of White-Tailed Deer Following Increased Timber Harvest and a Decline in Population Density

    Directory of Open Access Journals (Sweden)

    Shawn M. Crimmins

    2010-01-01

    Full Text Available We examined browsing patterns of white-tailed deer (Odocoileus virginianus on a site in the central Appalachians that experienced a substantial (>50% reduction in deer population density and an increase in the amount of timber harvest since 2001. We sampled woody browse in and immediately adjacent to 12 clearcuts ranging in age from 0–5 years postharvest in summer 2007. Clearcut-interior areas had higher woody browse abundance and browsing rates than clearcut-edge or mature forest areas. Woody browse abundance was slightly higher within individual clearcuts than in 2001 at higher population densities and lower timber harvest rates. Overall browsing rates declined from approximately 17% in 2001 to less than 5% during our study, suggesting that the combination of deer population control, and increasing the amount of timber harvest across the landscape can reduce herbivory to levels that may not impede growth and survival of forest vegetation.

  11. Long‑term ungulate exclusion reduces fungal symbiont prevalence in native grasslands

    Science.gov (United States)

    Jennifer A. Rudgers; Rebecca A. Fletcher; Eric Olivas; Carolyn A. Young; Nikki D. Charlton; Dean E. Pearson; John L. Maron

    2016-01-01

    When symbionts are inherited by offspring, they can have substantial ecological and evolutionary consequences because they occur in all host life stages. Although natural frequencies of inherited symbionts are commonly <100 %, few studies investigate the ecological drivers of variation in symbiont prevalence. In plants, inherited fungal endophytes can...

  12. Diallel analyze of yield and progress of the severity of leaf diseases in maize hybrids in two population density

    Directory of Open Access Journals (Sweden)

    Marcos Ventura Faria

    2015-02-01

    Full Text Available Seven commercial maize hybrids (AS1575, 2B688, Penta, GNZ2004, AG8021, Sprint e P30F53 were intercrossed in a complete diallel, excluded reciprocal, obtaining 21 crosses. The 28 treatments were evaluated in two environments characterized by different densities (62,500 and 90,000 plants ha-1, with the aim of selecting the most promising parents for generating base population to obtain lines. Two experiments were carried out in Guarapuava-PR, at randomized block design with three replications. We estimated the general (GCA and specific (SCA combining abilities for yield and disease severity assessed by the area under the common rust (Puccinia sorghi progress curve (AURPC and the area under the leaf spot (Cercospora zeae-maydis progress curve (AULPC. The effects of GCA and SCA were significant for grain yield and diseases severity in both densities, revealing the importance of both additive and non-additive effects. There GCA x densities interaction was significant only for grain yield. Crossings P30F53 x AG8021 and P30F53 x Penta had negative estimates of SCA for AURPC and AULPC on the environments average. Hybrids GNZ 2004 and P30F53 stood out showing positive GCA for grain yield and negative for AURPC and AULPC in both densities and therefore are recommended for generating base populations for obtaining lines adapted for both densities, conventional and denser plantings, given the current trends in management of maize.

  13. A low-density SNP array for analyzing differential selection in freshwater and marine populations of threespine stickleback (Gasterosteus aculeatus)

    DEFF Research Database (Denmark)

    Ferchaud, Anne-Laure; Pedersen, Susanne H.; Bekkevold, Dorte

    2014-01-01

    for rapid and cost efficient analysis of genetic divergence between freshwater and marine sticklebacks, we generated a low-density SNP (Single Nucleotide Polymorphism) array encompassing markers of chromosome regions under putative directional selection, along with neutral markers for background. Results...... have developed a cost-efficient low-density SNP array that allows for rapid screening of polymorphisms in threespine stickleback. The array provides a valuable tool for analyzing adaptive divergence between freshwater and marine stickleback populations beyond the well-established candidate gene...

  14. Spatio-temporal dynamics of a fish predator: Density-dependent and hydrographic effects on Baltic Sea cod population.

    Directory of Open Access Journals (Sweden)

    Valerio Bartolino

    Full Text Available Understanding the mechanisms of spatial population dynamics is crucial for the successful management of exploited species and ecosystems. However, the underlying mechanisms of spatial distribution are generally complex due to the concurrent forcing of both density-dependent species interactions and density-independent environmental factors. Despite the high economic value and central ecological importance of cod in the Baltic Sea, the drivers of its spatio-temporal population dynamics have not been analytically investigated so far. In this paper, we used an extensive trawl survey dataset in combination with environmental data to investigate the spatial dynamics of the distribution of the Eastern Baltic cod during the past three decades using Generalized Additive Models. The results showed that adult cod distribution was mainly affected by cod population size, and to a minor degree by small-scale hydrological factors and the extent of suitable reproductive areas. As population size decreases, the cod population concentrates to the southern part of the Baltic Sea, where the preferred more marine environment conditions are encountered. Using the fitted models, we predicted the Baltic cod distribution back to the 1970s and a temporal index of cod spatial occupation was developed. Our study will contribute to the management and conservation of this important resource and of the ecosystem where it occurs, by showing the forces shaping its spatial distribution and therefore the potential response of the population to future exploitation and environmental changes.

  15. High-density lipoproteins and adrenal steroidogenesis : A population-based study

    NARCIS (Netherlands)

    Buitenwerf, Edward; Kerstens, Michiel N.; Links, Thera P.; Kema, Ido P.; Dullaart, Robin P. F.

    BACKGROUND: Cholesterol trafficked within plasma lipoproteins, in particular high-density lipoproteins (HDL), may represent an important source of cholesterol that is required for adrenal steroidogenesis. Based on a urinary gas chromatography method, compromised adrenal function has been suggested

  16. Influence of population density on the concentration and speciation of metals in the soil and street dust from urban areas.

    Science.gov (United States)

    Acosta, J A; Gabarrón, M; Faz, A; Martínez-Martínez, S; Zornoza, R; Arocena, J M

    2015-09-01

    Street dust and soil from high, medium and low populated cities and natural area were analysed for selected physical-chemical properties, total and chemical speciation of Zn, Pb, Cu, Cr, Cd, Co, Ni to understand the influence of human activities on metal accumulation and mobility in the environment. The pH, salinity, carbonates and organic carbon contents were similar between soil and dust from the same city. Population density increases dust/soil salinity but has no influence on metals concentrations in soils. Increases in metal concentrations with population density were observed in dusts. Cu, Zn, Pb, Cr can be mobilized more easily from dust compared to the soil. In addition, population density increase the percentage of Pb and Zn associated to reducible and carbonate phase in the dust. The behaviour of metals except Cd in soil is mainly affected by physico-chemical properties, while total metal influenced the speciation except Cr and Ni in dusts. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Estimating the population density of the Asian tapir (Tapirus indicus) in a selectively logged forest in Peninsular Malaysia.

    Science.gov (United States)

    Rayan, D Mark; Mohamad, Shariff Wan; Dorward, Leejiah; Aziz, Sheema Abdul; Clements, Gopalasamy Reuben; Christopher, Wong Chai Thiam; Traeholt, Carl; Magintan, David

    2012-12-01

    The endangered Asian tapir (Tapirus indicus) is threatened by large-scale habitat loss, forest fragmentation and increased hunting pressure. Conservation planning for this species, however, is hampered by a severe paucity of information on its ecology and population status. We present the first Asian tapir population density estimate from a camera trapping study targeting tigers in a selectively logged forest within Peninsular Malaysia using a spatially explicit capture-recapture maximum likelihood based framework. With a trap effort of 2496 nights, 17 individuals were identified corresponding to a density (standard error) estimate of 9.49 (2.55) adult tapirs/100 km(2) . Although our results include several caveats, we believe that our density estimate still serves as an important baseline to facilitate the monitoring of tapir population trends in Peninsular Malaysia. Our study also highlights the potential of extracting vital ecological and population information for other cryptic individually identifiable animals from tiger-centric studies, especially with the use of a spatially explicit capture-recapture maximum likelihood based framework. © 2012 Wiley Publishing Asia Pty Ltd, ISZS and IOZ/CAS.

  18. A regional-scale, high resolution dynamical malaria model that accounts for population density, climate and surface hydrology.

    Science.gov (United States)

    Tompkins, Adrian M; Ermert, Volker

    2013-02-18

    The relative roles of climate variability and population related effects in malaria transmission could be better understood if regional-scale dynamical malaria models could account for these factors. A new dynamical community malaria model is introduced that accounts for the temperature and rainfall influences on the parasite and vector life cycles which are finely resolved in order to correctly represent the delay between the rains and the malaria season. The rainfall drives a simple but physically based representation of the surface hydrology. The model accounts for the population density in the calculation of daily biting rates. Model simulations of entomological inoculation rate and circumsporozoite protein rate compare well to data from field studies from a wide range of locations in West Africa that encompass both seasonal endemic and epidemic fringe areas. A focus on Bobo-Dioulasso shows the ability of the model to represent the differences in transmission rates between rural and peri-urban areas in addition to the seasonality of malaria. Fine spatial resolution regional integrations for Eastern Africa reproduce the malaria atlas project (MAP) spatial distribution of the parasite ratio, and integrations for West and Eastern Africa show that the model grossly reproduces the reduction in parasite ratio as a function of population density observed in a large number of field surveys, although it underestimates malaria prevalence at high densities probably due to the neglect of population migration. A new dynamical community malaria model is publicly available that accounts for climate and population density to simulate malaria transmission on a regional scale. The model structure facilitates future development to incorporate migration, immunity and interventions.

  19. Inferring cetacean population densities from the absolute dynamic topography of the ocean in a hierarchical Bayesian framework.

    Directory of Open Access Journals (Sweden)

    Mario A Pardo

    Full Text Available We inferred the population densities of blue whales (Balaenoptera musculus and short-beaked common dolphins (Delphinus delphis in the Northeast Pacific Ocean as functions of the water-column's physical structure by implementing hierarchical models in a Bayesian framework. This approach allowed us to propagate the uncertainty of the field observations into the inference of species-habitat relationships and to generate spatially explicit population density predictions with reduced effects of sampling heterogeneity. Our hypothesis was that the large-scale spatial distributions of these two cetacean species respond primarily to ecological processes resulting from shoaling and outcropping of the pycnocline in regions of wind-forced upwelling and eddy-like circulation. Physically, these processes affect the thermodynamic balance of the water column, decreasing its volume and thus the height of the absolute dynamic topography (ADT. Biologically, they lead to elevated primary productivity and persistent aggregation of low-trophic-level prey. Unlike other remotely sensed variables, ADT provides information about the structure of the entire water column and it is also routinely measured at high spatial-temporal resolution by satellite altimeters with uniform global coverage. Our models provide spatially explicit population density predictions for both species, even in areas where the pycnocline shoals but does not outcrop (e.g. the Costa Rica Dome and the North Equatorial Countercurrent thermocline ridge. Interannual variations in distribution during El Niño anomalies suggest that the population density of both species decreases dramatically in the Equatorial Cold Tongue and the Costa Rica Dome, and that their distributions retract to particular areas that remain productive, such as the more oceanic waters in the central California Current System, the northern Gulf of California, the North Equatorial Countercurrent thermocline ridge, and the more

  20. How will species respond to climate change? Examining the effects of temperature and population density on an herbivorous insect.

    Science.gov (United States)

    Laws, Angela Nardoni; Belovsky, Gary E

    2010-04-01

    An important challenge facing ecologists is to understand how climate change may affect species performance and species interactions. However, predicting how changes in abiotic variables associated with climate change may affect species performance also depends on the biotic context, which can mediate species responses to climatic change. We conducted a 3-yr field experiment to determine how the herbivorous grasshopper Camnula pellucida (Scudder) responds to manipulations of temperature and population density. Grasshopper survival and fecundity decreased with density, indicating the importance of intraspecific competition. Female fecundity tended to increase with temperature, whereas grasshopper survival exhibited a unimodal response to temperature, with highest survival at intermediate temperatures. Grasshopper performance responses to temperature also depended on density. Peak survival in the low-density treatment occurred in warmer conditions than for the high-density treatment, indicating that the intensity of intraspecific competition varies with temperature. Our data show that changes to the temperature regimen can alter grasshopper performance and determine the intensity of intraspecific competition. However, the effects of temperature on grasshopper performance varied with density. Our data indicate the importance of the biotic context in mediating species responses to climatic factors associated with global change.

  1. An Evaluation of Population Density Mapping and Built up Area Estimates in Sri Lanka Using Multiple Methodologies

    Science.gov (United States)

    Engstrom, R.; Soundararajan, V.; Newhouse, D.

    2017-12-01

    In this study we examine how well multiple population density and built up estimates that utilize satellite data compare in Sri Lanka. The population relationship is examined at the Gram Niladhari (GN) level, the lowest administrative unit in Sri Lanka from the 2011 census. For this study we have two spatial domains, the whole country and a 3,500km2 sub-sample, for which we have complete high spatial resolution imagery coverage. For both the entire country and the sub-sample we examine how consistent are the existing publicly available measures of population constructed from satellite imagery at predicting population density? For just the sub-sample we examine how well do a suite of values derived from high spatial resolution satellite imagery predict population density and how does our built up area estimate compare to other publicly available estimates. Population measures were obtained from the Sri Lankan census, and were downloaded from Facebook, WorldPoP, GPW, and Landscan. Percentage built-up area at the GN level was calculated from three sources: Facebook, Global Urban Footprint (GUF), and the Global Human Settlement Layer (GHSL). For the sub-sample we have derived a variety of indicators from the high spatial resolution imagery. Using deep learning convolutional neural networks, an object oriented, and a non-overlapping block, spatial feature approach. Variables calculated include: cars, shadows (a proxy for building height), built up area, and buildings, roof types, roads, type of agriculture, NDVI, Pantex, and Histogram of Oriented Gradients (HOG) and others. Results indicate that population estimates are accurate at the higher, DS Division level but not necessarily at the GN level. Estimates from Facebook correlated well with census population (GN correlation of 0.91) but measures from GPW and WorldPop are more weakly correlated (0.64 and 0.34). Estimates of built-up area appear to be reliable. In the 32 DSD-subsample, Facebook's built- up area measure

  2. Phylogenetic analysis of algal symbionts associated with four North American amphibian egg masses.

    Science.gov (United States)

    Kim, Eunsoo; Lin, Yuan; Kerney, Ryan; Blumenberg, Lili; Bishop, Cory

    2014-01-01

    Egg masses of the yellow-spotted salamander Ambystoma maculatum form an association with the green alga "Oophila amblystomatis" (Lambert ex Wille), which, in addition to growing within individual egg capsules, has recently been reported to invade embryonic tissues and cells. The binomial O. amblystomatis refers to the algae that occur in A. maculatum egg capsules, but it is unknown whether this population of symbionts constitutes one or several different algal taxa. Moreover, it is unknown whether egg masses across the geographic range of A. maculatum, or other amphibians, associate with one or multiple algal taxa. To address these questions, we conducted a phylogeographic study of algae sampled from egg capsules of A. maculatum, its allopatric congener A. gracile, and two frogs: Lithobates sylvatica and L. aurora. All of these North American amphibians form associations with algae in their egg capsules. We sampled algae from egg capsules of these four amphibians from localities across North America, established representative algal cultures, and amplified and sequenced a region of 18S rDNA for phylogenetic analysis. Our combined analysis shows that symbiotic algae found in egg masses of four North American amphibians are closely related to each other, and form a well-supported clade that also contains three strains of free-living chlamydomonads. We designate this group as the 'Oophila' clade, within which the symbiotic algae are further divided into four distinct subclades. Phylogenies of the host amphibians and their algal symbionts are only partially congruent, suggesting that host-switching and co-speciation both play roles in their associations. We also established conditions for isolating and rearing algal symbionts from amphibian egg capsules, which should facilitate further study of these egg mass specialist algae.

  3. Phylogenetic analysis of algal symbionts associated with four North American amphibian egg masses.

    Directory of Open Access Journals (Sweden)

    Eunsoo Kim

    Full Text Available Egg masses of the yellow-spotted salamander Ambystoma maculatum form an association with the green alga "Oophila amblystomatis" (Lambert ex Wille, which, in addition to growing within individual egg capsules, has recently been reported to invade embryonic tissues and cells. The binomial O. amblystomatis refers to the algae that occur in A. maculatum egg capsules, but it is unknown whether this population of symbionts constitutes one or several different algal taxa. Moreover, it is unknown whether egg masses across the geographic range of A. maculatum, or other amphibians, associate with one or multiple algal taxa. To address these questions, we conducted a phylogeographic study of algae sampled from egg capsules of A. maculatum, its allopatric congener A. gracile, and two frogs: Lithobates sylvatica and L. aurora. All of these North American amphibians form associations with algae in their egg capsules. We sampled algae from egg capsules of these four amphibians from localities across North America, established representative algal cultures, and amplified and sequenced a region of 18S rDNA for phylogenetic analysis. Our combined analysis shows that symbiotic algae found in egg masses of four North American amphibians are closely related to each other, and form a well-supported clade that also contains three strains of free-living chlamydomonads. We designate this group as the 'Oophila' clade, within which the symbiotic algae are further divided into four distinct subclades. Phylogenies of the host amphibians and their algal symbionts are only partially congruent, suggesting that host-switching and co-speciation both play roles in their associations. We also established conditions for isolating and rearing algal symbionts from amphibian egg capsules, which should facilitate further study of these egg mass specialist algae.

  4. Non-native acylated homoserine lactones reveal that LuxIR quorum sensing promotes symbiont stability.

    Science.gov (United States)

    Studer, Sarah V; Schwartzman, Julia A; Ho, Jessica S; Geske, Grant D; Blackwell, Helen E; Ruby, Edward G

    2014-08-01

    Quorum sensing, a group behaviour coordinated by a diffusible pheromone signal and a cognate receptor, is typical of bacteria that form symbioses with plants and animals. LuxIR-type N-acyl L-homoserine (AHL) quorum sensing is common in Gram-negative Proteobacteria, and many members of this group have additional quorum-sensing networks. The bioluminescent symbiont Vibrio fischeri encodes two AHL signal synthases: AinS and LuxI. AinS-dependent quorum sensing converges with LuxI-dependent quorum sensing at the LuxR regulatory element. Both AinS- and LuxI-mediated signalling are required for efficient and persistent colonization of the squid host, Euprymna scolopes. The basis of the mutualism is symbiont bioluminescence, which is regulated by both LuxI- and AinS-dependent quorum sensing, and is essential for maintaining a colonization of the host. Here, we used chemical and genetic approaches to probe the dynamics of LuxI- and AinS-mediated regulation of bioluminescence during symbiosis. We demonstrate that both native AHLs and non-native AHL analogues can be used to non-invasively and specifically modulate induction of symbiotic bioluminescence via LuxI-dependent quorum sensing. Our data suggest that the first day of colonization, during which symbiont bioluminescence is induced by LuxIR, is a critical period that determines the stability of the V. fischeri population once symbiosis is established. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

  5. Dynamics of a low-density tiger population in Southeast Asia in the context of improved law enforcement.

    Science.gov (United States)

    Duangchantrasiri, Somphot; Umponjan, Mayuree; Simcharoen, Saksit; Pattanavibool, Anak; Chaiwattana, Soontorn; Maneerat, Sompoch; Kumar, N Samba; Jathanna, Devcharan; Srivathsa, Arjun; Karanth, K Ullas

    2016-06-01

    Recovering small populations of threatened species is an important global conservation strategy. Monitoring the anticipated recovery, however, often relies on uncertain abundance indices rather than on rigorous demographic estimates. To counter the severe threat from poaching of wild tigers (Panthera tigris), the Government of Thailand established an intensive patrolling system in 2005 to protect and recover its largest source population in Huai Kha Khaeng Wildlife Sanctuary. Concurrently, we assessed the dynamics of this tiger population over the next 8 years with rigorous photographic capture-recapture methods. From 2006 to 2012, we sampled across 624-1026 km(2) with 137-200 camera traps. Cameras deployed for 21,359 trap days yielded photographic records of 90 distinct individuals. We used closed model Bayesian spatial capture-recapture methods to estimate tiger abundances annually. Abundance estimates were integrated with likelihood-based open model analyses to estimate rates of annual and overall rates of survival, recruitment, and changes in abundance. Estimates of demographic parameters fluctuated widely: annual density ranged from 1.25 to 2.01 tigers/100 km(2) , abundance from 35 to 58 tigers, survival from 79.6% to 95.5%, and annual recruitment from 0 to 25 tigers. The number of distinct individuals photographed demonstrates the value of photographic capture-recapture methods for assessments of population dynamics in rare and elusive species that are identifiable from natural markings. Possibly because of poaching pressure, overall tiger densities at Huai Kha Khaeng were 82-90% lower than in ecologically comparable sites in India. However, intensified patrolling after 2006 appeared to reduce poaching and was correlated with marginal improvement in tiger survival and recruitment. Our results suggest that population recovery of low-density tiger populations may be slower than anticipated by current global strategies aimed at doubling the number of wild tigers

  6. Model comparison on genomic predictions using high-density markers for different groups of bulls in the Nordic Holstein population

    DEFF Research Database (Denmark)

    Gao, Hongding; Su, Guosheng; Janss, Luc

    2013-01-01

    This study compared genomic predictions based on imputed high-density markers (~777,000) in the Nordic Holstein population using a genomic BLUP (GBLUP) model, 4 Bayesian exponential power models with different shape parameters (0.3, 0.5, 0.8, and 1.0) for the exponential power distribution...... relationship with the training population. Groupsmgs had both the sire and the maternal grandsire (MGS), Groupsire only had the sire, Groupmgs only had the MGS, and Groupnon had neither the sire nor the MGS in the training population. Reliability of DGV was measured as the squared correlation between DGV...... and DRP divided by the reliability of DRP for the bulls in validation data set. Unbiasedness of DGV was measured as the regression of DRP on DGV. The results indicated that DGV were more accurate and less biased for animals that were more related to the training population. In general, the Bayesian...

  7. Complete Genome Sequence of the Human Gut Symbiont Roseburia hominis

    DEFF Research Database (Denmark)

    Travis, Anthony J.; Kelly, Denise; Flint, Harry J

    2015-01-01

    We report here the complete genome sequence of the human gut symbiont Roseburia hominis A2-183(T) (= DSM 16839(T) = NCIMB 14029(T)), isolated from human feces. The genome is represented by a 3,592,125-bp chromosome with 3,405 coding sequences. A number of potential functions contributing to host...

  8. A nuptially transmitted Ichthyosproean symbiont of Tenebrio molitor (Coleoptera: Tenebrionidae)

    Science.gov (United States)

    The yellow mealworm, Tenebrio molitor, harbors a symbiont that has spores with a thick, laminated wall and infects the fat body and ventral nerve chord of adult and larval beetles. In adult males, there is heavy infection of the epithelial cells of the testes and between testes lobes with occasional...

  9. Symbiont Dependent Thermal Bleaching Susceptiblity in Two Reef ...

    African Journals Online (AJOL)

    Symbiont Dependent Thermal Bleaching Susceptiblity in Two Reef-building Corals, Stylophora pistillata and Platygyra ryukyuensis . ... Symbiodinium ITS2 types exhibit diverse photo-physiological responses to thermal stress, and may partially explain the variable bleaching susceptibilities of some hermatypic coral species.

  10. Effects of subsidized predators, resource variability, and human population density on desert tortoise populations in the Mojave Desert, USA

    Science.gov (United States)

    Esque, Todd C.; Nussear, Kenneth E.; Drake, K. Kristina; Walde, Andrew D.; Berry, Kristin H.; Averill-Murray, Roy C.; Woodman, A. Peter; Boarman, William I.; Medica, Phil A.; Mack, Jeremy S.; Heaton, Jill S.

    2010-01-01

    Understanding predator–prey relationships can be pivotal in the conservation of species. For 2 decades, desert tortoise Gopherus agassizii populations have declined, yet quantitative evidence regarding the causes of declines is scarce. In 2005, Ft. Irwin National Training Center, California, USA, implemented a translocation project including 2 yr of baseline monitoring of desert tortoises. Unusually high predation on tortoises was observed after translocation occurred. We conducted a retrospective analysis of predation and found that translocation did not affect the probability of predation: translocated, resident, and control tortoises all had similar levels of predation. However, predation rates were higher near human population concentrations, at lower elevation sites, and for smaller tortoises and females. Furthermore, high mortality rates were not limited to the National Training Center. In 2008, elevated mortality (as high as 43%) occurred throughout the listed range of the desert tortoise. Although no temporal prey base data are available for analysis from any of the study sites, we hypothesize that low population levels of typical coyote Canis latrans prey (i.e. jackrabbits Lepus californicus and other small animals) due to drought conditions influenced high predation rates in previous years. Predation may have been exacerbated in areas with high levels of subsidized predators. Many historical reports of increased predation, and our observation of a range-wide pattern, may indicate that high predation rates are more common than generally considered and may impact recovery of the desert tortoise throughout its range.

  11. Variability in body mass and sexual dimorphism in Danish red foxes (Vulpes vulpes) in relation to population density

    DEFF Research Database (Denmark)

    Pagh, Sussie; Hansen, Mette Sif; Jensen, Birger

    2017-01-01

    For the first time, temporal variability in body size and sexual dimorphism is revealed in foxes Vulpes vulpes from the same geographical area at over time. The weights and lengths of 552 Danish foxes were documented during three different periods: 1965–1977, 2012–2014 and the winter of 2015....../2016. During the first and the third periods, the fox population was below the carrying capacity due to hunting pressure and canine distemper, respectively. Adult males were significantly (p ...–1977 and compared to 2015/2016, compared to 2012–2014, when population density was high (the mean weight: 6.8 kg). However, no significant differences were found in the weight of females. Hence, sexual dimorphism ranged from 7.6 to 3.6 in adult foxes in low and high-density periods, respectively. During the winters...

  12. The First Estimates of Marbled Cat Pardofelis marmorata Population Density from Bornean Primary and Selectively Logged Forest.

    Directory of Open Access Journals (Sweden)

    Andrew J Hearn

    Full Text Available The marbled cat Pardofelis marmorata is a poorly known wild cat that has a broad distribution across much of the Indomalayan ecorealm. This felid is thought to exist at low population densities throughout its range, yet no estimates of its abundance exist, hampering assessment of its conservation status. To investigate the distribution and abundance of marbled cats we conducted intensive, felid-focused camera trap surveys of eight forest areas and two oil palm plantations in Sabah, Malaysian Borneo. Study sites were broadly representative of the range of habitat types and the gradient of anthropogenic disturbance and fragmentation present in contemporary Sabah. We recorded marbled cats from all forest study areas apart from a small, relatively isolated forest patch, although photographic detection frequency varied greatly between areas. No marbled cats were recorded within the plantations, but a single individual was recorded walking along the forest/plantation boundary. We collected sufficient numbers of marbled cat photographic captures at three study areas to permit density estimation based on spatially explicit capture-recapture analyses. Estimates of population density from the primary, lowland Danum Valley Conservation Area and primary upland, Tawau Hills Park, were 19.57 (SD: 8.36 and 7.10 (SD: 1.90 individuals per 100 km2, respectively, and the selectively logged, lowland Tabin Wildlife Reserve yielded an estimated density of 10.45 (SD: 3.38 individuals per 100 km2. The low detection frequencies recorded in our other survey sites and from published studies elsewhere in its range, and the absence of previous density estimates for this felid suggest that our density estimates may be from the higher end of their abundance spectrum. We provide recommendations for future marbled cat survey approaches.

  13. Density estimates of rural dog populations and an assessment of marking methods during a rabies vaccination campaign in the Philippines.

    Science.gov (United States)

    Childs, J E; Robinson, L E; Sadek, R; Madden, A; Miranda, M E; Miranda, N L

    1998-01-01

    We estimated the population density of dogs by distance sampling and assessed the potential utility of two marking methods for capture-mark-recapture applications following a mass canine rabies-vaccination campaign in Sorsogon Province, the Republic of the Philippines. Thirty villages selected to assess vaccine coverage and for dog surveys were visited 1 to 11 days after the vaccinating team. Measurements of the distance of dogs or groups of dogs from transect lines were obtained in 1088 instances (N = 1278 dogs; mean group size = 1.2). Various functions modelling the probability of detection were fitted to a truncated distribution of distances of dogs from transect lines. A hazard rate model provided the best fit and an overall estimate of dog-population density of 468/km2 (95% confidence interval, 359 to 611). At vaccination, most dogs were marked with either a paint stick or a black plastic collar. Overall, 34.8% of 2167 and 28.5% of 2115 dogs could be accurately identified as wearing a collar or showing a paint mark; 49.1% of the dogs had either mark. Increasing time interval between vaccination-team visit and dog survey and increasing distance from transect line were inversely associated with the probability of observing a paint mark. Probability of observing a collar was positively associated with increasing estimated density of the dog population in a given village and with animals not associated with a house. The data indicate that distance sampling is a relatively simple and adaptable method for estimating dog-population density and is not prone to problems associated with meeting some model assumptions inherent to mark-recapture estimators.

  14. Pigments Characterization and Molecular Identification of Bacterial Symbionts of Brown Algae Padinasp. Collected from Karimunjawa Island

    Directory of Open Access Journals (Sweden)

    Damar Bayu Murti

    2016-06-01

    Full Text Available The search for carotenoids in nature has been extensively studied because of their applications in foods. One treasure of the biopigment source is symbiotic-microorganisms with marine biota. The advantages of symbiont bacteria are easy to culture and sensitize pigments. The use of symbiont bacteria helps to conserve fish, coral reefs, seagrass, and seaweed. Therefore, the bacteria keeps their existence in their ecosystems. In this study, bacterial symbionts were successfully isolated from brown algae Padina sp. The bacterial symbionts had yellow pigment associated with carotenoids. The pigments were characterized using High Performance Liquid Chromatography (HPLC with a Photo Diode Array (PDA detector. The carotenoid pigments in the bacterial symbionts were identified as dinoxanthin, lutein and neoxanthin. Molecular identification by using a 16S rRNA gene sequence method, reveals that the bacterial symbionts were closely related to Bacillus marisflavi with a homology of 99%. Keywords :carotenoid pigments, brown algae, Padina, bacterial symbionts, 16S rRNA

  15. Effects of temporal variation in temperature and density dependence on insect population dynamics

    Science.gov (United States)

    Understanding effects of environmental variation on insect populations is important in light of predictions about increasing future climatic variability. In order to understand the effects of changing environmental variation on population dynamics and life history evolution in insects one would need...

  16. Forest tent caterpillar, Malacosoma disstria (Lepidoptera: Lasiocampidae mate-finding behavior is greatest at intermediate population densities: Implications for interpretation of moth capture in pheromone-baited traps.

    Directory of Open Access Journals (Sweden)

    Maya L. Evenden

    2015-07-01

    Full Text Available The forest tent caterpillar, Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae is a native forest defoliator with a broad geographic range in North America. Forest tent caterpillars experience cyclical population changes and at high densities, repeated defoliation can cause reduced tree growth and tree mortality. Pheromone-based monitoring of forest tent caterpillar moths can provide information on spatial and temporal patterns of incipient outbreaks. Pheromone-baited trap capture of male moths correlates to the number of eggs and pupae in a population but this relationship breaks down at high population densities, when moth trap capture declines. The objective of the current study is to understand the mechanisms that reduce trap capture at high population densities. We tested two different hypotheses: 1 at high population densities, male moth orientation to pheromone sources is reduced due to competition for pheromone plumes; and 2 moths from high density populations will be in poor condition and less likely to conduct mate-finding behaviors than moths from low density populations. A field study showed non-linear effects of density on male moth capture in female-baited traps. The number of males captured increased up to an intermediate density level and declined at the highest densities. Field cage studies showed that female moth density affected male moth orientation to female-baited traps, as more males were recaptured at low than high female densities. There was no effect of male density on the proportion of males that oriented to female-baited traps. Moth condition was manipulated by varying larval food quantity. Although feeding regimes affected the moth condition (size, there was no evidence of an effect of condition on mate finding or close range mating behavior. In the field, it is likely that competition for pheromone plumes at high female densities during population outbreaks reduces the efficacy of pheromone-baited monitoring

  17. Photic Volume in Photobioreactors Supporting Ultrahigh Population Densities of the Photoautotroph Spirulina platensis

    Science.gov (United States)

    Gitelson, A.; Qiuang, H.; Richmond, A.

    1996-01-01

    Characterization of the photic zone and light penetration depth in cultures with ultrahigh cell densities represents a major issue in mass cultures of phytoautotrophic microorganisms grown in enclosed photobioreactors. In a study of the effect of underwater optical properties on the penetration depth of photosynthetically active radiation, the inherent optical properties of algal suspensions, i.e., absorption and scattering coefficients, as well as their apparent optical properties, i.e., the reflectance and the vertical attenuation coefficient of downwelling irradiance, were determined by using high-spectral-resolution radiometric measurements. The vertical attenuation coefficient was used to estimate quantitatively the depth of light penetration into a reactor containing an ultrahigh cell density (chlorophyll concentration, up to 300,000 mg m(sup-3)). For such a high cell density, the photic volume in the reactor was found to be extremely small; nevertheless, it differed between the blue and red light (less than 0.06 mm) and the green light (about 0.5 mm). This suggests a singular role for green light under the unique circumstances existing in ultrahigh-cell-density cultures of photoautotrophs. PMID:16535309

  18. Low-density lipoprotein-lowering strategies: target versus maximalist versus population percentile.

    NARCIS (Netherlands)

    Sniderman, A.D.; Graaf, J. de; Couture, P.

    2012-01-01

    PURPOSE OF REVIEW: Maximalist low-density lipoprotein (LDL)-lowering strategies such as lowering LDL as much as possible or, alternatively, using the most potent LDL-lowering regimens have become increasingly popular. Almost all attention has focused on the potential advantages of these approaches

  19. Global Rural-Urban Mapping Project, Version 1 (GRUMPv1): Population Density Grid

    Data.gov (United States)

    National Aeronautics and Space Administration — The Global Rural-Urban Mapping Project, Version 1 (GRUMPv1) consists of estimates of human population for the years 1990, 1995, and 2000 by 30 arc-second (1km) grid....

  20. Increase in Population Density and Aggravation of Social and Psychological Problems in Areas with High-Rise Construction

    Directory of Open Access Journals (Sweden)

    Romanova Elena

    2018-01-01

    Full Text Available High-rise apartment houses have technical and economic advantages in areas with dense population. Their placement in the central part of the city allows increasing the number of living space in the limited territory, to bring population to the place of employment and reduce pendular migration. But increase in population density leads to psychological problems: level of a stress, fatigue increases, the number of phobias grows, infectious diseases extend quicker. These problems can be solved at resettlement of inhabitants to the suburb. However such decision leads to aggravation of a transport problem and the pulsing increase in population density in the downtown and on its suburb. To solve a transport problem, it is necessary not to increase the square of the cities. Therefore in the suburbs is also used high-rise construction. But high-rise residential districts on the suburb of the city get own social problems which are capable to destroy all advantages of high-rise construction.

  1. Earthworm Population Density in Sugarcane Cropping System Applied with Various Quality of Organic Matter

    OpenAIRE

    Nurhidayati, Nurhidayati; Arisoesilaningsih, Endang; Suprayogo, Didik; Hairiah, Kurniatun

    2012-01-01

    Earthworms population in the soil are greatly impacted by agricultural management, yet little is known about how the quality and quantity of organic matter addition interact in sugarcane cropping system to earthworm population. This study describes the effect of various organic matter and application rates on earthworms in sugarcane cropping system. Earthworms were collected in April, July and December from 48 experimental plots under five kinds of organic matter application : (1) cattle manu...

  2. Density, Demography, and Influential Environmental Factors on Overwintering Populations of Sogatella furcifera (Hemiptera: Delphacidae) in Southern Yunnan, China.

    Science.gov (United States)

    Hu, Shao-Ji; Fu, Da-Ying; Han, Zhong-Liang; Ye, Hui

    2015-01-01

    Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is the most serious pest on rice in southwestern China. Yunnan province is within this region and is a major overwintering area for S. furcifera in China. This field study was carried out over 4 yr (2010-2013) and focused on S. furcifera distribution, population density, and demography, as well as the relationship between various environmental factors and the distribution and density of overwintering S. furcifera in Yunnan. Our study demonstrated that overwintering populations of S. furcifera mainly occurred in valleys and lowlands below 25.02°N and 1,608 m above sea level (a.s.l.), where ratooning rice was present [corrected]. The overwintering range of S. furcifera has expanded in Yunnan compared with 20 yr ago, and regional climate change is believed to be the main contributing cause for this expansion. Environmental factor analysis showed that the mean air temperature of the coldest quarter and precipitation of the coldest quarter were two key factors that were strongly linked to the overwintering distribution and density of S. furcifera in Yunnan. Wintertime temperature was the principal influencing factor to determine the distribution and density of S. furcifera, while the effect of precipitation was indirect in that it influenced the insect's distribution via its host. This study documented the major overwintering areas of S. furcifera in Yunnan, which can be used to predict outbreak potential in the following spring. Hence, key climatic factors, overwintering distribution, and density of S. furcifera should be used when forecasting outbreaks in spring. © The Author 2015. Published by Oxford University Press on behalf of the Entomological Society of America.

  3. Sex differences in fingerprint ridge density in a Turkish young adult population: a sample of Baskent University.

    Science.gov (United States)

    Oktem, Hale; Kurkcuoglu, Ayla; Pelin, Ismail Can; Yazici, Ayse Canan; Aktaş, Gulnihal; Altunay, Fikret

    2015-05-01

    Fingerprints are considered to be one of the most reliable methods of identification. Identification of an individual plays a vital part of any medico-legal investigations. Dermatoglyphics is a branch of science that studies epidermal ridges and ridge patterns. Epidermal ridges are polygenic characteristics that form intrauterine 10-18 weeks and considered fully developed by the sixth month of fetal growth. Fingerprints are permanent morphological characteristics and criminal detection based on fingerprints is based on the principle that no two people can have identical fingerprints. Sex determination from fingerprints has been examined in different population. In this study we aimed to study fingerprint ridge density in Turkish population sample of Baskent University students. Fingerprints were obtained from 118 women, 88 men a total of 206 students aged between 17 and 28 years old by means of simple inking method. Fingerprints from all right and left hands fingers were collected in three different area of each. The ridges on fingerprints were counted diagonally on squares measuring 5 mm × 5 mm on radial, ulnar and inferior areas. The fingerprint ridge density in radial, ulnar and inferior areas and between sexes was compared statistically Mann Whitney U test and Friedman test. The ridge density was significantly greater in women in every region studied and in all fingers when compared to men. The fingerprint ridge density in the ulnar and radial areas of the fingerprints was significantly greater than the lower area. Fingerprint ridge density can be used by medico-legal examination for sex identification. Copyright © 2015 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

  4. Density, Demography, and Influential Environmental Factors on Overwintering Populations of Sogatella furcifera (Hemiptera: Delphacidae) in Southern Yunnan, China

    Science.gov (United States)

    Hu, Shao-Ji; Fu, Da-Ying; Han, Zhong-Liang; Ye, Hui

    2015-01-01

    Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is the most serious pest on rice in southwestern China. Yunnan province is within this region and is a major overwintering area for S. furcifera in China. This field study was carried out over 4 yr (2010–2013) and focused on S. furcifera distribution, population density, and demography, as well as the relationship between various environmental factors and the distribution and density of overwintering S. furcifera in Yunnan. Our study demonstrated that overwintering populations of S. furcifera mainly occurred in valleys and lowlands below 25.02°N and 1,680 m above sea level (a.s.l.), where ratooning rice was present. The overwintering range of S. furcifera has expanded in Yunnan compared with 20 yr ago, and regional climate change is believed to be the main contributing cause for this expansion. Environmental factor analysis showed that the mean air temperature of the coldest quarter and precipitation of the coldest quarter were two key factors that were strongly linked to the overwintering distribution and density of S. furcifera in Yunnan. Wintertime temperature was the principal influencing factor to determine the distribution and density of S. furcifera, while the effect of precipitation was indirect in that it influenced the insect’s distribution via its host. This study documented the major overwintering areas of S. furcifera in Yunnan, which can be used to predict outbreak potential in the following spring. Hence, key climatic factors, overwintering distribution, and density of S. furcifera should be used when forecasting outbreaks in spring. PMID:25978998

  5. The Influence on Population Weight Gain and Obesity of the Macronutrient Composition and Energy Density of the Food Supply.

    Science.gov (United States)

    Crino, Michelle; Sacks, Gary; Vandevijvere, Stefanie; Swinburn, Boyd; Neal, Bruce

    2015-03-01

    Rates of overweight and obesity have increased dramatically in all regions of the world over the last few decades. Almost all of the world's population now has ubiquitous access to low-cost, but highly-processed, energy-dense, nutrient-poor food products. These changes in the food supply, rather than decreases in physical activity, are most likely the primary driver of population weight gain and obesity. To-date, the majority of prevention efforts focus on personalised approaches targeting individuals. Population-wide food supply interventions addressing sodium and trans fat reduction have proven highly effective and comparable efforts are now required to target obesity. The evidence suggests that strategies focusing upon reducing the energy density and portion size of foods will be more effective than those targeting specific macronutrients. Government leadership, clearly specified targets, accountability and transparency will be the key to achieving the food supply changes required to address the global obesity epidemic.

  6. Density and climate influence seasonal population dynamics in an Arctic ungulate

    DEFF Research Database (Denmark)

    Mortensen, Lars O.; Moshøj, Charlotte; Forchhammer, Mads C.

    2016-01-01

    The locally migratory behavior of the high arctic muskox (Ovibos muschatus) is a central component of the breeding and winter survival strategies applied to cope with the highly seasonal arctic climate. However, altered climate regimes affecting plant growth are likely to affect local migration...... cover), forage availability (length of growth season), and the number of adult females available per male (operational sex ratio) influence changes in the seasonal density dependence, abundance, and immigration rate of muskoxen into the valley. The results suggested summer temperature as the major...... controlling factor in the seasonal, local-scale migration of muskoxen at Zackenberg. Specifically, higher summer temperatures, defined as the cumulative average daily positive degrees in June, July, and August, resulted in decreased density dependence and, consequently, increase in the seasonal abundance...

  7. Building the crops of tomorrow: advantages of symbiont-based approaches to improving abiotic stress tolerance.

    Science.gov (United States)

    Coleman-Derr, Devin; Tringe, Susannah G

    2014-01-01

    The exponential growth in world population is feeding a steadily increasing global need for arable farmland, a resource that is already in high demand. This trend has led to increased farming on subprime arid and semi-arid lands, where limited availability of water and a host of environmental stresses often severely reduce crop productivity. The conventional approach to mitigating the abiotic stresses associated with arid climes is to breed for stress-tolerant cultivars, a time and labor intensive venture that often neglects the complex ecological context of the soil environment in which the crop is grown. In recent years, studies have attempted to identify microbial symbionts capable of conferring the same stress-tolerance to their plant hosts, and new developments in genomic technologies have greatly facilitated such research. Here, we highlight many of the advantages of these symbiont-based approaches and argue in favor of the broader recognition of crop species as ecological niches for a diverse community of microorganisms that function in concert with their plant hosts and each other to thrive under fluctuating environmental conditions.

  8. Building the crops of tomorrow: advantages of symbiont-based approaches to improving abiotic stress tolerance

    Directory of Open Access Journals (Sweden)

    Devin eColeman-Derr

    2014-06-01

    Full Text Available The exponential growth in world population is feeding a steadily increasing global need for arable farmland, a resource that is already in high demand. This trend has led to increased farming on subprime arid and semi-arid lands, where limited availability of water and a host of environmental stresses often severely reduce crop productivity. The conventional approach to mitigating the abiotic stresses associated with arid climes is to breed for stress-tolerant cultivars, a time and labor intensive venture that often neglects the complex ecological context of the soil environment in which the crop is grown. In recent years, studies have attempted to identify microbial symbionts capable of conferring the same stress-tolerance to their plant hosts, and new developments in genomic technologies have greatly facilitated such research. Here, we highlight many of the advantages of these symbiont-based approaches and argue in favor of the broader recognition of crop species as ecological niches for a diverse community of microorganisms that function in concert with their plant hosts and each other to thrive under fluctuating environmental conditions.

  9. Gastrointestinal symbionts of chimpanzees in Cantanhez National Park, Guinea-Bissau with respect to habitat fragmentation.

    Science.gov (United States)

    Sá, Rui M; Petrášová, Jana; Pomajbíková, Kateřina; Profousová, Ilona; Petrželková, Klára J; Sousa, Cláudia; Cable, Joanne; Bruford, Michael W; Modrý, David

    2013-10-01

    One of the major factors threatening chimpanzees (Pan troglodytes verus) in Guinea-Bissau is habitat fragmentation. Such fragmentation may cause changes in symbiont dynamics resulting in increased susceptibility to infection, changes in host specificity and virulence. We monitored gastrointestinal symbiotic fauna of three chimpanzee subpopulations living within Cantanhez National Park (CNP) in Guinea Bissau in the areas with different levels of anthropogenic fragmentation. Using standard coproscopical methods (merthiolate-iodine formalin concentration and Sheather's flotation) we examined 102 fecal samples and identified at least 13 different symbiotic genera (Troglodytella abrassarti, Troglocorys cava, Blastocystis spp., Entamoeba spp., Iodamoeba butschlii, Giardia intestinalis, Chilomastix mesnili, Bertiella sp., Probstmayria gombensis, unidentified strongylids, Strongyloides stercoralis, Strongyloides fuelleborni, and Trichuris sp.). The symbiotic fauna of the CNP chimpanzees is comparable to that reported for other wild chimpanzee populations, although CNP chimpanzees have a higher prevalence of Trichuris sp. Symbiont richness was higher in chimpanzee subpopulations living in fragmented forests compared to the community inhabiting continuous forest area. We reported significantly higher prevalence of G. intestinalis in chimpanzees from fragmented areas, which could be attributed to increased contact with humans and livestock. © 2013 Wiley Periodicals, Inc.

  10. Building the crops of tomorrow: advantages of symbiont-based approaches to improving abiotic stress tolerance

    Energy Technology Data Exchange (ETDEWEB)

    Coleman-Derr, Devin [USDOE Joint Genome Institute (JGI), Walnut Creek, CA (United States); Tringe, Susannah G. [USDOE Joint Genome Institute (JGI), Walnut Creek, CA (United States)

    2014-06-06

    The exponential growth in world population is feeding a steadily increasing global need for arable farmland, a resource that is already in high demand. This trend has led to increased farming on subprime arid and semi-arid lands, where limited availability of water and a host of environmental stresses often severely reduce crop productivity. The conventional approach to mitigating the abiotic stresses associated with arid climes is to breed for stress-tolerant cultivars, a time and labor intensive venture that often neglects the complex ecological context of the soil environment in which the crop is grown. In recent years, studies have attempted to identify microbial symbionts capable of conferring the same stress-tolerance to their plant hosts, and new developments in genomic technologies have greatly facilitated such research. Here in this paper, we highlight many of the advantages of these symbiont-based approaches and argue in favor of the broader recognition of crop species as ecological niches for a diverse community of microorganisms that function in concert with their plant hosts and each other to thrive under fluctuating environmental conditions

  11. Declines in moose population density at Isle Royle National Park, MI, USA and accompanied changes in landscape patterns

    Science.gov (United States)

    De Jager, N. R.; Pastor, J.

    2009-01-01

    Ungulate herbivores create patterns of forage availability, plant species composition, and soil fertility as they range across large landscapes and consume large quantities of plant material. Over time, herbivore populations fluctuate, producing great potential for spatio-temporal landscape dynamics. In this study, we extend the spatial and temporal extent of a long-term investigation of the relationship of landscape patterns to moose foraging behavior at Isle Royale National Park, MI. We examined how patterns of browse availability and consumption, plant basal area, and soil fertility changed during a recent decline in the moose population. We used geostatistics to examine changes in the nature of spatial patterns in two valleys over 18 years and across short-range and long-range distance scales. Landscape patterns of available and consumed browse changed from either repeated patches or randomly distributed patches in 1988-1992 to random point distributions by 2007 after a recent record high peak followed by a rapid decline in the moose population. Patterns of available and consumed browse became decoupled during the moose population low, which is in contrast to coupled patterns during the earlier high moose population. Distributions of plant basal area and soil nitrogen availability also switched from repeated patches to randomly distributed patches in one valley and to random point distributions in the other valley. Rapid declines in moose population density may release vegetation and soil fertility from browsing pressure and in turn create random landscape patterns. ?? Springer Science+Business Media B.V. 2009.

  12. Consequences of severe habitat fragmentation on density, genetics, and spatial capture-recapture analysis of a small bear population.

    Directory of Open Access Journals (Sweden)

    Sean M Murphy

    Full Text Available Loss and fragmentation of natural habitats caused by human land uses have subdivided several formerly contiguous large carnivore populations into multiple small and often isolated subpopulations, which can reduce genetic variation and lead to precipitous population declines. Substantial habitat loss and fragmentation from urban development and agriculture expansion relegated the Highlands-Glades subpopulation (HGS of Florida, USA, black bears (Ursus americanus floridanus to prolonged isolation; increasing human land development is projected to cause ≥ 50% loss of remaining natural habitats occupied by the HGS in coming decades. We conducted a noninvasive genetic spatial capture-recapture study to quantitatively describe the degree of contemporary habitat fragmentation and investigate the consequences of habitat fragmentation on population density and genetics of the HGS. Remaining natural habitats sustaining the HGS were significantly more fragmented and patchier than those supporting Florida's largest black bear subpopulation. Genetic diversity was low (AR = 3.57; HE = 0.49 and effective population size was small (NE = 25 bears, both of which remained unchanged over a period spanning one bear generation despite evidence of some immigration. Subpopulation density (0.054 bear/km2 was among the lowest reported for black bears, was significantly female-biased, and corresponded to a subpopulation size of 98 bears in available habitat. Conserving remaining natural habitats in the area occupied by the small, genetically depauperate HGS, possibly through conservation easements and government land acquisition, is likely the most important immediate step to ensuring continued persistence of bears in this area. Our study also provides evidence that preferentially placing detectors (e.g., hair traps or cameras primarily in quality habitat across fragmented landscapes poses a challenge to estimating density-habitat covariate relationships using spatial

  13. A principled dimension-reduction method for the population density approach to modeling networks of neurons with synaptic dynamics.

    Science.gov (United States)

    Ly, Cheng

    2013-10-01

    The population density approach to neural network modeling has been utilized in a variety of contexts. The idea is to group many similar noisy neurons into populations and track the probability density function for each population that encompasses the proportion of neurons with a particular state rather than simulating individual neurons (i.e., Monte Carlo). It is commonly used for both analytic insight and as a time-saving computational tool. The main shortcoming of this method is that when realistic attributes are incorporated in the underlying neuron model, the dimension of the probability density function increases, leading to intractable equations or, at best, computationally intensive simulations. Thus, developing principled dimension-reduction methods is essential for the robustness of these powerful methods. As a more pragmatic tool, it would be of great value for the larger theoretical neuroscience community. For exposition of this method, we consider a single uncoupled population of leaky integrate-and-fire neurons receiving external excitatory synaptic input only. We present a dimension-reduction method that reduces a two-dimensional partial differential-integral equation to a computationally efficient one-dimensional system and gives qualitatively accurate results in both the steady-state and nonequilibrium regimes. The method, termed modified mean-field method, is based entirely on the governing equations and not on any auxiliary variables or parameters, and it does not require fine-tuning. The principles of the modified mean-field method have potential applicability to more realistic (i.e., higher-dimensional) neural networks.

  14. Consequences of severe habitat fragmentation on density, genetics, and spatial capture-recapture analysis of a small bear population.

    Science.gov (United States)

    Murphy, Sean M; Augustine, Ben C; Ulrey, Wade A; Guthrie, Joseph M; Scheick, Brian K; McCown, J Walter; Cox, John J

    2017-01-01

    Loss and fragmentation of natural habitats caused by human land uses have subdivided several formerly contiguous large carnivore populations into multiple small and often isolated subpopulations, which can reduce genetic variation and lead to precipitous population declines. Substantial habitat loss and fragmentation from urban development and agriculture expansion relegated the Highlands-Glades subpopulation (HGS) of Florida, USA, black bears (Ursus americanus floridanus) to prolonged isolation; increasing human land development is projected to cause ≥ 50% loss of remaining natural habitats occupied by the HGS in coming decades. We conducted a noninvasive genetic spatial capture-recapture study to quantitatively describe the degree of contemporary habitat fragmentation and investigate the consequences of habitat fragmentation on population density and genetics of the HGS. Remaining natural habitats sustaining the HGS were significantly more fragmented and patchier than those supporting Florida's largest black bear subpopulation. Genetic diversity was low (AR = 3.57; HE = 0.49) and effective population size was small (NE = 25 bears), both of which remained unchanged over a period spanning one bear generation despite evidence of some immigration. Subpopulation density (0.054 bear/km2) was among the lowest reported for black bears, was significantly female-biased, and corresponded to a subpopulation size of 98 bears in available habitat. Conserving remaining natural habitats in the area occupied by the small, genetically depauperate HGS, possibly through conservation easements and government land acquisition, is likely the most important immediate step to ensuring continued persistence of bears in this area. Our study also provides evidence that preferentially placing detectors (e.g., hair traps or cameras) primarily in quality habitat across fragmented landscapes poses a challenge to estimating density-habitat covariate relationships using spatial capture

  15. Effect of Trait Heritability, Training Population Size and Marker Density on Genomic Prediction Accuracy Estimation in 22 bi-parental Tropical Maize Populations.

    Science.gov (United States)

    Zhang, Ao; Wang, Hongwu; Beyene, Yoseph; Semagn, Kassa; Liu, Yubo; Cao, Shiliang; Cui, Zhenhai; Ruan, Yanye; Burgueño, Juan; San Vicente, Felix; Olsen, Michael; Prasanna, Boddupalli M; Crossa, José; Yu, Haiqiu; Zhang, Xuecai

    2017-01-01

    Genomic selection is being used increasingly in plant breeding to accelerate genetic gain per unit time. One of the most important applications of genomic selection in maize breeding is to predict and select the best un-phenotyped lines in bi-parental populations based on genomic estimated breeding values. In the present study, 22 bi-parental tropical maize populations genotyped with low density SNPs were used to evaluate the genomic prediction accuracy ( r MG ) of the six trait-environment combinations under various levels of training population size (TPS) and marker density (MD), and assess the effect of trait heritability ( h 2 ), TPS and MD on r MG estimation. Our results showed that: (1) moderate r MG values were obtained for different trait-environment combinations, when 50% of the total genotypes was used as training population and ~200 SNPs were used for prediction; (2) r MG increased with an increase in h 2 , TPS and MD, both correlation and variance analyses showed that h 2 is the most important factor and MD is the least important factor on r MG estimation for most of the trait-environment combinations; (3) predictions between pairwise half-sib populations showed that the r MG values for all the six trait-environment combinations were centered around zero, 49% predictions had r MG values above zero; (4) the trend observed in r MG differed with the trend observed in r MG / h , and h is the square root of heritability of the predicted trait, it indicated that both r MG and r MG / h values should be presented in GS study to show the accuracy of genomic selection and the relative accuracy of genomic selection compared with phenotypic selection, respectively. This study provides useful information to maize breeders to design genomic selection workflow in their breeding programs.

  16. Effect of Trait Heritability, Training Population Size and Marker Density on Genomic Prediction Accuracy Estimation in 22 bi-parental Tropical Maize Populations

    Directory of Open Access Journals (Sweden)

    Ao Zhang

    2017-11-01

    Full Text Available Genomic selection is being used increasingly in plant breeding to accelerate genetic gain per unit time. One of the most important applications of genomic selection in maize breeding is to predict and select the best un-phenotyped lines in bi-parental populations based on genomic estimated breeding values. In the present study, 22 bi-parental tropical maize populations genotyped with low density SNPs were used to evaluate the genomic prediction accuracy (rMG of the six trait-environment combinations under various levels of training population size (TPS and marker density (MD, and assess the effect of trait heritability (h2, TPS and MD on rMG estimation. Our results showed that: (1 moderate rMG values were obtained for different trait-environment combinations, when 50% of the total genotypes was used as training population and ~200 SNPs were used for prediction; (2 rMG increased with an increase in h2, TPS and MD, both correlation and variance analyses showed that h2 is the most important factor and MD is the least important factor on rMG estimation for most of the trait-environment combinations; (3 predictions between pairwise half-sib populations showed that the rMG values for all the six trait-environment combinations were centered around zero, 49% predictions had rMG values above zero; (4 the trend observed in rMG differed with the trend observed in rMG/h, and h is the square root of heritability of the predicted trait, it indicated that both rMG and rMG/h values should be presented in GS study to show the accuracy of genomic selection and the relative accuracy of genomic selection compared with phenotypic selection, respectively. This study provides useful information to maize breeders to design genomic selection workflow in their breeding programs.

  17. Influence of CH4 and H2S availability on symbiont distribution, carbon assimilation and transfer in the dual symbiotic vent mussel Bathymodiolus azoricus

    Directory of Open Access Journals (Sweden)

    R. S. Santos

    2008-12-01

    Full Text Available High densities of mussels of the genus Bathymodiolus are present at hydrothermal vents of the Mid-Atlantic Ridge. It was previously proposed that the chemistry at vent sites would affect their sulphide- and methane-oxidizing endosymbionts' abundance. In this study, we confirmed the latter assumption using fluorescence in situ hybridization on Bathymodiolus azoricus specimens maintained in a controlled laboratory environment at atmospheric pressure with one, both or none of the chemical substrates. A high level of symbiosis plasticity was observed, methane-oxidizers occupying between 4 and 39% of total bacterial area and both symbionts developing according to the presence or absence of their substrates. Using H13CO3− in the presence of sulphide, or 13CH4, we monitored carbon assimilation by the endosymbionts and its translocation to symbiont-free mussel tissues. Carbon was incorporated from methane and sulphide-oxidized inorganic carbon at rates 3 to 10 times slower in the host muscle tissue than in the symbiont-containing gill tissue. Both symbionts thus contribute actively to B. azoricus nutrition and adapt to the availability of their substrates. Further experiments with varying substrate concentrations using the same set-up should provide useful tools to study and even model the effects of changes in hydrothermal fluids on B. azoricus' chemosynthetic nutrition.

  18. Host–symbiont recombination versus natural selection in the response of coral–dinoflagellate symbioses to environmental disturbance

    Science.gov (United States)

    LaJeunesse, Todd C.; Smith, Robin; Walther, Mariana; Pinzón, Jorge; Pettay, Daniel T.; McGinley, Michael; Aschaffenburg, Matthew; Medina-Rosas, Pedro; Cupul-Magaña, Amilcar L.; Pérez, Andrés López; Reyes-Bonilla, Hector; Warner, Mark E.

    2010-01-01

    Mutualisms between reef-building corals and endosymbiotic dinoflagellates are particularly sensitive to environmental stress, yet the ecosystems they construct have endured major oscillations in global climate. During the winter of 2008, an extreme cold-water event occurred in the Gulf of California that bleached corals in the genus Pocillopora harbouring a thermally ‘sensitive’ symbiont, designated Symbiodinium C1b-c, while colonies possessing Symbiodinium D1 were mostly unaffected. Certain bleached colonies recovered quickly while others suffered partial or complete mortality. In most colonies, no appreciable change was observed in the identity of the original symbiont, indicating that these partnerships are stable. During the initial phases of recovery, a third species of symbiont B1Aiptasia, genetically identical to that harboured by the invasive anemone, Aiptasia sp., grew opportunistically and was visible as light-yellow patches on the branch tips of several colonies. However, this symbiont did not persist and was displaced in all cases by C1b-c several months later. Colonies with D1 were abundant at inshore habitats along the continental eastern Pacific, where seasonal turbidity is high relative to offshore islands. Environmental conditions of the central and southern coasts of Mexico were not sufficient to explain the exclusivity of D1 Pocillopora in these regions. It is possible that mass mortalities associated with major thermal disturbances during the 1997–1998 El Niño Southern Oscillation eliminated C1b-c holobionts from these locations. The differential loss of Pocillopora holobionts in response to thermal stress suggests that natural selection on existing variation can cause rapid and significant shifts in the frequency of particular coral–algal partnerships. However, coral populations may take decades to recover following episodes of severe selection, thereby raising considerable uncertainty about the long-term viability of these communities

  19. Differential temporal changes of primary and secondary bacterial symbionts and whitefly host fitness following antibiotic treatments

    Science.gov (United States)

    Zhang, Chang-Rong; Shan, Hong-Wei; Xiao, Na; Zhang, Fan-Di; Wang, Xiao-Wei; Liu, Yin-Quan; Liu, Shu-Sheng

    2015-01-01

    Where multiple symbionts coexist in the same host, the selective elimination of a specific symbiont may enable the roles of a given symbiont to be investigated. We treated the Mediterranean species of the whitefly Bemisia tabaci complex by oral delivery of the antibiotic rifampicin, and then examined the temporal changes of its primary symbiont “Candidatus Portiera aleyrodidarum” and secondary symbiont “Ca. Hamiltonella defensa” as well as host fitness for three generations. In adults treated with rifampicin (F0), the secondary symbiont was rapidly reduced, approaching complete disappearance as adults aged. In contrast, the primary symbiont was little affected until later in the adult life. In the offspring of these adults (F1), both symbionts were significantly reduced and barely detectable when the hosts reached the adult stage. The F1 adults laid few eggs (F2), all of which failed to hatch. Mating experiments illustrated that the negative effects of rifampicin on host fitness were exerted via female hosts but not males. This study provides the first evidence of differential temporal reductions of primary and secondary symbionts in whiteflies following an antibiotic treatment. Studies that disrupt functions of bacterial symbionts must consider their temporal changes. PMID:26510682

  20. Functional equivalence and evolutionary convergence in complex communities of microbial sponge symbionts.

    Science.gov (United States)

    Fan, Lu; Reynolds, David; Liu, Michael; Stark, Manuel; Kjelleberg, Staffan; Webster, Nicole S; Thomas, Torsten

    2012-07-03

    Microorganisms often form symbiotic relationships with eukaryotes, and the complexity of these relationships can range from those with one single dominant symbiont to associations with hundreds of symbiont species. Microbial symbionts occupying equivalent niches in different eukaryotic hosts may share functional aspects, and convergent genome evolution has been reported for simple symbiont systems in insects. However, for complex symbiont communities, it is largely unknown how prevalent functional equivalence is and whether equivalent functions are conducted by evolutionarily convergent mechanisms. Sponges represent an evolutionarily divergent group of species with common physiological and ecological traits. They also host complex communities of microbial symbionts and thus are the ideal model to test whether functional equivalence and evolutionary convergence exist in complex symbiont communities across phylogenetically divergent hosts. Here we use a sampling design to determine the phylogenetic and functional profiles of microbial communities associated with six sponge species. We identify common functions in the six microbiomes, demonstrating the existence of functional equivalence. These core functions are consistent with our current understanding of the biological and ecological roles of sponge-associated microorganisms and also provide insight into symbiont functions. Importantly, core functions also are provided in each sponge species by analogous enzymes and biosynthetic pathways. Moreover, the abundance of elements involved in horizontal gene transfer suggests their key roles in the genomic evolution of symbionts. Our data thus demonstrate evolutionary convergence in complex symbiont communities and reveal the details and mechanisms that underpin the process.

  1. Maternal effects and population regulation: maternal density-induced reproduction suppression impairs offspring capacity in response to immediate environment in root voles Microtus oeconomus.

    Science.gov (United States)

    Bian, Jiang-Hui; Du, Shou-Yang; Wu, Yan; Cao, Yi-Fan; Nie, Xu-Heng; He, Hui; You, Zhi-Bing

    2015-03-01

    The hypothesis that maternal effects act as an adaptive bridge in translating maternal environments into offspring phenotypes, and thereby affecting population dynamics has not been studied in the well-controlled fields. In this study, the effects of maternal population density on offspring stress axis, reproduction and population dynamics were studied in root voles (Microtus oeconomus). Parental enclosures for breeding offspring were established by introducing six adults per sex into each of 4 (low density) and 30 adults per sex into each of another 4 (high density) enclosures. Live-trapping started 2 weeks after. Offspring captured at age of 20-30 days were removed to the laboratory, housed under laboratory conditions until puberty, and subsequently used to establish offspring populations in these same enclosures, after parental populations had been removed. [Correction added on 8 January 2015 after first online publication: '10-20 days' has been changed to '20-30 days.'] Offspring from each of the two parental sources were assigned into four enclosures with two for each of the two density treatments used in establishing parental populations (referred to as LL and LH for maternally unstressed offspring, assigned in low and high density, and HL and HH for maternally stressed offspring, assigned in low and high density). Faecal corticosterone metabolites (FCM) levels, offspring reproduction traits and population dynamics were tested following repeated live-trapping over two seasons. Differential fluctuations in population size were observed between maternally density-stressed and density-unstressed offspring. Populations in LL and LH groups changed significantly in responding to initial density and reached the similar levels at beginning of the second trapping season. Populations in HL and HH groups, however, were remained relatively steady, and in HL group, the low population size was sustained until end of experiment. Maternal density stress was associated with

  2. Housefly population density correlates with shigellosis among children in Mirzapur, Bangladesh: a time series analysis.

    Science.gov (United States)

    Farag, Tamer H; Faruque, Abu S; Wu, Yukun; Das, Sumon K; Hossain, Anowar; Ahmed, Shahnawaz; Ahmed, Dilruba; Nasrin, Dilruba; Kotloff, Karen L; Panchilangam, Sandra; Nataro, James P; Cohen, Dani; Blackwelder, William C; Levine, Myron M

    2013-01-01

    Shigella infections are a public health problem in developing and transitional countries because of high transmissibility, severity of clinical disease, widespread antibiotic resistance and lack of a licensed vaccine. Whereas Shigellae are known to be transmitted primarily by direct fecal-oral contact and less commonly by contaminated food and water, the role of the housefly Musca domestica as a mechanical vector of transmission is less appreciated. We sought to assess the contribution of houseflies to Shigella-associated moderate-to-severe diarrhea (MSD) among children less than five years old in Mirzapur, Bangladesh, a site where shigellosis is hyperendemic, and to model the potential impact of a housefly control intervention. Stool samples from 843 children presenting to Kumudini Hospital during 2009-2010 with new episodes of MSD (diarrhea accompanied by dehydration, dysentery or hospitalization) were analyzed. Housefly density was measured twice weekly in six randomly selected sentinel households. Poisson time series regression was performed and autoregression-adjusted attributable fractions (AFs) were calculated using the Bruzzi method, with standard errors via jackknife procedure. Dramatic springtime peaks in housefly density in 2009 and 2010 were followed one to two months later by peaks of Shigella-associated MSD among toddlers and pre-school children. Poisson time series regression showed that housefly density was associated with Shigella cases at three lags (six weeks) (Incidence Rate Ratio = 1.39 [95% CI: 1.23 to 1.58] for each log increase in fly count), an association that was not confounded by ambient air temperature. Autocorrelation-adjusted AF calculations showed that a housefly control intervention could have prevented approximately 37% of the Shigella cases over the study period. Houseflies may play an important role in the seasonal transmission of Shigella in some developing country ecologies. Interventions to control houseflies should be

  3. Are populations of European earwigs, Forficula auricularia, density dependent?

    DEFF Research Database (Denmark)

    Moerkens, R.; Leirs, H; Peusens, G.

    2009-01-01

    . Extensive knowledge of regulating processes of populations is therefore crucial for efficient orchard management. A 2-year phenological study in several apple and pear orchards in Belgium showed a significant displacement of third instars during the second brood in relation to the presence of adults. We...

  4. Topological Population Analysis from Higher order Densities I: Hartree-Fock Level

    Czech Academy of Sciences Publication Activity Database

    Bochicchio, R.; Lain, L.; Torre, A.; Ponec, Robert

    2000-01-01

    Roč. 28, 1-3 (2000), s. 83-90 ISSN 0259-9791 R&D Projects: GA AV ČR IAA4072006 Keywords : population analysis * multicenter bonds Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.817, year: 2000

  5. Detection of emerald ash borer, Agrilus planipennis, at low population density

    Science.gov (United States)

    Melissa J. Porter; Michael D. Hyslop; Andrew J. Storer

    2011-01-01

    The exotic emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae), was first discovered in North America in Detroit, MI, in 2002. This beetle has killed millions of ash trees in several states in the United States and in Canada, and populations of this insect continue to be detected. EAB is difficult to detect when it invades new...

  6. Investment in constitutive immune function by north American elk experimentally maintained at two different population densities

    Science.gov (United States)

    Cynthia J. Downs; Kelley M. Stewart; Brian L. Dick; Daniel E Crocker

    2015-01-01

    Natural selection favors individuals that respond with effective and appropriate immune responses to macro or microparasites. Animals living in populations close to ecological carrying capacity experience increased intraspecific competition, and as a result are often in poor nutritional condition. Nutritional condition, in turn, affects the amount of endogenous...

  7. Effects of human population density and proximity to markets on coral reef fishes vulnerable to extinction by fishing.

    Science.gov (United States)

    Brewer, T D; Cinner, J E; Green, A; Pressey, R L

    2013-06-01

    Coral reef fisheries are crucial to the livelihoods of tens of millions of people; yet, widespread habitat degradation and unsustainable fishing are causing severe depletion of stocks of reef fish. Understanding how social and economic factors, such as human population density, access to external markets, and modernization interact with fishing and habitat degradation to affect fish stocks is vital to sustainable management of coral reef fisheries. We used fish survey data, national social and economic data, and path analyses to assess whether these factors explain variation in biomass of coral reef fishes among 25 sites in Solomon Islands. We categorized fishes into 3 groups on the basis of life-history characteristics associated with vulnerability to extinction by fishing (high, medium, and low vulnerability). The biomass of fish with low vulnerability was positively related to habitat condition. The biomass of fishes with high vulnerability was negatively related to fishing conducted with efficient gear. Use of efficient gear, in turn, was strongly and positively related to both population density and market proximity. This result suggests local population pressure and external markets have additive negative effects on vulnerable reef fish. Biomass of the fish of medium vulnerability was not explained by fishing intensity or habitat condition, which suggests these species may be relatively resilient to both habitat degradation and fishing. © 2012 Society for Conservation Biology.

  8. Increasing Public Awareness of Direct-to-Consumer Genetic Tests: Health Care Access, Internet Use, and Population Density Correlates

    International Nuclear Information System (INIS)

    Rutten, L. J. F.; Gollust, S. E.; Naveed, S.; Moser, R. P.

    2012-01-01

    Uncertainty around the value of and appropriate regulatory models for direct-to-consumer (DTC) genetic testing underscores the importance of tracking public awareness of these services. We analyzed nationally representative, cross-sectional data from the Health Information National Trends Survey in 2008 (n=7, 674) and 2011 (n=3, 959) to assess population-level changes in awareness of DTC genetic testing in the U.S. and to explore socio demographic, health care, Internet use, and population density correlates. Overall, awareness increased significantly from 29% in 2008 to 37% in 2011. The observed increase in awareness from 2008 to 2011 remained significant (OR=1.39) even when adjusted for socio demographic variables, health care access, Internet use, and population density. Independent of survey year, the odds of awareness of DTC genetic tests were significantly higher for those aged 50-64 (OR=1.64), and 65-74 (O R=1.60); college graduates (OR=2.02 ); those with a regular source of health care (OR=1.27); those with a prior cancer diagnosis (OR=1.24); those who use the Internet (OR=1.27); and those living in urban areas ( OR=1.25). Surveillance of awareness-along with empirical data on use of and response to genetic risk information-can inform public health and policy efforts to maximize benefits and minimize risks of DTC genetic testing.

  9. Using non-invasively collected genetic data to estimate density and population size of tigers in the Bangladesh Sundarbans

    Directory of Open Access Journals (Sweden)

    M. Abdul Aziz

    2017-10-01

    Full Text Available Population density is a key parameter to monitor endangered carnivores in the wild. The photographic capture-recapture method has been widely used for decades to monitor tigers, Panthera tigris, however the application of this method in the Sundarbans tiger landscape is challenging due to logistical difficulties. Therefore, we carried out molecular analyses of DNA contained in non-invasively collected genetic samples to assess the tiger population in the Bangladesh Sundarbans within a spatially explicit capture-recapture (SECR framework. By surveying four representative sample areas totalling 1994 km2 of the Bangladesh Sundarbans, we collected 440 suspected tiger scat and hair samples. Genetic screening of these samples provided 233 authenticated tiger samples, which we attempted to amplify at 10 highly polymorphic microsatellite loci. Of these, 105 samples were successfully amplified, representing 45 unique genotype profiles. The capture-recapture analyses of these unique genotypes within the SECR model provided a density estimate of 2.85 ± SE 0.44 tigers/100 km2 (95% CI: 1.99–3.71 tigers/100 km2 for the area sampled, and an estimate of 121 tigers (95% CI: 84–158 tigers for the total area of the Bangladesh Sundarbans. We demonstrate that this non-invasive genetic surveillance can be an additional approach for monitoring tiger populations in a landscape where camera-trapping is challenging.

  10. Abundance of plankton population densities in relation to bottom soil textural types in aquaculture ponds

    Directory of Open Access Journals (Sweden)

    F. Siddika

    2012-06-01

    Full Text Available Plankton is an important food item of fishes and indicator for the productivity of a water body. The present study was conducted to evaluate the effects of bottom soil textural conditions on abundance of plankton in aquaculture pond. The experiment was carried out using three treatments, i.e., ponds bottom with sandy loam (T1, with loam (T2 and with clay loam (T3. The ranges of water quality parameters analyzed were suitable for the growth of plankton during the experimental period. Similarly, chemical properties of soil were also within suitable ranges and every parameter showed higher ranges in T2. A total 20 genera of phytoplankton were recorded belonged to Chlorophyceae (7, Cyanophyceae (5, Bacillariophyceae (5, Euglenophyceae (2 and Dinophyceae (1. On the other hand, total 13 genera of zooplankton were recorded belonged to Crustacea (7 and Rotifera (6. The highest ranges of phytoplankton and zooplankton densities were found in T2 where low to medium-type bloom was observed during the study period. Consequently, the mean abundance of plankton (phytoplankton and zooplankton density was significantly highest in T2. The highest abundance of plankton in the T2 indicated that pond bottom with loamy soil is suitable for the growth and production of plankton in aquaculture ponds.

  11. Surveillance of malaria vector population density and biting behaviour in western Kenya.

    Science.gov (United States)

    Ototo, Ednah N; Mbugi, Jenard P; Wanjala, Christine L; Zhou, Guofa; Githeko, Andrew K; Yan, Guiyun

    2015-06-17

    Malaria is a great public health burden and Africa suffers the largest share of malaria-attributed deaths. Despite control efforts targeting indoor malaria transmission, such as insecticide-treated bed nets (ITNs) and deployment of indoor residual spraying, transmission of the parasite in western Kenya is still maintained. This study was carried out to determine the impact of ITNs on indoor vector densities and biting behaviour in western Kenya. Indoor collection of adult mosquitoes was done monthly in six study sites in western Kenya using pyrethrum spray collections from 2012 to 2014. The rotator trap collections were done in July-August in 2013 and May-June in 2014. Mosquitoes were collected every 2 h between 18.00 and 08.00 h. Human behaviour study was conducted via questionnaire surveys. Species within Anopheles gambiae complex was differentiated by PCR and sporozoite infectivity was determined by ELISA. Species distribution was determined and bed net coverage in the study sites was recorded. During the study a total of 5,469 mosquito vectors were collected from both PSC and Rotator traps comprising 3,181 (58.2%) Anopheles gambiae and 2,288 (41.8%) Anopheles funestus. Compared to all the study sites, Rae had the highest density of An. gambiae with a mean of 1.2 (Pbiting time poses significant threats to the current malaria vector control strategies which heavily rely on indoor controls.

  12. Influence of Trypaea australiensis population density on benthic metabolism and nitrogen dynamics in sandy estuarine sediment: A mesocosm simulation

    Science.gov (United States)

    Jordan, Mark A.; Welsh, David T.; Dunn, Ryan J. K.; Teasdale, Peter R.

    2009-02-01

    Laboratory mesocosm incubations were undertaken to investigate the influence of natural densities of the thalassinidean shrimp, Trypaea australiensis (marine yabby) on sediment oxygen demand (SOD), inorganic nutrient fluxes, and the N-cycle processes of nitrification, denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Mesocosms (~ 0.1 m 2 × 55 cm deep) of sieved, natural T. australiensis inhabited sands were continually flushed with fresh seawater and pre-incubated for two weeks prior to being assigned to one of three treatments; control (no additions), low yabby density (40 T. australiensis m - 2 ) or high yabby density (80 T. australiensis m - 2 ). Thereafter, SOD and sediment-water column inorganic nutrient fluxes were determined periodically over a 38 day period. On the final day rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were also determined using the 15N-isotope pairing technique. Yabbies consistently and significantly ( p nitrification rates by 31 and 46% in the low and high density treatments. However, somewhat surprisingly T. australiensis population density had no effect on rates of denitrification and DNRA despite the higher rates of nitrification and higher equilibrium water column nitrate concentration. Indeed, nitrate reduction processes became an increasingly unimportant element with increasing yabby density with for example, N 2 generated by coupled nitrification-denitrification representing 11.5, 5.2 and 2.8% of the total inorganic-N recycled to the water column in the control, low density and high density yabby treatments, respectively. Overall, the major influence of T. australiensis in the studied low organic matter content, sandy sediments was to enhance coupling between the benthic and pelagic systems through increased rates of inorganic nitrogen regeneration in the sediment and enhanced export of this nitrogen to the water column. Our results also suggest that the influences of

  13. Population density and climate shape early-life survival and recruitment in a long-lived pelagic seabird.

    Science.gov (United States)

    Fay, Rémi; Weimerskirch, Henri; Delord, Karine; Barbraud, Christophe

    2015-09-01

    1. Our understanding of demographic processes is mainly based on analyses of traits from the adult component of populations. Early-life demographic traits are poorly known mainly for methodological reasons. Yet, survival of juvenile and immature individuals is critical for the recruitment into the population and thus for the whole population dynamic, especially for long-lived species. This bias currently restrains our ability to fully understand population dynamics of long-lived species and life-history theory. 2. The goal of this study was to estimate the early-life demographic parameters of a long-lived species with a long immature period (9-10 years), to test for sex and age effects on these parameters and to identify the environmental factors encountered during the period of immaturity that may influence survival and recruitment. 3. Using capture-mark-recapture multievent models allowing us to deal with uncertain and unobservable individual states, we analysed a long-term data set of wandering albatrosses to estimate both age- and sex-specific early-life survival and recruitment. We investigated environmental factors potentially driving these demographic traits using climatic and fisheries covariates and tested for density dependence. 4. Our study provides for the first time an estimate of annual survival during the first 2 years at sea for an albatross species (0·801 ± 0·014). Both age and sex affected early-life survival and recruitment processes of this long-lived seabird species. Early-life survival and recruitment were highly variable across years although the sensitivity of young birds to environmental variability decreased with age. Early-life survival was negatively associated with sea surface temperature, and recruitment rate was positively related to both Southern Annular Mode and sea surface temperature. We found strong evidence for density-dependent mortality of juveniles. Population size explained 41% of the variation of this parameter over the

  14. Symbiont acquisition as neoseme: origin of species and higher taxa

    Science.gov (United States)

    Bermudes, D.; Margulis, L.

    1987-01-01

    We examine the hypothesis that, in the origin of species and higher taxa of eukaryotes, symbiont acquisition followed by partner integration has been equivalent to neoseme appearance leading to speciation. The formation of stable symbiotic associations involves partner-surface recognition, behavioral and metabolic interaction, and, in some cases, gene product (RNA, protein) and genic (RNA, DNA) integration. This analysis is applied here to examples of neosemes that define specific taxa and to neosemes in plants, fungi, and animals that involve the appearance of new types of tissue. If this hypothesis is correct--if the origin of major genetic variation leading to speciation and even higher taxa may occur through symbiont acquisition and integration--then the analysis of "origins of species and higher taxa" becomes analogous to the study of microbial community ecology.

  15. Comparative Genomic Analysis of Holospora spp., Intranuclear Symbionts of Paramecia

    Directory of Open Access Journals (Sweden)

    Sofya K. Garushyants

    2018-04-01

    Full Text Available While most endosymbiotic bacteria are transmitted only vertically, Holospora spp., an alphaproteobacterium from the Rickettsiales order, can desert its host and invade a new one. All bacteria from the genus Holospora are intranuclear symbionts of ciliates Paramecium spp. with strict species and nuclear specificity. Comparative metabolic reconstruction based on the newly sequenced genome of Holospora curviuscula, a macronuclear symbiont of Paramecium bursaria, and known genomes of other Holospora species shows that even though all Holospora spp. can persist outside the host, they cannot synthesize most of the essential small molecules, such as amino acids, and lack some central energy metabolic pathways, including glycolysis and the citric acid cycle. As the main energy source, Holospora spp. likely rely on nucleotides pirated from the host. Holospora-specific genes absent from other Rickettsiales are possibly involved in the lifestyle switch from the infectious to the reproductive form and in cell invasion.

  16. A nuptially transmitted ichthyosporean symbiont of Tenebrio molitor (Coleoptera: Tenebrionidae).

    Science.gov (United States)

    Lord, Jeffrey C; Hartzer, Kris L; Kambhampati, Srinivas

    2012-01-01

    The yellow mealworm, Tenebrio molitor, harbors a symbiont that has spores with a thick, laminated wall and infects the fat body and ventral nerve chord of adult and larval beetles. In adult males, there is heavy infection of the epithelial cells of the testes and between testes lobes with occasional penetration of the lobes. Spores are enveloped in the spermatophores when they are formed at the time of mating and transferred to the female's bursa copulatrix. Infection has not been found in the ovaries. The sequence of the nuclear small subunit rDNA indicates that the symbiont is a member of the Ichthyosporea, a class of protists near the animal-fungi divergence. © 2012 The Author(s) Journal of Eukaryotic Microbiology © 2012 International Society of Protistologists.

  17. Ideotype population exploration: growth, photosynthesis, and yield components at different planting densities in winter oilseed rape (Brassica napus L.).

    Science.gov (United States)

    Ma, Ni; Yuan, Jinzhan; Li, Ming; Li, Jun; Zhang, Liyan; Liu, Lixin; Naeem, Muhammad Shahbaz; Zhang, Chunlei

    2014-01-01

    Rapeseed is one of the most important edible oil crops in the world and the seed yield has lagged behind the increasing demand driven by population growth. Winter oilseed rape (Brassica napus L.) is widely cultivated with relatively low yield in China, so it is necessary to find the strategies to improve the expression of yield potential. Planting density has great effects on seed yield of crops. Hence, field experiments were conducted in Wuhan in the Yangtze River basin with one conventional variety (Zhongshuang 11, ZS11) and one hybrid variety (Huayouza 9, HYZ9) at five planting densities (27.0×10(4), 37.5×10(4), 48.0×10(4), 58.5×10(4), 69.0×10(4) plants ha(-1)) during 2010-2012 to investigate the yield components. The physiological traits for high-yield and normal-yield populations were measured during 2011-2013. Our results indicated that planting densities of 58.5×10(4) plants ha(-1) in ZS11 and 48.0×10(4) plants ha(-1) in HYZ9 have significantly higher yield compared with the density of 27.0×10(4) plants ha(-1) for both varieties. The ideal silique numbers for ZS11 and HYZ9 were ∼0.9×10(4) (n m(-2)) and ∼1×10(4) (n m(-2)), respectively, and ideal primary branches for ZS11 and HYZ9 were ∼250 (n m(-2)) and ∼300 (n m(-2)), respectively. The highest leaf area index (LAI) and silique wall area index (SAI) was ∼5.0 and 7.0, respectively. Moreover, higher leaf net photosynthetic rate (Pn) and water use efficiency (WUE) were observed in the high-yield populations. A significantly higher level of silique wall photosynthesis and rapid dry matter accumulation were supposed to result in the maximum seed yield. Our results suggest that increasing the planting density within certain range is a feasible approach for higher seed yield in winter rapeseed in China.

  18. Hyperthermic survival of Chinese hamster ovary cells as a function of cellular population density at the time of plating

    International Nuclear Information System (INIS)

    Highfield, D.P.; Holahan, E.V.; Holahan, P.K.; Dewey, W.C.

    1984-01-01

    The survival of synchronous G 1 or asynchronous Chinese hamster ovary cells in vitro to heat treatment may depend on the cellular population density at the time of heating and/or as the cells are cultured after heating. The addition of lethally irradiated feeder cells may increase survival at 10 -3 by as much as 10- to 100-fold for a variety of conditions when cells are heated either in suspension culture or as monolayers with or without trypsinization. The protective effect associated with feeder cells appears to be associated with close cell-to-cell proximity. However, when cells are heated without trypsinization about 24 hr or later after plating, when adaptation to monolayer has occurred, the protective effect is reduced; i.e., addition of feeder cells enhances survival much less, for example, about 2- to 3-fold at 10 -2 -10 -3 survival. Also, the survival of a cell to heat is independent of whether the neighboring cell in a microcolony is destined to live or die. Finally, if protective effects associated with cell density do occur and are not controlled, serious artifacts can result as the interaction of heat and radiation is studied; for example, survival curves can be moved upward, and thus changed in shape as the number of cells plated is increased with an increase in the hyperthermic treatment or radiation dose following hyperthermia. Therefore, to understand mechanisms and to obtain information relevant to populations of cells in close proximity, such as those in vivo, these cellular population density effects should be considered and understood

  19. [Effects of eutrophication on distribution and population density of Corbicula fluminea and Bellamya sp. in Chaohu Lake].

    Science.gov (United States)

    Deng, Daogui; Li, Hongyuan; Hu, Wanming; Zhou, Qiong; Guo, Longgen

    2005-08-01

    The investigation on the distribution an d population density of C. fluminea and Bellamya sp. in Chaohu Lake during September 2001 and September 2002 showed that in the west region of the lake where was seriously eutrophic, the density and biomass of C. fluminea were 5.1 ind. x m(-2) and 17.87 g x m(-2) in 2001, and 8.8 ind. x m(-2) and 47.29 g x m(-2) in 2002, while those of Bellamya sp. were 13.3 ind. x m(-2) and 45.45 g x m(-2) in 2001, and 3.8 ind. x m(-2) and 12.56 g x m(-2) in 2002, respectively. In the east region of the lake where was eutrophic, the density and biomass of C. fluminea were 23.8 ind. x m(-2) and 67.86 g x m(-2) in 2001, and 29.2 ind. x m(-2) and 96.18 g x m(-2) in 2002, while those of Bellamya sp. were 10.1 ind. x m(-2) and 32.00 g x m(-2) in 2001, and 9.4 ind. x m(-2) and 31.21 g x m(-2) in 2002, respectively. The density and biomass of C. fluminea and Bellamya sp. were declined with increasing eutrophication. In hypertrophic region, C. fluminea and Bellamya sp. were absent. The density and biomass of the two species were obviously higher in littoral than in pelagic region. The distribution type of C. fluminea was core-model, while that of Bellamya sp. was random. The correlation between the density and biomass of C. fluminea and Bellamya sp. and water depth was not significant (P > 0.05). The biomass of Bellamya sp. was negatively correlated with water TN (P fluminea only had a significantly negative correlation with PO4-P(P fluminea in the lake nowadays. The effects of other environmental factors on the population distribution and growth of C. fluminea and Bellamya sp. were also discussed.

  20. Diminished UV-absorbing nets reduce the Spreads and population density of Macrosiphum euphorbiae in lettuce.

    OpenAIRE

    Legarrea, S.; Díaz, B. M.; Plaza, M.; Barrios, L.; Morales, Ignacio; Viñuela Sandoval, Elisa; Fereres Castiel, Alberto

    2012-01-01

    UV-absorbing covers reduce the incidence of injurious insect pests and viruses in protected crops. In the present study, the effect of a UV-absorbing net (Bionet) on the spatio-temporal dynamics of the potato aphid on lettuce plants was evaluated. A field experiment was conducted during three seasons in two identical tunnels divided in four plots. A set of lettuce plants were artificially infested with Macrosiphum euphorbiae adults and the population was estimated by counting aphids on ev...

  1. Wolbachia symbiont infections induce strong cytoplasmic incompatibility in the tsetse fly Glossina morsitans.

    Directory of Open Access Journals (Sweden)

    Uzma Alam

    2011-12-01

    Full Text Available Tsetse flies are vectors of the protozoan parasite African trypanosomes, which cause sleeping sickness disease in humans and nagana in livestock. Although there are no effective vaccines and efficacious drugs against this parasite, vector reduction methods have been successful in curbing the disease, especially for nagana. Potential vector control methods that do not involve use of chemicals is a genetic modification approach where flies engineered to be parasite resistant are allowed to replace their susceptible natural counterparts, and Sterile Insect technique (SIT where males sterilized by chemical means are released to suppress female fecundity. The success of genetic modification approaches requires identification of strong drive systems to spread the desirable traits and the efficacy of SIT can be enhanced by identification of natural mating incompatibility. One such drive mechanism results from the cytoplasmic incompatibility (CI phenomenon induced by the symbiont Wolbachia. CI can also be used to induce natural mating incompatibility between release males and natural populations. Although Wolbachia infections have been reported in tsetse, it has been a challenge to understand their functional biology as attempts to cure tsetse of Wolbachia infections by antibiotic treatment damages the obligate mutualistic symbiont (Wigglesworthia, without which the flies are sterile. Here, we developed aposymbiotic (symbiont-free and fertile tsetse lines by dietary provisioning of tetracycline supplemented blood meals with yeast extract, which rescues Wigglesworthia-induced sterility. Our results reveal that Wolbachia infections confer strong CI during embryogenesis in Wolbachia-free (Gmm(Apo females when mated with Wolbachia-infected (Gmm(Wt males. These results are the first demonstration of the biological significance of Wolbachia infections in tsetse. Furthermore, when incorporated into a mathematical model, our results confirm that Wolbachia can

  2. Genomics of "Candidatus Synechococcus spongiarium", a Cyanobacterial Sponge Symbiont

    Energy Technology Data Exchange (ETDEWEB)

    Slaby, Beate M. [Univ. of Wuerzburg (Germany); Copeland, Alex [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.; Woyke, Tanja [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.; Hentschel, Ute [Univ. of Wuerzburg (Germany)

    2014-03-21

    Marine sponges (Porifera): ancient metazoans of ecological importance, that produce bioactive secondary metabolites and interact with various microorganisms including cyanobacteria1: Marine Synechococcus spp.: cyanobacteria, important contributors to the global carbon cycle and major primary producers in the oceans2 Ca. S. spongiarum: an ecotype of this genus, widespread and abundant symbiont of various marine sponges around the world3, e.g. Aplysina aerophoba

  3. Estimating the population density of Iberian wild goat Capra pyrenaica and mouflon Ovis aries in a Mediterranean forest environment

    Directory of Open Access Journals (Sweden)

    Rita Tinoco Torres

    2014-04-01

    Full Text Available Aim of study: To manage and conserve wild populations effectively, a good understating of population density is critical. During 2010, the density of Iberian wild goat Capra pyrenaica and mouflon Ovis aries were estimated.Area of study: The area is situated in Muela de Cortes Game Reservation (Spain, a Mediterranean forest plateau, after a mange Sarcoptes scabiei outbreak that affected both species. Material and methods: To measure the abundance, sex ratio and productivity of the Iberian wild goat and mouflon. Field work was conducted during spring (after parturition and autumn (during rut by walking along itineraries, using a Distance Sampling approach. Main results: Based on DS, the best relative fit of model and adjustment term for Iberian wild goat was hazard-rate cosine, based on the lowest AIC score. The average density for Iberian wild goat was 4 km-2 (95% CI: 2,3 – 6,9 (after parturition and 3,6 km-2 (95% CI: 2 – 6.6 (during rut. Average estimation was 1,422 goats (95% CI: 813 – 2,487 after parturition and 1,308 during rut (95% CI: 725 – 2,362. Mouflon best relative fit of model and adjustment term was uniform cosine after parturition, based on the lowest AIC score. The best relative fit of model and adjustment term for mouflon was hazard-rate cosine, based on the lowest AIC score. The average density was 6.8 mouflon km-2 (95% CI: 4.7 – 9,9 after parturition and 7,4 mouflon km-2 (95% CI: 4,4 – 12,5 during rut. Average estimation was 2,440 mouflon after parturition (95% CI: 1,673 – 3,558 and 2,678 during rut (95% CI: 1,589 – 4,515. Research highlights: The area represents one of the largest continental free-living populations of mouflon in Europe and a relevant area for Iberian wild goat, where it has survived for centuries and spread into the East Iberia. This study suggests that the survey methods used are suitable and sustainable with available field personnel for quantifying changes in wild goat and mouflon populations

  4. Relationship between snail population density and infection status of snails and fish with zoonotic trematodes in Vietnamese carp nurseries

    DEFF Research Database (Denmark)

    Clausen, Jesper Hedegaard; Madsen, Henry; Murrell, Kenneth Darwin

    2012-01-01

    ponds. Previous risk assessment on FZT transmission in the Red River Delta of Vietnam identified carp nursery ponds as major sites of transmission. In this study, we analyzed the association between snail population density and heterophyid trematode infection in snails with the rate of FZT transmission......Fish-borne zoonotic trematodes (FZT) are a food safety and health concern in Vietnam. Humans and other final hosts acquire these parasites from eating raw or under-cooked fish with FZT metacercariae. Fish raised in ponds are exposed to cercariae shed by snail hosts that are common in fish farm...

  5. Influences of population, building, and traffic densities on urban heat island intensity in Chiang Mai City, Thailand

    Directory of Open Access Journals (Sweden)

    Kammuang-Lue Niti

    2015-01-01

    Full Text Available This research aims to evaluate the Urban Heat Island Intensity (UHII and study the influences of population density, building density, and traffic density on the UHII in Chiang Mai city on each season and time. The surrounding air temperature was measured by thermocouples at a constant height of 2 m above the road by mobile surveying approach. The surveyed routes were divided into urban routes and rural routes. The UHII was calculated from the average surrounding air temperature difference between the urban and the rural areas. Experimental investigations were carried out in two seasons, consisting of summer (March-May, 2014 and winter (December 2013-February 2014. Experimental investigations were carried out in two periods, which were a daytime period (01.00-03.00 pm and a nighttime period (10.00 pm-00.00 am on Mondays, Wednesdays, and Sundays. The results show that the UHII in summer day, summer night, winter day, and winter night were 1.07°C, 1.27°C, 0.58°C, and 1.34°C, respectively. This implies that the temperature in Chiang Mai city’s urban area is higher than that in the rural area the entire year. Moreover, it was found that the UHII in summer day, winter day, and winter night were primarily affected by the traffic density with the sensitivity percentage of 87.50%, 72.73%, and 63.33%, respectively. In contrast, the UHII in summer night was mainly affected by the building density with the sensitivity percentage of 50.00%.

  6. Optimizing Use of Girdled Ash Trees for Management of Low-Density Emerald Ash Borer (Coleoptera: Buprestidae) Populations.

    Science.gov (United States)

    Siegert, Nathan W; McCullough, Deborah G; Poland, Therese M; Heyd, Robert L

    2017-06-01

    Effective survey methods to detect and monitor recently established, low-density infestations of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), remain a high priority because they provide land managers and property owners with time to implement tactics to slow emerald ash borer population growth and the progression of ash mortality. We evaluated options for using girdled ash (Fraxinus spp.) trees for emerald ash borer detection and management in a low-density infestation in a forested area with abundant green ash (F. pennsylvanica). Across replicated 4-ha plots, we compared detection efficiency of 4 versus 16 evenly distributed girdled ash trees and between clusters of 3 versus 12 girdled trees. We also examined within-tree larval distribution in 208 girdled and nongirdled trees and assessed adult emerald ash borer emergence from detection trees felled 11 mo after girdling and left on site. Overall, current-year larvae were present in 85-97% of girdled trees and 57-72% of nongirdled trees, and larval density was 2-5 times greater on girdled than nongirdled trees. Low-density emerald ash borer infestations were readily detected with four girdled trees per 4-ha, and 3-tree clusters were as effective as 12-tree clusters. Larval densities were greatest 0.5 ± 0.4 m below the base of the canopy in girdled trees and 1.3 ± 0.7 m above the canopy base in nongirdled trees. Relatively few adult emerald ash borer emerged from trees felled 11 mo after girdling and left on site through the following summer, suggesting removal or destruction of girdled ash trees may be unnecessary. This could potentially reduce survey costs, particularly in forested areas with poor accessibility. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

  7. Choosing the best method to estimate the energy density of a population using food purchase data.

    Science.gov (United States)

    Wrieden, W L; Armstrong, J; Anderson, A S; Sherriff, A; Barton, K L

    2015-04-01

    Energy density (ED) is a measure of the energy content of a food component or diet relative to a standard unit of weight. Widespread variation in ED assessment methodologies exist. The present study aimed to explore the feasibility of calculating the ED of the Scottish diet using UK food purchase survey data and to identify the most appropriate method for calculating ED for use in the development of a Scottish Dietary Goal that captures any socioeconomic differences. Energy density was calculated using five different methods [food; food and milk; food, milk and energy containing (non-alcoholic) beverages; food, milk and all non-alcoholic beverages; and all food and beverages]. ED of the Scottish diet was estimated for each of the ED methods and data were examined by deprivation category. Mean ED varied from 409 to 847 kJ 100 g(-1) depending on the method used. ED values calculated from food (847 kJ 100 g(-1) ) and food and milk (718 kJ 100 g(-1) ) were most comparable to other published data, with the latter being a more accurate reflection of all food consumed. For these two methods, there was a significant gradient between the most and least deprived quintiles (892-807 and 737-696 kJ 100 g(-1) for food and food and milk, respectively). Because the World Cancer Research Fund recommendations are based on ED from food and milk, it was considered prudent to use this method for policy purposes and for future monitoring work of the Scottish Diet to ensure consistency of reporting and comparability with other published studies. © 2014 The British Dietetic Association Ltd.

  8. Bacterial and fungal symbionts of parasitic Dendroctonus bark beetles.

    Science.gov (United States)

    Dohet, Loïc; Grégoire, Jean-Claude; Berasategui, Aileen; Kaltenpoth, Martin; Biedermann, Peter H W

    2016-09-01

    Bark beetles (Curculionidae: Scolytinae) are one of the most species-rich herbivorous insect groups with many shifts in ecology and host-plant use, which may be mediated by their bacterial and fungal symbionts. While symbionts are well studied in economically important, tree-killing species, little is known about parasitic species whose broods develop in living trees. Here, using culture-dependent and independent methods, we provide a comprehensive overview of the associated bacteria, yeasts and filamentous fungi of the parasitic Dendroctonus micans, D. punctatus and D. valens, and compare them to those of other tree-inhabiting insects. Despite inhabiting different geographical regions and/or host trees, the three species showed similar microbial communities. Enterobacteria were the most prevalent bacteria, in particular Rahnella, Pantoea and Ewingella, in addition to Streptomyces Likewise, the yeasts Candida/Cyberlindnera were the most prominent fungi. All these microorganisms are widespread among tree-inhabiting insects with various ecologies, but their high prevalence overall might indicate a beneficial role such as detoxification of tree defenses, diet supplementation or protection against pathogens. As such, our results enable comparisons of symbiont communities of parasitic bark beetles with those of other beetles, and will contribute to our understanding of how microbial symbioses facilitate dietary shifts in insects. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  9. On the accumulation of radionuclids by lichen symbionts

    International Nuclear Information System (INIS)

    Nifontova, M.G.; Kulikov, N.V.

    1983-01-01

    The aim of investigation is the quantitative estimation of ability and role of separate symbionts in the accumulation of radionuclides. As investigation volumes, dUrably cUltivated green lichen alga Trebouxia erici and lichen fungi extracted from Cladonia rangiferina, Parmelia caperata and Acarospora fuscata are used. The accumulation of radioactive isotopes with fUngi and seaweeds is estimated according to accUmulation coefficients (AC) which are the ratio of radiation concentration in plants and agarized medium. Radionuclide content ( 90 Sr and 137 Cs) is determined radiometrically. A special series of eXperiments is done to investigate radionuclide accumulation dependences with lichen seaweed and fungi on light conditions. It is shown that both symbionts of lichen-seaweek and fungus take part in the accumulation of radionuclide from outer medium (atmospheric fall-out and soil). However fungus component constituting the base of structural organization of thallus provides the greater part of radionuclides accumulated by the plant. Along with this the violation of viability of seaweed symbionts particularly in the case of light deficiency brings about the reduction of 137 Cs sorption by seaweeds and tells on the total content of radiocesium in plant thallus

  10. Allometric scaling of population variance with mean body size is predicted from Taylor’s law and density-mass allometry

    Science.gov (United States)

    Cohen, Joel E.; Xu, Meng; Schuster, William S. F.

    2012-01-01

    Two widely tested empirical patterns in ecology are combined here to predict how the variation of population density relates to the average body size of organisms. Taylor’s law (TL) asserts that the variance of the population density of a set of populations is a power-law function of the mean population density. Density–mass allometry (DMA) asserts that the mean population density of a set of populations is a power-law function of the mean individual body mass. Combined, DMA and TL predict that the variance of the population density is a power-law function of mean individual body mass. We call this relationship “variance–mass allometry” (VMA). We confirmed the theoretically predicted power-law form and the theoretically predicted parameters of VMA, using detailed data on individual oak trees (Quercus spp.) of Black Rock Forest, Cornwall, New York. These results connect the variability of population density to the mean body mass of individuals. PMID:23019367

  11. Invasion rate and population characteristics of the invasive round goby Neogobius melanostomus: effects of density and invasion history

    DEFF Research Database (Denmark)

    Azour, Farivar; Deurs, Mikael van; Behrens, Jane

    2015-01-01

    ). The established population revealed a broad age distribution and a 1:1 gender ratio, while fish from a recently invaded site were primarily of intermediate ages with a male-biased gender ratio. Otolith analyses suggested that the oldest individuals from the recently invaded area experienced superior growth...... Baltic Sea. Further analyses showed that fish from an established high-density round goby population were slow-growing and displayed poorer condition (weight at age and hepatosomatic index) compared to fish sampled from recently invaded locations (i.e. at the forefront of the distribution range......Round goby Neogobius melanostomus is currently one of the most wide-ranging invasive fish species in Europe and North America. The present study demonstrates how the distribution of round goby has expanded from 2008 to 2013 at a rate of about 30 km yr−1 along the Danish coastline in the western...

  12. Studying the Complex Communities of Ants and Their Symbionts Using Ecological Network Analysis.

    Science.gov (United States)

    Ivens, Aniek B F; von Beeren, Christoph; Blüthgen, Nico; Kronauer, Daniel J C

    2016-01-01

    Ant colonies provide well-protected and resource-rich environments for a plethora of symbionts. Historically, most studies of ants and their symbionts have had a narrow taxonomic scope, often focusing on a single ant or sym