Intraspecific Variation in Home Range Overlap with Habitat Quality: A Comparison among Brown Bear Populations

We developed a conceptual model of spatial organization in vertebrates based upon changes in home range overlap with habitat quality. We tested the model using estimates of annual home ranges of adult females and densities for 30 populations of brown bears (Ursus arctos) in North America. We used seasonality as a surrogate of habitat quality, measured as the coefficient of variation among monthly actual evapotranspiration values for areas in which study populations were located. We calculated home range overlap for each population as the product of the average home range size for adult females and the estimated population density of adult females. Home range size varied positively with seasonality; however, home range overlap varied with seasonality in a nonlinear manner. Areas of low and high seasonality supported brown bears with considerable home range overlap, but areas of moderate seasonality supported brown bears with low home range overlap. These results are consistent with behavioural theory predicting a nonlinear relationship between food availability and territoriality.     

Earlier Migration Timing,Decreasing Phenotypic Variation,and Biocomplexity in Multiple Salmonid Species

Climate-induced phenological shifts can influence population, evolutionary, and ecological dynamics, but our understanding of these phenomena is hampered by a lack of long-term demographic data. We use a multi-decade census of 5 salmonid species representing 14 life histories in a warming Alaskan stream to address the following key questions about climate change and phenology: How consistent are temporal patterns and drivers of phenology for similar species and alternative life histories? Are shifts in phenology associated with changes in phenotypic variation? How do phenological changes influence the availability of resource subsidies? For most salmonid species, life stages, and life histories, freshwater temperature influences migration timing – migration events are occurring earlier in time (mean = 1.7 days earlier per decade over the 3–5 decades), and the number of days over which migration events occur is decreasing (mean = 1.5 days per decade). Temporal trends in migration timing were not correlated with changes in intra-annual phenotypic variation, suggesting that these components of the phenotypic distribution have responded to environmental change independently. Despite commonalities across species and life histories, there was important biocomplexity in the form of disparate shifts in migration timing and variation in the environmental factors influencing migration timing for alternative life history strategies in the same population. Overall, adult populations have been stable during these phenotypic and environmental changes (λ ≈1.0), but the temporal availability of salmon as a resource in freshwater has decreased by nearly 30 days since 1971 due to changes in the median date of migration timing and decreases in intra-annual variation in migration timing. These novel observations advance our understanding of phenological change in response to climate warming, and indicate that climate change has influenced the ecology of salmon populations, which will have important consequences for the numerous species that depend on this resource.     

Communal Roost Site Selection in a Neotropical Harvestman: Habitat Limitation vs. Tradition

Many species have been reported to form roosting (resting, sleeping) aggregations at ‘traditional’ sites, but the alternative hypothesis that specific sites are used repeatedly because of habitat limitation is rarely tested. We studied the roosting behavior of a species of harvestman (Opiliones, Prionostemma sp.) at a lowland rainforest site in Nicaragua. Both sexes roosted by day in spiny palm trees, dispersed at dusk to forage, and rejoined aggregations just before dawn. The distribution of harvestmen among spiny palms was significantly clumped, and harvestman density did not correlate with spiny palm density. Aggregations formed repeatedly in a small subset of the available spiny palms and the same sites were used in two different years (2001, 2003). Nevertheless, the membership of aggregations was fluid; individual harvestmen were found at multiple roosts and moved up to 0.2 km per night. Translocated animals often returned to the roost where they had been released or nearby roosts but were never found at previously unused sites. The high consistency of site use but low site fidelity of individuals suggests that roost sites differed conspicuously (to the harvestmen) from sites that were not used. We found no univariate or multivariate differences between used and unused sites, however, in the characteristics of the trees or microclimate. These results conflict with the habitat limitation hypothesis but are consistent with the traditional site use hypothesis. The tradition may be mediated by a site‐labeling chemical, a mechanism that does not require individual site fidelity. We discuss these results in relation to the proposed functions of roosting aggregations.     

Geographical Range and Local Abundance of Tree Species in China

Most studies on the geographical distribution of species have utilized a few well-known taxa in Europe and North America, with little research in China and its wide range of climate and forest types. We assembled large datasets to quantify the geographic ranges of tree species in China and to test several biogeographic hypotheses: 1) whether locally abundant species tend to be geographically widespread; 2) whether species are more abundant towards their range-centers; and 3) how abundances are correlated between sites. Local abundances of 651 species were derived from four tree plots of 20–25 ha where all individuals ≥1 cm in stem diameter were mapped and identified taxonomically. Range sizes of these species across China were then estimated from over 460,000 geo-referenced records; a Bayesian approach was used, allowing careful measures of error of each range estimate. The log-transformed range sizes had a bell-shaped distribution with a median of 703,000 km², and >90% of 651 species had ranges >10⁵ km². There was no relationship between local abundance and range size, and no evidence for species being more abundant towards their range-centers. Finally, species’ abundances were positively correlated between sites. The widespread nature of most tree species in China suggests few are vulnerable to global extinction, and there is no indication of the double-peril that would result if rare species also had narrow ranges.     

Genomic Analysis of Natural Selection and Phenotypic Variation in High-Altitude Mongolians

Deedu (DU) Mongolians, who migrated from the Mongolian steppes to the Qinghai-Tibetan Plateau approximately 500 years ago, are challenged by environmental conditions similar to native Tibetan highlanders. Identification of adaptive genetic factors in this population could provide insight into coordinated physiological responses to this environment. Here we examine genomic and phenotypic variation in this unique population and present the first complete analysis of a Mongolian whole-genome sequence. High-density SNP array data demonstrate that DU Mongolians share genetic ancestry with other Mongolian as well as Tibetan populations, specifically in genomic regions related with adaptation to high altitude. Several selection candidate genes identified in DU Mongolians are shared with other Asian groups (e.g., EDAR), neighboring Tibetan populations (including high-altitude candidates EPAS1, PKLR, and CYP2E1), as well as genes previously hypothesized to be associated with metabolic adaptation (e.g., PPARG). Hemoglobin concentration, a trait associated with high-altitude adaptation in Tibetans, is at an intermediate level in DU Mongolians compared to Tibetans and Han Chinese at comparable altitude. Whole-genome sequence from a DU Mongolian (Tianjiao1) shows that about 2% of the genomic variants, including more than 300 protein-coding changes, are specific to this individual. Our analyses of DU Mongolians and the first Mongolian genome provide valuable insight into genetic adaptation to extreme environments.     

Local Movement as a Measure of Habitat Quality in Stream Salmonids

Habitat assessments are often based on the premise that spatial variation in population density arises from, and accurately reflects, underlying differences in quality among habitats. Nonetheless, this premise has been criticized on both theoretical and empirical grounds. Habitat quality perhaps is best evaluated by examining behavioural processes which directly influence habitat use. We present an approach based on the assumption that measures of local movement, such as habitat-specific immigration and loss rates, provide useful indicators of habitat quality. A dynamic turnover model was used in conjunction with mark-recapture techniques to estimate movement parameters for brook charr, Salvelinus fontinalis, and Atlantic salmon, Salmo salar, in different stream habitats during the summer. Immigration and loss rates were derived from mark-recapture experiments covering short periods of time (6 days). Movement-based rankings of habitat quality for both charr (pools glides > riffles) and salmon (riffles > glides > pools) were in agreement with results from earlier studies. Over evaluation periods of up to 65 days, observed abundances were highly variable in time and fluctuated about the equilibrium abundances calculated from movement parameters in the short-term experiments, suggesting that movement-based parameters may be more stable than measures of abundance for evaluating salmonid habitat. Because the approach based on movement behaviour focuses on immigration and loss, two processes that directly generate density differentials between habitats, it provides a more reliable mechanistic basis for understanding habitat selection than do traditional approaches based on density–quality relationships.     

Patch Connectivity and Genetic Variation in Two Congeneric Grasshopper Species with Different Habitat Preferences

Two congeneric species of grasshopper, Stenobothrus lineatus and S. stigmaticus, are compared in an analysis of genetic structure relative to their observed mobility, and to the spatial structure of their habitat networks. The species differ in their habitat requirements, the latter being rarer and more restricted to isolated patches. We tested for different patch connectivity between the two species in an analysis of genetic variance (based on allozymes) under the assumption that, besides isolation, rarity influences the genetic parameters. Between the species we found no differences in genetic structure as estimated by F_ST; i.e., no isolation effects and no apparent differences between the species in the potential to move between habitat fragments on either a local or regional scale were found. However, the amount of genetic variation in the more widely distributed and less xerothermic S. lineatus was significantly higher than in S. stigmaticus. Some consistency with observed philopatry within patches was found (F_IS > 0), but we consider regular dispersal events of medium and especially long distance to cause the habitat linking. We conclude that the connectivity between occupied patches inferred by genetic analyses can seldom be derived from low observed life-time movements recorded by conventional marking studies. Consequences of applying observed relative to indirect dispersal estimates for the examination of grasshopper metapopulations are discussed.     

Trophic Niche in a Raptor Species: The Relationship between Diet Diversity,Habitat Diversity and Territory Quality

Recent research reports that many populations of species showing a wide trophic niche (generalists) are made up of both generalist individuals and individuals with a narrow trophic niche (specialists), suggesting trophic specializations at an individual level. If true, foraging strategies should be associated with individual quality and fitness. Optimal foraging theory predicts that individuals will select the most favourable habitats for feeding. In addition, the “landscape heterogeneity hypothesis” predicts a higher number of species in more diverse landscapes. Thus, it can be predicted that individuals with a wider realized trophic niche should have foraging territories with greater habitat diversity, suggesting that foraging strategies, territory quality and habitat diversity are inter-correlated. This was tested for a population of common kestrels Falco tinnunculus. Diet diversity, territory occupancy (as a measure of territory quality) and habitat diversity of territories were measured over an 8-year period. Our results show that: 1) territory quality was quadratically correlated with habitat diversity, with the best territories being the least and most diverse; 2) diet diversity was not correlated with territory quality; and 3) diet diversity was negatively correlated with landscape heterogeneity. Our study suggests that niche generalist foraging strategies are based on an active search for different prey species within or between habitats rather than on the selection of territories with high habitat diversity.     

Chemical Variation in a Dominant Tree Species: Population Divergence,Selection and Genetic Stability across Environments

Understanding among and within population genetic variation of ecologically important plant traits provides insight into the potential evolutionary processes affecting those traits. The strength and consistency of selection driving variability in traits would be affected by plasticity in differences among genotypes across environments (G×E). We investigated population divergence, selection and environmental plasticity of foliar plant secondary metabolites (PSMs) in a dominant tree species, Eucalyptus globulus. Using two common garden trials we examined variation in PSMs at multiple genetic scales; among 12 populations covering the full geographic range of the species and among up to 60 families within populations. Significant genetic variation in the expression of many PSMs resides both among and within populations of E. globulus with moderate (e.g., sideroxylonal A h²op = 0.24) to high (e.g., macrocarpal G h²op = 0.48) narrow sense heritabilities and high coefficients of additive genetic variation estimated for some compounds. A comparison of Qst and Fst estimates suggest that variability in some of these traits may be due to selection. Importantly, there was no genetic by environment interaction in the expression of any of the quantitative chemical traits despite often significant site effects. These results provide evidence that natural selection has contributed to population divergence in PSMs in E. globulus, and identifies the formylated phloroglucinol compounds (particularly sideroxylonal) and a dominant oil, 1,8-cineole, as candidates for traits whose genetic architecture has been shaped by divergent selection. Additionally, as the genetic differences in these PSMs that influence community phenotypes is stable across environments, the role of plant genotype in structuring communities is strengthened and these genotypic differences may be relatively stable under global environmental changes.     

Phenotypic Variation in Senescence in Miscanthus: Towards Optimising Biomass Quality and Quantity

Senescence impacts the harvestable biomass yield and quality in Miscanthus. Very early autumn senescence shortens the canopy duration reducing yield potential. When senescence is too late or slow, the crop does not ripen sufficiently before harvest, resulting in high moisture and nutrient offtakes that reduce biomass quality. In this study, variation in senescence was monitored over 3?years in a trial of 244 Miscanthus genotypes planted in four replicate blocks. The experiment comprised 199 genotypes of Miscanthus sinensis, 36 genotypes of Miscanthus sacchariflorus, and 9 genotypes of Miscanthus?×?giganteus. On average, M. sinensis genotypes remained greener for longer than M. sacchariflorus genotypes. There was a strong correlation between senescence and moisture content at harvest in 2007 and 2008 (R ²?=?0.59, R ²?=?0.57, respectively; n?=?244). The senescence rate of M.?×?giganteus, an interspecific hybrid between M. sinensis and M. sacchariflorus, was found to lie between the two parental species groups. Environmental signals likely to be involved in the timing and rate of senescence, such as variation in photoperiod and thermal time that occurred through the growing season were investigated. Interactions between individual environmental signals and senescence were difficult to separate. The majority of plants senesced consistently between replicate blocks, and rank order was mostly consistent across all years suggesting strong genotypic control of senescence. This study provides valuable information for the future optimisation of Miscanthus, and potentially other energy grasses, where new varieties are needed to maximise net energy yields and crop quality for different end uses in different global regions.     

甘肃莲花山血雉春夏季栖息地选择

2012年4~8月,在甘肃莲花山国家级自然保护区采用无线电遥测技术并结合野外观察,对血雉春季和夏季的栖息地特征进行了比较研究。逻辑斯蒂回归分析表明,雪深度、灌木盖度和距水源距离是影响血雉春季栖息地选择的主要因子;夏季血雉以乔木数量、灌木高度和坡向作为栖息地选择的主要因子。t检验和U检验结果表明:乔木胸径、针叶树数量、灌木高度、灌木盖度、苔藓盖度、草盖度在春、夏两个季节内差异极显著,而坡向在两个季节内差异显著。     

No Habitat Selection during Spring Migration at a Meso-Scale Range across Mosaic Landscapes: A Case Study with the Woodcock (Scolopax rusticola)

Success of migration in birds in part depends on habitat selection. Overall, it is still poorly known whether there is habitat selection amongst landbird migrants moving across landscapes. Europe is chiefly covered by agro-forestry mosaic landscapes, so migratory species associated to either agricultural landscapes or woodland habitats should theoretically find suitable stopover sites along migration. During migration from wintering to breeding quarters, woodcocks (Scolopax rusticola) tagged with PTT satellite-tracking transmitters were used to test for the hypothesis that migrants associated to agro-forest habitats have no habitat selection during migration, at a meso-scale level. Using a GIS platform we extracted at a meso-scale range habitat cover at stopover localities. Results obtained from comparisons of soil covers between points randomly selected and true stopover localities sites revealed, as expected, the species may not select for particular habitats at a meso-scale range, because the habitat (or habitats) required by the species can be found virtually everywhere on their migration route. However, those birds stopping over in places richer in cropland or mosaic habitats including both cropland and forest and with proportionally less closed forest stayed for longer than in areas with lower surfaces of cropland and mosaic and more closed forest. This suggests that areas rich in cropland or mosaic habitat were optimal.     

Long-Term Habitat Use by Mountain Gorillas (Gorilla gorilla beringei). 1. Consistency, Variation, and Home Range Size and Stability

Mountain gorillas are highly folivorous. Food is abundant and perennially available in much of their habitat. Still, limited research has shown that single gorilla groups heavily used areas where food biomass and quality were relatively high and where they met daily nutritional needs with relatively low foraging effort. Also, ecological factors influenced solitary males less than groups with females. Long-term data on habitat use by multiple mountain gorilla social units and more extensive data on variation in food distribution, presented here, confirm that food distribution influences areal occupation densities across groups and over time. These data also confirm the group/solitary male distinction and show that food distribution became more important for one male once he acquired females. Groups used 25 km ² , and inter-annual home range and core area overlap was often low. Annual home range and core area size varied considerably within groups and across years. It bore no simple relationship to group size and estimated group biomass. Core areas were biased samples of total home ranges and were relatively good foraging areas. One group abruptly shifted its home range in response to male mating competition. Home ranges of two others expanded from 1981 to 1987, though at a decreasing rate. Data on one such group, which varied considerably in size, are consistent with arguments that costs of scramble competition are low except in unusually large groups. Low site fidelity, low scramble costs, and high home range overlap should decrease the ecological costs of female transfer.     

Phenotypic Variation and Fitness in a Metapopulation of Tubeworms (Ridgeia piscesae Jones) at Hydrothermal Vents

We examine the nature of variation in a hot vent tubeworm, Ridgeia piscesae, to determine how phenotypes are maintained and how reproductive potential is dictated by habitat. This foundation species at northeast Pacific hydrothermal sites occupies a wide habitat range in a highly heterogeneous environment. Where fluids supply high levels of dissolved sulphide for symbionts, the worm grows rapidly in a “short-fat” phenotype characterized by lush gill plumes; when plumes are healthy, sperm package capture is higher. This form can mature within months and has a high fecundity with continuous gamete output and a lifespan of about three years in unstable conditions. Other phenotypes occupy low fluid flux habitats that are more stable and individuals grow very slowly; however, they have low reproductive readiness that is hampered further by small, predator cropped branchiae, thus reducing fertilization and metabolite uptake. Although only the largest worms were measured, only 17% of low flux worms were reproductively competent compared to 91% of high flux worms. A model of reproductive readiness illustrates that tube diameter is a good predictor of reproductive output and that few low flux worms reached critical reproductive size. We postulate that most of the propagules for the vent fields originate from the larger tubeworms that live in small, unstable habitat patches. The large expanses of worms in more stable low flux habitat sustain a small, but long-term, reproductive output. Phenotypic variation is an adaptation that fosters both morphological and physiological responses to differences in chemical milieu and predator pressure. This foundation species forms a metapopulation with variable growth characteristics in a heterogeneous environment where a strategy of phenotypic variation bestows an advantage over specialization.     

Relative Nitrogen Limitation at Steady-state Nutrition as a Determinant of Plasticity in Five Grassland Plant Species

Partitioning of biomass between roots and different shoot partshas often been used to explain the response of plants to variationsin resource availability. There are still many uncertaintiesin the importance of this trait for plant performance, and clearguidelines on how partitioning should be quantified in relationto growth rate and resource supply are of fundamental importancefor such an understanding. This paper reports an attempt toshow how plant nitrogen status relates to root:shoot partitioningand other plastic responses, in a manner that can be used forquantitative predictions. The reactions to nitrogen limitationof five grassland plant species, with different ecological demands,were compared. The species used were the forbs Polygala vulgarisand Crepis praemorsa, and the grasses Danthonia decumbens, Agrostiscapillaris and Dactylis glomerata. The experiment was conductedin a climate chamber where the plants were grown hydroponically(1) under non-limiting nutrient conditions and (2) at a steady-statenitrogen limitation, which enabled the plants to express halfof their growth potential. The relative growth rate (RGR) ofthe species was strongly related to plant nitrogen concentration(PNC) and leaf area ratio (LAR), whereas the effects on netassimilation rate (NAR) were very small. Despite large differencesin maximum relative growth rate, the species showed remarkablesimilarities in dry matter partitioning between root and shoot.It is concluded that root:shoot partitioning can be treatedas a direct function of the relative resource limitation ofthe plant. The difficulty of attaining well-defined levels ofresource limitation in soil, other solid substrates and manyhydroponic systems may be the most important reason for thedivergent results in earlier studies. Better knowledge of soil-rootinteractions, and plant responses to the whole span of resource-supplylevels, is required for a thorough understanding of how nutrientslimit growth. Copyright 1999 Annals of Botany Company Growth rate, plant strategies, plasticity, partitioning, biomass, nitrogen, nutrient limitation, grassland.     

Regional Variation in Parasite Species Richness and Abundance in the Introduced Range of the Invasive Lionfish,Pterois volitans

Parasites can play an important role in biological invasions. While introduced species often lose parasites from their native range, they can also accumulate novel parasites in their new range. The accumulation of parasites by introduced species likely varies spatially, and more parasites may shift to new hosts where parasite diversity is high. Considering that parasitism and disease are generally more prevalent at lower latitudes, the accumulation of parasites by introduced hosts may be greater in tropical regions. The Indo-Pacific lionfish (Pterois volitans) has become widely distributed across the Western Atlantic. In this study, we compared parasitism across thirteen locations in four regions, spanning seventeen degrees of latitude in the lionfish''s introduced range to examine potential spatial variation in parasitism. In addition, as an initial step to explore how indirect effects of parasitism might influence interactions between lionfish and ecologically similar native hosts, we also compared parasitism in lionfish and two co-occurring native fish species, the graysby grouper, Cephalopholis cruentata, and the lizardfish, Synodus intermedius, in the southernmost region, Panama. Our results show that accumulation of native parasites on lionfish varies across broad spatial scales, and that colonization by ectoparasites was highest in Panama, relative to the other study sites. Endoparasite richness and abundance, on the other hand, were highest in Belize where lionfish were infected by twice as many endoparasite species as lionfish in other regions. The prevalence of all but two parasite species infecting lionfish was below 25%, and we did not detect an association between parasite abundance and host condition, suggesting a limited direct effect of parasites on lionfish, even where parasitism was highest. Further, parasite species richness and abundance were significantly higher in both native fishes compared to lionfish, and parasite abundance was negatively associated with the condition index of the native grouper but not that of the lionfish or lizardfish. While two co-occurring native fishes were more heavily parasitized compared to lionfish in Panama any indirect benefits of differential parasitism requires further investigation. Future parasitological surveys of lionfish across the eastern coast of North America and the Lesser Antilles would further resolve geographic patterns of parasitism in invasive lionfish.     

Variation in Intergroup Relationships Among Species and Among and Within Local Populations of African Apes

International Journal of Primatology - Although many animals typically defend key resources from conspecifics during encounters, tolerant encounters also occur frequently in some primate species....     

Tissue Culture-Induced Heritable Genomic Variation in Rice,and Their Phenotypic Implications

Background

Somaclonal variation generally occurs in plants regenerated from tissue culture. However, fundamental issues regarding molecular characteristics, mutation rates and mutation spectra of plant somatic variation as well as their phenotypic relevance have been addressed only recently. Moreover, these studies have reported highly discrepant results in different plant species and even in the same plant genotype.

Methodology/principal findings

We investigated heritable genomic variation induced by tissue culture in rice by whole genome re-sequencing of an extensively selfed somaclonal line (TC-reg-2008) and its wild type (WT) donor (cv. Hitomebore). We computed the overall mutation rate, single nucleotide polymorphisms (SNPs), small scale insertions/deletions (Indels) and mobilization of transposable elements (TEs). We assessed chromosomal distribution of the various types of genomic variations, tested correlations between SNPs and Indels, and examined concomitancy between TE activity and its cytosine methylation states. We also performed gene ontology (GO) analysis of genes containing nonsynonymous mutations and large-effect mutations, and assayed effects of the genomic variations on phenotypes under both normal growing condition and several abiotic stresses. We found that heritable somaclonal genomic variation occurred extensively in rice. The genomic variations distributed non-randomly across each of the 12 rice chromosomes, and affected a large number of functional genes. The phenotypic penetrance of the genomic variations was condition-dependent.

Conclusions/significance

Tissue culture is a potent means to generate heritable genetic variations in rice, which bear distinct difference at least in space (chromosomal distribution) from those occurred under natural settings. Our findings have provided new information regarding the mutation rate and spectrum as well as chromosomal distribution pattern of somaclonal variation in rice. Our data also suggest that rice possesses a strong capacity to canalize genetic variations under normal growing conditions to maintain phenotypic robustness, which however can be released by certain abiotic stresses to generate variable phenotypes.     

Community-Level Physiological Profiles of Cloacal Microbes in Songbirds (Order: Passeriformes): Variation Due to Host Species, Host Diet, and Habitat

The relationship between microorganisms and birds has received increased attention recently. The state of knowledge of this relationship, however, is based largely on examination of sick or dead birds, and knowledge of the prevalence and community structure and function of microbes in healthy wild populations is limited. Using carbon substrate utilization profiles, microbial communities were examined in 91 cloacal samples from 14 species within apparently healthy summer and winter passerine populations. Within each season, gradient lengths and eigenvalues from ordination analyses suggested that many samples differed in their carbon substrate utilization and several had very different communities. Cloacal microbe carbon utilization profiles were distinguishable among host species, season-specific diet, and study site in the ordination analyses. However, these patterns were only observed for the analysis of the summer data set. The results of this study support the idea that the avian host’s microbial community, relative to carbon substrate utilization, is related to host diet. Previously, this pattern had only been reported for potential pathogens isolated from the avian cloaca. Study site–specific patterns in the ordination analysis suggest that environmental conditions at a particular study site may influence cloacal microbial communities in birds. Results of this study indicate that examination of community-level physiological profiles may be a useful technique for distinguishing among avian cloacal samples, similar to that already established for discriminating aqueous and soil samples. Future studies that correlate microbe physiological profiles to condition-based indices of avian hosts may be most useful for eventually using the profile as an indicator of environmental conditions experienced by hosts.