筛选
科学数据
统计数据
共检索到31834条 ,权限内显示50条;
Data from: Cryptic diversity and discordance in single-locus species delimitation methods within horned lizards (Phrynosomatidae: Phrynosoma)
- 负责人：
- DOI：
- doi:10.5061/dryad.r7989
- 摘要：
- Biodiversity reduction and loss continues to progress at an alarming rate, and thus there is widespread interest in utilizing rapid and efficient methods for quantifying and delimiting taxonomic diversity. Single-locus species-delimitation methods have become popular, in part due to the adoption of the DNA barcoding paradigm. These techniques can be broadly classified into tree-based and distance-based methods depending on whether species are delimited based on a constructed genealogy. Although the relative performance of these methods has been tested repeatedly with simulations, additional studies are needed to assess congruence with empirical data. We compiled a large data set of mitochondrial ND4 sequences from horned lizards (Phrynosoma) to elucidate congruence using four tree-based (single-threshold GMYC, multiple-threshold GMYC, bPTP, mPTP) and one distance-based (ABGD) species delimitation models. We were particularly interested in cases with highly uneven sampling and/or large differences in intraspecific diversity. Results showed a high degree of discordance among methods, with multiple-threshold GMYC and bPTP suggesting an unrealistically high number of species (29 and 26 species within the P. douglasii complex alone). The single-threshold GMYC model was the most conservative, likely a result of difficulty in locating the inflection point in the genealogies. mPTP and ABGD appeared to be the most stable across sampling regimes and suggested the presence of additional cryptic species that warrant further investigation. These results suggest that the mPTP model may be preferable in empirical data sets with highly uneven sampling or large differences in effective population sizes of species.
Data from: Occupancy models for citizen-science data
- 负责人：
- DOI：
- doi:10.5061/dryad.rq9453m
- 摘要：
- 1. Large-scale citizen science projects, such as atlases of species distribution, are an important source of data for macroecological research, for understanding the effects of climate change and other drivers on biodiversity, and for more applied conservation tasks, such as early-warning systems for biodiversity loss. 2. However, citizen-science data are challenging to analyse because the observation process has to be taken into account. Typically, the observation process leads to heterogeneous and non-random sampling, false absences, false detections and spatial correlations in the data. Increasingly, occupancy models are being used to analyse atlas data. 3. We advocate a dual approach to strengthen inference from citizen science data for the questions the programme is intended to address. 1) the survey design should be chosen with a particular set of questions and associated analysis strategy in mind and 2) the statistical methods should be tailored not only to those questions, but also to the specific characteristics of the data. 4. We review the consequences of particular survey design choices that typically need to be made in atlas-style citizen science projects. These include spatial resolution of the sampling units, allocation of effort in space, and collection of information about the observation process. On the analysis side, we review extensions of the basic occupancy models that are frequently necessary with atlas data, including methods for dealing with heterogeneity, non-independent detections, false detections and violation of the closure assumption. 5. New technology, such as cell phone apps and fixed remote detection devices, are revolutionizing citizen science projects. There is an opportunity to maximise the usefulness of the resulting data sets if the protocols are rooted in robust statistical designs and data analysis issues are being considered. Our review provides guidelines for designing new projects and an overview of the current methods that can be used to analyse data from such projects.
Data from: Failure to coordinate management in transboundary populations hinders the achievement of national management goals: the case of wolverines in Scandinavia
- 负责人：
- DOI：
- doi:10.5061/dryad.rd300kf
- 摘要：
- 1. Large carnivores are expanding in Europe, and their return is associated with conflicts that often result in policies to regulate their population size through culling. Being wide-ranging species, their populations are often distributed across several jurisdictions, which may vary in the extent to which they use lethal control. This creates the conditions for the establishment of source-sink dynamics across borders, which may frustrate the ability of countries to reach their respective management objectives. 2. To explore the consequences of this issue, we constructed a vec-permutation projection model, applied to the case of wolverines in south-central Scandinavia, shared between Norway (where they are culled) and Sweden (where they are protected). We evaluated the effect of compensatory immigration on wolverine population growth rates, and if the effect was influenced by the distance to the national border. We assessed to what extent compensatory immigration had an influence on the number of removals needed to keep the population at a given growth rate. 3. In Norway the model estimated a stable trend, whereas in Sweden it produced a 10% annual increase. The effect of compensatory immigration corresponded to a 0.02 reduction in population growth rate in Sweden and to a similar increase in Norway. This effect was stronger closer to the Norwegian-Swedish border, but weak when moving away from it. An average of 33 wolverines were shot per year in the Norwegian part of the study area. If no compensatory immigration from Sweden had occurred, 28 wolverines shot per year would have been sufficient to achieve the same goal. About 15.5% of all the individuals harvested in Norway between 2005-2012 were compensated for by immigrants, causing a decrease in population growth rate in Sweden. 4. Synthesis and applications. When a population is transboundary, the consequences of management decisions are also transboundary, even though the political bodies in charge of those decisions, the stakeholders who influence them, and the taxpayers who finance them are not. It is important that managers and citizens be informed that a difference in management goals can reduce the efficiency, and increase the costs, of wildlife management.
Data from: Territorial males can sire more offspring in nests with smaller doors in the cichlid Lamprologus lemairii
- 负责人：
- DOI：
- doi:10.5061/dryad.rd47d
- 摘要：
- To examine how territorial males counter reproductive parasites, we examined the paternity of broods guarded by territorial males using 5 microsatellite loci and factors that determine siring success in a wild population of the Lake Tanganyika cichlid Lamprologus lemairii. Females enter rock holes (nests) and spawn inside, and territorial males release milt over the nest openings. Sneakers attempt to dart into the nests, but territorial males often interrupt the attempt. The body size of territorial males (territorial defense ability) and the size of nest opening (the ability to prevent sneakers from nest intrusions) are predicted to be factors that affect paternity at the premating stage, whereas milt quality traits are factors that affect paternity at the postmating stage. Parentage analyses of 477 offspring revealed that most clutches have few or no cuckolders, and territorial males sired >80% of eggs in 7 of the 10 analyzed clutches. Larger territorial males that spawned in nests with narrower openings had greater siring success. In contrast, none of the milt traits affected the siring success. These suggest that territorial male L. lemairii adopt premating strategies whereby they effectively prevent reproductive parasitism.
Data from: Comparing the prediction of joint species distribution models with respect to characteristics of sampling data
- 负责人：
- DOI：
- doi:10.5061/dryad.rd55f
- 摘要：
- Biotic interactions have been rarely included in traditional species distribution models, wherein Joint Species Distribution Models (JSDMs) emerge as a feasible approach to incorporate environmental factors and interspecific interactions simultaneously, making it a powerful tool for analyzing the structure and assembly processes of biotic communities. However, the predictability and statistical robustness of JSDMs are largely unknown because of the lack of research efforts for those newly developed models. This study systematically evaluated the performances of five JSDMs in predicting the occurrence and biomass of multiple species, with a particular focus on diverse characteristics of sampling data, including type of response variables, number of sampling sites, and the number of species included in models. In general, most models yielded satisfactory performances on fitting to observed data and on the estimation of environmental effects; however, they showed less well performances in evaluating species associations, and their predictability had large variations. The JSDMs showed inconsistent performances between the goodness-of-fit and predictability in cross-validation, and the Boral model was relatively robust than others. The predictability of JSDMs was less influenced by sample sizes and substantially improved by incorporating rare species. This study contributes to an appropriate model selection and application of JSDMs.
Data from: Horizontal transfer of facultative endosymbionts is limited by host relatedness
- 负责人：
- DOI：
- doi:10.5061/dryad.rd71s
- 摘要：
- Heritable microbial symbionts can have important effects on many aspects of their hosts’ biology. Acquisition of a novel symbiont strain can provide fitness benefits to the host, with significant ecological and evolutionary consequences. We measured barriers to horizontal transmission by artificially transferring facultative symbionts from the grain aphid, Sitobion avenae, and five other aphid species into two clonal genotypes of S. avenae. We found the symbiont Hamiltonella defensa establishes infections more easily following a transfer from the same host species and that such infections are more stable. Infection success was also higher when the introduced symbiont strain was more closely related to the strain that was originally present in the host (but which had previously been removed). There were no differences amongst successfully established symbiont strains in their effect on aphid fecundity. H. defensa did not confer protection against parasitoids in our S. avenae clones, although it often does in other aphid hosts. However, strains of the symbiont Regiella insecticola originating from two host species protected grain aphids against the pathogenic fungus Pandora neoaphidis. This study helps describe the extent to which facultative symbionts can act as a pool of adaptations that can be sampled by their eukaryote hosts.
Data from: Out in the cold and sick: low temperatures and fungal infections impair a frog's skin defenses
- 负责人：
- DOI：
- doi:10.5061/dryad.rd736bd
- 摘要：
- Amphibians worldwide continue to battle an emerging infectious disease, chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd). Southern leopard frogs, Rana sphenocephala, are known to become infected with this pathogen, yet they are considered 'of least concern' for declines due to chytridiomycosis. Previous studies have shown that R. sphenocephala secretes four antimicrobial peptides (AMPs) onto their skin which may play an important role in limiting susceptibility to chytridiomycosis. Here we examined the (1) effects of temperature and AMP depletion on infections with Bd and (2) effects of temperature and Bd infection on the capacity to secrete AMPs in juvenile leopard frogs. Pathogen burden and mortality were greater in frogs exposed to Bd at low temperature but did not increase following monthly AMP depletion. Both low temperature and Bd exposure reduced the capacity of juvenile frogs to restore peptides after monthly depletions. Frogs held at 14°C were poorly able to restore peptides in comparison with those at 26°C. Frogs held at 26°C were better able to restore their peptides, but when exposed to Bd, this capacity was significantly reduced. These results strongly support the hypothesis that both colder temperatures and Bd infections impair the capacity of juvenile frogs to produce and secrete AMPs, an important component of their innate defense against chytrid fungi and other pathogens. Thus, in the face of unpredictable climate changes and enzootic pathogens, assessments of disease risk should consider the potential for effects of environmental variation and pathogen exposure on the quality of host defenses.
Data from: A conifer–angiosperm divergence in the growth vs shade tolerance trade-off underlies the dynamics of a New Zealand warm-temperate rain forest
- 负责人：
- DOI：
- doi:10.5061/dryad.rf025
- 摘要：
- 1. A central tenet of forest ecology is that succession and regeneration dynamics are driven by an interspecific trade-off between juvenile growth rates in high light and shade tolerance. There is evidence, however, that a single trade-off axis may fail to explain the dynamics of mixed conifer-angiosperm rainforests in the southern hemisphere, especially in New Zealand. 2. We tested for growth vs shade tolerance trade-offs by measuring juvenile growth of five podocarps and five broadleaved canopy angiosperms across a wide range of light environments in a New Zealand warm-temperate rainforest. The light compensation point of growth was used as a measure of species light requirements, which we then compared with height growth in 10% light, approximating the environments encountered beneath small tree-fall gaps. 3. Despite considerable overlap between the ranges of both growth rates and compensation points found in the two lineages, major axis tests showed that the growth vs shade tolerance trade-off differed significantly between podocarp and angiosperm species. At a common compensation point, angiosperms were faster-growing than podocarps in 10% light. However, juveniles of these angiosperm species were notably scarce in the more open environments associated with forest margins. 4. Synthesis. A conifer–angiosperm divergence in the growth vs shade tolerance trade-off may explain long-standing problems of the dynamics of these forests. Although juveniles of most lowland podocarps can tolerate considerable shade, the more vigorous response of broadleaved angiosperms to small canopy openings enables them to out-compete podocarps in old-growth stands. The greater abundance of podocarp juveniles on forest margins cannot be attributed to them outcompeting angiosperm species where light is abundant, and is likely to reflect superior resistance to frost and/or drought. The drivers of the dynamics of New Zealand's podocarp–broadleaved forests therefore differ appreciably from those ascribed to tropical and north-temperate forests.
Data from: Using a forest dynamics model to link community assembly processes and traits structure
- 负责人：
- DOI：
- doi:10.5061/dryad.rf551
- 摘要：
- 1. Trait-based approaches have been increasingly used to understand the role of environmental and biotic filters on species assembly. However, our understanding of the relationships between traits and community assembly processes remain limited. Indeed, various assembly processes may lead to similar functional patterns, and the effects of a given process may vary with the considered traits. Especially, competition can result in trait divergence or convergence depending on whether the trait is related to niche differences or to species’ competitive abilities. 2. In this study, we used a process-based forest gap-model to explore the effect of environmental and biotic assembly processes on the functional diversity of tree communities along a productivity gradient of 11 sites across central Europe. In a simulation experiment, we (i) disentangled the effects of environmental and biotic filtering on community structure, and (ii) tested whether competition resulted in trait divergence or convergence. 3. Our results confirmed the expected decrease in species richness with decreasing site fertility. We detected environmental filtering for traits related to both species environmental requirements and species competitive ability, highlighting that environmental trait filtering can affect all aspects of tree life-history strategies. 4. We observed convergence of traits related to growth and light capture resulting from competition for light, suggesting that tree species assembly is mainly driven by differences in competitive abilities. Additionally, the observed trait convergence was stronger in more productive sites than in less fertile ones, reflecting the impact of environmental conditions on competitive interactions. 5. Synthesis. Our study shows that process-based forest models can help to test whether functional traits composition reveal the signature of community assembly processes. This process-based approach challenges the classical view on the links between traits and mechanisms driving community assembly.
Data from: Cold adaptation in the Asian tiger mosquito’s native range precedes its invasion success in temperate regions
- 负责人：
- DOI：
- doi:10.5061/dryad.rb0qk13
- 摘要：
- Adaptation to environmental conditions within the native range of exotic species can condition the invasion success of these species outside their range. The striking success of the Asian tiger mosquito, Aedes albopictus, to invade temperate regions has been attributed to the winter survival of diapause eggs in cold environments. In this study, we evaluate genetic polymorphisms (SNPs) and wing morphometric variation among three biogeographical regions of the native range of A. albopictus. Reconstructed demographic histories of populations show an initial expansion in Southeast Asia and suggest that marine regression during late Pleistocene and climate warming after the last glacial period favored expansion of populations in southern and northern regions respectively. Searching for genomic signatures of selection, we identified significantly differentiated SNPs among which several are located in or within 20kb distance from candidate genes for cold adaptation. These genes involve cellular and metabolic processes and several of them have been shown to be differentially expressed under diapausing conditions. The three biogeographical regions also differ for wing size and shape, and wing size increases with latitude supporting Bergmann’s rule. Adaptive genetic and morphometric variation observed along the climatic gradient of A. albopictus native range suggests that colonization of northern latitudes promoted adaptation to cold environments prior to its worldwide invasion.
