Find research datasets worth reusing

Fig. 5 in P e r s p e c t i v e Integrating current methods for the preservation of amphibian genetic resources and viable tissues to achieve best practices for species conservation

Fig. 5. Decision tree used for specimens euthanized to obtain tissue. Blue indicates steps in the decision tree. Green indicates procedures that will lead to preservation of tissues for genetic study. Purple indicates procedures that lead to achieving multiple goals, including cell culture and obtaining gametes for current or future ARTs. NOTE: Breeding and IVF can result in offspring that can be used for genetic purposes, thereby achieving multiple goals.

Fig. 6 in P e r s p e c t i v e Integrating current methods for the preservation of amphibian genetic resources and viable tissues to achieve best practices for species conservation

Fig. 6. Decision tree used to obtain tissue from live animals. Blue indicates steps in the decision tree. Green indicates procedures that will lead to preservation of tissues for genetic study. Purple indicates procedures that lead to achieving multiple goals, including obtaining gametes for current or future ARTs. NOTE: Breeding and IVF can result in offspring that can be used for genetic purposes, thereby achieving multiple goals.

Fig. 4 in P e r s p e c t i v e Integrating current methods for the preservation of amphibian genetic resources and viable tissues to achieve best practices for species conservation

Fig. 4. Length of time from cell culture initiation to freezing for amphibian cell lines in San Diego Zoo's Frozen Zoo®. Low = 19 days; high = 596 days; average = 154 days.

Fig. 3 in P e r s p e c t i v e Integrating current methods for the preservation of amphibian genetic resources and viable tissues to achieve best practices for species conservation

Fig. 3. The "tissue piecing" protocol used to preserve viable cells for establishment of cell lines in the future. A) Tissue is cut into long, thin strips. B) Tissue is diced into 1 mm3 fragments before adding medium containing 10% DMSO as a cryoprotectant. C) Prepared tissue is stored in LN2 until future cell culture is possible; those without cell culture capability can transport samples using a dry shipper to maintain cold-chain.

Fig. 2 in P e r s p e c t i v e Integrating current methods for the preservation of amphibian genetic resources and viable tissues to achieve best practices for species conservation

Fig. 2. Procedures used to obtain amphibian eggs or sperm for use in ARTs. A) Gravid female Leopard Frog (Lithobates sp.) after gonadotropic hormone injection. B) Expressing eggs into container by pressing on abdomen and pushing thumb toward cloaca; eggs can be fertilized (i.e., IVF) by fresh or cryopreserved sperm. Sperm can similarly be released from males by pushing towards the cloaca and releasing sperm naturally (in season) or after injection of gonadotropic hormones (e.g., HIS).

Fig. 1 in P e r s p e c t i v e Integrating current methods for the preservation of amphibian genetic resources and viable tissues to achieve best practices for species conservation

Fig. 1. Role of genetic resource collections in the research and conservation of amphibians. Green indicates the storage of tissues in biobanks. Purple indicates procedures associated with ARTs that lead to achieving multiple goals in amphibian research and conservation. Asterisk (*) denotes tissue or methodologies that are not currently used in ARTs but may be possible in the future. NOTE: For a more complete list of ARTs reference Clulow et al. (2014).

opencc-zeroJul 2020View details →

Data from: Multiple glacial refugia and contemporary dispersal shape the genetic structure of an endemic amphibian from the Pyrenees

Historical factors (colonization scenarios, demographic oscillations) and contemporary processes (population connectivity, current population size) largely contribute to shaping species' present-day genetic diversity and structure. In this study, we use a combination of mitochondrial and nuclear DNA markers to understand the role of Quaternary climatic oscillations and present-day gene flow dynamics in determining the genetic diversity and structure of the newt Calotriton asper (Al. Dugès, 1852), endemic to the Pyrenees. Mitochondrial DNA did not show a clear phylogeographic pattern and presented low levels of variation. In contrast, microsatellites revealed five major genetic lineages with admixture patterns at their boundaries. Approximate Bayesian computation analyses and linear models indicated that the five lineages likely underwent separate evolutionary histories and can be tracked back to distinct glacial refugia. Lineage differentiation started around the Last Glacial Maximum at three focal areas (western, central and eastern Pyrenees) and extended through the end of the Last Glacial Period in the central Pyrenees, where it led to the formation of two more lineages. Our data revealed no evidence of recent dispersal between lineages, whereas borders likely represent zones of secondary contact following expansion from multiple refugia. Finally, we did not find genetic evidence of sex-biased dispersal. This work highlights the importance of integrating past evolutionary processes and present-day gene flow and dispersal dynamics, together with multilocus approaches, to gain insights into what shaped the current genetic attributes of amphibians living in montane habitats.

opencc-zeroAug 2020View details →

The roles of climate, geography and natural selection as drivers of genetic and phenotypic differentiation in a widespread amphibian Hyla annectans (Anura: Hylidae)

The role of geological events and Pleistocene climatic fluctuations as drivers of current patterns of genetic variation in extant species has been a topic of continued interest among evolutionary biologists. Nevertheless, comprehensive studies of widely distributed species are still rare, especially from Asia. Using geographically extensive sampling of many individuals and a large number of nuclear single nucleotide polymorphisms (SNPs), we studied the phylogeography and historical demography of Hyla annectans populations in southern China. Thirty-five sampled populations were grouped into seven clearly defined genetic clusters that closely match phenotype-based subspecies classification. These lineages diverged 2.32–5.23 million years ago, a timing that closely aligns with the rapid and drastic uplifting of the Qinghai-Tibet Plateau and adjacent southwest China. Demographic analyses and species distribution models indicate that different populations of this species have responded differently to past climatic changes. In the Hengduan Mountains, most populations experienced a bottleneck, whereas the populations located outside of the Hengduan Mountains have gradually declined in size since the end of the last glaciation. In addition, the levels of phenotypic and genetic divergence were strongly correlated across major clades. These results highlight the combined effects of geological events and past climatic fluctuations, as well as natural selection, as drivers of contemporary patterns of genetic and phenotypic variation in a widely distributed anuran in Asia.

opencc-zeroSep 2020View details →

Data from: Landscape genetics reveals unique and shared effects of urbanization for two sympatric pool-breeding amphibians

Metapopulation-structured species can be negatively affected when landscape fragmentation impairs connectivity. We investigated the effects of urbanization on genetic diversity and gene flow for two sympatric amphibian species, spotted salamanders (Ambystoma maculatum) and wood frogs (Lithobates sylvaticus), across a large (>35,000 km2) landscape in Maine, USA, containing numerous natural and anthropogenic gradients. Isolation by distance (IBD) patterns differed between the species. Spotted salamanders showed a linear and relatively high variance relationship between genetic and geographic distance (r = 0.057; p < 0.001); whereas, wood frogs exhibited a strongly non-linear and lower variance relationship (r = 0.429; p < 0.001). Scale dependence analysis of IBD found gene flow has its most predictable influence (strongest IBD correlations) at distances up to 9 km for spotted salamanders and up to 6 km for wood frogs. Estimated effective migration surfaces revealed contrasting patterns of high and low genetic diversity and gene flow between the two species. Population isolation, quantified as the mean IBD residuals for each population, was associated with local urbanization and less genetic diversity in both species. The influence of geographic proximity and urbanization on population connectivity was further supported by distance-based redundancy analysis and multiple matrix regression with randomization. Resistance surface modelling found interpopulation connectivity to be influenced by developed land cover, light roads, interstates, and topography for both species, plus secondary roads and rivers for wood frogs. Our results highlight the influence of anthropogenic landscape features within the context of natural features and broad spatial genetic patterns, in turn supporting the premise that while urbanization significantly restricts interpopulation connectivity for wood frogs and spotted salamanders, specific landscape elements have unique effects on these two sympatric species.

opencc-zeroNov 2020View details →

Predicting amphibian intraspecific diversity with machine learning: Challenges and prospects for integrating traits, geography, and genetic data

The growing availability of genetic datasets, in combination with machine learning frameworks, offer great potential to answer long-standing questions in ecology and evolution. One such question has intrigued population geneticists, biogeographers, and conservation biologists: What factors determine intraspecific genetic diversity? This question is challenging to answer because many factors may influence genetic variation, including life history traits, historical influences, and geography, and the relative importance of these factors varies across taxonomic and geographic scales. Furthermore, interpreting the influence of numerous, potentially correlated variables is difficult with traditional statistical approaches. To address these challenges, we analyzed repurposed data using machine learning and investigated predictors of genetic diversity, focusing on Nearctic amphibians as a case study. We aggregated species traits, range characteristics, and >42,000 genetic sequences for 299 species using open-access scripts and various databases. After identifying important predictors of nucleotide diversity with random forest regression, we conducted follow-up analyses to examine the roles of phylogenetic history, geography, and demographic processes on intraspecific diversity. Although life history traits were not important predictors for this dataset, we found significant phylogenetic signal in genetic diversity within amphibians. We also found that salamander species at northern latitudes contain lower genetic diversity. Data repurposing and machine learning provide valuable tools for detecting patterns with relevance for conservation, but concerted efforts are needed to compile meaningful datasets with greater utility for understanding global biodiversity.

opencc-zeroDec 2017View details →

Data from: Landscape genetic inferences vary with sampling scenario for a pond breeding amphibian

A critical decision in landscape genetic studies is whether to use individuals or populations as the sampling unit. This decision affects the time and cost of sampling and may affect ecological inference. We analyzed 334 Columbia spotted frogs at 8 microsatellite loci across 40 sites in northern Idaho to determine how inferences from landscape genetic analyses would vary with sampling design. At all sites, we compared a proportion available sampling scheme (PASS), in which all samples were used, to resampled datasets of 2-11 individuals. Additionally, we compared a population sampling scheme (PSS) to an individual sampling scheme (ISS) at 18 sites with sufficient sample size. We applied an information theoretic approach with both restricted maximum likelihood and maximum likelihood estimation to evaluate competing landscape resistance hypotheses. We found that PSS supported a low-density forest model (0.87) and ISS supported this model as well as additional models when testing hypotheses of landcover types that create the greatest resistance to gene flow for Columbia spotted frogs. Increased sampling density and study extent, seen by comparing PSS to PASS, showed a change in model support from a model of only low-density forest to a model of only high-density forest. As number of individuals increased, model support converged at 7 individuals for ISS to PSS. ISS may be useful to increase study extent and sampling density, but may lack power to provide strong support for the correct model with microsatellite datasets. Our results highlight the importance of additional research on sampling design effects on landscape genetics inference.

opencc-zeroJan 2024View details →

Supplementary material: Machine learning and phylogenetic models identify predictors of genetic variation in Neotropical amphibians

Aim: Intraspecific genetic variation is key for adaptation and survival in changing environments and is known to be influenced by many factors, including population size, dispersal, and life history traits. We investigated genetic variation within Neotropical amphibian species to provide insights into how natural history traits, phylogenetic relatedness, climatic, and geographic characteristics can explain intraspecific genetic diversity. Location: Neotropics. Taxon: Amphibians. Methods: We assembled datasets using open-access databases for natural history traits, genetic sequences, phylogenetic trees, climatic, and geographic data. For each species, we calculated overall nucleotide diversity (π) and tested for isolation by distance (IBD) and isolation by environment (IBE). We then identified predictors of π, IBD, and IBE using Random Forest (RF) regression or RF classification. We also fitted phylogenetic generalized linear mixed models (PGLMMs) to predict π, IBD, and IBE. Results: We compiled 4,052 mitochondrial DNA sequences from 256 amphibian species (230 frogs and 26 salamanders), georeferencing 2,477 sequences from 176 species that were not linked to occurrence data. RF regressions and PGLMMs were congruent in identifying range size and precipitation (σ) as the most important predictors of π, influencing it positively. RF classification and PGLMMs identified minimum elevation as an important predictor of IBD; most species without IBD tended to occur at higher elevations. Maximum latitude and precipitation (σ) were the best predictors of IBE, and most species without IBE occur at lower latitudes and in areas with more variable precipitation. Main conclusions: This study identified predictors of genetic variation in Neotropical amphibians using both machine learning and phylogenetic methods. This approach was valuable to determine which predictors were congruent between methods. We found that species with small ranges or living in zones with less variable precipitation tended to have low genetic diversity. We also showed that Western Mesoamerica, Andes, and Atlantic Forest biogeographic units harbor high diversity across many species that should be prioritized for protection. These results could play a key role in the development of conservation strategies for Neotropical amphibians.

opencc-zeroMar 2024View details →

Genetic insight into a polygenic trait using a novel Genome Wide Association approach in a wild amphibian population

Body size variation is central in the evolution of life history traits in amphibians, but the underlying genetic architecture of this complex trait is still largely unknown. Herein, we studied the genetic basis of body size and fecundity of the alternative morphotypes in a wild population of the Greek smooth newt (Lissotriton graecus). By combining a Genome-wide association approach with linkage disequilibrium network analysis, we were able to identify clusters of highly correlated loci thus maximizing sequence data for downstream analysis. The putatively associated variants explained 12.8% to 44.5% of the total phenotypic variation in body size and were mapped to genes with functional roles in the regulation of gene expression and cell cycle processes. Our study is the first to provide insights into the genetic basis of complex traits in newts and provides a useful tool to identify loci potentially involved in fitness related traits in small data sets from natural populations in non-model species.

opencc-zeroMar 2022View details →

Reduced genetic diversity associated with the northern expansion of an amphibian species with high habitat-specialization, Ascaphus truei, resolved using two types of genetic markers

Reconstruction of historical relationships between geographic regions within a species' range can indicate dispersal patterns and help predict future responses to shifts in climate. Ascaphus truei (coastal tailed frog) is an indicator species of the health of forests and perennial streams in the Coastal and Cascade Mountains of the Pacific Northwest of North America. We used two genetic techniques — microsatellite and genotype-by-sequencing (GBS) — to compare the within region genetic diversity of populations near the northern extent of the species' range (British Columbia, Canada) to two geographic regions in British Columbia and two in Washington, USA, moving towards the core of the range. Allelic richness and heterozygosity declined substantially as latitude increased. The northernmost region had the lowest mean expected heterozygosities for both techniques (microsatellite, M = 0.20, SE = 0.080; GBS, M = 0.025, SE = 0.0010) and the southernmost region had the highest (microsatellite, M = 0.88, SE = 0.054; GBS, M = 0.20, SE = 0.0029). The northernmost regions (NC and MC) clustered together in population structure models for both genetic techniques. Our discovery of reduced diversity may have important conservation and management implications for population connectivity and the response of A. truei to climate change.

opencc-zeroAug 2022View details →

Determinants of genetic diversity and species richness of North American amphibians

Aim: Ecological limits on population sizes and the number of species a region can sustain are thought to simultaneously produce spatial patterns in population genetic diversity and species richness due to the effects of random drift operating in parallel across population and community levels. Here, we test the extent to which resource-based environmental limits jointly determine these patterns of biodiversity in amphibians. Location: North America. Taxon: Amphibians. Methods: We repurposed open, raw microsatellite data from 19 species sampled at 554 sites in North America and mapped nuclear genetic diversity at the continental scale. We then tested whether ecological limits defined by resource availability and environmental heterogeneity could simultaneously shape biogeographic patterns in genetic diversity and species richness with structural equation modeling. Results: Spatial patterns of population genetic diversity run opposite patterns of species richness and genetic differentiation. However, while measures of resource availability and niche heterogeneity predict 89% of the variation in species richness, these landscape metrics were poor predictors of genetic diversity. Main conclusions: Although heterogeneity appears to be an important driver of genetic and species biodiversity patterns in amphibians, variation in genetic diversity both within and across species makes it difficult to infer general processes producing spatial patterns of amphibian genetic diversity. This result differs from those found in endotherms and may be due to the considerable life history variation found across amphibians.