A peripheral view: post‐glacial history and genetic diversity of an amphibian in northern landscapes

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AbstractAimWhere post‐glacial colonization and founder events are numerous, peripheral populations tend to have reduced genetic diversity as compared to their centrally located counterparts. Such decrease in genetic variability can limit their potential to adapt to changes in their environment. At northern latitudes for instance, populations are often living in conditions close to their physiological limits. Thus, identifying the levels of genetic diversity in peripheral populations is key to estimating the potential for adaptation to ongoing environmental change. In this context, we investigated the distribution of genetic diversity at the northern edge of the wood frog's (Lithobates sylvaticus) range by reconstructing its post‐glacial history in an area where phylogeographical data were lacking.LocationJames Bay area (north‐central Canada).MethodsDNAwas extracted from 463 wood frog tissue samples from 17 localities. Seven microsatellite loci were used to quantify genetic diversity and evaluate genetic structure through estimates of the fixation index, isolation‐by‐distance analyses and Bayesian clustering algorithms (tessandstructure). Phylogeographical relationships were investigated using single nucleotide polymorphisms in theND2/tRNATRPmitochondrial genes. Phylogenetic trees were built using the neighbour‐joining and the maximum likelihood inference methods implemented inmega5.ResultsOur analyses identified a contact zone between two colonizing lineages originating from one glacial refugium. Populations in this contact zone present sympatrically distributed haplotypes from both lineages and higher genetic variation than the surrounding populations. Population structure analyses revealed the differentiation of three genetic clusters, each covering large areas around the coast of James Bay.Main conclusionsOur study suggests that higher than expected genetic diversity and gene flow may be present in peripheral populations. Such adaptive potential is critical in areas of upcoming development and environmental changes. Thus, our study emphasizes the importance of understanding species post‐glacial history for the prediction of future evolutionary trends and species distributions.