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

Abstract

Aim Where 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. Location James Bay area (north‐central Canada). Methods DNA was 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 (tess and structure). Phylogeographical relationships were investigated using single nucleotide polymorphisms in the ND2/tRNATRP mitochondrial genes. Phylogenetic trees were built using the neighbour‐joining and the maximum likelihood inference methods implemented in mega5. Results Our 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 conclusions Our 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.

Ancient female philopatry, asymmetric male gene flow, and synchronous population expansion support the influence of climatic oscillations on the evolution of South American sea lion (Otaria flavescens)

“…After Bonferroni corrections, only three loci deviated from HWE but they were not consistent between populations ( S4 Table in Appendix for details). Overall, only 6% of within populations locus pairs demonstrated significant linkage disequilibrium ( P <0.05) ( S4 Table in Appendix), but again these were not consistent, indicating low multilocus interactions [ 61 ]. Since the deviations were not consistent across most loci and populations, we did not exclude any loci from the analyses.…”

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

“…Studies on the northern range expansion of amphibians in western North America were often focused in and near the United States or used low‐resolution genetic markers (Dudaniec et al, 2012; Goebel et al, 2009; Kuchta & Tan, 2005; Metzger et al, 2015; Nielson et al, 2006; Pelletier et al, 2015; Pelletier & Carstens, 2016; Recuero et al, 2006; Ripplinger & Wagner, 2004). The studies that have included geographic regions well north of the southern fringe of the LGM often focused on species with broad distributions or variable habitat requirements (D'Aoust‐Messier & Lesbarrères, 2015; Goebel et al, 2009; Lee‐Yaw & Irwin, 2012; Lee‐Yaw et al, 2008).…”

“…Studying populations established following major climatic shifts helps us understand the historical processes that influenced a species’ current geographic distribution. Populations colonized because of dispersal during northern range expansion after the Last Glacial Maximum (LGM), around 25,000 years ago, will likely have experienced more genetic drift than populations in ice‐free habitats, resulting in lower genetic diversity due to founder or bottleneck effects (D'Aoust‐Messier & Lesbarrères, 2015; Eckert et al, 2008; Sagarin & Gaines, 2002; Shafer et al, 2010). However, in areas colonized from multiple refugia, populations may have higher than expected genetic diversities (Petit et al, 1998).…”