Using genetic variation to infer associations with climate in the common frog, Rana temporaria

Recent and historical species' associations with climate can be inferred using molecular markers. This knowledge of population and species-level responses to climatic variables can then be used to predict the potential consequences of ongoing climate change. The aim of this study was to predict responses of Rana temporaria to environmental change in Scotland by inferring historical and contemporary patterns of gene flow in relation to current variation in local thermal conditions. We first inferred colonization patterns within Europe following the last glacial maximum by combining new and previously published mitochondrial DNA sequences. We found that sequences from our Scottish samples were identical to (92%), or clustered with, the common haplotype previously identified from Western Europe. This clade showed very low mitochondrial variation, which did not allow inference of historical colonization routes but did allow interpretation of patterns of current fine-scale population structure without consideration of confounding historical variation. Second, we assessed fine-scale microsatellite-based patterns of genetic variation in relation to current altitudinal temperature gradients. No population structure was found within altitudinal gradients (average FST=0.02), despite a mean annual temperature difference of 4.5 °C between low- and high-altitude sites. Levels of genetic diversity were considerable and did not vary between sites. The panmictic population structure observed, even along temperature gradients, is a potentially positive sign for R. temporaria persistence in Scotland in the face of a changing climate. This study demonstrates that within taxonomic groups, thought to be at high risk from environmental change, levels of vulnerability can vary, even within species.