European common frog (Rana temporaria) recolonised Switzerland from multiple glacial refugia in northern Italy via trans- and circum-Alpine routes

The high mountain ranges of western Europe had a profound effect on the biotic recolonisation of Europe from glacial refugia. The Alps present a particularly interesting case because they form an absolute barrier to dispersal for most taxa, obstructing recolonisation from multiple refugia in northern Italy. Here we investigate the effect of the European Alps on the phylogeographic history of the European common frog Rana temporaria. Based on partial cytochrome b and COXI sequences from Switzerland, we find two mitochondrial lineages roughly north and south of the alpine ridge, with contact zones between them in eastern and western Switzerland. The northern haplogroup falls within the previously identified western European haplogroup, while the southern haplogroup is unique to Switzerland. We find that the lineages diverged ~110 kya, at approximately the onset of the last glacial glaciation; this indicates that they are from different glacial refugia. Phylogenetic analyses suggest that t...