Bank Voles in Southern Eurasia: Vicariance and Adaptation

Phylogeographic lineages are interpreted as the product of repeated isolation in glacial refugia, leading to vicariant differentiation. Being restricted to a given geographic area could also promote adaptive divergence in response to local conditions. The role of phylogeny and climate in the evolution of the bank vole (Myodes glareolus) was investigated here, focusing on molar tooth shape, a morphological feature related to the exploitation of food resources. A balanced role of phylogeny and climate was demonstrated. Response to environmental factors led to morphological convergence of bank voles from different lineages living in similar environments, and to within-lineage divergence in extreme environments. An important interaction of climate and phylogeny was found, suggesting that each lineage is living in a particular environment. This lineage-specific adaptation to a range of environmental conditions may have conditioned the potential of post-glacial recolonization of each lineage. Morphological covariation with environmental conditions further highlights the potential of adaptation of this species.