Adaptive evolution during an ongoing range expansion: the invasive bank vole (Myodes glareolus) in Ireland.

Range expansions are extremely common, but have only recently begun to attract attention in terms of their genetic consequences. As populations expand, demes at the wave front experience strong genetic drift, which is expected to reduce genetic diversity and potentially cause 'allele surfing', where alleles may become fixed over a wide geographic area even if their effects are deleterious. Previous simulation models show that range expansions can generate very strong selective gradients on dispersal, reproduction, competition and immunity. To investigate the effects of range expansion on genetic diversity and adaptation, we studied the population genomics of the bank vole (Myodes glareolus) in Ireland. The bank vole was likely introduced in the late 1920s and is expanding its range at a rate of Ì´2.5 km yr-1. Using Genotyping by Sequencing (GBS), we genotyped 281 bank voles at 5,979 SNP loci. Fourteen sample sites were arranged in three transects running from the introduction site to the...