Genetic structure of bank vole populations in the contact zone of two lineages in north-eastern Poland

The genetic structure of rodent populations may reflect their glacial and postglacial history. We studied the genetic structure of bank vole Myodes glareolus populations in north-eastern Poland, where two divergent mtDNA lineages met in the secondary contact zone. We investigated 441 specimens from 24 local populations using 10 microsatellite loci. We detected two clusters according to STRUCTURE and three genetic clusters in Geneland analysis. The observed spatial pattern of those groups was concordant with previously described distribution of mtDNA lineages in the area. The width of the transition zone between the genetic groups varied from 2.3 to 180.2 km in various parts of the study area. The observed genetic structure and the localization of range borders between the detected genetic clusters in the western part of study area were correlated with open, deforested habitats, which may have suppressed gene flow between the clusters.