Metapopulation genetic structure in the water vole, Arvicola terrestris, in NE Scotland

The genetic structure of nine colonies of the water vole, Arvicola terrestr is, in one area of NE Scotland was studied. Non-destructive samples from 47 8 individuals (mostly immature animals) were typed for 12 microsatellites. Cases of Hardy-Weinberg disequilibrium were frequent within all colonies. T he five colonies ill the inland part of the study area also showed frequent cases of linkage disequilibrium. All colonies showed high levels of geneti c diversity (unbiased H=0.52-0.74). All five colonies sampled in successive years showed significant annual changes in genetic composition.,All coloni es showed genetic differentiation from each other, whether measured by aver age theta, pairwise theta or pairwise Nei's genetic distance. The spatial p attern of genetic differentiation was consistent with either a stepping-sto ne model over the whole study area or an island model within the coastal an d inland parts and art intervening barrier to gene flow. The study suggeste d that the genetic structure of colonies of A. terrestris often departs fro m the equilibrium states assumed by traditional methods for the study of ge ne flow, and that a parentage-based approach Mould be fruitful. (C) 1999 Th e Linnean Society of London.