The colonization of Ireland by mammals has been the subject of extensive study using genetic methods and forms a central problem in understanding the phylogeography of European mammals after the Last Glacial Maximum. Ireland exhibits a de-pauperate mammal fauna relative to Great Britain and continental Europe, and a range of natural and anthropogenic processes have given rise to its modern fauna. Previous Europe-wide surveys of the European badger (Meles meles) have found conflicting microsatellite and mitochondrial DNA evidence in Irish populations, suggesting Irish badgers have arisen from a combination of populations with close relationships in Great Britain and in Scandinavia, and admixture between recently introduced and longer established populations. The extent and history of contact between British and Irish badger populations, however, remains unclear.  We use comprehensive genetic data from Great Britain and Ireland to demonstrate that badgers in Ireland’s northeastern and southeastern counties are genetically similar to contemporary British populations.  Simulation analyses suggest this admixed population arose in Ireland 600-700 (CI 100-2600) years before the present most likely through the introduction of British badgers by people. These findings add to our knowledge of the complex colonization history of Ireland by mammals, and the central role of humans in facilitating it.

Tissue samples (muscle) from badgers were collected from ongoing road traffic accident tuberculosis surveys in Northern Ireland and badger culling in the Republic of Ireland.

DNA was extracted and subjected to genotyping of 14 microsatellite markers using capillary gel electrophoresis.

Genotype data was analysed using STRUCTURE to determine hierarchical clustering in genetic data, discriminant analysis of principal components (DAPC) with basic population genetic statistics determined using standard computational tools.