Demographic history of a recent invasion of house mice on the isolated I sland of G ough

Island populations provide natural laboratories for studying key contributors to evolutionary change, including natural selection, population size and the colonization of new environments. The demographic histories of island populations can be reconstructed from patterns of genetic diversity. House mice ( M us musculus ) inhabit islands throughout the globe, making them an attractive system for studying island colonization from a genetic perspective. G ough I sland, in the central S outh A tlantic O cean, is one of the remotest islands in the world. House mice were introduced to G ough I sland by sealers during the 19th century and display unusual phenotypes, including exceptionally large body size and carnivorous feeding behaviour. We describe genetic variation in G ough I sland mice using mitochondrial sequences, nuclear sequences and microsatellites. Phylogenetic analysis of mitochondrial sequences suggested that G ough I sland mice belong to M us musculus domesticus , with the maternal lineage possibly originating in E ngland or F rance. Cluster analyses of microsatellites revealed genetic membership for G ough I sland mice in multiple coastal populations in W estern E urope, suggesting admixed ancestry. G ough I sland mice showed substantial reductions in mitochondrial and nuclear sequence variation and weak reductions in microsatellite diversity compared with W estern E uropean populations, consistent with a population bottleneck. Approximate B ayesian computation ( ABC ) estimated that mice recently colonized G ough I sland (~100 years ago) and experienced a 98% reduction in population size followed by a rapid expansion. Our results indicate that the unusual phenotypes of G ough I sland mice evolved rapidly, positioning these mice as useful models for understanding rapid phenotypic evolution.