Genetic structure of insular Mediterranean populations of the house mouse

The genetic structure of six western Mediterranean island populations of Mus musculus domesticus were investigated by means of an electrophoretic analysis at 34 loci and compared to that of five neighbouring mainland populations. No reduction in variability (H = 0.09 for both island and mainland samples) was observed in the island populations except for a very small island (6 ha), in which one-third of the variability was lost. Patterns of colonization inferred from a Wagner cluster analysis and the distribution of rare variants suggest that, although these island populations are clearly related to European mainland mice, their genetic structure is the result of multiple founding events from sources dispersed throughout the Mediterranean Basin. Furthermore, the presence of the same rare alleles in Sardinia, Corsica and Piana, suggest that the three islands share a common history of colonization.
Estimates of genetic distance and gene flow indicate that the level of genie differentiation is greater between island and mainland populations that between the latter due to geographic isolation. Multiple founder events and post-colonization evolution are the factors that best explain the observed levels of genie variability and differentiation in these Mediterranean islands.