Genetic diversity in the Eurasian otter, Lutra lutra, in Scotland. Evidence from microsatellite polymorphism

The relationship between microsatellite diversity and geographical fragmentation and isolation was studied in Scottish populations of the Eurasian otter, Lutra lutra.The geographic range of the study encompassed isolated archipelagos, islands adjacent to the Scottish mainland and both fragmented and continuous mainland populations.Tissue samples of 496 individuals from across Scotland were assayed for polymorphism at ten microsatellites.The isolation of populations on Shetland, and to a lesser degree on Orkney, was associated with reduced levels of microsatellite diversity.Most of the remaining island and fragmented mainland populations contained levels of microsatellite diversity similar to the high levels observed in the continuous mainland populations.Unexpectedly, both island and continuous mainland populations showed similar rates of departures from mutation-drift equilibrium.Such departures could have arisen from a variety of local demographic processes besides population bottlenecks.Gene flow appeared to be a major factor maintaining microsatellite diversity in all of these populations except the one on Shetland.