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

The relationship between microsatellite diversity and geographical fragment ation and isolation was studied in Scottish populations of the Eurasian ott er, Lutra lutra. The geographic range of the study encompassed isolated arc hipelagos, islands adjacent to the Scottish mainland and both fragmented an d continuous mainland populations. Tissue samples of 496 individuals from a cross Scotland were assayed for polymorphism at ten microsatellites. The is olation of populations on Shetland, and to a lesser degree on Orkney, was a ssociated with reduced levels of microsatellite diversity. Most of the rema ining island and fragmented mainland populations contained levels of micros atellite diversity similar to the high levels observed in the continuous ma inland populations. Unexpectedly, both island and continuous mainland popul ations showed similar rates of departures from mutation-drift equilibrium S uch departures could hale arisen from a variety of local demographic proces ses besides population bottlenecks. Gene Row appeared to be a major factor maintaining microsatellite diversity in all of these populations except the one on Shetland. (C) 1999 The Linnean Society of London.