Genetic diversity and landscape genetic structure of otter (Lutra lutra) populations in Europe

Abstract

Eurasian otter populations strongly declined and partially disappeared due to global and local causes (habitat destruction, water pollution, human persecution) in parts of their continental range. Conservation strategies, based on reintroduction projects or restoration of dispersal corridors, should rely on sound knowledge of the historical or recent consequences of population genetic structuring. Here we present the results of a survey performed on 616 samples, collected from 19 European countries, geno- typed at the mtDNA control-region and 11 autosomal

microsatellites. The mtDNA variability was low (nucleo- tide diversity = 0.0014; average number of pairwise dif- ferences = 2.25), suggesting that extant otter mtDNA lineages originated recently. A star-shaped mtDNA net- work did not allow outlining any phylogeographic infer- ence. Microsatellites were only moderately variable (Ho = 0.50; He = 0.58, on average across populations), the average allele number was low (observed Ao = 4.9, range 2.5–6.8; effective Ae = 2.8; range 1.6–3.7), sug- gesting small historical effective population sizeotters likely originated from the expansion of a single refugial population. Bayesian clustering and landscape genetic analyses however indicate that local populations are genetically differentiated, perhaps as consequence of post-glacial demographic fluctuations and recent isolation. These results delineate a framework that should be used for implementing conservation programs in Europe, particu- larly if they are based on the reintroduction of wild or captive-reproduced otters.