Genetic diversity and individual identification of reintroduced otters (Lutra lutra) in north-eastern Spain by DNA genotyping of spraints

During the last century, otter populations in the Mediterranean area of the Iberian Peninsula were dramatically reduced and disappeared in many localities. A reintroduction programme was established in north-eastern Spain (Muga and Fluvia basins and the Aiguamolls de l'Empordaa wetlands), by releasing 42 otters from four different Iberian populations, between 1995 and 2002. In order to evaluate the success of the reintroduction programme, we investigated microsatellite variation in the native populations of released otters as well as in the population present in the release area in 2004. We used non-invasively collected samples as the DNA source to avoid disturbing the animals in the wild. Laboratory procedures included the screening of samples and a multiple-tubes approach to detect and correct genotyping errors. Our results show that founders have been replaced by descendants in the release area and the population is in Hardy-Weinberg equilibrium, with a 1:1 sex ratio. Western Iberian otters-representing two-thirds of the founder group and released earlier-have greatly contributed to the genetic composition of the current population. The genetic patterns of otters found in a basin north of the studied area suggest a common origin with the released population. We also detected in a few otters the presence of alleles not identified in the original founder group, and we shall discuss the possible origin of these alleles.