Evidence of a fine-scale genetic structure for the endangered Pyrenean desman (Galemys pyrenaicus) in the French Pyrenees

The Pyrenean desman (Galemys pyrenaicus) is a small semi-aquatic mammal endemic to the Pyrenean Mountains and the northern half of the Iberian Peninsula where it lives in mountain streams of cold and well-oxygenated flowing waters (Nores et al. 2007). This species is currently considered as vulnerable in the IUCN Red List (Fernandes et al. 2008) and has been suffering from habitat loss and fragmentation for decades, inevitably impacting its distribution. The ecology and biology of this species are poorly known, notably because of its elusive behavior and its primarily nocturnal activity (Stone 1987, Bertrand 1994). Its distribution area is even not definitively established. Furthermore, a recent genetic study, based on mitochondrial and intronic sequences (Igea et al. 2013), showed that the genetic variability of the Pyrenean desman is very low in the Pyrenees. In this study we investigated the potential existence of a genetic structure and gene flow at a smaller scale using 24 polymorphic microsatellites loci. As the Pyrenean desman is a very elusive species, we completed our sample collection of tissues with faeces samples coming from the French distribution area of this species. Doing so, we successfully identify 70 individuals out of 355 faeces samples. Bayesian analyses revealed a cryptic genetic structure in our data set. Three clusters were evidenced (one western, one central and one eastern) and gene flow appears to be limited between these clusters (min. Fst value of 0.2).