Conservation genetics of a wide-ranged temperate snake: same species, different locations, and different behaviour

Even though reptiles are threatened worldwide, few studies address their conservation, especially snakes. The goal of our study was to measure the genetic structure of a widely distributed temperate reptile, the smooth snake Coronella austriaca using microsatellite markers in two different areas at the core (Alsace, north-eastern France) and at the edge (Wallonia, southern Belgium) of its range. We sampled 506 individuals in 38 localities (respectively 10 and 28). Analysis of genetic structure conducted with a clustering method detected three clusters in Alsace, one group gathering all populations but two. In Wallonia, differentiation was observed on both sides of the Meuse River and in the Southern Ardenne region (southernmost sampling sites). Spatial autocorrelation analysis showed that statisticaly more related individuals occur together up to a distance of 2.8 km in Alsace and up to 10 km in Wallonia. Isolation by distance was detected in Wallonia but the distance explained a very limited part of the differentiation (r = 0.033), whereas no isolation-by-distance pattern was detected in Alsace. Even though genetic differentiation between populations separated by large rivers, highways, or crop fields was detected, dispersal between populations seem currently sufficient to avoid any kind of genetic drift in both regions. These results are similar to a previous study conducted in Poland, but strongly contrast with another analysis held in England which detected a sharp genetic structuring among populations that are geographically close. We consequently suggest that discrepancies could be related to the ecology of island populations and smaller densities.