Population genetic structure and sex-biased dispersal of the hazel dormouse (Muscardinus avellanarius) in a continuous and in a fragmented landscape in central Italy

Habitat fragmentation hinders the dispersal process, which, in turn, causes changes to the genetic variability of populations. The aim of this study was to evaluate the effects of fragmentation on the genetic population features of the hazel dormouse (Muscardinus avellanarius), a small rodent living in forest habitats, using seven microsatellite loci. We compared (i) the genetic variability and population structure, (ii) the scale of the spatial structuring, and (iii) the possible presence and effect of a sex-biased dispersal in two populations living, respectively, in a continuous and in a fragmented landscape in central Italy. Although all microsatellite loci were always polymorphic, in the fragmented population the observed heterozygosity was usually lower than expected, and 5 out of 7 loci were not at Hardy–Weinberg Equilibrium. The fragmented population was found to be strongly structured. These results showed that there was a hindrance of the gene flow between subpopulations, and in some cases even a virtual ecological isolation, as confirmed by the absence of covariation between the pairwise genetic and Euclidean distances. Some clues of female-biased dispersal were found, but even the dispersing sex showed dispersal problems in several cases. The strong differences in the genetic features between the continuous and fragmented population, indicate that the hazel dormouse strongly suffers from habitat fragmentation. This happens even when several neighbouring habitats remnants persist and remain partially connected by verges along crop fields. Thus, the fragmented landscape needs urgent measures to restore ecological connectivity through a more effective management plan of the hedgerows network.