Phylogenetic and morphometrics assessment of the evolutionary history of the hazel dormouse: Muscardinus avellanarius

The hazel dormouse, Muscardinus avellanarius is a hibernating rodent, member of the Gliridae family. At the European level, the hazel dormouse is a strictly protected species listed in Annex IV of the " Fauna-Flora -Habitat Directive" ( Directive 92/43/EEC ) and Annex II of the Bern Convention. Concrete conservation measures must be implemented to maintain long-term viable populations of this species. To develop appropriate tools for conservation, it is essential to understand the origin and the evolution of this species whose ancestor appeared 17 million years ago. To this aim, it is fundamental to analyze the evolutionary history of the species in both a geographic dimension (spatial) and a temporal scale. Both mitochondrial and nuclear markers revealed a complex phylogeographic pattern for the hazel dormouse with the presence of two highly divergent and allopatric genetic lineages, respectively distributed in South-Western and Central-Eastern Europe. The presence of two highly differentiated phylogenetic lineages might question the taxonomic status of the hazel dormouse. Our work has highlighted the difficulty of delineating species boundaries and stressed the importance of integrating complementary approaches to achieve further taxonomic work. We used a quantitative analysis of intra- specific phenotypic variation as a complementary tool of the molecular approach by studying the upper first molar (UM1) in hazel dormouse populations. The analysis of phenotypic feature appears as a valuable complement to genetic analyses, providing a complementary insight into evolutionary processes, such as differentiation by vicariance or adaptation to different environments. A geographic structure emerges from the morphometric pattern of differentiation, partially corresponding to the expectations based on the genetic results. The knowledge acquired through this study might add a significant piece of the puzzle for the understanding of the evolutionary history of the common dormouse and might have important implications for its conservation.