Aquatic and terrestrial water voles: phylogeography and morphometrics

Water voles from the genus Arvicola display an amazing ecological versality, with aquatic and terrestrial populations. Their taxonomic status and evolutionary relationships has caused a long-standing dispute. Two aquatic (sapidus, amphibius) and one fossorial species (scherman) are currently described.
We used mitochondrial cytochrome b (cytb) gene sequences to reconstruct the phylogenetic relationships among fossorial and aquatic water voles belonging to A. amphibius (formely terrestris) collected in various regions of Europe. We combined 147 new sequences collected mostly in France, Germany and Great Britain, with available datasets from the entire range to provide an up-to-date phylogeny of this species. Phylogenetic and network reconstructions retrieved 4 major lineages all containing fossorial and aquatic morphotypes, discarding the view of each ecotype corresponding to a distinct species.
Morphometric analyses of skull shape were performed on a set of aquatic and fossorial populations documenting the main lineages. Fossorial and aquatic populations tend to display convergent morphological features related to their ecology, blurring a part of the phylogenetic signal. Different allometric trajectories related to the constraints of the aquatic vs. subterranean habitats may contribute to this morphological convergence.