Evolutionary history of two allopatric Terricola species (Arvicolinae, Rodentia) from molecular, morphological, and palaeontological data.
Résumé
To investigate the phylogenetic and phylogeographical relationships of arvicolines, we use several Western European ground voles. More particularly, our study is focused on Microtus (Terricola) savii and M. (T.) pyrenaicus. These two allopatric species are usually considered as having originated from the same ancestor, possibly M. (T.) mariaclaudiae. We propose molecular and morphological approaches: nucleotidic data from the mitochondrial cytochrome b and 12S rRNA genes and global morphological analyses from the first lower molar. Four other Terricola species (multiplex, lusitanicus, duodecimcostatus, subterraneus) were added to the data set for both analyses, and two other vole species (Clethrionomys glareolus and Chionomys nivalis) as outgroup to the molecular analysis, and five fossil populations to the morphological one. Palaeontological data are also widely taken into account. Both molecular and morphological analyses indicate that intra-Terricola relationships reflect the presentday geographical distribution of our data set species. Our results show that M. (T.) savii and M. (T.) pyrenaicus are from separate speciation events leading to two different biogeographical groups, respectively the Alpine–Italian group and the French–Iberian group, the latter being much more homogeneous. These speciation events could be related to Quaternary climatic changes, which induced southward migration, leading first to M. (T.) savii and second to M. (T.) pyrenaicus. The classical hypothesis of a geographical speciation for these two taxa from M. (T.) mariaclaudiae is invalid. However, the morphological data suggest a potential phylogenetic relationship between M. (T.) mariaclaudiae (ancestor) and M. (T.) pyrenaicus (descendant).