Molecular phylogenetics and phylogeographic structure of Sorex bedfordiae based on mitochondrial and nuclear DNA sequences

- We examined patterns of genetic diversity in Sorex bedfordiae.
- Strong geographic structure recovered largely corresponds to mountain and river systems.
- Demographic analyses suggest Pleistocene expansion events.
- Genetic evidence confirms the species status of two striped shrews.

The southeastern margin of the Tibetan Plateau is characterized by complex topography and a discontinuous landscape, creating a sky island situation. However, the way topography shapes genetic structures and demographic histories of endemic species has not been well studied. We examined the phylogeographic pattern and demographic histories of Sorex bedfordiae, a dispersal-limited small mammal, using three nuclear genes [1977 bp] and two mitochondrial genes [1794 bp] with comprehensive molecular approaches. We recovered five well-supported clades whose distributions are along mountain ridges and roughly subdivided by large rivers. Demographic expansions in the middle Pleistocene were strongly supported by both nuclear and mitochondrial genes. Our results support the hypothesis that sky island topography and river systems strongly affect the genetic structure of non-aquatic terrestrial species. We further clarify that S. bedfordiae and S. cylindricauda are valid sibling species, whereas S. excelsus is most likely a geographic subspecies of S. bedfordiae.