Genetic signature of demographic history explains the current sympatric distribution of sibling species of Craseomys (Rodentia: Arvicolinae)

Sequences of mitochondrial DNA were analysed in two vole species (Craseomys rex and Craseomys rufocanus), which are closely related based on phylogeny, morphology, and ecology. In Hokkaido, Japan, they occur sympatrically in forests, but Craseomys rufocanus also inhabits open fields. Capture records of 2532 specimens from 114 localities confirmed the widespread and fragmented distribution of Craseomys rufocanus and Craseomys rex and indicated that abundance of Craseomys rufocanus was 9.2–19.8 times higher than that of Craseomys rex. The phylogenetic tree illustrated four regional clades for Craseomys rex, but no distinct clades for Craseomys rufocanus. The observed mismatch distribution of Craseomys rufocanus matched with a spatial expansion model, indicating population expansion through range extension with frequent migration. Using 47 haplotypes from 151 Craseomys rex and 302 haplotypes from 1037 Craseomys rufocanus, a skyline plot revealed that Craseomys rufocanus increased during the Last Glacial Cycle (LGC) when grassy vegetation dominated forests. Craseomys rex expanded following forest recovery following LGC survival. The current effective population size (Ne) of Craseomys rufocanus was 15.9–33.8 times higher than that of Craseomys rex, in good agreement with capture records. Population expansion of Craseomys rufocanus during the LGC resulted in range extension and its current distribution, whereas the current range of Craseomys rex was derived from glacial refugia.