Comparative phylogeography of the endemic Japanese weasel (Mustela itatsi) and the continental Siberian weasel (Mustela sibirica) revealed by complete mitochondrial genome sequences

Abstract

We analyzed the complete mitochondrial genome for 26 individuals of the endemic Japanese weasel (Mustela itatsi) and 20 individuals of its continental sister species, the Siberian weasel (Mustela sibirica). These species diverged an estimated 1.19 Mya, in the Early Pleistocene. Mustela itatsi comprised two haplotype clades that diverged an estimated 0.93 Mya, in the Middle Pleistocene: a northern (Honshu) clade comprising geographically distinct basal, northern, and eastern subclades, and a western paraphyletic group, as well as a southern clade comprising geographically distinct subclades on Kyushu, Shikoku, and adjacent small islands. Our results indicate a single migration of an ancestral population from the Korean Peninsula to southern Japan across an Early Pleistocene land bridge, followed by allopatric speciation of M. itatsi in Japan. The southern lineage appears to have remained in place, whereas the range of the northern lineage expanded stepwise from south-western to northern Honshu between 0.31 and 0.11 Mya. Mustela sibirica also comprised two main clades that diverged an estimated 0.67 Mya; one containing haplotypes from continental Russia and Tsushima Island (Japan), and the other containing haplotypes from Korea, China, and Taiwan. The M. sibirica population on Tsushima Island is likely a relict from the continental Russian population.