Evolutionary History of Geographically Isolated Populations of the Lesser Japanese Mole (Mogera imaizumii) Inferred from Mitochondrial Cytochrome b Gene Sequences

The lesser Japanese mole (Mogera imaizumii) is mainly distributed in eastern Honshu, the largest island of the Japanese archipelago. From central Honshu to the western islands, on the other hand, is almost exclusively inhabited by their closely related species, the large Japanese mole (M. wogura), with several allopatric fragmented populations of M. imaizumii. Our study aims to analyze the phylogenetic relationships and historical dynamics of M. imaizumii populations in western Japan using mitochondrial cytochrome b gene (Cytb) sequences (1140 bp). The findings indicate that the populations in western Honshu (Mt. Hiba), Shikoku (Mts. Ishizuchi and Tsurugi), and two offshore islands (Dogo and Shodoshima) belonged to a distinct lineage (Mim-IV) that diverged about 700 000 years ago from the three major lineages previously identified in eastern Japan and the Kii Peninsula. Mim-IV harbored closely related Cytb sequences within the lineage, with genetic divergences occurring at least 200 000 years ago. We hypothesize that the genetic structures of M. imaizumii and M. wogura in western Japan may have been formed by the repeated expansion and contraction in response to the recurrent environmental fluctuations during the 100 000-year Quaternary glacial cycle. Published online 25 December, 2024; Print publication 31 January, 2025