Permalink : http://hdl.handle.net/2115/38451

KEYWORDS : Clethrionomys rufocanus;Daikoku Island;mtDNA;The gray-sided vole

Based on their skull morphology voles found on Daikoku Island have been regarded as a distinct form of Clethrionomys rufocanus (Sundevall, 1846) but their taxonomic status has been controversial: the vole population on this island was once identified to be a subspecies of Neoashizomys sikotanensis Tokuda, 1935, then named N. s. akkeshii, but Ota (1956) insisted that the voles there are C. rufocanus. Their ecological features are also fascinating; their population abundance greatly fluctuates from extremely low to very high densities. Because of these unique morphological and ecological characteristics distinct genetic features are also expected compared with those of the mainland voles. We thus compared the ecological, morphological, and genetic features of the voles from Daikoku Island with populations from mainland Hokkaido. Although the Daikoku population largely fluctuated from low to high density, the amplitude was within the range that has been frequently observed in the eastern part of Hokkaido. A single unique mtDNA haplotype was observed in Daikoku, which was different from the 145 haplotypes observed in the mainland and other island populations, though they were closely related each other. Genetic diversity indices of the Daikoku population were greatly lower than those of mainland populations. Our results on the cranial measurements were consistent with those of Ref. 4, 5 that the Daikoku voles, generally, have larger skull dimensions than those of the mainland. Principal Component Analysis indicated morphological differentiation between the Daikoku voles and those of the mainland. Our genetic and morphological results confirm that the Daikoku vole is a local form of the gray-sided vole, Clethrionomys rufocanus, which relatively recently originated from mainland Hokkaido.