Morphological variation of mice, Mus musculus on the Ogasawara Islands, and their relationship to those on the Izu Islands, Japan

抄録

Morphological variation was examined in the house mouse, Mus musculus, from the islands of Chichijima and Hahajima in the Ogasawara archipelago, Japan, and compared with that of mice from five islands in the more northerly Izu Island chain. Mice from the two Ogasawara islands were similar in body-, mandible-, and molar-sizes, and incidence of molar tubercles, indicating that they are genetically closely related, while substantial divergences were seen between populations on the different islands, and between samples collected from Chichijima in 1977/1980 and in 1999. The Ogasawara mice showed affinities with the European house mouse M. musculus domesticus in their body sizes and were distinct from those from the Izu Islands (Hachijojima, Kozushima, Miyakejima, Nijima, and Oshima) and Honshu, which were identified as being Japanese wild mice, M. m. molossinus, based on their body and mandibular dimensions. The mice from Ogasawara and Nijima (Izu Islands), however, shared a unique variant of molar tubercles, implying that there may have been genetic exchange between the islands. These findings are concordant with historical records of human immigration to these islands during the 19th century.