Morphometric variation of house mice (<i>Mus musculus</i>) on the Izu Islands

Abstract

We conducted univariate and multivariate statistical analyses of the morphometry of five island populations of the house mouse Mus musculus, from the Izu Islands (Oshima, Nijima, Kozushima, Miyakejima, Hachijojima), and compared them with three populations from the Japanese mainland of Honshu (from Kamogawa, Yokosuka, and Kawazu). Analyses were based on bodies, mandibles and molars. According to the analyses based on the mandible and molar measurements, the island samples differed from each other, and many of them also differed from the Honshu samples, although there was no evidence of positive directional variation, such as gigantism, in the insular samples. Cluster analyses of morphological distance, based on mandible and molar measurements, indicated that the island populations, with the exception of that on Oshima, were closely related to those on Honshu, while the Oshima population was slightly more distantly related. These results indicate that the divergence of the island populations is mainly attributable to the genetic variation of the initial founders and to subsequent isolation. The differentiation of the island populations may have taken place as recently as within the past 1,200 years.