GEOGRAPHIC-VARIATION AND SEXUAL SIZE DIMORPHISM IN MAUREMYS MUTICA (CANTOR, 1842) (REPTILIA, BATAGURIDAE), WITH DESCRIPTION OF A NEW SUBSPECIES FROM THE SOUTHERN RYUKYUS, JAPAN

The batagurid turtle, Mauremys mutica, is widely distributed in tropic al to temperate East Asia. Analyses of morphometric characters and col oration revealed that the southern Ryukyu populations of this species are much diverged from the other populations, presumably as a result o f their long geographical isolation. We describe those populations as a new subspecies, M. m. kami. Analysis of geographic variation also su ggested that distinctly isolated populations of the central and northe rn Ryukyus, and Kyoto and Shiga Prefectures of central Japan have orig inated from animals artificially introduced from the Yaeyama Group, an d Taiwan, respectively. We confirmed the absence of ''larger female'' sexual size dimorphism (SSD) in M. mutica unlike most other aquatic ba tagurids, and further demonstrated variation in SSD pattern between th e subspecies: in M. m. kami, the adult male has a significantly greate r carapace length than adult females, whereas the adult carapace lengt h does not differ significantly between sexes in the nominotypical sub species. It is hypothesized that these dimorphic patterns evolved from the widely prevailing ''larger female'' condition through epigamic se lection involving forcible copulatory behavior.