Population Systematics of Takydromus tachydromoides (Reptilia : Squamata)

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Just as planned in the proposal, sampling of fresh specimens of Takydromu tachydromoides was carried out in some islands of the Tokara and Osumi Island Groups, as well as in some localities of southern Kyushu, from which only a few specimens had been available yet. Then, sampling efforts were extended to other localities in the remaining region of Kyushu (Nagasaki and Oita) and adjacent islands (e.g., Goto Islands and Iki), as well as in Western Honshu (Kyoto), Central Honshu (Mie and Gifu), Vicinity of Tokyo (Ibaragi, North-central Honshu (Ishikawa), North-eastern Honshu (Sendai), and Hokkaido (Sapporo). Special efforts were made to obtain fresh materials from both high and low altitude areas of Yakushima Island, because some previous authors noted that the populations from these regions might be morphologically distinct from each other. Tissues were obtained from these materials and were subjected to molecular phylogenetic analyses. The remaining parts were preserved and subjected to … More morphological analyses together with other specimens loaned from museums and other researchers.Morphologically, prominent variations were recognized between samples from the Tokara Island Group and Kyushu+Honshu+Hokkaido samples, but these two assemblages were more or less bridged by the Osumi Island samples. Analyses of sequence variations in mitochondrial 12S and 16S rRNA genes yielded trees that indicate prominent dichotomy between the Tokara+Osumi populations and whole of the remainder. This result, along with available paleogeographical and paleoclimatic information, strongly suggests that populations from these two areas actually represent different biological species. On the other hand, altitudinal divergence on Yakushima Island was not supported at all. Very little variation was recognized among all samples from Gifu and more northern localities. This suggests that populations from the northern half of Japan represent rapid post glacier dispersals during the Late Pleistocene-Holocene period. Less