Genetic variation of Littorina horikawai endemic to the western coast and the adjacent islands around Kyushu, Japan inferred by mtDNA analyses

抄録

We demonstrated the genetic variation and population structure of a direct developing marine gastropod, Littorina horikawai which is endemic species distributed in the western coast of Kyushu, Japan and is found mainly on the adjacent islands. We conducted the field survey and sampling covering most of the distribution area of L. horikawai. In total, we collected 173 individuals from 13 localities (between Tsushima Island and Yakushima Island) and determined the sequences of mitochondrial DNA, the cytochrome b (CYTB) gene. We detected a significant genetic population differentiation in L. horikawai despite the limited distribution area of the western coast of Kyushu. Also, its haplotype distribution is mainly consistent with the geographical structure: the northern part of Kyushu, the central islands, and the southern islands. However, some haplotypes obtained from the Goto Islands which is located in the border between the northern part of Kyushu and the central islands do not correspond to the above geographic distribution. The high level of genetic differentiation of L. horikawai compared to other low dispersal Littorina species despite its narrow distribution range may be due to its predominantly fragmented island habitats. Although it is necessary for understanding the detailed evolutionary history of L. horikawai to perform the high-resolution genetic analysis, our present findings indicated that a high level of genetic differentiation of L. horikawai occurred even in a narrow distribution range because of not only the ecological traits linking to dispersal ability but also its discontinuous pattern such as the island inhabitation.