Validity and historical process of formation of the center of endemism for reptiles in the southern Tokara Islands

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Three islands of the Tokara Group (Takarajima, Kodakarajima and Kojima), located on the southwestern side of the Tokara Tectonic Strait, are known to accommodate, despite their small areas and low environmental diversities, a group of terrestrial animals that are taxonomically recognized as endemic species. Using the reptiles as a model group, we examined the validity of such a taxonomic view from a phylogenetic standpoint. We also inferred the process. Of formation of such a characteristic fauna in the southern Tokara islands. We conducted molecular phylogenetic analyses for three lineages: (1)Trimeresurus tokarensis, a species endemic to the southern Tokara islands, and T. flavoviridis, a close relative of the former, from the Amami and the Okinawa Groups; (2) Cyclophiops semicarinatus from the southern Tokara Islands, where the species is know to have reduced its body size, and from the Amami and the Okinawa Groups; and (3) a putative undescribed species of the genus Gekko endemic to the southern Tokara islands, and its closest relatives, G. hokouensis and G. yakuensis from the neighboring islands. Of these, lineages (1) and (2) shared a same phylogeographical pattern, (southern Tokara Amami) Okinawa, and very small genetic distances between the former two island groups. The lineage (3), on the other hand, showed a distinct differentiation between representatives from the southern Tokara and other areas. These results suggest that the southern Tokara has been serving as a site for long isolation for some terrestrial organisms, giving rise to phylogenetically distinct entities (as represented by Gekko sp.) on the one hand, and also acted as a site for rapid phenetic changes possibly under extreme insular environments on the other hand.