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

托卡拉群岛的三个岛屿（高岛、Kodakarajima和小岛）位于托卡拉构造海峡的西南侧，尽管面积小，环境多样性低，但已知可以容纳一组陆地动物，这些动物在分类学上被认为是特有物种。以爬行动物为模型群，我们从系统发育的角度检验了这种分类学观点的有效性。我们还推断了这个过程。在托卡拉群岛南部形成这样一种有特色的动物群。我们对3个谱系进行了分子系统发育分析：(1)托卡拉群岛南部特有的Trimeresurus tokarensis和来自Amami群和冲绳岛群的T. flavoviridis是前者的近亲；(2)产自托卡拉群岛南部的半圆眼鱼（Cyclophiops semiarinatus），已知该物种的体型已缩小，产自奄美群和冲绳群；(3)托卡拉群岛南部特有的一种推测未被描述的盖柯属，以及邻近岛屿上的近亲G. hokouensis和G. yakuensis。其中，谱系(1)和(2)具有相同的系统地理模式，（南Tokara Amami）冲绳，前两个岛屿群之间的遗传距离很小。另一方面，谱系(3)在托卡拉南部和其他地区的代表之间表现出明显的差异。这些结果表明，托卡拉南部一直是一些陆生生物长期隔离的场所，一方面产生了系统发育上不同的实体（以Gekko sp.为代表），另一方面也可能在极端岛屿环境下发生快速的表型变化。

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.