Secondary contact of two cryptic Hokou gecko groups in the Izu Islands, Japan.

We analyzed the mitochondrial DNA of Gekko hokouensis collected from the Izu Islands (maybe an introduced population) and the Nansei Islands (native population), both in Japan. A molecular phylogenetic analysis suggested that G. hokouensis of Japan belongs to a cryptic monophyletic group different from that of the currently discovered sample of China. Furthermore, the Japanese clade of G. hokouensis is differentiated into two subclades (Clade 1 and Clade 2 in this article). In the Nansei Islands, these two subclades form a complicated nested-distribution pattern and do not coexist on any of the islands, whereas both clades appear to coexist in the Izu Islands. The two clades exhibit high genetic diversity in the Nansei islands, which are the source population. Surprisingly, it has been revealed that high genetic diversity has also been maintained in the Izu Islands, which are the introduced population, in each clade. AMOVA has also revealed that the genetic differentiation between the populations in the Izu Islands and the Nansei Islands was not significant in each clade. These results suggest that the population of the Izu Islands is now in secondary contact between two clades by multiple migrations from various regions of the Nansei Islands.