Origin and intraspecific diversification of the scincid lizard Ateuchosaurus pellopleurus with implications for historical island biogeography of the Central Ryukyus of Japan

Abstract

The Central Ryukyus, a group of islands in southwestern Japan, harbor many endemic reptiles and amphibians, and the geographic ranges of the endemics are limited to south of the Tokara Gap, an old sea strait. Ateuchosaurus pellopleurus is a lizard with an exceptionally wide geographic range that encompasses the Central Ryukyus and north of the Tokara Gap. The intraspecific geographic variation of this species and the divergence time between A. pellopleurus and its sister species in southern China, Ateuchosaurus chinensis, were assessed by molecular phylogeographic analyses. The results indicated that the populations north of the gap were established by recent northward dispersal, prior to which the distribution of this species was limited to the Central Ryukyus. The estimated divergence time between A. pellopleurus and A. chinensis was in the Oligocene or Miocene, which was concordant with the divergence times of most Central Ryukyu endemics. These results demonstrated that A. pellopleurus is essentially a Central Ryukyu endemic that shares a common biogeographic history with other endemics. The common divergence times suggested that isolation of the endemics from their sister species in surrounding areas are attributable to geographic isolation by a tectonic event in the Miocene. In addition, A. pellopleurus showed distinct divergence between the populations in the northern and southern parts of the Central Ryukyus, and further diversification within and between islands in the southern part. Comparison of the phylogeographic patterns between this species and other endemics revealed that the present diversity in the Central Ryukyu endemics was formed by a complex history that involved occasional dispersal rather than simple vicariance events.