Molecular Phylogeny and Biogeography of the Cyrtodactylus chauquangensis Group

The Cyrtodactylus chauquangensis species group is a large limestone karst radiation of bent-toed geckos with at least 28 nominal species and has a broad distribution range with seven species found in northwestern Thailand, five in south-central China, five in northern Laos and 11 in northern Vietnam. To trace the biogeographic pattern of this group, we reconstruct its phylogenetic relationships and evolutionary history using three mitochondrial genes and four nuclear genes. Our results show that the C. chauquangensis species group is monophyletic, which can be divided into at least seven subclades. In terms of biogeography, the group might have originated from the Northwest Uplands of the Indochina region, including northern Laos and part of northwestern Vietnam, during the early Miocene and subsequently dispersed into northwestern Thailand. It later colonized the northern Annamites, Northeast Lowland, Northeast Uplands, and South-central China. A majority of lineages within this group likely diverged during the Miocene epoch when the East Asian monsoon was developed and increased precipitation in the region. The changing climate might have promoted plant diversity and provided suitable habitats and food resources for members of the C. chauquangensis group. In addition, the elevated rate of precipitation probably accelerated the dissolution of the limestone substrate and profoundly influenced the development of the karst region. The results of our study further highlight the importance of this unique period of time in shaping evolutionary histories of many different taxonomic groups in the region.