Molecular phylogeny and biogeography of the Cyrtodactylus angularis group: diversification in a global biodiversity hotspot

Cyrtodactylus is the third-largest genus of vertebrates, with nearly 400 nominal species. Comprising at least 21 members, the C. angularis species group represents a diverse clade in Indochina, a main center of the genus’ radiation. Recent works, which have attempted to resolve the phylogenetic relationships among the congeners but primarily used a couple of mitochondrial loci and sparse taxon sampling, could not provide a robust phylogenetic hypothesis. In addition, important aspects of its evolutionary and biogeographic history have not been addressed in previous research. To fill these gaps, data from three mitochondrial and four nuclear loci were analyzed for all recognized taxa. The largest dataset to date for the group helps produce highly congruent phylogenetic relationships among the species and recover, for the first time, six evolutionarily independent clades with high confidence (except for the bootstrap value in Group III). Using this well-corroborated phylogenetic framework to infer the species group’s evolutionary history, this study offers novel hypotheses on its origin and colonization and speciation events in Indochina. The results suggest that the group first emerged in the Oligocene, while most of its lineages started to diverge in the Miocene, when the East Asian summer monsoon developed and might have brought about large-scale vegetation change. Moreover, the Mekong Lowlands are likely the ancestral area of the C. angularis group, whereas most of the remaining members, except for Group II, originate from the Annamite Mountain Range. The study once again highlights the importance of the Annamite landscape, a global biodiversity hotspot, in maintaining evolutionary processes for many endemic and evolutionarily distinct vertebrates.