The reptiles of Tinhosa Grande islet (Gulf of Guinea): A taxonomic update and the role of Quaternary sea level fluctuations in their diversification

ABSTRACT The reptile fauna of Tinhosa Grande islet, Gulf of Guinea, comprises an endemic skink, Trachylepis adamastor, and an unidentified species of gecko of the genus Hemidactylus. Until recently, no molecular data were available for either species, impeding their phylogenetic placement. However, due to several synapomorphic characters, it was suggested that the Tinhosa Grande population would be related to the congeners of the neighbouring islands of Príncipe and São Tomé. In a recent survey of Tinhosa Grande islet we collected fresh material of both species, allowing us to examine their phylogenetic relationships to the other members of their respective genera occurring on the neighbouring islands using multigene Bayesian and maximum likelihood analyses. In contrast with the morphological results and previous taxonomic allocations, our molecular results suggest that both T. adamastor and the unidentified Hemidactylus sp. are conspecific with their Príncipe counterparts, Trachylepis principensis and Hemidactylus principensis. While today Tinhosa and Príncipe differ strongly in their environmental conditions, we show that the islands have been repeatedly merged into a single landmass as a result of Quaternary sea level fluctuations. We suggest that the repeated fusion of the islands during low sea levels could have impeded the phylogenetic divergence of both populations, while contrasting habitats might have simultaneously promoted some morphological differences.