A previously unrecognized radiation of ranid frogs in Southern Africa revealed by nuclear and mitochondrial DNA sequences

Abstract

In sub-Saharan Africa, amphibians are represented by a large number of endemic frog genera and species of incompletely clarified phylogenetic relationships. This applies especially to African frogs of the family Ranidae. We provide a molecular phylogenetic hypothesis for ranids, including 11 of the 12 African endemic genera. Analysis of nuclear ( rag-1, rag-2, and rhodopsin genes) and mitochondrial markers (12S and 16S ribosomal RNA genes) provide evidence for an endemic clade of African genera of high morphological and ecological diversity thus far assigned to up to five different subfamilies: Afrana, Cacosternum, Natalobatrachus, Pyxicephalus, Strongylopus, and Tomopterna. This clade has its highest species diversity in southern Africa, suggesting a possible biogeographic connection with the Cape Floral Region. Bayesian estimates of divergence times place the initial diversification of the southern African ranid clade at ∼62–85 million years ago, concurrent with the onset of the radiation of Afrotherian mammals. These and other African ranids ( Conraua, Petropedetes, Phrynobatrachus, and Ptychadena) are placed basally within the Ranoidae with respect to the Eurasian groups, which suggests an African origin for this whole epifamily.