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 clariWed 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 Wve diVerent 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 diversiWcation 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. 

The phylogenetic position and diversity of the enigmatic mongrel frog Nothophryne Poynton, 1963 (Amphibia, Anura)

“…In previous studies (Bossuyt et al, 2006;Frost et al, 2006;van der Meijden et al, 2011van der Meijden et al, , 2005 Tomopterna is the sister taxon to all other members of Cacosterninae, whereas in the present study and in Pyron and Wiens' (2011) phylogeny, Anhydrophryne Hewitt, 1919 is placed in this position. However, this part of the pyxicephalid tree is relatively poorly supported and will require further sampling of genes and species to resolve the precise positions of genera within Cacosterninae with confidence.…”

“…It has been hypothesised that pyxicephalids originated in Southern Africa where medium to large sized ancestors resembling some extant genera (i.e. Pyxicephalus and Tomopterna) occupied savannah and lowland forests (van der Meijden et al, 2011(van der Meijden et al, , 2005. Our habitat-reconstruction analyses (Fig.…”

“…Since then, our understanding of the phylogenetic placement of Nothophryne has become further confused by the unstable phylogenetic relationships of higher taxa within ranids (e.g., Frost et al, 2006;Pyron and Wiens, 2011;van der Meijden et al, 2005). An example of this is its inclusion in Phrynobatrachidae sensu Dubois (1992), based exclusively on phenetic comparisons.…”

“…In order to make comparisons with other African ranid frogs (van der Meijden et al, 2011(van der Meijden et al, , 2005, we amplified and sequenced four widely used markers in amphibian phylogenetics, comprising segments of two partial mitochondrial genes 12SrRNA (12S) and 16SrRNA (16S) and two nuclear genes, rhodopsin exon 1 (RHOD), and recombination activating gene 1 (RAG1). PCR was performed using Illustra PuReTaq…”

Global patterns of diversification in the history of modern amphibians

“…Recent analyses of a single-gene data set (19) have resulted in the first timetree for amphibian evolution but provided relatively broad confidence intervals for divergence times. Other molecular clock analyses have been focused on specific parts of the amphibian tree, such as the basal splits among and within the three orders (20,21) or the origin of single taxa (22)(23)(24)(25)(26). To obtain a more precise and comprehensive overview of amphibian net diversification through the Mesozoic and early Tertiary, we constructed an evolutionary timetree based on a 3.75-kb data set, combining one mitochondrial and four nuclear gene fragments for 171 amphibians.…”