Evolutionary relationships in the African frog family Ptychadenidae, including the first molecular analysis, range extension, and distribution modelling of the monotypic genus Lanzarana

Abstract

The family Ptychadenidae contains three ecologically and morphologically distinct genera: the widespread, species-rich and above-ground dwelling Ptychadena, the less widespread and diverse, burrowing Hildebrandtia, and the little-known, burrowing, monotypic Lanzarana, endemic to Somalia. Previous morphological studies placed Lanzarana in a sister position to Hildebrandtia and these two genera as sister to Ptychadena. However, our analyses of mitochondrial and multilocus nuclear DNA data revealed Lanzarana as a sister lineage to Ptychadena (divergence ∼28 Mya), and Hildebrandtia sister to them (∼42 Mya). This suggests that the common ancestor of ptychadenids may have exhibited a burrowing lifestyle similar to Hildebrandtia and Lanzarana, rather than the more active, above-ground lifestyle of Ptychadena. In addition, based upon analysis of available mitochondrial DNA data, we have identified major clades within the genus Ptychadena and propose them as four species groups, with the P. mascareniensis group being the first diverging lineage (∼20 Mya). We also report four new localities of Lanzarana largeni from central Somaliland, south-western Puntland, southern Somalia and south-eastern Ethiopia, extending the presently known range of the species westward. This represents the first official record of L. largeni from Ethiopia. An ecological niche model of L. largeni for present climatic conditions identifies extensive climatically highly suitable areas in central Somalia and south-eastern Ethiopia. A model for future climatic conditions estimates a substantial extension of climatically suitable areas to northern Somalia and north-eastern Kenya, likely due to predicted more humid conditions accompanying the increase of temperatures in the western Indian Ocean.