Complex patterns of continental speciation: molecular phylogenetics and biogeography of sub-Saharan puddle frogs (Phrynobatrachus)

Puddle frogs (Anura: Phrynobatrachidae) are one of the most species-rich sub-Saharan amphibian groups, occupying an extraordinarily diverse range of habitats. We construct the first phylogeny of puddle frogs, utilizing mitochondrial (12S rRNA, valine-tRNA, and 16S rRNA) and nuclear (RAG-1) DNA. Phylogenetic analyses are conducted using separate and combined partitions under maximum parsimony, maximum likelihood, and Bayesian criterion. Monophyly of the Phrynobatrachidae is well supported, and three major clades of Phrynobatrachus are identified. We reconstructed a biogeographic history using habitat preference, elevation, and geographic distribution. Habitat niches appear to be conserved between sister species, with the majority of species favoring forest over savanna habitats and the most recent common ancestor of the Phrynobatrachidae reconstructed as a forest species. Analyses of elevational data identify three independent colonizations of highland regions, one in each of the three major clades. Ancestral reconstructions support an East African origination of puddle frogs. Most species are restricted to one of five sub-Saharan regions and are distributed within the Eastern, Central, and Western zones with far fewer species in Southern Africa. These results elucidate the complex patterns of spatial niche partitioning that have contributed to the diversification of this widely distributed, sub-Saharan genus.