Biogeography and diversification dynamics of the African woodpeckers

Abstract

The dynamics of species accumulation of African terrestrial vertebrates over time remains underexplored in comparison with those in the New World, despite Africa hosting about 25% of the world’s avian diversity. This lack of knowledge hampers our understanding of the fundamental processes that drive biodiversity and the dynamics of speciation. To begin to address this gap, we reconstructed species-level phylogenies of two unrelated clades of African woodpeckers (12 species of Geocolaptes/Campethera and 13 species of Chloropicus/Mesopicos/Dendropicos/Ipophilus) that diverged from their closest Indo-Malayan relatives at similar times. Our results demonstrate that the current taxonomy is misleading: three (Campethera, Dendropicos and Mesopicos) out of four polytpic genera/subgenera are not monophyletic. Our results also show that current estimates of diversity at the species level are significantly understated, as up to 18 species for the ‘Campethera clade’ and 19 for the ‘Dendropicos clade’ could be recognized. The first splits within both clades involve species that are largely restricted to the Guineo-Congolian biogeographic regions, followed by later adaptations to particular habitats (forest versus savannah) and colonization of other regions (e.g. Southern Africa), each of which occurred multiple times in both clades. Assuming a conservative species delimitation scheme, our results indicate that diversification rates are decreasing through time for both clades. Applying a more extreme species recognition scheme (18 and 19 species for the Campethera and Dendropicos clades, respectively), our results support a decrease in diversification rates only for the Dendropicos clade and thus underline the importance of the number of species included in our diversification analyses. Greater ecological diversity of the Campethera clade where multiple species exhibit either an arboreal or terrestrial foraging strategy might explain the constant diversification rates through time we found under the eighteen species scheme.