Speciation in African Forest Robins (Stiphrornis): Species Limits, Phylogenetic Relationships, and Molecular Biogeography

Abstract

The monotypic genus Stiphrornis (Aves: Turdidae) is revised under a phylogenetic species concept to include four species, one of which, from the southwest Central African Republic, is new. Mitochondrial DNA sequence data are analyzed to explore the phylogenetic relation-ships within Stiphrornis. These data indicate relatively high levels of sequence divergence among the species and corroborate their recognition as diagnosable taxa, a conclusion also supported by morphological evidence. These findings, along with the allopatric distributions of the species, compel attention to their phylogenetic and spatial history, which was not ex-plored when this group was ascribed to a single ‘‘biological’ ’ species. Data reviewed here also suggest that the northwest Congo Basin forest, where the new species was discovered, is more zoogeographically complex than has been previously sus-pected. In addition, application of a phylogenetic species concept emphasizes the narrow en-demism of S. gabonensis and S. sanghensis, along with its implications for conserving their threatened habitats. The findings of this paper also reinforce the notion that patterns of geographic variation in the lowland forests of West and Central Africa are still incompletely understood and that the impact of environmental and geological history on the diversification of the forest avifauna has not yet been fully explored.