Diversification across major biogeographic breaks in the African Shining/Square-tailed drongos complex (Passeriformes: Dicruridae)

Surprisingly, little is known about the extent of genetic structure within widely distributed and polytypic African species that are not restricted to a particular habitat type. The few studies that have been conducted suggested that speciation among African vertebrates may be intrinsically tied to habitat and the dynamic nature of biome boundaries. In the present study, we assessed the geographic structure of genetic variation across two sister-species of drongos, the Square-tailed Drongo (Dicrurus ludwigii) and the Shining Drongo (D. atripennis), that are distributed across multiple sub-Saharan biogeographic regions and habitat types. Our results indicate that D. ludwigii consists of two strongly divergent lineages, corresponding to an eastern-southern lineage and a central-western lineage. Furthermore, the central-western lineage may be more closely related to D. atripennis, a species restricted to the Guineo-Congolian forest block, and it should therefore be ranked as a separate species from the eastern-southern lineage. Genetic structure is also recovered within the three primary lineages of the D. atripennis-D. ludwigii complex, suggesting that the true species diversity still remains underestimated. Additional sampling and data are required to resolve the taxonomic status of several further populations. Overall, our results suggest the occurrence of complex diversification patterns across habitat types and biogeographic regions in sub-Saharan Africa birds.