Historical diversification and biogeography of the endemic southern African dung beetle genus, Epirinus (Scarabaeidae: Scarabaeinae)

Abstract

The role of the geological uplift and climatic changes during the late Cenozoic on the species diversification of southern African dung beetles is not fully understood. Therefore, we use a divergence-time-estimated phylogeny, macroevolutionary analyses and ecological niche modelling under different climatic scenarios to investigate diversification of the endemic southern African genus, Epirinus. We predict the ancestral range and vegetation type occupied by Epirinus and how late Cenozoic climatic fluctuations and resulting vegetation changes affected speciation and extinction of Epirinus species. Our results suggest that the genus originated in forest with radiation into three geographical centres: (a) north-east escarpment forest and highland grassland; (b) south-east forest; and (c) south-west lowlands to north-east uplands in open vegetation. Reduced speciation rates in the mid-Miocene and increased extinction rates during the drier and cooler Plio-Pleistocene coincide with the replacement of forest by grassland or savanna in southern Africa. The drier climate in southern Africa may have driven extensive contraction of shaded vegetation, forcing an adaptation of forest inhabitants to upland grassland environments, or driving Epirinus species to extinction. Our study supports hypothesis of climatically driven diversification of Epirinus whereas ecological niche modelling across different geological periods suggest that the south-east and, to a lesser extent, the west coast of South Africa as stable areas.