Did dung beetles arise in Africa? A phylogenetic hypothesis based on five gene regions

Abstract

Scarabaeinae dung beetle phylogenetics are poorly understood, although recent phylogenetic reconstruction based on morphology and molecular analyses are congruent on the hypothesis that the oldest Gondwana tribes are polyphyletic and that representatives of the ancestral groups are found in Africa. We present a molecular phylogeny of the African representatives of the two oldest tribes, Canthonini (the putative ancestor of all "rollers") and Dichotomiini (thought to represent the ancestral "tunnellers"), based on partial sequence data from two mitochondrial and three nuclear genes, extracted from eight of the nine dichotomiine genera and 17 of the 23 genera of Canthonini. Three well-supported lineages were consistently obtained. Divergence times estimated the origin of the two tribes at around 56 million years ago (MYA) with the splits of the three dung beetle lineages being estimated to have taken place between 40 and 34MYA. The ages of these splits and subsequent radiation of the modern dung beetle groups concur with those predicted by the fossil record and coincide with the proposed age of radiation of the large mammal groups with whose dung most African dung beetles are still associated. Dispersal of dung beetle groups from Africa is proposed as a biogeographic model, and evidence is presented that dung beetles disperse quickly and widely across continents, and even oceans.