Phylogeographic pointers to conservation needs: South Africa's flagship dung beetle,Circellium bacchus

Abstract

Circellium bacchus is South Africa's largest ball-rolling dung beetle and a habitat specialist of dense bush. It is also wingless, a rare phenomenon amongst large dung beetles and, unusual for the group, only females construct and bury brood balls. She cares for the single brood for 4–5 months, and lives for 3–5 years. The beetles currently occur in two separate populations in South Africa, one in the south-east and one consisting of at least eight fragmented sub-populations in the south-west. Here, we use both mitochondrial and nuclear DNA sequences to infer the evolutionary history of this species. The Eastern and Western populations are genetically separated by 14% mitochondrial sequence divergence, sharing only a single nuclear haplotype. Mitochondrial and nuclear data indicate that C. bacchus belongs to an ancient (Eocene) relict lineage and that the Eastern and Western populations appear to have been separated by Pliocene continental uplift and a relictual Pleistocene block of temperate forest. Subsequent Plio-Pleistocene climatic change caused further fragmentation of the Western population, now exacerbated by human-induced land transformation. The Eastern and Western populations are identifiable as two distinctly separate entities of possible species status, but with definite need for recognition as evolutionary significant units. The Western sub-populations are genetically significantly different enough to be defined and recognised as management units. The Eastern population is largely distributed in the Addo Elephant National Park where its persistence is currently secure, but the sub-populations of the Western lineage occur as fragments of various sizes in a matrix of agriculturally transformed landscape.