Phylogeny, historical biogeography and divergence time estimates of the genus Colophon Gray (Coleoptera : Lucanidae)

Abstract

The flightless Cape High-mountain stag beetle genus Colophon (Coleoptera: Lucanidae) is studied. All species are endemic to the Cape Floristic Region of the Western Cape, South Africa. The study aimed to determine the specific and phylogenetic status of the described species of Colophon and to determine the main factors driving their evolution by testing the hypothesis of a lowland origin. This was achieved by analysing the mitochondrial COI, 16S rRNA and nuclear CAD genes, using a maximum likelihood and Bayesian approach. Timing of key biogeographical events in the diversification of Colophon was estimated in BEAST. The combined molecular dataset supports the described species. High genetic divergence was found between the described taxa. The mean estimated divergence of the genus was mid-Cretaceous, with a split into two lineages during the early Paleocene to mid Eocene. Species divergence was shown to have occurred during mid to late Miocene. Most species of Colophon showed an allopatric distribution, although contact zones between geographically adjacent species are likely. Climate seems to be the main driving factor behind Colophon evolution and the hypothesis of a lowland origin appears to be supported.