Allopatric speciation in the flightless Phoberus capensis (Coleoptera : Trogidae) group, with description of two new species

Abstract

The name Phoberus capensis (Scholtz) is applied to a small flightless, keratinophagous beetle endemic to the Cape Floristic Region of South Africa. Its gross distribution stretches from roughly 1000 km from the Cederberg (S32°24'22" E19°04'50") to Grahamstown (S33°20'07" E26°32'50"). The populations are spatially discrete, restricted to relict forests of the southern Cape and disjunct high montane refugia of the Cape Fold Mountains. We test the hypothesis that there is more than one distinct species nested within the name P. capensis. Phylogenetic relationships among populations were inferred using molecular sequence data. The results support three distinct evolutionary lineages, which were also supported by morphological characters. Divergence time estimates suggest Pliocene-Pleistocene diversification. Based on these results, it is suggested that the P. capensis lineage experienced climatically-driven allopatric speciation with sheltered Afrotemperate forests and high mountain peaks serving as important refugia in response to climatic ameliorations. The P. capensis complex thus represents a speciation process in which flight-restricted populations evolved in close allopatry, possibly as recently as the Pleistocene. Two divergent and geographically distinct lineages are described as novel species: The new species, P. disjunctus sp. n. and P. herminae sp. n., are illustrated by photographs of habitus and male aedeagi.