A multilocus perspective on phylogenetic relationships in the Namib darkling beetle genus Onymacris (Tenebrionidae)

Tenebrionid beetles, common constituent faunae of arid ecosystems worldwide, are particularly abundant in Africa’s Namib and Kalahari deserts. Within this region, flightless, diurnal members of the tribe Adesmiini are among the more intensively studied of all desert beetles, especially with regard to ecology. Much of this research centers on Onymacris, a psammophilous genus largely endemic to the Namib. Here we present the first molecular phylogenetic analysis conducted for Onymacris, emphasizing relationships among other adesmiines. Our multilocus phylogeny identifies a strongly supported clade containing Onymacris and two other genera, Eustolopus and Physadesmia—an assemblage recovered in earlier morphological analyses. However, Onymacris is not monophyletic; rather, we demonstrate its paraphyly with respect to the genus Physadesmia, identified as the sister taxon to the white-bodied species of Onymacris. In turn, the Physadesmia-‘white’ Onymacris clade is the sister group to the remaining (black-bodied) Onymacris. Non-monophyly of ‘black’ versus ‘white’ Onymacris is corroborated by distribution patterns and nodal age estimates, which suggest separate origins in different dune systems.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Phylogeny of the African tenebrionid beetle genus Onymacris is inferred. ► Using mitochondrial and nuclear genes the monophyly of Onymacris is rejected. ► Onymacris is instead paraphyletic with respect to Physadesmia. ► Molecular clock dating reveals close correspondence with Namib dunefield geology. ► Black-bodied and white-bodied clades of Onymacris have different centers of origin.