Onymacris Allard 1885 (Tenebrionidae) is a charismatic genus of beetles endemic to the Namib Desert and known worldwide for its fog-basking abilities and taxa that exhibit unique white, tan and striped elytral coloration. Although Onymacris is considered a model system within desert organisms, past studies regarding behavior, ecology, and physiology did not take phylogenetic relationships into account and thus provide a limited scope for downstream comparative evolutionary studies. Despite increased interest in the phylogenetics of Onymacris during the last few decades, none of these studies have been able to infer a complete phylogeny due to limited specimen sampling. Here, we present a robust sub-genomic phylogeny inferred using ultraconserved elements (UCEs) for all Onymacris species and subspecies, totaling 21 named taxa and several outgroups. This phylogeny provides the missing phylogenomic resource needed for studying questions regarding ecology, coloration, dispersal, and fog-basking abilities. We evaluate the relationship between Onymacris and Physadesmia globasa, an all-black beetle currently nested within Onymacris as sister to the ‘white’ clade. Additionally, this phylogeny allows us to examine several populations of ‘white’ Onymacris species suspected of being evolutionarily distinct lineages requiring species delimitation. Our UCE dataset will be transformative for current and future examination of the molecular systematics and ecology of Onymacris, especially regarding the evolution and potential function of white elytra in xeric-dwelling beetles as such widespread color variations are unknown from any other desert tenebrionid species.
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