(1st Place) Colorless but never dull: untangling population genomics and color evolution of "white" darkling beetles (Onymacris)

In the Namib Desert, one of the largest and oldest deserts, the genus Onymacris contains a rarity for darkling beetles (Tenebrionidae) – the presence of eight species with striking ‘white’ elytra (ranging from stark white to tan/striped). This study seeks to examine the phylogenetic relationships among white Onymacris species to test whether multiple derivations of white elytra is due to convergence or introgression. Population genomic data (3RAD) was generated from all white species of Onymacris with intraspecific sampling for four widespread species (O. marginipennis, O. bicolor, O. candidipennis, O. langi cornelii). Phylogenetic trees were inferred from 995 loci using concatenated and coalescent-based methods. The analyses supported two clades: langi and bicolor each of which contain species with pure white elytra. Variational autoencoder (VAE) clustering analysis shows a pattern of genetically isolated populations (bicolor) and gene flow indicating introgression (langi). These analyses also infer a potential new Angolan species sister to O. marginipennis in need of evaluation. Ancestral character state and biogeographic reconstruction resolve the timing of white species’ color expression against the backdrop of sand sea emergence and increased aridity in the Namib, a landscape renown for ‘pocket speciation’ and an impressive amount of darkling beetle diversity accounting for nearly 80% of the known endemic beetle fauna. Dynamic coloration provides a fascinating system through which to examine the role of ecological pressures and evolutionary mechanisms but requires a phylogenetic framework to understand organisms’ potential adaptations to extreme environments, which is increasingly vital in the face of global trends aridity trends.