Preliminary phylogenomic analyses reveal multiple reversions to nocturnal behavior and morphology within the primarily diurnal tribe Adesmiini (Coleoptera: Tenebrionidae)

Abstract

The darkling beetle tribe Adesmiini (Tenebrionidae: Pimeliinae) is a prominent part of African and western Palearctic desert faunas, with most species being day-active fast-running detritivores. Taxonomic diversity within the tribe is highest in the southern Afrotropical realm (where all genera are present); only 1 genus, the species-rich Adesmia, occurs north of the Sahara. Despite notable species, such as the fog-basking beetle Onymacris unguicularis (a focal taxon in desert ecological research), Adesmiini has undergone few modern taxonomic or phylogenetic studies. Hence, generic concepts and pronounced diurnal activity, rare in the primarily nocturnal family Tenebrionidae, remain poorly explored. To investigate evolutionary relationships and diurnal origins within the tribe, we generated a genomic dataset of 529 protein-coding genes across 43 species spanning 10 of 11 Adesmiini genera. Our resulting phylogeny for the tribe rejects the monophyly of 5 currently recognized Adesmiini genera (i.e., Adesmia, Metriopus, Onymacris, Physadesmia, and Stenocara). Ancestral state reconstruction of diurnal activity using eye shape as a proxy supports the hypothesis that Adesmiini were primitively diurnal, followed by at least 4 shifts to nocturnal or crepuscular activity.