Venomics and Systematics of Robber Flies (Diptera: Asilidae)

Abstract

Robber flies or assassin flies (Diptera: Asilidae) are a diverse family of venomous predators. The evolutionary history of this venom is poorly known. We leveraged venom transcriptomes from a diversity of robber flies and non-venomous relatives to construct venom gene families and study patterns of positive selection therein. We find that robber fly venoms have relatively few sites under positive selection, consistent with the hypothesis that the venoms of older lineages are dominated by negative selection acting to maintain toxic function. A well-supported and comprehensive phylogenetic framework is needed for further evolutionary studies in robber flies. Unfortunately, the current morphology-based higher classification is not fully supported by molecular studies using traditional molecular markers. We leveraged the recently developed Diptera-wide UCE bait set to compile the largest dataset to date, comprising 151 robber flies and 2,496 loci. Our comprehensive phylogeny confirms that the current classification is flawed and provides a foundation for a thorough revision of these higher taxa. Building on these results, a world catalog of the genera of Asilidae is presented, as well as a revised classification of the subfamilies, tribes, and subtribes. This catalog also includes a hypothesized phylogeny of all higher taxa, a brief analysis of taxonomic trends in generic names, and a preliminary dichotomous key to, and diagnoses for, all higher taxa.