Phylogenomic and Morphological Reevaluation of the Bee Tribes Biastini, Neolarrini, and Townsendiellini (Hymenoptera: Apidae) With Description of Three New Species of Schwarzia

Abstract Bees of the tribes Biastini, Neolarrini, and Townsendiellini are cleptoparasites in the subfamily Nomadinae (Hymenoptera, Apidae) and parasitize solitary bees. Understanding their phylogenetic relationships has proven difficult for many decades. Previous research yielded ambiguous results because of conflicting phylogenetic signals of larval and adult morphological characters. Molecular data settled some of this disparity but our knowledge remains fragmented due to limited taxon sampling and the discovery of a new lineage associated with Biastini: the enigmatic Schwarzia Eardley, 2009. Schwarzia has unusual morphological features and seems transitional between previously established taxa. This puts limits on our ability to diagnose the groups, understand their antiquity and biogeography, and study the evolution of host-choice. To address this, we integrate phylogenomics and morphology to establish a fossil-calibrated phylogeny for the tribes Biastini, Neolarrini, and Townsendiellini. We show that Schwarzia is indeed closely related to Biastes Panzer, 1806, but Biastes itself is paraphyletic in respect to Neopasites Ashmead, 1898, and even Biastini is paraphyletic due to Townsendiella Crawford, 1916, which is sister to Rhopalolemma Roig-Alsina, 1991. To ensure monophyly, we lower Neopasites to subgeneric rank within Biastes and resurrect Melittoxena Morawitz, 1873 as a third subgenus. We then assess the diagnosability of different tribal concepts and establish an expanded tribe Neolarrini that includes Biastini and Townsendiellini as new synonyms for Neolarrini. Neolarrini in this new, expanded sense likely originated in the Nearctic in the mid-Eocene and is, as far we know, composed exclusively of parasites of oligolectic hosts. Lastly, our continued efforts to find the rare Schwarzia in Eastern Africa led to the discovery of three new species, which are described herein.