Phylogenomics and historical biogeography of the cleptoparasitic bee genus Nomada (Hymenoptera: Apidae) using ultraconserved elements

Phylogenomics and biogeography of the small carpenter bees (Apidae: Xylocopinae: Ceratina)

Small carpenter bees in the genus Ceratina are behaviourally diverse, species-rich, and cosmopolitan, with over 370 species and a range including all continents except Antarctica. Here, we present the first comprehensive phylogeny of the genus based on ultraconserved element (UCE) phylogenomic data, covering a total of 185 ingroup specimens representing 22 of the 25 current subgenera. Our results support most recognized subgenera as natural groups, but we also highlight several groups in need of taxonomic revision - particularly the nominate subgenus Ceratina sensu stricto - and several clades that likely need to be described as new subgenera. In addition to phylogeny, we explore the evolutionary history of Ceratina through divergence time estimation and biogeographic reconstruction. Our findings suggest that Ceratinini split from its sister tribe Allodapini about 72 million years ago. The common ancestor of Ceratina emerged in the Afrotropical realm approximately 42 million years ago, near the Middle Eocene Climatic Optimum. Multiple subsequent dispersal events led to the present cosmopolitan distribution of Ceratina, with the majority of transitions occurring between the Afrotropics, Indomalaya, and the Palearctic. Additional movements also led to the arrival of Ceratina in Madagascar, Australasia, and a single colonization of the Americas. Dispersal events were asymmetrical overall, with temperate regions primarily acting as destinations for migrations from tropical source regions.

The genome sequence of Fabricius' Nomad Bee, Nomada fabriciana (Linne, 1767)

We present a genome assembly from an individual female Nomada fabriciana (Fabricius' Nomad Bee; Arthropoda; Insecta; Hymenoptera; Apidae). The genome sequence is 233.6 megabases in span. Most of the assembly is scaffolded into 12 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 19.4 kilobases in length. Gene annotation of this assembly on Ensembl identified 9,700 protein coding genes.

Harrison's rule corroborated for the body size of cleptoparasitic cuckoo bees (Hymenoptera: Apidae: Nomadinae) and their hosts

Harrison’s rule, that body size is positively correlated between parasites and hosts, has been reported in a range of taxa, but whether the rule is applicable to cleptoparasitic insects is poorly understood. Subfamily Nomadinae, the largest group of cleptoparasitic bees, usurp the nests of a variety of host bees. Within the subfamily, Nomada exploits the most diverse hosts, using at least ten genera from five families. Here, we reassess the phylogeny of Nomadinae, including the expanded sampling of the genus Nomada, to explore host shift fluctuations throughout their evolutionary history and test the applicability of Harrison’s rule for the subfamily. Our phylogenetic results are mostly congruent with previous investigations, but we infer the tribe Hexepeolini as a sister taxon to the tribe Nomadini. Additionally, the results reveal discrepancies with the traditional classifications of Nomada. Ancestral state reconstruction of host use indicates that, early in their evolution, parasites used closer relatives, before attacking less related groups later. Lastly, we confirm Harrison’s rule in Nomadinae, supporting that body size dynamics influence the host shifts of cleptoparasitic bees.