UCE phylogenomics and biogeography of the agriculturally important mason bee subgenus Osmia (Osmia)

One of the most important non-Apis groups of bees for agriculture is the mason bee subgenus Osmia (Osmia), or Osmia sensu stricto (s.s.). Out of the 29 known species, four have been developed as managed pollinators for orchards and several others have been considered for use. Additionally, the group is important as a source of non-native pollinators, given that several species have been intentionally or accidentally introduced into new areas, with at least two species becoming established. Osmia s.s. occurs naturally throughout the temperate zone but has most of its species diversity in Europe and Asia. Despite the group's importance, few studies have examined its phylogeny or taxonomy comprehensively, and none have included a formal biogeographic analysis. Here, we integrate molecular phylogenomic data from Ultra-Conserved Elements (UCEs), near complete taxon sampling, and a diversity of analytical approaches to robustly infer the group's phylogeny, divergence times, and biogeographic history. We also demonstrate how mitochondrial sequence data can be extracted from UCE data and combined with data from public repositories in order to test the phylogeny, examine species boundaries, and identify specimen-associated, non-bee DNA. We confidently resolve the phylogeny of Osmia s.s., finding little conflict across analyses, and confirm with strong support that the Nearctic species O. ribifloris is the sister group to all remaining species. Biogeographic analyses indicate that the group originated during the Late Miocene in the West Nearctic (WN) plus East Palearctic region following dispersal from the EP into the WN across the Bering land bridge prior to its closure 5.5-4.8 Ma. The mtDNA results highlight several taxonomic problems in the subgenus, supporting the conclusion that several species most likely need to be synonymized. Overall, the new phylogeny provides a robust estimate of relationships among agriculturally important species and relatives and should prove to be a useful resource for future research efforts.