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

One of the most agriculturally important non-Apis groups of bees is the mason bee subgenus Osmia (Osmia), or Osmia sensu stricto. 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. 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. In this study we integrated molecular phylogenomic data from Ultra-Conserved Elements (UCEs), near complete taxon sampling, and a diversity of analytical approaches to robustly infer phylogeny and biogeographic history Osmia s.s. In order to examine species boundaries, we also skimmed mitochondrial sequence data from UCE sequences and combined these sequences with data from public repositories. 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. The mtDNA results highlight several taxonomic problems in the subgenus, suggesting that several species might need to be synonymized.