Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/8/2008
Publication Date: 10/1/2008
Citation: Praz, C.J., Muller, A., Danforth, B.N., Griswold, T.L., Widmer, A., Dorn, S. 2008. Phylogeny and Biogeography of Bees of the Tribe Osmiini (Hymenoptera: Megachilidae). Molecular Phylogenetics and Evolution 49:185-197. Interpretive Summary: The mason bees (the bee tribe Osmiini) are a very diverse group of over a thousand species of pollinators found throughout North America, Europe, Africa, and temperate Asia. They are of considerable importance because of their potential as manageable crop pollinators. Most species nest in wood or stems, making them easier to manipulate than the vast majority of bees that nest in soil. Work to identify species in this still poorly known group is hampered by the lack of a solid historical framework of relationships that will provide the taxonomic base for needed revisions. Such revisionary studies will allow accurate identifications of these abundant pollinators. DNA sequences from three genes were used to determine relationships among supposed mason bees. The results show that some of the bees traditionally included in the group are not closely related and should be removed. Generic limits within this bee tribe are defined. The DNA work suggests that mason bees originated in Europe and that there have been frequent colonization events between Europe and North America that go both ways. The habit of nesting in wood or stems probably facilitated this movement.
Technical Abstract: The Osmiini (Megachilidae) constitute a taxonomically and biologically diverse tribe of bees. To resolve their generic and suprageneric relationships, we inferred a phylogeny based on three nuclear genes (Elongation factor 1-alpha, LW-rhodopsin and CAD) applying both parsimony and Bayesian methods. Our phylogeny, which includes 95 osmiine species representing 18 of the 19 currently recognized genera, is well resolved with high support for most basal nodes. The core osmiine genera were found to form a well-supported monophyletic group, but four small genera, Noteriades, Afroheriades, Pseudoheriades and possibly Ochreriades, formerly included in the Osmiini, do not appear to belong within this tribe. Our phylogeny results in the following taxonomic changes: Stenosmia and Hoplosmia are reduced to subgeneric rank in Hoplitis and Osmia, respectively, Micreriades is recognized as a subgenus in Hoplitis and the subgenus Nasutosmia is transferred from Hoplitis to Osmia. We inferred a biogeographic scenario for the Osmiini applying maximum likelihood inference and models of character evolution. We provide evidence that the Osmiini originated in the Palearctic, and that extensive exchanges occurred between the Palearctic and the Nearctic. The latter finding may relate to the fact that many osmiine species nest in wood or in stems, facilitating dispersal by overseas transport of the nests.