Submitted to: Systematic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/21/2013
Publication Date: 5/8/2013
Citation: Rightmyer, M.G., Griswold, T.L., Brady, S. 2013. Phylogeny and systematics of the bee genus Osmia (Hymenoptera: megachilidae) with emphasis on North American melanosmia: new subgenera, synonymies, and nesting biology revisited. Systematic Entomology. 38:561-576. Interpretive Summary: The mason bee genus Osmia includes a large number of species, more than 150 in the United States, that are very important as pollinators of native plants and as potential crop pollinators. Species in the group are often difficult to differentiate and the relationships within the genus have been unclear. Using multiple genes this study provides a family tree of relationships. The result is a revised taxonomy in the genus that includes two new subgenera. Important biological traits, and the structural characters that relate to them, are mapped onto the family tree. The taxonomic status of North American species is updated, with 15 previously valid species placed into synonymy. This study provides the foundation for future revisionary studies of individual subgenera.
Technical Abstract: The predominantly holarctic bee genus Osmia is species-rich and behaviorally diverse. A robust phylogeny of this genus is important for understanding the evolution of the immense variety of morphological and behavioral traits exhibited by this group. We infer a phylogeny of Osmia using DNA sequence data obtained from three nuclear genes (elongation factor 1-a, LW-rhodopsin and CAD) and the mitochondrial gene COI. Our phylogeny provides strong support for the recognition of Hapsidosmia and Thysanosmia, new subgenera. The former is a monotypic subgenus containing Osmia iridis Cockerell, while the latter contains many species formerly placed in Centrosmia Robertson. Our taxon sampling places special attention on North American members of the subgenus Melanosmia; we discuss the novel placement of a number of species traditionally assigned to Melanosmia and examine the relative support for alternative classifications of this species-rich subgenus. We refine the morphological diagnostic characters that serve to define Acanthosmioides Ashmead and show that the clade is derived within Melanosmia s. l. We demonstrate more cohesive patterns of nest substrate use in Thysanosmia and Acanthosmioides than was previously believed to occur, reconsider character polarity of aspects of the female mandible, and show that a large number of morphological characters have evolved convergently within the genus. In order to facilitate discussion of relevant taxa, we propose the following 15 new synonymies: O. bakeri Sandhouse under O. melanopleura Cockerell; O. crenulaticornis Michener under O. pinorum Cockerell; O. claremontensis Michener under O. sedula Sandhouse; O. cockerelli Sandhouse under O. dakotensis Michener; O. francisconis White under O. enixa Sandhouse; O. hurdi White under O. austromaritima Michener; O. sladeni Sandhouse under O. nifoata Cockerell; O. titusi Cockerell under O. phenax Cockerell; O. subtrevoris Cockerell, O. physariae Cockerell, and O. erecta Michener under O. giliarum Cockerell; and O. universitatis Cockerell, O. integrella Cockerell, O. amala Cockerell, and O. metitia Cockerell under O. nigrifrons Cresson, new synonymies. We remove O. wyomingensis Michener from synonymy with O. nifoata Cockerell, new status, and O. pinorum Cockerell from synonymy with O. physariae Cockerell, new status.