A phylogenetic analysis of nesting behavior in the genus Osmia (Hymenoptera : Megachilidae)

Cladistic analysis is used to study the evolution of 29 biological characte rs related to nesting behavior, nest provisioning, oviposition, cocoon spin ning, defecation, and life cycle (nest characters) in 11 species of Osmia b ees (Hymenoptera: Megachilidae) and two outgroup genera. A molecular phylog eny based on 38 allozyme loci-as-characters and a combined character phylog eny are produced to compare with the nest character phylogeny. All phylogen etic trees support the monophyly of the genus Osmia and the subgenus Osmia (Osmia) with Osmia ribifloris Cockerell basal to the other species in this subgenus. The subgenus Helicosmia (=Chalcosmia) is resolved as a sister cla de to O. (Osmia) in the molecular tree and as sister to the subgenus Cephal osmia in the nest character and combined trees. Incomplete biological infor mation from additional species of all three subgenera is provided to suppor t the consistency of nest characters at the subgeneric level and their use in the establishment of subgeneric phylogenies in the family Megachilidae.