9801274 Thomson This research will assess the effect of the European honey bee, Apis mellifera, on the native solitary bee, Osmia pumila. Previous studies investigating the effects of invasive social insects concentrated on native social species. This study focuses on native solitary species, which may be more vulnerable to competition with social species. The importance of competitive effects relative to other factors influencing O. pumila fitness will be determined with field and enclosure studies. Field experiments will provide measures of reproductive success of O. pumila at different densities of honey bees. The mechanism of interaction will be investigated by examining possible shifts in resource use of O. pumila associated with increased honey bee density. Enclosure experiments will test for indirect effects of competition on O. pumila fitness mediated through increased parasitism rates. Data from both approaches will allow some predictions of O. pumila population dynamics under different competitive regimes. These experiments will yield timely information on a ubiquitous and prolific introduced species whose beneficial and detrimental impacts are being debated currently in ecological and agricultural arenas. This system's unique features allow a robust experimental design, but the results are broadly applicable to work on biological invasions, particularly those involving social insects.
