Approximately 18 Osmia species are native to the Commonwealth of Virginia. Among the exotic Osmia species in Virginia, two mason bee species introduced from Japan are now established in the United States. The Japanese horn-faced bee, Osmia cornifrons, was intentionally introduced by United States Department of Agriculture researchers successfully in the 1960’s-70’s for crop pollination services. In 2002, another Japanese mason bee, Osmia taurus, was first documented in the United States, and at this time, there is no explanation for how O. taurus arrived in the US. This study examines the rise in relative abundance and dominance of O. taurus across Maryland and Virginia through 600 pan-trapping events from 2002-2015.
Results/Conclusions:
After accounting for sampling effort and then aggregation of collection events based on close distances (close distance = collection efforts occurring within 1.2km), O. taurus exhibited a strong increase in relative abundance in trapping events across years, from accounting for an average 12% per location of all Osmia collected between 2002-2008 (n=25 aggregated sampling events, 1,311 Osmia specimens) but then accounting for an average of 39% per location of all Osmia collected between 2009-2015 (n=56 aggregated sampling events, 2,600 specimens). Osmia taurus was found in only 11 of 24 aggregated sampling events between 2002-2008 but was found in 56 of 56 sampling events 2009-2015. With the pattern of rapid and dominant increase of O. taurus, future work should elucidate which mechanisms facilitate spread and proliferation of exotic Osmia and whether their increase has a deleterious impact on native Osmia.