Native Mason Bees Decline in the Wake of Non-Native Mason Bee Introductions

In the Eastern United States, two mason bee species from Asia have become recently established. The Japanese horn-faced bee, Osmia cornifrons Radoszkowski 1887, was intentionally introduced from Japan by the United States Department of Agriculture (USDA) in the 1970’s for crop pollination services. In 2002, another mason bee from Asia, Osmia taurus Smith 1873, was first documented in the United States, without record of its being intentionally imported. My dissertation first documents trends of native Osmia species decline with the concurrent increase of non-native Osmia taurus (Chapter 1) from 2003-2017. In Chapter 2, I investigate the occurrence of fungi originally described in Japan (genus Ascosphaera) now expanding their host range to native Osmia species in Virginia. In Chapter 3, I evaluate the differential climatic distributions of O. taurus and O. cornifrons in Virginia that offer clues for why O. taurus has such a marked regional increase since 2003 compared to unchanging levels of O. cornifrons. Lastly, in Chapter 4, I sought to evaluate the conservation utility of “bee hotels” for native springtime Osmia. I document how bee hotels in anthropogenically disturbed landscapes offer disparate outcomes for native and non-native Osmia species. In particular, non-native Osmia are attacked by parasitic wasps less frequently than native Osmia inside these nesting structures even though non-native Osmia are found most frequently inside bee hotels. Bee hotels may facilitate a demographic release of the invasive O. taurus, and these negative outcomes for native Osmia in bee hotels call into question the conservation utility of bee hotels in the Virginia springtime season.