Abstract
A potential driver of pollinator declines that has been hypothesized but seldom documented is the introduction of exotic pollinator species. International trade often involves movement of many insect pollinators, especially bees, beyond their natural range. For agricultural purposes or by inadvertent cargo shipment, bee species successfully establishing in new ranges could compete with native bees for food and nesting resources. In the Mid-Atlantic United States, two Asian species of mason bee (Osmia taurus and O. cornifrons) have become recently established. Using pan-trap records from the Mid-Atlantic US, we examined catch abundance of two exotic and six native Osmia species over the span of fifteen years (2003–2017) to estimate abundance changes. All native species showed substantial annual declines, resulting in cumulative catch losses ranging 76–91% since 2003. Exotic species fared much better, with O. cornifrons stable and O. taurus increasing by 800% since 2003. We characterize the areas of niche overlap that may lead to competition between native and exotic species of Osmia, and we discuss how disease spillover and enemy release in this system may result in the patterns we document.
Highlights
A potential driver of pollinator declines that has been hypothesized but seldom documented is the introduction of exotic pollinator species
Annual capture rates for the genus Osmia as a whole significantly decreased at a mean of 6.64% per year for the species with n > 50 specimens, and declining at a mean of 7.25% per year when all Osmia records were included in the dataset (Fig. 2, Table 1)
We report a significant surge in the abundance of the exotic solitary bee species Osmia taurus with concurrent losses of all six native Osmia species in our analysis
Summary
A potential driver of pollinator declines that has been hypothesized but seldom documented is the introduction of exotic pollinator species. In the Mid-Atlantic United States, two Asian species of mason bee (Osmia taurus and O. cornifrons) have become recently established. One outcome of species introductions is the potential for competitive interactions with native species, especially those that are most closely related to the introduced species. When closely related species co-occur and overlap in key parts of their life cycle, negative competitive interactions may result, potentially altering ecological and evolutionary trajectories[1]. The success of exotic species establishing in their new range may be facilitated by several factors, including escaping enemies from its home r ange[2] and introducing novel enemies, such as exotic diseases, to native competitors in the new range[3]. In addition to native Osmia, two mason bee species introduced from Asia have recently naturalized
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