Nest Pollen Provisions from an Urban Population of Megachile campanulae (Hymenoptera: Megachilidae) in Minnesota are Consistent with Oligolectic Classification.

The conservation of bees is crucial for maintaining the essential ecological services they provide. Understanding bee species' risk of extinction is a key part of conservation efforts, and can include assessment of dietary specialization, which has been linked to higher extinction risk. Dietary specialization in bees, called oligolecty, occurs when females select pollen only from closely related plants to feed their larvae. While the solitary bee, Megachile (Chelostomoides) campanulae (Robertson 1903), has been associated with flowers in the genus Campanula L. (Campanulaceae: Asterales), evidence from pollen analysis is limited, and dietary classification is reported inconsistently. This study examined dietary specialization of M. campanulae by inspecting pollen provisions from 16 nest cells in three urban neighborhoods in Minneapolis and Saint Paul, Minnesota. Each provision contained more than 90% Campanula pollen. While limited to one urban area, these findings are consistent with the definition of oligolecty. This outcome suggests that to conserve M. campanulae, people must also conserve Campanula flowers. We recommend including native Campanula species in seed mixes, especially in areas where non-native Campanula is being removed.