Wild bee and Apis mellifera floral resource selection in agriculturally dominated landscapes

Enhancing floral resources on conservation grasslands in agro-ecosystems is an important strategy for improving pollinator habitat. Many seed mix recommendations for pollinator habitat are in-part based on anecdotal evidence or field observations of bees visiting forbs (i.e., use). However, there is limited information on which forbs are preferred or selected by bees (higher use than expected based on availability). Furthermore, little is known about which forbs successfully establish on private lands enrolled in US Department of Agriculture (USDA) conservation programs and the potential pollinator value of those forbs. We examined floral selection by wild bees and Apis mellifera on grasslands in the upper Midwest using a 5-year dataset containing over 8,000 plant-bee interactions. We found that wild bees selected more native forb species than Apis mellifera, and Apis mellifera selected only four species throughout the growing season. Forb selection by wild bees was generally different than Apis mellifera, suggesting seed mixes may need to be tailored specifically to different bee taxa. We also obtained the original seed mixes of specific private-land, USDA enrollments and used an observational approach to assess which seeded forb species had the highest blooming detection rates and lowest cost. We identified 17 forbs as having higher than average blooming detection rates and lower than average cost. Pairing forb preference data with establishment research and monetary cost can assist natural resource managers with designing more cost-effective seed mixes for pollinators, while maximizing investment in federal conservation programs.