Quid Pro Quo? A Review on Bee Utilization of Pollinator-Independent Crops

Abstract Previous exploration has found that bee visitation tends to benefit yields of many pollinator-independent crops. However, the reverse of this relationship—if pollinator-independent crops benefit bees—has not been extensively studied or explicitly reviewed. Therefore, we initiated a review of the literature using Web of Science and EBSCOhost to determine whether: 1) bees collect pollen from pollinator-independent crops, and 2) pollinator-independent crops provided adequate nutrition for bees. These factors help establish if pollinator-independent crops could benefit bees. We found 45 peer-review articles that included bee pollen trap data on 13 pollinator-independent crops (self-pollinating and wind-pollinated plants), with Zea mays, Brassica napus, and Glycine max pollen most often found in pollen traps. Pollinator-independent crops averaged 12% of total pollen loads, but due to high variability, the median was only 1.6%. Pollen from pollinator-independent crops increased in landscapes with more agricultural cover, but our data was heavily skewed towards honey bees (Apis mellifera). We found the average crude protein for B. napus and G. max was high enough to support honey bee requirements (>20%), along with providing essential amino acids; however, average crude protein and essential amino acids may be lacking in Z. mays. Although some pollinator-independent crops are found in pollen traps and provide adequate resources for bees, they may fail to provide temporally stable resources and chemical-free space. For improved health and reproduction, bees need access to semi-natural landscapes within diverse cropping systems to increase diet mixing. This will help amplify the mutualistic relationship between bees and pollinator-independent crops.