Applications to agriculture and conservation
A frequently collected pollen morphotype, Fabaceae_Tricoloporate pollen, likely came from a mix of white clover and alfalfa, as honey bee and bumble bee foragers carrying pollen pellets were often observed foraging for pollen on these plant species (personal observation). While there were fields of soybean (Glycine max ) at the agricultural research station, the pollen of which could not be reliably distinguished from alfalfa or white clover in this study, soybean flowers are cleistogamous, and may not actually open and be accessible to bees (Erickson, 1975). On the other hand, alfalfa and white clover contain nutritional rewards that are attractive to pollinators, and white clover is frequently documented as being an abundantly collected pollen type by honey bees (Keller, Fluri, & Imdorf, 2005). In other agricultural systems, the prevalence of weedy plants, such as white clover in collected pollen has been documented for honey bees (Requier et al., 2018), along with bumble bees and other wild bees (reviewed in Bretagnolle and Gaba 2015). In this study, bees did forage on diverse weedy resources such as those from Fabaceae and Asteraceae on the experimental farm, in addition to probable garden resources such as Geraniaceae by honey bees. Furthermore, we did not observe more than a few pollen grains (contamination levels) coming from maize over the entirety of the study despite the presence of maize fields at the agricultural research station. Honey bees have previously been observed collecting maize when available, but it may actually decrease the longevity of individuals when consumed exclusively (Höcherl, Siede, Illies, Gätschenberger, & Tautz, 2012). These results suggest that bees avoid corn pollen when more favorable resources are present and emphasizes the importance of providing diverse resources for bees that persists throughout the flowering season in human altered systems.