Pollination ecology in a selenium-accumulating plant: impacts on visitation and survival of the honey bee

Selenium (Se) has contaminated soils and plants in the western USA and other regions where pollination can be critical to the functioning of both agricultural and natural ecosystems, yet we know very little about how pollutants can impact insect pollinators. Se can be biotransferred and biomagnified throughout the food web, and has negative impacts on plants and the herbivores that feed on them. The overall goal of this study was to investigate both the sublethal and lethal effects of a plant-accumulated pollutant on a common insect pollinator. Using a plant species known to accumulate Se in the pollen and nectar, we conducted a two-year field study examining the pollination ecology of a common, weedy plant (radish, Raphanus sativus L.) and its pollinator, the honey bee (Apis mellifera L.), by quantifying floral traits, pollen limitation, as well as honey bee foraging visits. Se-treated plants remained attractive to honey bees and were not pollen limited. In laboratory studies, honey bee foragers and larvae were fed Se in artificial diet and survival was quantified. Inorganic forms of Se were most toxic to foragers, whereas selenomethionine was only toxic at the highest concentrations. Given that pollinators such as the honey bee cannot avoid Se compounds in the plant tissues they are foraging on, they will suffer similar adverse effects as seen in other insect guilds. Our study sheds light on how plant-accumulated pollutants such as Se can impact pollinators through a lack of recognition or modification in foraging behaviors that result in reduced survival.