D3091: Evaluating taxonomic and morphological relationships between pollen and medicinal effects in bumble bees

Host diet can influence disease outcomes in several ways including through nutrition, secondary chemicals, and by increasing resistance to pathogens. Sunflower pollen consumption dramatically and consistently reduces infections of Crithidia bombi, a prevalent trypanosomatid gut parasite, in Bombus impatiens, the common eastern bumble bee. While the specific medicinal properties of sunflower pollen are not understood, a prior study determined that the echinate pollen exine plays a role. Echinate pollen is a common trait of plants in the Asteraceae family, and a survey of the medicinal effects of seven Asteraceae pollens of varying echinate morphology found that consumption of all pollen tested reduced gut C. bombi infections in bees to varying degrees, relative to a smooth control pollen (buckwheat). Here we expanded this survey of pollen by evaluating the effects of ten additional Asteraceae pollens as well as two echinate non- Asteraceae species. To test the role of pollen morphology on medicinal effects, we compared pollen spine lengths to C. bombi infection intensities of bees relative to control pollen (buckwheat). Our preliminary results show that all pollen types with spine lengths of at least 1 micron significantly reduced C. bombi infection intensities relative to bees consuming buckwheat pollen. However, Asteraceae pollens with equivalent spine lengths to non-Asteraceae pollen reduced infections to a significantly greater degree. Preliminary findings suggest that both pollen’s echinate morphology and taxonomic identity play key roles in mediating this medicinal effect. Results from this study may inform the planting of pollinator habitats that reduce pathogens in bees.