The effect of bumblebee caste on individuals\u27 response to medicinal pollen

Insect pollinators are important for natural and agricultural ecosystems. They are responsible for maintenance and reproduction of many endangered flowering plant species as well as pollinating crops that are economically important. However, insect pollinator populations, particularly for bumblebees, are declining and while the causes are not entirely known, it is hypothesized that habitat fragmentation, pesticides, climate change, and disease are among the most likely causes. My study focuses on the common eastern bumblebee (Bombus impatiens ) and one of its common parasites Crithidia bombi . Past research by Giacomini et al. (in review) found that sunflower pollen significantly reduced Crithidia loads in B. impatiens workers. However, there is very little research on how pollen might affect the reproductive castes of bee: drones and queens. B. impatiens drones, queens, and workers were infected with Crithidia and fed either sunflower pollen or mixed wildflower pollen for seven days. They were then dissected and their Crithidia loads assessed. The sample size for queens was too small to include in formal analysis. We constructed a statistical model to test the effect of diet on each caste and found the interaction between diet and caste to be significant. Sunflower pollen significantly lowered Crithidia load in workers while diet in drones did not significantly affect Crithidia counts. This inverse effect could be explained by differences in physiology and life history. Drones are haploid and workers and queens are diploid, which could cause some of the variation in the response we found. Drones hatch late in the summer, so the availability of flowers differs from when workers are hatched in the spring. Because B. impatiens are important pollinators, the impact of diet on pathogenic loads is an important area of study. Future research should include other pollen types of late and early blooming flowers as well as increased sample sizes for both drones and queen