Individual bumble bees have small, unique, and persistent foraging repertoires: implications for disease transmission

Abstract

Generalist species forage on a variety of resources, but individual members may specialize on a smaller subset of those resources. Previous attempts to incorporate intraspecific resource specialization in models of disease spread by pollinators have assumed specialization on one flower species, completely partitioning the plant-pollinator network, and very gradual changes in specialization, over days or weeks. These assumptions have not been demonstrated empirically but are critical to model conclusions. Here, we used palynology from sequential pollen loads of individual common eastern bumble bees (Bombus impatiens) to explore their foraging preferences and how they change over time. We found individuals in a bumble bee colony exhibited unique repertoires of two to three flower species while the full-colony repertoire was up to three times larger and varied by time of year. Floral constancy of individual bees lasted roughly ten days before turning over. We developed a disease transmission model parametrized with these empirical results, finding that R0 decreased with each additional flower species in a repertoire, which reduces the separation between theorized disease transmission subnetworks. Our results provide novel insight into the foraging behaviors of social bumble bees and improves understanding of how disease transmission occurs in complex plant-pollinator networks.