Abstract
Animal pollinators, like the generalist bumble bees (Apidae: Bombus spp.), ensure that a majority of flowering plants, including a third of food crops, bear fruit or seed. However, amid such anthropogenic pressures as increasing pesticide use, climate change, and disease spread that threaten bumble bee abundance and diversity, human land use decisions also loom large. Understanding how bumble bees respond to land cover during solitary and social phases of their life cycle will enable better conservation decisions for the future. Here, we document associations of bumble bee nest-seeking, pollen foraging, and colony performance with land cover using studies of commercial bumble bee colonies and wild bumble bee queens in Virginia. Bumble bee colonies in agricultural, grassland, and forested land cover types foraged consistently on Trillium pollen (i.e., clover) over time; however, colonies placed in agriculture land cover peaked in total mass earlier, at a lower weight, than colonies in other land uses. Meanwhile, across the landscape, solitary bumble bee queens foraged on more Lamium pollen (i.e., dead-nettle) at sites with more cropland, and more Prunus pollen (i.e., cherry) at sites with more development; but ultimately, pollen use varied more over time than among land cover contexts or Bombus species. Lastly, queens searched for nest sites in wooded habitats more frequently than expected by random. Altogether, this research demonstrates the flexible foraging strategies of bumble bees and highlights the ways in which human land use can influence their foraging and nesting behaviors and, in turn, fitness.
