Foraging strategy predicts species-specific patterns of pollen foraging by honey bees and bumble bees

Authors: MINAHAN, DANIEL - University Of Wisconsin; Brunet, Johanne

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2019
Publication Date: 2/26/2019
Citation: Minahan, D., Brunet, J. 2019. Foraging strategy predicts species-specific patterns of pollen foraging by honey bees and bumble bees. Ecology and Evolution. PLoS ONE 14(2):e0212561. https://doi.org/10.1371/journal.pone.0212561.
DOI: https://doi.org/10.1371/journal.pone.0212561

Interpretive Summary: Pollinators are in decline and it is important to design pollinator friendly habitats to help conserve their populations. However, the resources necessary to support different bee species can vary. In addition, bees need resources available throughout the foraging season. Understanding similarities and differences in pollen foraging strategies between pollinator species will help the design of pollinator friendly habitats that can sustain a variety of bee species. We compared pollen collected by bumble bees and honey bees throughout the foraging season at three distinct sites. Honey bees were more likely to collect pollen from a single plant family during a foraging trip relative to bumble bees. Bumble bee colonies tended to collect pollen from more plant families and collected more diverse pollen relative to honey bees. Both bee species collected less diverse pollen early in the foraging season. Bumble bees indicated a preference for some plant groups while honey bees tended to forage randomly. The respective foraging strategy, dance communication of honey bees vis-a-vis the traplining of bumble bees, predicted these different patterns of pollen collection. This information is useful to anyone interested in bee conservation, but applies directly to agencies and researchers working at developing habitats to help preserve diverse bee species.

Technical Abstract: Honey bees and bumble bees are generalist eusocial bees that collect resources from a variety of plant taxa. Both bee species have distinct foraging strategies that affect patterns of resource collection, with implications for designing pollinator friendly habitat management schemes. Using a comparative approach, we examined the pollen foraging patterns of the honey bee (Apis mellifera) and common eastern bumble bee (Bombus impatiens) in a developed suburban-agricultural landscape. We tested predictions stemming from the bees’ known foraging strategies of dance communication or trapline foraging, respectively. We collected pollen from returning foragers of each bee species over five time periods at each of three sites. We quantified the frequency of flower constant foragers and the richness and diversity of pollen collected by a colony, along with exploring preferences by comparing the taxonomic identity of pollen collected to the resources available. Within individual foraging trips, honey bees collected pollen from a single plant family more frequently than bumble bees throughout the summer, except during August, when both bee species had a similar frequency of family constant foragers. The number of pollen families collected by colonies varied differentially between the two bee species over time. However, pollen diversity was greater for bumble bees relative to honey bees, and both bee species collected less diverse pollen in June. Finally, bumble bees preferred Fabaceae_Tricolporate pollen, and avoided Apiaceae pollen, while honey bees foraged randomly. These results support the hypothesis that foraging strategies affect how bees exploit pollen resources. The dance communication of honey bees was associated with a greater frequency of flower constant foragers, lower diversity of collected pollen, and random foraging among available resources. In contrast, trapline foraging by bumble bees was linked to less frequent flower constant foraging bouts, greater pollen diversity, and preference for some plant types. Explicitly considering pollinator foraging strategy when designing agri-environment schemes will facilitate the development of pollinator friendly habitats that also support pollination of bee-dependent crops.