Linking the foraging behavior of three bee species to pollen dispersal and gene flow

Authors: Brunet, Johanne; ZHAO, YANG - University Of Wisconsin; CLAYTON, MURRAY - University Of Wisconsin

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2019
Publication Date: 2/26/2019
Citation: Brunet, J., Zhao, Y., Clayton, M.K. 2019. Linking the foraging behavior of three bee species to pollen dispersal and gene flow. PLoS One. 14(2):e0212561. https://doi.org/10.1371/journal.pone.0212561.
DOI: https://doi.org/10.1371/journal.pone.0212561

Interpretive Summary: This study compares the foraging behaviors of three distinct bee species, the European honey bee, Apis mellifera L., the common eastern bumble bee, Bombus impatiens Cr., and the alfalfa leafcutting bee, Megachile rotundata F., foraging on Medicago sativa flowers, with the goal of identifying behaviors that affect gene flow. All foraging behaviors differed among bee species with bumble bees traveling the longest net distances, honey bees preferring some overall directions and leafcutting bees, but not bumble bees or honey bees, moving randomly within foraging bouts. Specific foraging behaviors were ranked in order to predict relative gene flow risks. These relative risks (gene flow distances) were then tested against existing empirical gene flow data. Tripping rate and net distance traveled within a patch were both identified as good indicators of gene flow, but contrary to expectations, residence did not predict gene flow of the different bee species. This discrepancy occurred because other behaviors affecting gene flow, besides residence, differed among the bee species. Therefore, a change in a specific behavior is a better predictor of gene flow for a given bee species than when comparing bee species. We illustrate how the foraging behaviors identified as affecting gene flow can be used to design management strategies that mitigate gene flow. This study identified foraging behaviors that impact gene flow and these results are important because they can guide the design of management practices to mitigate gene flow and improve coexistence of seed production markets. This information is of interest to scientists interested in pollinator foraging behavior and gene flow and will benefits farmers, seed producers from different markets and regulatory agencies interested in the coexistence of different seed production markets in alfalfa and other genetically engineered insect-pollinated crops.

Technical Abstract: The foraging behavior of pollinators can influence pollen dispersal and gene flow. Identifying foraging behaviors with high impact on pollen dispersal can guide the design of pollinator strategies to mitigate gene flow and facilitate the coexistence of seed production markets. The current study examines and compares the foraging behaviors of three bee species, the European honey bee, Apis mellifera L., the common eastern bumble bee, Bombus impatiens Cr., and the alfalfa leafcutting bee, Megachile rotundata F., foraging on Medicago sativa flowers. Distances traveled, residence (number of flowers visited in a foraging bout) and tripping rate are compared among bee species and statistical tests are used to detect directionality of movement over all foraging bouts and preference for some directions. Every foraging behavior examined differed among bee species. Each behavior was ranked by bee species and predictions of gene flow risk were tested against existing empirical gene flow data. Tripping rate was highlighted as a behavior linked to gene flow. Distances traveled at a local scale predicted relative gene flow distances at the landscape level. Contrary to expectations, residence was not a reliable indicator of gene flow for the distinct bee species; the reasons for such discrepancy are examined. This study is the first to link pollinator foraging behavior to gene flow and use the information to guide the development of management strategies to mitigate gene flow. With the increase in GE crops over the landscape, the approach developed here could benefit a variety of insect-pollinated crops.