The number of glyphosate resistant seeds produced by each of three bee species as they visit alfalfa flowers in sequence during a foraging bout

Since the release of genetically engineered (GE) crops, there has been increased concern about the introduction of GE genes into non-GE fields of a crop and their spread to feral or wild cross-compatible relatives. More recently, attention has been given to the differential impact of distinct pollinators on gene flow, with the goal of developing isolation distances associated with specific managed pollinators. To examine the differential impact of bee species on gene movement, we quantified the relationship between the probability of getting a GE seed in a pod, and the order in which a flower was visited, or the cumulative distance traveled by a bee in a foraging bout. We refer to these relationships as ‘seed curves’ and compare these seeds curves among three bee species. The experiments used Medicago sativa L. plants carrying three copies of the glyphosate resistance (GR) allele as pollen donors (M. sativa is a tetraploid), such that each pollen grain carried the GR allele, and convent..., The experiments were carried out inside cages set up in a greenhouse room at the University of Wisconsin Walnut Street Greenhouse in Madison, WI, USA. A smaller 2.0 x 2.0 x 1.8 m cage adjoined a larger 4.0 x 2.0 x 1.8 m cage (Fig 1). The frames of the cages were made of PVC tubing and were covered with mosquito netting (Skeeta, Inc., Bradenton, FL, USA) which was also used to separate the two adjacent cages. Glyphosate-resistant (GR) alfalfa plants, also known as Roundup Ready (RR) alfalfa, were placed in the small cage and used as pollen donors in the experiment. Conventional alfalfa plants were placed in the large cage and used as pollen recipients.
The GR plants used as pollen donors had a single copy of the GR gene, and at least three copies of the GR allele. Because alfalfa is a tetraploid, all pollen grains of plants with at least three copies of the GR allele will carry at least one GR allele. Because the GR allele is dominant, one copy of the gene suffices for the expression of...,