Impact of Bee Species and Plant Density on Alfalfa Pollination and Potential for Gene Flow

Johanne Brunet,Christy M Stewart

doi:10.1155/2010/201858

Abstract

In outcrossing crops like alfalfa, various bee species can contribute to pollination and gene flow in seed production fields. With the increasing use of transgenic crops, it becomes important to determine the role of these distinct pollinators on alfalfa pollination and gene flow. The current study examines the relative contribution of honeybees, three bumble bee species, and three solitary bee species to pollination and gene flow in alfalfa. Two wild solitary bee species and one wild bumble bee species were best at tripping flowers, while the two managed pollinators commonly used in alfalfa seed production, honeybees and leaf cutting bees, had the lowest tripping rate. Honeybees had the greatest potential for gene flow and risk of transgene escape relative to the other pollinators. For honeybees, gene flow and risk of transgene escape were not affected by plant density although for the three bumble bee species gene flow and risk of transgene escape were the greatest in high-density fields.

Highlights

Different pollinators are expected to vary with respect to their relative role in the pollination of specific crops
This study examines the relative contribution of distinct bee species to pollination and gene flow in alfalfa and determines whether and how distinct bee species are affected by plant density, a feature of the landscape known to influence gene flow
The number of flowers visited per raceme, the proportion of open flowers visited on a raceme, the number of flowers tripped on a raceme, and the proportion of visited flowers that were tripped, were each affected by bee species (P < .05) but not by plant density (Table 1)

Summary

Introduction

Different pollinators are expected to vary with respect to their relative role in the pollination of specific crops. The tripping rate varies between bee species visiting alfalfa racemes [1, 7, 8] and distinct species deposit different quantities of pollen on cranberry flowers during a single visit to a flower [2]. The pollen load carried by a pollinator between pollen donors and recipients is expected to turn over more rapidly as a pollinator visits a greater number of plants per unit distance traveled. We know little about whether distinct insect pollinators react differentially to these various landscape attributes and whether these different responses affect pollen dispersal

Methods

Results

Conclusion