PREDICTING THE CONSEQUENCES OF PLANT SPACING AND BIASED MOVEMENT FOR POLLEN DISPERSAL BY HONEY-BEES

The distance that pollen is dispersed has important ecological and evolutionary implications. Nevertheless, our understanding of the mechanism that generates spatial patterns of pollen dispersal in animal-pollinated plants, namely the combined processes of pollinator movement and pollen deposition, is at present qualitative. I show how easily measured characteristics of pollinator movement and pollen deposition can be used to build models that generate quantitative predictions about pollen dispersal distance. A field experiment in which I followed honey bees (Apis mellifera) foraging on one-dimensional arrays of mustard plants (Brassica campestris) indicated that individual honeybees have a biased direction of movement and alter their movement patterns in response to plant spacing. I used the model to explore the potential consequences of biased movement and plant spacing for pollen dispersal. Biased movement results in an increase in the expected pollen dispersal distance. In addition, the predicted dispersal distance increased with increasing interplant distance. These results demonstrate that models of pollen spatial dynamics based on individual pollinator behavior can be used to explore the consequences of plant spatial arrangement for gene flow in plant populations.