Professor Tufts University Medford, MA, United States
Background/Question/Methods Foraging bees often exhibit floral constancy, which is the tendency to sequentially visit conspecific flowers. Constancy has major repercussions for plant fitness because most plants rely on animal pollinators and most pollen transfer occurs within a small number of floral visits after pollen is collected. Bee foraging constancy as observed in nature emerges from the interaction of a bee’s behavioral program and its foraging environment. The effects of bee behavior and the local environment on bee constancy are attributed to at least four distinct mechanisms frequently confounded in the literature: context-independent preferences for particular plant species, preferential visitation to the same species as the previous plant visited (simple constancy), the spatial arrangement of plants, and the relative abundances of co-flowering species. To disentangle these mechanisms, we followed individual bee flight paths within patches where all flowering plants were mapped, and we used step selection models to estimate how each mechanism influences the probability of selecting any particular plant given the available plants in a multi-species community.
Results/Conclusions We found that simple constancy was positive: bees preferred to visit the same plant species sequentially. Additionally, bees preferred to travel short distances and maintain their direction of travel between plants. After accounting for distance, we found no significant effect of site-level plant relative abundances on bee foraging choices. To explore the importance of the spatial arrangement of plants for bee foraging choices, we compared our full model containing all parameters to one with spatial arrangement removed. Due to bees’ tendency to select nearby plants, combined with strong intraspecific plant clumping, spatial arrangement was responsible for about 50% of the total observed constancy. Our results suggest that floral constancy may be overestimated in studies that do not account for the spatial arrangement of plants, especially in systems with intraspecific plant clumping. Plant spatial patterns at within-site scales are important for pollinator foraging behavior and pollination success.