Influence of local density and sex ratio on pollination in an ambophilous flowering plant

PREMISE OF THE STUDY: Variation in local density and sex ratio in dioecious plants can affect mating success through the actions of pollen vectors, principally generalist insects or wind. Increased density and male-biased sex ratios should promote pollen transfer and seed production, but their combined effects have not been investigated for ambophilous species, which exhibit both insect and wind pollination.

METHODS: We manipulated density (low vs. high) and sex ratio (1:1 vs. 3:1 male-biased) in arrays of dioecious ambophilous Thalictrum pubescens. We quantified visitation rates and foraging time to examine whether pollinators exhibited sex-specific preferences and determined the seed set of arrays.       

KEY RESULTS: Pollinators visited more plants per foraging bout at high than low density. Visitation rates and foraging times of visitors were greater for male than female plants but did not depend on the density or sex ratio of arrays. However, whereas solitary bees displayed...