Pollinator foraging preferences affect male, but not female, fitness in plants in a co-flowering community

A diverse array of floral traits are shaped by selection mediated by pollinating insects. The behavioral responses of these insects, and their sensory capacities, affect conspecific pollen dispersal and seed set, and therefore gene flow and fitness. As we learn more about the strong preferences of pollinating insects for specific macronutrients in pollen, it is clear that floral nutritional traits may also be affected by selection mediated by visitation patterns of flying insects. We evaluated elements of male and female fitness in a community of co-flowering plant species, and determined the extent to which these elements were related to pollinator visitation and preference for pollen nutrition. In particular, we assessed whether pollen protein content among these plants affected insect preferences, and whether those preferences then had an effect on male or female fitness of the plants. We found that pollen protein levels correlated with our measures of pollinator preference and male plant fitness, but not female plant fitness. These results are compelling in the light of differential sex-based selection in plant-pollinator communities, and suggest a dynamic and context-dependent landscape of selective pressures mediated by insect visitation.