Coflowering community context influences female fitness and alters the adaptive value of flower longevity in Mimulus guttatus.

A major goal in evolutionary biology is to incorporate the complexity of multispecies interactions into our understanding of microevolutionary processes within populations. Although considerable work has been done on antagonistic interactions (e.g., plant-herbivore), little attention has been paid to the evolutionary implications of context dependency in mutualistic interactions (e.g., plant-pollinator). In this study, we use seep communities to evaluate how coflowering species richness affects key aspects of pollination (visitation rate and conspecific and heterospecific pollen receipt) of Mimulus guttatus. We assessed the importance of coflowering diversity in mediating floral evolution by determining whether species richness was associated with variation in flower size, longevity, and stigma-anther distance and by conducting a reciprocal transplant experiment in two contrasting pollination environments. We found lower visitation rates and higher heterospecific pollen transfer to M. guttatus growing in high-diversity coflowering communities compared to low-diversity coflowering communities. We found a positive correlation between flower longevity and coflowering species richness. Furthermore, our reciprocal transplant experiment showed that extended flower longevity was advantageous only in high-diversity seeps and identified coflowering diversity as the most likely selective agent. Our results suggest that coflowering diversity can promote floral trait differentiation among populations, in this case, flower longevity.