Print PageThe floral density of a plant population can greatly influence both the quantity and quality of pollinator services and reproductive success. By directing pollinator behavior, floral display can affect pollinator visitation rates, the number of flowers a pollinator visits per plant, and even pollinator community composition. In plant species that rely on insect-mediated pollination, these factors can significantly impact fruit and seed production. I studied the effects of floral density on pollination and reproductive output in Penstemon pachyphyllus (Plantaginaceae) growing in southwestern Utah. Using a naturally-occurring population, I compared pollinator behavior, visitation rates, plant and insect community composition, and reproductive success (fruit-to-flower ratio and the average seeds per fruit) in a reduced (50%) floral density treatment and a control.
Results/Conclusions
I found that while the pollinator community and pollinator foraging habits were the same in the control and treatment plots, there is evidence that higher floral density contributed to greater numbers of insect visitors and higher fruit-to-flower ratios. These results suggest that floral density is important to the reproductive success of P. pachyphyllus, and imply that factors other than floral density drive the insect community composition and pollinator behavior.
