EFFECTS OF HERBIVORY ON FLORAL TRAITS AND FLORAL REWARDS OF ASCLEPIAS SYRIACA
Luis Aguirre1, Manson Jessamyn2.
1University of Illinois at Chicago, Chicago, IL, 2University of Alberta, Edmonton, AB, CA.
Herbivory and pollination both incur energetic costs for plants, as plants must invest in defenses while simultaneously investing in rewards and attractants. The presence and intensity of herbivory may affect how much energy and resources a plant may spend on reproduction. In this experimental study, we tested different modes and durations of herbivory in Asclepias syriaca to assess whether the investment of energy in herbivore defense affects the reproductive potential of these plants. To measure whether herbivory has a detrimental effect on reproduction we looked at differences in reproductive traits in groups with various herbivory simulations. We measured floral traits, floral rewards, and rates of pollinia removal and deposition as a proxy for pollination to assess the effects of herbivory. The results obtained showed hood size and ovule size were significantly affected by herbivory, with a trend toward smaller hoods and ovules, while nectar traits had non-significant trends toward a general reduction in nectar quantity and quality. These responses varied by duration but not by mode of herbivory. However, we did not see any reduction in pollination when plants were treated with several simulated modes and durations of herbivory. Our results suggest that although herbivory has a direct effect on reproduction related traits, other factors, such as weather, may be driving pollination responses in this system. We conclude that purely mechanical simulations of herbivory may not affect the pollination efficiency in Asclepias syriaca.