D3088: Effects of herbivory on pollinator success and reproduction

A growing body of recent literature has shown that herbivory can affect pollination. For example, plants can respond to herbivory by altering metabolic pathways to produce defensive chemicals; these defensive chemicals can spread to pollen and nectar which can impact pollinator fitness. Abiotic factors such as elevation may also affect the strength of indirect interaction between herbivores and pollinators. Herbivory has been found to decrease at higher elevations due to lower temperatures and shorter seasons for insect herbivores. Hence, host plants at high elevations are often found to be less defended than their lower-elevation conspecifics. I tested how herbivory in the floral community changes across an elevational gradient and how herbivory affects the reproduction of pollinators. I placed 30 trap nests along an elevational gradient in Logan canyon, UT. Herbivory levels were measured at each trap nest site across the gradient. Nests were checked weekly to remove straws filled by nesting bees and offspring were counted and reared to determine their health. I predict that percent herbivory will be negatively correlated with pollinator reproductive success and offspring health. Additionally, I predict that herbivory will be highest at low elevations and decrease with elevation. Thus, negative effects of herbivory on pollination will be greatest at low elevations. If this prediction holds true, there are important implications of this research in relation to climate change. As temperatures rise, higher elevations may experience more herbivory, which could alter plant-pollinator interactions.