Professor University of Massachusetts Amherst Amherst, Massachusetts, United States
Pollination is an ecological phenomenon of great importance in natural communities, but little is known about the effects that trophic interactions have on this process at the community level. In many plants, deposition of conspecific pollen is imperative for reproduction and is tied directly to the behavior of their pollinators. Pollinator behavior is determined by floral traits, but many floral traits often respond negatively to herbivory attacks. The aims of this project are to determine how herbivory to a dominant plant species affects pollinator behavior, and how these changes affect reproduction in undamaged neighboring species. Here, we performed a natural experiment in a milkweed-dominated community in which we simulated herbivory to milkweeds (Asclepias syriaca) by removing foliar tissue and applying jasmonic acid. We compared pollinator behavior in herbivory and control plots by analyzing pollen loads of floral visitors as to determine degrees of floral fidelity. We also measured the quality of pollination services to undamaged neighboring plants by assessing pollen deposition and seed production in undamaged neighboring plant species.
Our results indicate that herbivory to a dominant plant species has community wide effects on pollination services. We observed a drastic change in the composition of pollinators visiting flowering plant species. Similarly, our results indicate that herbivory to the dominant plant species has negative effects on the reproduction of neighboring plants. We observed reductions in conspecific pollen deposition on one neighboring plant species (Vicia cracca). These observations provide evidence corroborating the hypothesis that herbivory alters pollinator behavior and can reduce plant reproduction at the community level. The reductions in pollination highlight the drastic role that herbivory can have in a community through indirect effects.