PARENT SESSION
Poster Session #4: Herbivory.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Effect of productivity and predators on herbivores in gaps and understory of a tropical rain forest.

Richards, Lora^*,1, Coley, Phyllis¹, ¹ University of Utah, Salt Lake City, UT

ABSTRACT- One of the central questions in ecology is "What controls herbivore populations such that they do not consume all the plants?" Herbivores are limited by a combination of suitable food availability and predator pressure. I am examining how natural changes in productivity affect trophic interactions by comparing the forces on herbivores in treefall gaps and the understory in a lowland tropical moist forest of Panama. I hypothesized that resources would limit consumers in the understory, where productivity is lower. In contrast, in gaps where productivity is higher, resources are more abundant and predators should limit consumers. Gaps have more resources available to herbivores in the form of higher young leaf densities (5.5/m squared in gaps and .5/m squared in the understory). In addition, gap species have more nutritional and less tough mature leaves than understory species. I also found that herbivore densities were four times higher on gap species than on understory species. In addition, gap species had higher herbivory (61.9 % herbivore damaged leaves) than understory species (33.7%). Predator densities were also four times higher on gap species than understory species. Perhaps because of the higher predator densities, artificial clay caterpillars suffered higher "predation rates" in gaps (18% per day in gaps and 11% per day in the understory) as well. As predicted, these data indicate higher resources and higher predation rates in gaps compared to the understory.

KEY WORDS: Productivity, Herbivores, Predators, Tropics