DISSERTATION RESEARCH: Food Webs in Space: The Interplay Between Dispersal and Trophic Interactions

Cornell University, Ithaca NY

Investigators

Abstract

Trophic interactions (the consumption of prey by predators) define the flow of energy and nutrients in food webs. Many organisms involved in trophic interactions are also able to move (disperse) among areas of suitable habitat. For example, after eating a prey item in one patch of habitat, a predator may disperse to another habitat patch before consuming additional prey. Such dispersal of organisms may affect the outcome of trophic interactions by altering the size of populations within patches. At the same time, trophic interactions may influence population sizes, and thus determine the number of organisms available to disperse among patches. As a result, trophic interactions and dispersal likely combine to dictate the structure and dynamics of food webs at the local (within-patch) and regional (among-patch) scales. This study uses a system of freshwater rock pools on Appledore Island, Maine to determine how dispersal and trophic interactions combine to influence local and regional food-web dynamics. The simple rock-pool food web consists of phytoplankton, herbivorous zooplankton, and a predatory water bug (Trichocorixa). Previous research shows that predation by Trichocorixa strongly affects local food webs and that Trichocorixa is capable of dispersing among rock pools. A field experiment will be used to quantify the local and regional effects of dispersal by Trichocorixa on the rock-pool food web. A specific mathematical model has been developed to predict the outcomes of this experiment, and this model will be extended to other ecosystems in order to determine the general effects of dispersal on local and regional food-web dynamics. This study combines theoretical and empirical approaches to increase understanding of the role of spatial structure in food-web dynamics. As such, results of this research will inform the conservation and management of ecosystems threatened by habitat fragmentation. This project supports the dissertation research of one graduate student and provides the opportunity for an undergraduate to be involved in field research as part of a multi-university internship program. Results will be disseminated broadly through scientific publications and presentations, lectures to undergraduate courses, and outreach to local high school students, teachers, and the general public.