November 10, 2010 – "The Ecology of Fear and the Ecosystem: How Predation Risk Drives Ecosystem Nutrient Dynamics"
Oswald J. Schmitz, Oastler Professor of Population and Community Ecology, Yale University
Oswald J. Schmitz will present insights into species interactions and ecosystem functioning gained during 17 years research in a New England old-field ecosystem. That research resolved how predator species influence ecosystem functioning, mediated by direct and indirect interactions with their leaf chewing herbivore prey and a diversity of herbaceous plant species. The presentation will address the role of consumers in influencing nutrient transfer through an ecosystem. The reigning view is that the rate and efficiency of nutrient transfer up the food chain is constrained by herbivore-specific capacity to secure N-rich compounds for survival and production. This presentation will, however, show how physiological stress response of grasshopper herbivores to fear of spider predation alters the nature of the nutrient constraint from nitrogen to carbon and accordingly the elemental stoichiometry of herbivore body tissue and excreta and of the plant community from which grasshoppers select their diet. Schmitz concludes by advancing conceptual theory on how flexible herbivore physiological responses to the fear of predation provide a fundamental mechanism to explain context dependence in the nature of trophic control over ecological stoichiometry and nutrient transfer in ecosystems.