Dissertation Research: Incorporating Ecological Stoichiometry into a Multi-trophic, Multi-resource Community Framework

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DIG DEB-0105014 - Leibold, M. and Hall, S.Why do environmental changes affect composition of species among different localities? What role do species play in the cycling of energy and nutrients in ecosystems? These important yet difficult questions still challenge ecologists' mechanistic understanding of nature. However, recent experimental and theoretical evidence suggests that a new approach to studying species interactions may help ecologists tackle and integrate these two questions. This approach, called "ecological stoichiometry", incorporates constraints imposed by mass balance of key nutrients (such as phosphorus and nitrogen) into descriptions of plant-herbivore interactions. Our research program focuses upon improving these descriptions and evaluating the importance of stoichiometry in complex natural and semi-natural, experimental conditions. Currently, we are learning that, in ponds, species composition of zooplankton grazers is sensitive to changes in the relative proportion of phosphorus and carbon contained in their algal food. Furthermore, the elemental quality of this food is driven, at least in part, by the relative and absolute supply of light and nutrients to pond ecosystems. In our future work, we plan to more intensely quantify temporal dynamics of plant-grazer interactions in differing light:nutrient environmental regimes and with differing levels of predation pressure upon grazers. This focus upon dynamics will enable us to more quantitatively evaluate the role that "ecological stoichiometry" may play in nature and to integrate it into extant mathematical theory. Ultimately, our goal is to understand how supply of key resources to ecosystems influences composition of plant and herbivore species and flow of energy through food webs. "Ecological stoichiometry" may provide a valuable framework to achieve this goal.