9407591 Cooper Although recent theoretical and empirical investigations have indicated the profound influence of spatial heterogeneity on the dynamics of populations and communities, there have been few examinations of the effects of consumers on spatial heterogeneity of their resources. In this research, the PI will apply spatial statistics to the analysis of large experiments manipulating grazers, predators, and nutrients to quantify the effects of consumers and nutrients on spatial heterogeneity in lower trophic levels in streams. The PI will also quantify the distributional responses of consumers to different aspects of patchiness in their resources. The design incorporates both a budget approach, so that we can determine the mechanisms responsible for direct predator effects (prey emigration vs predator consumption), and multi-trophic level interactions, so that the PI's can examine the direct and interactive effects of different predators (trout, stoneflies) on their prey (invertebrates) and their prey's resources (algae). Subsidiary investigations will determine scales of patchiness and overlap in consumers and their resources in natural streams. This research will be guided by trophic chain models for open systems that incorporate spatial heterogeneity. %%% The proposed research is the first to explicitly use spatial statistics to address the effects of consumers on the spatial heterogeneity of their resources. This approach will greatly expand our understanding of how top-down forces effect community structure and dynamics within a spatially-explicit context.
