Herbivory in Streams: Context-dependent Species Interactions and Functional Redundancy

Colorado State University, Fort Collins CO

Investigators

Abstract

0075352 Poff This project will investigate the ability of mobile herbivores (grazers) to regulate the structure and function of the autotrophic community (e.g., algae), and how this relationship varies with changing environmental conditions. The research approach is to elucidate the mechanisms underlying the outcomes of interactions among herbivore species under a range of physical conditions. Herbivores that graze bottom communities in streams will be included in a series of experiments whereby the dominant environmental gradient (current velocity) is altered. Experiments will assess autotrophic biomass accumulation and community composition across the environmental gradient, as well as the functional redundancy among grazer species in regulating algal communities. The experimental approaches are well integrated so that it will be possible to scale-up experiments and make mechanistic predictions about the magnitude of multi-species herbivory under variable environmental conditions. Results of this study may extend to other ecosystems with spatial heterogeneity in physical conditions and with a variety of herbivorous species. Moreover, the research has significant implications for understanding co-existence of consumers and the degree of "redundancy" or "substitutability" among species. Such understanding is critical for supporting successful restoration of stream and river ecosystems.