Dissertation Research: Role of a Dominant Grazer in a Headwater Stream Food Web
The proposed research addresses a fundamental question in ecology: what determines the structure of food webs? In general, a suite of manipulative field experiments is designed to quantify the control that herbivorous species can exert on stream food webs. Manipulations of the abundance and phenology of a dominant grazing invertebrate (Glossosoma), in combination with stable isotope analyses, will determine if the presence and density of Glossosoma control the use of algae and detritus (alternative energy sources in streams) by other species of consumers. Because Glossosoma is relatively invulnerable to predation as a consequence of its morphology (a stone case), it may prevent predator species from exerting controls over herbivores. This will be quantified with regard to a common predator, the Giant Pacific Salamander (Dicamptodon tenebrosus). The proposed work will test in a rigorous manner, the hypothesis that herbivores exert "intermediate control" over the structure of food webs.
