Meeting Abstract
Non-consumptive effects (NCEs) occur when stimuli from predators illicit a behavioral, physiological, or morphological response in prey species. Prey often alter their foraging habits in response to NCEs, which can initiate a trophic cascade that impacts a third trophic level, commonly a primary producer. This model is well studied in terms of abundance and behavior of the constituent species. However, the mechanisms underlying the physiological response of primary producers to changes in herbivory pressure driven by NCEs remain understudied. We hypothesized that the presence of predators in the environment would cause an observable reduction in foraging behavior of prey species. The resultant drop in herbivory pressure would then be followed by a decrease in the amount of defensive chemicals found in plant tissues. We tested this hypothesis using a new tri-trophic model at the Stream Research Facility at the University of Michigan Biological Station. Our model consisted of Micropterus salmoides to provide a predatory stimulus, Orconectes rusticus as the herbivorous prey, and three plants Myriophyllum sibericum, Elodea canadensis, & Chara macroalgae as the responsive primary producers. A two by two fully factorial experiment was performed using eight flow through stream mesocosms fed with strained river water that ran for 48hrs per trial cycle. Macrophytes were present in all trials, while the presence of bass odor, and presence of crayfish were factors. A mixed effects modeling approach in R was used to analyze our data. We found that crayfish consumed more plant tissue when predator odor was present, and plants gained more weight in predator odor positive, herbivore free trials.
