RUI: ARE THE EFFECTS OF SIZE-STRUCTURE ON TROPHIC CASCADES MEDIATED BY DEMOGRAPHIC FEEDBACKS?

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In this project, the investigators will address how size-structure (i.e., variance in the body size distribution) of predators alters effects of the predators on prey assemblages and prey resources. They will further explore how interactions among size classes (e.g., cannibalism and competition) influence the development of size structure. Salamanders are the predators in the study. This project will provide exceptional opportunities for undergraduate students to learn the scientific method through the development and execution of independent research projects. It will significantly build research capacity among three undergraduate institutions in Kentucky, one of which is a minority-serving institution. Students will gain first-hand experience in designing and implementing experiments, in analyzing and managing data, and in communicating science to diverse public audiences. Each of these institutions lacks independent resources and programs to engage students in research. This project serves the Nation's interests by providing resources needed to train students in complex problem solving through rigorous experimental design.Previous research suggests that size structure of top predators can significantly influence trophic interactions, and may explain observed variation in the strength of trophic cascades, yet few empirical studies have focused on these questions. This project will combine experiments and field studies to test hypotheses regarding the interaction of predator size structure, density, and cannibalism, the resulting community dynamics, and the demographic feedback mechanisms thought to generate variation in size structure. Predators that vary in size can exhibit both consumptive effects, through cannibalism, and non-consumptive effects on the survival of their offspring. They also influence the abundance of other predators and competitors. When taken together, these diverse effects could modify entire food webs, ultimately altering the size structure of future predator populations and thus future trophic cascades. Undergraduate students will work in teams to test the diverse mechanisms proposed to generate variation in size structure using a series of mesocosm experiments and field studies. Experiments and field observations will quantify the impact of predator size structure on trophic cascades and determine how demographic feedbacks affect annual variation in predator size structure. Results will provide new insight into how the loss or recovery of top predators can affect ecosystems, with implications for conservation and management. Students will participate in science education activities to engage undergraduate non-science majors and K-12 students and contribute to an interactive learning module to extend the impacts of this project to students and citizens throughout the nation and globe.This project is supported by NSF's Experimental Program to Stimulate Competitive Research.