Ecological Factors Promoting Polyphagy in Insect Herbviores

George Washington University, Washington DC

Investigators

Abstract

Because most caterpillars feed on a very small subset of the plant species in their environment, the existence of species with broad diets (generalists) is enigmatic. In this project, a set of generalist forest caterpillars will be used to test two alternative hypotheses for how their broad diets are maintained: the 'ecological tradeoffs hypothesis' and the 'risk-spreading hypothesis.' To test these hypotheses, the survival, growth, and reproduction of four caterpillar species will be examined on eight unrelated host plant at two sites over three years. The risk of attack from natural enemies (predators and parasites) will be compared among host plants at multiple life stages. In addition, the background pattern of host plant preference will be quantified through field censuses of caterpillars at each site to determine if insect preferences are adaptive. The results of this study will illuminate the unresolved debate over the importance of natural enemies in the evolution of insect diet breadth. Because a large number of economic pests are generalists, developing our understanding of how host plant associations develop and are maintained can aid long-term biological control efforts. An important facet of this project is the development and implementation of an elementary education module on insect evolutionary ecology. In addition, the project will train a team of undergraduates in ecological research.