Collaborative Research: The Effects of Hostplant Chemistry and Invertebrate Predators on Caterpillar Foraging and Hostplant Fitness

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Two of the major factors that affect the foraging patterns of insect herbivores are hostplant chemistry and natural enemies. However, the relative importance of hostplant chemistry and predation in determining foraging patterns of insect herbivores and the degree to which these factors interact are largely unknown. The range of expression of hostplant defensive chemistry, using a system of iridoid glycosides in plaintain, will be controlled using cloned genotypes that have been previously characterized chemically. In an experimental garden, the foraging patterns of two caterpillar species, a specialist and a generalist, in the absence and presence of two different kinds of invertebrate predators, wasps and stinkbugs, will be assessed. Concurrently, the corresponding iridoid and nutritional chemistry of the hostplant , and the iridoid chemistry and growth rate of the caterpillars will be determined. In addition, plant fitness due to the presence and absence of the herbivores' predators will be examined. The results will indicate the relative importance of hostplant chemistry and predators in determining the ecology of foraging patterns of two representative caterpillar species and the ensuing effects on the herbivores' hostplant.