Dissertation Research: The Roles of Predation and Plant Chemistry in the Evolution of the Host Plant Specialization

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Predators may play an important role in the evolution of diet specialization in phytophagous insects. This research will test the hypothesis that specialists are chemically and morphologically better defended against predation than generalists by offering both generalist and specialist lepidopteran larvae to two different invertebrate predators, Apiomerus pictipes (assassin bug) and Polistes carnifex (paper wasp) at Palo Verde National Park, Costa Rica. To test separately for the importance of prey chemistry as a determinant of predator rejections, we will also offer caterpillar extracts to the same predators. Results indicating that prey chemistry is an important deterrent to predators would only provide relatively weak evidence that plant chemistry is also important. Therefore, to test the importance of plant chemistry we will also rear specialist caterpillars on artificial diets containing varying amounts of host plant and offer those caterpillars and their extracts to the predators. Diet breadth of phytophagous insects is an important and current issue to evolutionary biology and ecology, including the potential for herbivorous insects to become serious agricultural pests. This project is the first to test the combined importance of plant chemistry and predation in determining diet breadth.