Dissertation Research: Plant-herbivore community assembly and the problem of specificity: Do insect herbivores specialize among sympatric, congeneric plants in tropical forests?

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There are more tree species in a half-hectare of tropical forest in Ecuador than in all of temperate Europe, Asia, and North America combined. This raises the question of how large numbers of ecologically similar species manage to coexist despite intense competition for light, water, space, and nutrients. One popular idea argues that insects may give an advantage to rare plant species by attacking successful plants when and where they become abundant. Yet this hypothesis could only work if insects have highly specialized diets. This research project will test that hypothesis through a study of the diet of all insects that are found to eat tropical forest plants in the coffee family. To this end, several thousand beetles, caterpillars, grasshoppers, and other insects will be collected in the rainforest in Panama. In order to identify the plants that a particular insect has eaten, DNA will be taken from the insect stomachs and the plant from which it came identified using DNA signatures unique to each species of plant. Plants will also be studied for differences in their chemistry that may protect them from insect pests. Results will be used to examine whether plant chemistry influences insect feeding, and whether insects are specialized enough to maintain the plant diversity of tropical forests by eating the most abundant plant species. Illuminating the role of insects in maintaining the tree diversity of tropical rainforests will shed light on one of the persistent mysteries of earth's most diverse ecosystem.The proposed research requires molecular lab work at the University of Michigan as well as fieldwork at facilities of the Smithsonian Tropical Research Institute in Panama, providing opportunity for interdisciplinary training of students. Laboratory work in molecular methods will include training of two graduate students in a University of Michigan program for non-traditional and underrepresented students. Furthermore, this research will contribute samples and molecular data on insect and plant specimens to public collections at the University of Michigan and the Smithsonian Tropical Research Institute.