U.S.-Mexico Dissertation Research: Ontogenetic Variation In Plant Response: Consequences For Herbivores and Plants

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0228229MarquisThis Americas Program thesis enhancement project will support dissertation research by Ms. Karina Boege, under the supervision of Dr. Robert J. Marquis of the University of Missouri-St. Louis, with the assistance of Dr. Rodolfo Dirzo of the Universidad Nacional Autonoma de Mexico, UNAM in Mexico City. The research will evaluate the consequences of changes in plant quality, architecture, and tolerance associated with plant development. Changes in plant quality and architecture may modify the relative importance of plants as food (i.e., bottom-up forces) and shelter (i.e., influencing top-down forces) as they affect herbivores. As a result, the amount of herbivory a plant suffers may vary during plant ontogeny. Moreover, changes in tolerance will influence plant performance at different developmental stages as affected by herbivore attack.Specific objectives of this study are to: 1) quantify developmental changes in defensive and nutritional traits of Casearia corymbosa, a neotropical tree in the tropical dry forest of Chamela, Mexico; 2) evaluate how ontogenetic variation in defensive traits, plant size, and resource availability for C. corymbosa affects herbivore density, community structure, and leaf damage, through the modification of plant quality as food for herbivores and the impacts of one component of the third trophic level (insectivorous birds); 3) assess the consequences of such changes for plant performance at different developmental stages; and 4) determine the degree to which different ontogenetic stages differ in tolerance to herbivore attack, and evaluate if such differences are promoted by changes in carbohydrate allocation to different plant organs. The analysis of the interactive impacts of bottom-up and top-down forces as influenced by plant ontogeny provides an opportunity to describe the simultaneous effects of factors that have been identified to independently influence herbivory received by plants. In addition, the evaluation of both defensive and tolerance strategies at different ontogenetic stages allows a clearer understanding of the impacts of herbivory on plant fitness, integrating the different resistance strategies that plants may express during life-history to reduce the negative impacts of herbivory. Overall, this study will contribute to our understanding of the factors that may influence the evolution of plant resistance traits mediated by herbivores and their natural enemies.