REU: The Interaction of Insect Herbivory, Environmental Stress, and Host Resistance

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Dr. Whitham of Northern Arizona State University will continue a study of pinyon pine, Pinus edulis, which grows on the ash and cinder fields of Northern Arizona's Sunset Crater. The pine is water and nutrient stressed, and although adjacent sites suffer little herbivory, stressed pinyons suffer many-fold increases in attack by 3 insect herbivores. This chronic and acute herbivory results in a herbivore-mediated sex change in the tree, altered tree architecture and greatly reduced growth. Five basic lines of research will be continued: 1. experimentally manipulate stress and herbivore loads to separate cause and effect, 2. quantify the chemical and/or genetic basis of resistance, 3. quantify the impacts of insect herbivory on the host's root, crown, and reproductive systems, 4. quantify the impacts of host resistance on herbivore survival and seed dispersal, and 5. reconstruct the past 200 years of chronic insect attack. With the multidisciplinary skills of 6 researchers, rapid progress has been made in examining these questions by employing insect transfer experiments, tree transplant experiments, supplemental water and fertilizing experiments, primary and secondary plant biochemistry, dendrochronology, and electrophoresis. Because of the extremes of environmental conditions encountered, the obvious impacts of herbivory on these plants and our ability to experimentally manipulate the major components, the system represents a model for integrating major factors in plant-herbivore interactions.