Evolution of Integrated Phenotypic Plasticity: Geographic Variation and Genetic Constraints

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9806775 Thompson Many animals, including insects, are able to occupy and thrive in a wide variety of environments. Often this ability to persist in regions with different elevation, climate, and vegetation is the result of individual adjustments to local conditions, a phenomenon termed phenotypic plasticity. For example, many insect species develop larger body size and longer wings in response to high nutrient diets and/or high temperature during development. These plastic changes in response to local environments may cause increases in reproductive output and mobility that, in turn, cause insect population increases and agricultural damage if the insects feed on plants important to humans. The questions addressed in this research concern how grasshoppers evolve the ability to adjust morphological traits to local environmental conditions and the functional consequences of the coordination or integration of plastic changes in head and body morphology. Lesser migratory grasshoppers, Melanoplus sanquinipes, will be sampled from regions of the western United States that differ in summer temperature. Progeny of these grasshoppers will be raised in four combinations of high and low temperature and high and low nutrient diet to measure plastic changes in body size, head size, leg length, and wing length and quantify genetic variation for these traits. The investigator will determine if grasshopper populations from California, Nevada, and Utah are genetically different and whether the populations harbor phenotypic plasticity for environmental conditions they do not normally encounter. Grasshopper jumping, flight, feeding, and egg-laying performance will be measured to determine if coordinated plastic changes in head, body, leg, and wing size enhance the ability of grasshoppers to survive and reproduce in different temperature and food plant environments. In addition to answering specific questions about the integration of phenotypic plasticity in populations of grasshoppers, this research will te st several general hypotheses about the importance of genetic variation and environmental heterogeneity in the evolution of plastic traits.