Consequences of elevated carbon dioxide and ozone for interactions between deciduous trees and lepidopteran folivores

Projections indicate that approximately half of the world's forests are expected to experience elevated levels of CO₂ and O₃ by 2100. These pollutants are known to alter various aspects of tree phytochemistry, and in turn, insect performance. The research presented here focuses on two areas in which our knowledge of CO₂ and O₃ effects on tree-insect interactions is limited. First, I investigated the effects of CO₂₋ and seasonally-mediated changes in foliar quality on multiple generations of a leaf-chewing insect. Second, I determined the individual and interactive effects of CO₂ and O₃ on foliar quality and on the performance of leaf-feeding insects.; CO₂ enrichment and seasonal progression affected tree phytochemistry and, in turn, insect performance, but the magnitude and direction of change depended on tree species. Furthermore, this study found evidence that the effects of CO₂ varied over multiple insect generations, but the response differed among tree species. Based on the combined effects of CO ₂ enrichment and seasonal progression on two insect generations, this study suggests that insect host utilization patterns might be altered, resulting in changes in community composition.; Tree phytochemistry and insect performance responded differently to elevated levels of CO₂ and O₃ depending on whether the pollutants were administered alone or in combination. Furthermore, CO₂ and O₃ affected tree-insect interactions differently depending on plant genotype. Elevated O₃ appeared to affect foliar chemistry more than elevated CO₂; however, the overall response of phytochemistry to both pollutants was moderate. These slight changes in phytochemistry typically translated to moderate changes in larval performance. However, generalizing the response of elevated CO₂ and O₃ on plant-tree interactions is difficult because each tree and insect species responded differently. Furthermore, other aspects of insect performance, not just larval growth and development, were affected by CO₂ and O₃. These studies demonstrated that under future atmospheric conditions, where more than one pollutant is likely to affect plant-insect interactions, relationships between plants and insects will likely be altered although the magnitude of responses will depend on tree and insect species.