The ecological and evolutionary processes involved in interactions between terrestrial plants and their herbivores provide a rich arena of study. My research addresses many aspects within this arena, including structuring forces of arthropod herbivore communities, plant modular constraints to herbivory, allocation costs of resistance, local adaptation of plants, and plant hybridization. Nevertheless, the central objective of my research is to address this question--how do plants resist herbivores and in what ways does resistance evolve? Plants commonly demonstrate resistance to herbivores in two ways--through defense (i.e., by deterring herbivore feeding) and through tolerance (i.e., by withstanding herbivore damage), so my research encompasses both of these aspects, tolerance and defense. In addition, my research often entails an examination of plant genetic variation, as genetic variation in resistance traits is a prerequisite for a response to natural selection. Still, because natural selection acts on the phenotype, and because environmental effects can dramatically alter the degree to which a genotype expresses resistance, my research also incorporates the study of genotype by environment interactions.