Ecological and evolutionary constraints of plant tolerance to herbivory

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Some plants can tolerate herbivory and tissue damage without reductions in fitness (or yield), yet we know very little about the evolution and ecology of tolerance traits, or even the mechanisms involved in plant compensatory ability. Moreover, we still lack a basic understanding of whether the two components of plant defense against herbivores – resistance (avoiding being eaten) and tolerance (enduring being eaten) – differ in their ecological and evolutionary relationships to plant growth and reproduction. This is despite the fact that the expression and fixation of tolerance responses within plant populations may have immense ecological consequences, e.g. through decreasing the effectiveness of biocontrol agents for invasive weeds, or supporting a more diverse insect community in crops. Indeed, theory suggests that tolerance of herbivory may fundamentally differ from plant resistance in its effects on the population dynamics of insect herbivores and their natural enemies, e.g by avoiding the evolutionary arms race typical in plant-insect resistance evolution. A greater understanding of plant tolerance traits and impact could not only resolve some of the outstanding ecological and evolutionary questions around variation in plant defense and specificity in plant-insect interactions, but also produce an actionable target for plant improvement and protection programs.******My proposed research program's long-term objective is to provide a mechanistic and genetic framework to understand the ecology and evolution of plant tolerance of herbivory. To achieve this, HQP in my lab and I will use field, greenhouse, and laboratory experiments to: 1) Identify biochemical and physiological mechanisms of tolerance; 2) Explore genetic markers for tolerance traits; 3) Determine ecological impacts of tolerance on key biotic interactions; and 4) Compare the evolution of tolerance in plant populations that have experienced ecological and evolutionary divergence. In particular, the comparison of traits among populations that span a gradient of plant-insect interactions (e.g. domesticated crops and their wild relatives), will be a powerful approach to understand the relationships among plant traits and insect population dynamics across ecological and evolutionary time scales. ******There is transformative potential for incorporating the genetic and biochemical mechanisms of plant tolerance to herbivory in plant breeding and crop production. Plant tolerance could have a large impact on plant yields despite high insect loads, and could slow and disrupt the evolution of pest resistance, which underscores the urgency of this research. Indeed, as tolerance responses in plants are likely related to a multitude of stress responses, including to drought, temperature and herbicide application, the products of this research program will be applicable to other plant improvements beyond pest management. **