Dynamics of a Native Iris-Herbivore Association: Effects of Salinity, Herbivory, and Genetic Variation

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This project will investigate the interaction between different types of plant stress in a population of native iris growing under a range of salinity conditions and herbivory. Both salinity and herbivory can be important sources of plant stress, and both can induce the production of abscisic acid (ABA) and jasmonic acid (JA). Variation in the production of these hormones among individual plants appears to be genetically influenced. The magnitude of the stress induction response can directly affect plant growth and reproduction as well as resistance to herbivore attack. This project combines field experiments with laboratory analyses to 1) examine the relationship between phytohormone induction and iris and herbivore performance, 2) quantify gene flow and genetic structure in the iris and herbivore populations, and 3) determine if iris and iris herbivores are locally adapted to their microenvironment. Both ABA and JA are growth regulators that influence plant tolerance to environmental and herbivore-mediated stress. Thus the results of this project have important economic implications. This study will be the first to determine the concentrations and fluctuations of stress-induced ABA and JA in a natural plant population, and can therefore advance our general understanding of the role played by phytohormones in plant stress tolerance. Plant resistance to pests and pathogens is both genetically and environmentally based. By quantifying salinity stress and determining the genetic structure of the plant and herbivore populations, this study can determine what plant genotypes are associated with tolerance and susceptibility to salinity and herbivory stress, as well as the herbivore genotypes associated with virulence. This information can then be applied to managed systems in which stress tolerance is an important component.