Dissertation Research: Costs of Plasticity in Plant Defense: Sexual and Asexual Fitness Across Years

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One characteristic of invasive weeds that may contribute to their success is their ability to actively respond to herbivores. Understanding the spread of weeds therefore requires studying how these responses, called "induced defenses", may evolve. While many invasive weeds live for many years and can reproduce asexually through underground stems, previous studies of defense evolution have only measured sexual reproduction (seed set) over one year. This project examines the evolution of induced defenses in the weed Solanum carolinense by using genetic analysis to measure both sexual and asexual reproduction. Sexual reproduction and defenses have already been measured in an ongoing field experiment over one year; re-sprouts from this experiment will be identified using microsatellite DNA analysis to quantify reproduction in a second year. The relationship between defenses and combined reproduction will indicate how induced defenses are expected to evolve in natural populations.This project will address how herbivores affect the evolution and asexual spread of a noxious weed that is also a host for several economically important insect pests, including the Colorado potato beetle. Better understanding of how weeds succeed is relevant to developing better management of weeds and invasive species. Additionally, this project will develop genetic markers for future studies and provide undergraduate research training.