Date on Master's Thesis/Doctoral Dissertation

8-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biology

Degree Program

Biology, PhD

Committee Chair

Emery, Sarah

Committee Member

Yanoviak, Stephen

Committee Member

Running, Mark

Committee Member

Schultz, David

Committee Member

Schaeffer, Robert

Author's Keywords

plant-herbivore interactions; volatiles; lima bean; eavesdropping

Abstract

Eavesdropping is defined as the act of an organism taking advantage of a cue that was not originally intended for them for their own gain. Plant-mediated eavesdropping is a widely documented phenomenon and eavesdropping cues range from oviposition cues to airborne volatile compounds. Eavesdropping is predicted to be widespread because eavesdropping confers a fitness advantage. In plants, eavesdropping on herbivore-induced plant volatiles (HIPVs) often results in enhanced resistance profiles upon herbivory. As a result of this enhanced resistance, it is predicted that eavesdropping alone incurs minor costs due to resource shifts towards inducible defense responses. Although HIPV-mediated eavesdropping is widely documented, few studies have investigated ecological factors that impact costs of eavesdropping, especially under field conditions. In this dissertation, I investigated factors that impact a plant’s utilization of volatile cues, and how eavesdropping affects growth and defense profiles in eavesdropping plants. In the second chapter, I studied how exposure to a ubiquitous plant derived compound, the green-leaf volatile cis-3-hexenyl acetate (z3HAC), affected Phaseolus lunatus (Lima bean) and Capsicum annuum var. Cayenne (Cayenne pepper). Although they were exposed to identical treatments, exposed pepper plants experienced vegetative and reproductive costs while lima bean had increased growth from volatile exposure alone. In the subsequent field season, I found that duration of exposure to z3HAC significantly impacted overall growth in lima bean. To determine if volatile blends differentially impact growth and defense profiles, I manipulated neighboring herbivore and plant identity to assess costs of eavesdropping. While neighboring plant identity had some effects on overall biomass, herbivore identity impacted resource allocation towards indirect defenses. To determine why plant-plant eavesdropping is observed, I used seeds collected from the experiment in chapter 4 and grew them in the next field season. Counter to our predictions, maternal eavesdropping had no effect on plant performance such as growth and defense. These results indicate that the costs and benefits of eavesdropping under field conditions are extremely nuanced and impacted by environmental variation, such as herbivore pressure and abiotic stress.

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