Date of Award:

8-2026

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Moria Robinson

Committee

Moria Robinson

Committee

Fabiane Mundim

Committee

Ian Pearse

Abstract

Climate change will alter precipitation worldwide, causing more frequent and severe drought events worldwide. Drought affects many ecological processes, including plant-herbivore interactions, which are critical to biodiversity and ecosystem health. A variety of plant characteristics can influence herbivory – such as how hairy, nutritious, or toxic a leaf is – and drought has been shown to alter many of these traits. Unique characteristics of herbivore species are also important: herbivores can either feed on a variety of plants (generalists) or a group of closely related plants (specialists). Specialists can cope with traits of the plants they eat, while generalists are often susceptible to plant trait changes. Under stressful climates, plants experience different levels of herbivory by different herbivore species, altering the survival of both plants and herbivores. If the amount of plant tissue eaten by herbivores changes, this affects how nutrients move through ecosystems. Studies that combine multiple plant traits and insect herbivore species are important to understand drought’s ecological effects. Here I investigate how drought severity affects traits that make a plant attractive to herbivores, and subsequent impacts on herbivory from a generalist and a specialist herbivore. I exposed wild tobacco (Nicotiana attenuata) to three levels of drought, and fed them to caterpillars of the beet armyworm (Spodoptera exigua) or the tobacco hornworm (Manduca sexta). I measured plant traits and the amount of leaf eaten. Drought changed plant traits, and those traits often shifted in contrasting directions. Drought affected herbivory, with both generalist and specialist herbivores eating less on moderately stressed plants. These findings help us understand how drought changes plant-herbivore interactions, finding that severe drought may positively affect herbivores through elevated nutrition, while moderate drought may be costly due to a combination of greater plant defense without the benefit of greater nutrients. Consistent effects on herbivory suggest that the consequences of drought may be more universal across herbivore communities than previously thought. A better understanding of how drought alters the outcomes of plant-herbivore interactions will help us make better conservation decisions about how to protect biodiversity under drought and better predict how climate change will impact ecosystem processes.

Download

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .