Term of Award

Spring 2022

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


Department of Biology

Committee Chair

Edward Mondor

Committee Member 1

Scott Harrison

Committee Member 2

Joshua Gibson


As atmospheric carbon dioxide (CO2) levels continue to rise, it is important to study how economically important organisms, like the pea aphid, Acyrthosiphon pisum, will react to these conditions. The pea aphid feeds on the phloem of crop plants like alfalfa, peas, and fava beans, where it not only directly harms the plant but also can spread plant viruses. A wide variety of factors can influence pea aphid fecundity and behavior. Some of these factors are abiotic, like atmospheric conditions, and some are biotic, like microorganisms with which the pea aphid has a mutualistic relationship. In this thesis, pea aphids with and without the facultative symbiont Hamiltonella defensa, were reared in either ambient CO2 or elevated CO2 concentrations. Pea aphid fecundity and behavior was assessed to determine if the presence of H. defensa impacted aphid fitness under atmospheric conditions associated with global climate change. I found that aphids harboring H. defensa had approximately twice as many offspring as uninfected aphids, but offspring production was not significantly influenced by CO2 level, and there was no significant interaction between H. defensa and CO2 level. In addition to offspring production, I found that behavior was also influenced by the symbiont. I found that aphids with H. defensa had greater responses to alarm pheromone compared to those without the symbiont. There was also a significant interaction on aphid dispersal behavior between the presence of H. defensa and CO2 level; aphids with a symbiont had higher dispersal rates in ambient CO2, but the dispersal response between infected and uninfected individuals did not differ at high CO2 levels. As CO2 levels continue to increase, variation in phenotypic expression in response to these environmental conditions may become evident, resulting in altered predator-prey dynamics and associated community functioning.

Research Data and Supplementary Material


Included in

Entomology Commons