Undergraduate Honors Theses

Thesis Defended

Spring 2016

Document Type


Type of Thesis

Departmental Honors


Ecology and Evolutionary Biology

First Advisor

Dr. Brett Melbourne

Second Advisor

Dr. Pieter Johnson

Third Advisor

Dr. Don Grant

Fourth Advisor

Dr. Caroline Tucker


Climate change is altering regional temperatures, forcing species to respond to new environmental challenges. Current research suggests that temperature affects population dynamics of species, altering the timing of species abundance. However, little is known about the combined effects of temperature and interspecific competition. In this study, we examined how temperature and competition with the competitor Vorticella sp. affected the population dynamics of the common zooplankton, Daphnia magna. We examined how temperature and Vorticella both affect D. magna’s maximum population size, the timing of population growth, and the final population size. Overall, our results suggest that high temperature and Vorticella presence, in combination, can impact the timing of population growth, as well as alter life history characteristics, for D. magna. These results suggest that Vorticella delay D. magna’s population growth only when temperatures are high, and that Daphnia respond to high temperatures morphologically through reduction in size. Temperature and Vorticella presences did not significantly impact the final population sizes, indicating that although the initial population dynamics are affected by these stressors, final population size was not changed. Because climate change can alter phenological timing of plant and animal species, further insight into the effect of temperature change on population dynamics of zooplankton will benefit scientific understanding as to how key trophic species, such as primary consumers, respond to increased temperature in freshwater aquatic ecosystems.