Date of Graduation

Spring 5-20-2021

Document Type


Degree Name

Master of Science in Biology


College of Arts and Sciences



First Advisor

John R. Paul

Second Advisor

April M. Randle

Third Advisor

Naupaka B. Zimmeman


How climate shapes the niche of a species is a core interest in evolution and ecology. Research on the evolution of climatic niches can inform us on the historical relationship between organisms and their climate, and, in an era of great environmental change, what that relationship may look like in the future. In this study, I tested an essential idea in the history of climate niche research, the Climatic Variability Hypothesis, by comparing the thermal niche breadth of coastal and inland populations of Mimulus guttatus. Using thermal performance results from this experiment, I also forecasted how the suitability of thermal habitat may change for these populations. Unexpectedly, coastal and inland populations did not differ in thermal niche breadth. All populations possess relatively wide performance curves. However, I found other interesting differences in their thermal performance curves that are deserving of further research. Because populations differed little in their performance curves, they all show similar responses to temperature increases. These increases are actually projected to bring more favorable thermal conditions for all populations. However, this is only assuming that plants have plentiful water. Drier conditions caused by climate change may outweigh benefits from warmer temperatures. Of course, measuring and quantifying the climatic niche of an organism and predicting its future are complex tasks. I introduce what I hope are improvements, if only minor, to methods that have previously been used.