Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Stephen J. Mullin


Food webs provide a useful conceptual framework for evaluating the relationships that exist within ecological systems. Characterizing the interactions within these webs can improve our understanding of how communities are structured and what mechanisms stabilize them. Untangling these interactions can be an intractable problem in complex systems and insights gained from conventional methods are often accompanied by inherent sources of bias. This study used stable isotope analysis, an alternative to traditional methods, to investigate the roles and relative contributions of consumers at the top of a food web to community structure and stability. I compared the niche parameters of five syntopic semi-aquatic snake species using the ratios of naturally occurring carbon and nitrogen isotopes to determine their relative trophic positions and estimate the contributions of potential prey sources to their diets. Analyses using Bayesian mixing models revealed evidence of niche partitioning among consumer groups and indicated that competitive dynamics have helped to shape the structure of this community. I identified ontogenetic differences in the trophic niches occupied by distinct age classes from three consumer species. I also detected temporal shifts in trophic structure that might be the result of intra-annual variation in resource availability. While competition appears to play a role in structuring this community, the trophic niches occupied by consumer groups seem to be somewhat plastic. Temporal shifts in resource availability have the potential to influence not only the relationships among competing consumers, but also their interactions with prey groups. Future research should examine how periodic fluctuations in prey abundance influences the connectivity, and by extension the stability, of this community.

Graduate Program

Biological Sciences