Graduation Date

Fall 2022

Document Type



Master of Science degree with a major in Biology

Committee Chair Name

Catalina Cuellar-Gempeler

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Erik Jules

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Matthew Hurst

Third Committee Member Affiliation

Community Member or Outside Professional

Fourth Committee Member Name

Thomas Miller

Subject Categories



Biodiversity-ecosystem function (BEF) research aims to explain how species and their environments interact with each other. Microbial communities engage in vital biogeochemical pathways in a variety of natural ecosystems, and yet there are large knowledge gaps about the specific metabolic pathways in which they are involved. Degradation specifically contributes to nitrogen cycling globally through the breakdown of large organic nitrogen compounds into small inorganic nitrogen that is necessary for the survival of many other organisms. In this study, I focused on the degradative function of the inquiline microbial communities found within the carnivorous pitcher plant, Darlingtonia californica. Darlingtonia grows in nitrogen poor soils and relies on the microorganisms inside of its pitcher to break down insect prey into bioavailable nutrients. The purpose of this study was to identify if specific nitrogen metabolic pathways are driven by Darlingtonia bacterial diversity. Fourteen known bacterial isolates were grown in monoculture as well as in mixed cultures of 2-5 species. Additionally, bacteria were collected from Darlingtonia pitchers and acclimated in the lab, and serial dilution was performed to produce a diversity gradient. These lab communities were also compared to samples collected from Shasta County, Plumas County, and Del Norte County in California to define the scope of natural diversity observed in this experiment. Communities were given fruit flies as food to compare degradation over 11 days using the broad degradation metric of fly mass loss, and the specific nitrogen function metrics of enzymatic activity of chitinase and protease, and solubilized protein, ammonia, and nitrate concentrations. While I found increases in degradation potential of higher diversity cultured communities, these positive relationships were not seen in the more complex serial dilution communities. Additionally, nitrogen processing may not be driving insect degradation, as nitrogen metrics could not describe the loss of fly mass observed in this study. Redundant and overlapping functions in this system may allow Darlingtonia to maintain insect prey consumption at a range of microbial diversity levels. The benefits of biodiversity on nutrient cycling are commonly discussed, citing positive relationships between the two, however expanding our understanding of redundant relationships between microorganisms and degradation will also strengthen our understanding of the drivers of global biogeochemical cycling and interactions between bacteria and their hosts

Citation Style



Thesis/Project Location