Graduation Date

Fall 2023

Document Type



Master of Science degree with a major in Biology

Committee Chair Name

Paul Bourdeau

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Sean Craig

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Erik Jules

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Eve Robinson

Fourth Committee Member Affiliation

Community Member or Outside Professional


Biodiversity, Invasion, Environmental variation, Invasive species, Biotic resistance

Subject Categories



The theory of biotic resistance predicts that more diverse communities should be less susceptible to invasion by novel species, but given the opposing results of multiple observational and experimental studies in marine systems, it is unclear how changes in environmental conditions can affect invasion success in communities that differ in diversity. I used marine fouling communities to test how the diversity of the species present in an initial community (hereafter termed “resident species”) affected the establishment and growth of all species not present in the initial communities (hereafter termed “novel species”) at two locations at the Eureka Public Marina, in Humboldt CA. I found that the less diverse communities ended up with a higher percent cover of novel species despite significant differences between both experimental locations in water motion, propagule pressure, and nudibranch abundance. These results support the biotic resistance hypothesis, in that more diverse communities were less invaded by novel species and suggest that environmental conditions may need to differ drastically to drive differences in invasion success.

Citation Style




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