First Advisor

Kristofor Voss


Regis College

Degree Name

MS Environmental Biology

Document Type

Thesis - Open Access

Number of Pages

77 pages


This study aims to provide a deeper understanding of the role of competition in food webs, and more specifically, in trophic cascades induced by biodiversity loss. Trophic cascades are food web disturbances that result from the removal of an important species, often a predator, and lead to dramatic changes in herbivore and plant populations. It is critical to understand the mechanisms that drive and mitigate trophic cascades, because global biodiversity loss is increasing. Previous research suggests that biodiversity, specifically intraguild biodiversity with members in the same trophic level, is an important factor in reducing the negative effects of trophic cascades. High biodiversity increases competition, which limits population growth of individual species. Research on competition in relation to trophic cascades is scarce, prompting the need for more direct study.

I plan to test the hypothesis that increased herbivorous insect biodiversity will decrease typical trophic cascade strength, by increasing competition between the herbivores and reducing plant loss. Using microcosm ecosystems in fish tanks, I will study a three-trophic-level food chain where a predator is present, and a two-trophic-level cascade where the predator has been removed. By manipulating herbivore diversity and predator presence in the tanks, I will investigate how herbivore diversity influences competition, and how the effect of changing herbivore diversity differs in food webs with and without predators. I expect that higher herbivore diversity will yield higher average plant biomass compared to herbivore monoculture treatments, and that plant biomass will be greater in tanks where the predator is present. Maintaining high biodiversity within ecosystems ensures that another mechanism, competition, maintains stable levels of herbivores and protects against major plant loss. My study will provide information to aid in management practices to help sustain ecosystems experiencing biodiversity loss.

Date of Award

Spring 2018

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