Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

Foundation species provide the structure for other species and can significantly affect the composition and overall diversity within a community. Multiple foundation species can coexist within a community, and each can have differential impacts. My dissertation aims to understand the effects different foundation species have on diversity and the community assembly processes responsible for structuring diversity within their respective communities.

First, I quantified the diversity of groundcover plants within the prominent foundation species, bunchgrasses, (dominated by Shizachyrium scoparium) compared to groundcover plant diversity within patches of the alternative foundation species bracken fern (Pteridium aquilinum) and gallberry (Ilex glabra). I also investigated the effect foundation species can have on higher trophic levels, specifically arthropods. I found that the diversity of groundcover plants and arthropods was inhibited by the alternative foundation species and enhanced by the prominent foundation species, bunchgrasses.

Next, I investigated the possible community assembly processes associated with each foundation species that could either favor the particular foundation species or be responsible for structuring the rest of the groundcover plant diversity. I investigated abiotic filtering as a possible process by examining the abiotic conditions within the environments dominated by each foundation species. I found that in general, abiotic conditions did not differ between each foundation species. Next, I investigated competition as a possible mechanism. I examined the effect of vegetation removal treatments on plant diversity to investigate the process of competitive release. I found that the diversity of forbs did not differ between the different vegetation removal experiments within areas dominated by each foundation species. However, grass diversity increased in treatments where the foundation species was removed.

Lastly, I examined how foundation species affect plant diversity within another ecosystem. I found that tree seedling diversity was lower within understory patches dominated by a fern species within a lowland tropical rainforest in Costa Rica. This could provide evidence that this fern species acts as a foundation species within this community and aligns with previous findings that foundation species have the potential to decrease diversity, although the processes may be different.

Date

8-22-2022

Committee Chair

Harms, Kyle

Available for download on Thursday, August 21, 2025

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