Masters Theses

Date of Award

5-2025

Degree Type

Thesis

Degree Name

Master of Science

Major

Ecology and Evolutionary Biology

Major Professor

Stephanie N. Kivlin

Committee Members

Stephanie N. Kivlin, Suzan Kalisz, Daniel Simberloff

Abstract

Invasive plant species are a ubiquitous global change pressures across ecosystems and pose serious threats to plant diversity and productivity. Despite their prevalence, the impact of invasive plants on native plant communities is often unpredictable. One way that native plants may be impacted by plant invasions is via mutualism disruption of their nutrient-acquiring mycorrhizal fungal symbionts belowground, specifically arbuscular mycorrhizal (AM) fungi, by allelochemicals produced by invasive plants. AM fungi associate with ~90% of terrestrial plant species, and play a crucial role in nutrient cycling, plant growth, and overall soil health. A common invasive species in North American temperate forests is Alliaria petiolata (Brassicaceae), commonly called garlic mustard, which was introduced to North America via Europe in the 1800’s. Garlic mustard produces secondary allelochemicals that are toxic to soil bacteria and fungi, including AM fungi, and can have long-term effects on plant community composition and ecosystem services. I hypothesized that AM fungal-plant mutualism disruption is common following garlic mustard invasion, therefore native plant mycorrhizal fungal interactions can be used as a metric to assess the impacts of invasion across similar ecosystems. My research addresses two questions. (1) To what extent do allelopathic invasive plants alter the species richness and composition of mycorrhizal fungi in the roots of native plants, and (2) how are bipartite networks of native plants and AM mycorrhizal fungi rewired following invasion and to what extent does this affect plant-mycorrhizal fungal network stability? By assaying AM fungi in roots of native understory plant species from the Trillium Trail field site in Fox Chapel, Pennsylvania I address long-term impacts of invasive species on mycorrhizal fungal-plant networks and their wider implications for ecosystem stability and restoration.

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