James Amon (Committee Member), Chris Barton (Committee Member), Wayne Carmichael (Committee Member), Don Cipollini (Advisor), Carl Friese (Committee Member)
Doctor of Philosophy (PhD)
Garlic mustard (GM), Alliaria petiolata, a European biennial herb invasive in North America, produces secondary metabolites that may contribute to its invasive success by allelopathically inhibiting growth of native plants. I tested this hypothesis by determining the levels, and stability, of these compounds in field soils. I also explored differences in the phytochemical profiles of GM and closely related North American species, and biogeographic differences in allelopathic effects on North American and European arbuscular mycorrhizal fungi (AMF). Furthermore, I exposed a North American annual herb, pale jewelweed (Impatiens pallida), and its AMF, to GM extracts in order to determine how GM metabolites interact to inhibit growth throughout the formation of mycorrhizal symbioses. Additionally, I determined whether or not allelopathic inhibition remained significant when resource competition was also occurring, by exposing jewelweed plants grown at various densities to GM extracts. Also, I assessed allelopathic effects on AMF diversity by performing terminal restriction fragment length polymorphism analysis on AMF DNA isolated from field soils collected either in or outside of GM populations. Finally, I explored how three methods commonly used to kill GM influenced the health of jewelweed plants later planted in the same soil. Secondary metabolites produced by GM decompose too quickly to account for long term inhibition, suggesting that degradates of these compounds are bioactive. None of the compounds produced by GM were found in four North American species, and North American AMF were more sensitive to allelopathic effects than European AMF. I found strong inhibition of seed germination and growth of uncolonized plants, but AMF appeared to protect colonized jewelweed plants from any allelopathic effects. Allelopathic effects were not as significant as effects of resource competition on jewelweed plant size. AMF diversity was lower in sites with GM than without. During simulated restorations, jewelweed plants were larger and more colonized by AMF in soils with the least amount of dead GM tissue remaining. GM can be allelopathic, but effects may not be strong enough to drive its invasive success. Instead, allelopathic effects may be more important in maintaining an invasion and must be addressed during restoration of invaded sites.
Department or Program
Department of Earth and Environmental Sciences
Year Degree Awarded
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