Iriart, Veronica
(2024)
Ecological impacts of anthropogenic stress from a contemporary herbicide on species interactions involving plants.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Global use of herbicides to meet food demands and its associated chemical pollution have surged in recent decades. While the effects of off-target herbicide exposures on some crop species are known, we know little of how wild plants in proximity to agriculture, i.e. at the ‘agro-ecological interface’, are impacted or how their species interactions tied to essential ecosystem services are likewise affected. Across three dissertation chapters, I investigated these important—yet previously undescribed—ecological consequences of herbicide use. In Chapter 1, I performed a greenhouse experiment to characterize the growth and flowering of 25 plant species common to agro-ecosystems following herbicide exposure via ‘drift’ (atmospheric chemical movement). In
Chapter 2, I focused on a key member of these agro-ecosystems, the legume Trifolium pratense, and conducted a plant-microbe study to investigate the impacts of herbicide drift on the mutualism between plants and nitrogen-fixing bacteria (rhizobia). I further explored this topic in Chapter 3,
where I simultaneously exposed T. pratense and rhizobia to herbicidal chemicals in the rhizosphere—the region surrounding roots where plants and microbes interact and herbicides can
also contaminate—in a microcosm experiment. In all chapters, I used dicamba, a highly-used synthetic auxin herbicide known for off-target movement, to simulate exposures. Results conveyed that despite comprising only ~0.5-1% of what is typically applied in agriculture, off-target dicamba
concentrations can significantly impact wild plants and their species interactions. Exposure to dicamba drift inhibited or in some cases enhanced plant growth, depending on the species, and it also had species-specific effects on flowering phenology. As these traits relate to plant-plant competition for resources and pollination, these alterations would probably influence interactions between plant species in nature. Additionally, dicamba exposure either from drift or the rhizosphere reduced the growth promoting benefits of rhizobia, but the degree of reduction depended on rhizobial genotype, and other traits including nitrogen fixation were also mediated by interactions between rhizobial genotypes and the herbicide environment. Altogether, my dissertation relays timely insights into the ecological impacts of off-target herbicide exposures, the biological forces which mediate them, and the evolutionary trajectories that may follow them.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
27 August 2024 |
| Date Type: |
Publication |
| Defense Date: |
13 May 2024 |
| Approval Date: |
27 August 2024 |
| Submission Date: |
30 June 2024 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
212 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Biological Sciences |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
herbicide, herbicide drift, plant ecology, ecology and evolution, plant-rhizobia, mutualism, symbiosis, flowering, species interactions, coflowering |
| Date Deposited: |
27 Aug 2024 13:41 |
| Last Modified: |
27 Aug 2024 13:41 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/46642 |
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