Herbivory on nitrogen-fixing plants
Abstract/Contents
- Abstract
- Nitrogen is an essential element for the growth and development of all organisms, yet it is often scarce in terrestrial systems. Nitrogen-fixing plants (fixers) have evolved to circumvent such nitrogen limitations by forming symbiotic associations with microbes that convert atmospheric nitrogen gas (N2) into biologically usable ammonia (NH3). Considering the advantage of having an additional nitrogen source in the face of widespread nitrogen limitations, one might expect nitrogen-fixing plants to surpass non-fixing plants in competition. Surprisingly, however, non-fixing plants often outnumber fixers in numerous instances, even in nitrogen-poor systems. At present, we lack a comprehensive understanding of the underlying dynamics that prevent fixers from outcompeting non-fixers in terms of fitness and abundance. One popular hypothesis suggests that tissue loss from herbivory limits fixer growth and abundance. This theory proposes that herbivores preferentially consume the leaves of fixers at higher rates than non-fixers, primarily due to the higher nitrogen concentrations found in fixers. However, to date, this theory lacks robust supporting research. In this dissertation, I aimed to fill this knowledge gap with empirical data. To achieve this, I performed a systematic review and meta-analysis of the existing literature in Chapter 2. Subsequently, in Chapter 3, I conducted a multi-year experiment in the Mediterranean region of California, USA. I hypothesized that: 1) fixers would have significantly higher leaf nitrogen concentrations than non-fixers; 2) fixers would exhibit higher rates of leaf herbivory than non-fixers; and 3) leaf nitrogen content would positively correlate with herbivory. The results of the meta-analysis supported all three hypotheses. The results from the herbivory experiment were similar, with fixers exhibiting 25% more leaf nitrogen and double the leaf herbivory rate as non-fixers. However, no significant relationship between herbivory and nitrogen levels was observed. These findings provide the first comprehensive assessment of the concept that fixers experience greater herbivory than non-fixers, utilizing multiple empirical approaches.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2023; ©2023 |
| Publication date | 2023; 2023 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Costa, Suchana |
|---|---|
| Degree supervisor | Field, Christopher B |
| Thesis advisor | Field, Christopher B |
| Thesis advisor | Dirzo, Rodolfo |
| Thesis advisor | Peay, Kabir |
| Degree committee member | Dirzo, Rodolfo |
| Degree committee member | Peay, Kabir |
| Associated with | Stanford University, School of Humanities and Sciences |
| Associated with | Stanford University, Department of Biology |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Suchana H. Costa. |
|---|---|
| Note | Submitted to the Department of Biology. |
| Thesis | Thesis Ph.D. Stanford University 2023. |
| Location | https://purl.stanford.edu/sx695hx1475 |
Access conditions
- Copyright
- © 2023 by Suchana Costa
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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