Thesis
Mutualist distribution constrains the spread of the invasive legume Medicago polymorphia across the landscape
Washington State University
Master of Science (MS), Washington State University
12/2019
DOI:
https://doi.org/10.7273/000003970
Handle:
https://hdl.handle.net/2376/123266
Abstract
Cooperation with mutualists can fuel the success of invasive species, which drive the deterioration of native communities. The spread of invasive species can be constrained or promoted by the distributions of the mutualists they rely on, which presents an opportunity for managing biological invasions. Yet, the ways in which the geographical distributions of mutualists shape the range limits and invasion dynamics of introduced species remains a frontier in evolutionary ecology. The legume family (Fabaceae) includes noxious invaders whose success is tied to their mutualism with nitrogen-fixing rhizobium bacteria. We examine whether the availability of compatible rhizobia limit the spread of an invasive legume at both small (50 m) and large (continental) spatial scales across natural invasion fronts. Using greenhouse experiments we simulated the dispersal of Medicago polymorpha into soils at increasing distances from the host patch. Mutualist availability rapidly declines close to zero within 20 m of established plant patches. Plant fitness and the percentage of leaf nitrogen derived from symbiotic nitrogen fixation decline precipitously with distance from the host patch. The decline of fitness due to the lack of rhizobium mutualists differs among M. polymorpha genotypes. As M. polymorpha colonizes novel areas, seeds that disperse even short distances from established patches are likely to be mutualist limited, and given that plant lineages exhibit genetic variation upon which selection could act to reduce dependence on rhizobia, our findings suggest that symbiosis traits in the invader could evolve over the course of invasion.
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Details
- Title
- Mutualist distribution constrains the spread of the invasive legume Medicago polymorphia across the landscape
- Creators
- Zoie Christine Lopez
- Contributors
- Stephanie S Porter (Advisor) - Washington State University, School of Biological Sciences
- Awarding Institution
- Washington State University
- Academic Unit
- School of Biological Sciences
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890803801842
- Language
- English
- Resource Type
- Thesis