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Mutualistic rhizobia reduce plant diversity and alter community composition
1Kellogg Biological Station and Department of Plant Biology, Michigan State University, Hickory Corners, MI, 49060, USA, keller47@msu.edu.
Oecologia
|September 24, 2014
Summary
The presence of nitrogen-fixing rhizobia significantly reduced plant community diversity and altered composition by increasing the dominance of their legume hosts. This highlights the crucial role of mutualistic interactions in shaping plant communities, especially in nutrient-limited environments.
Area of Science:
- Ecology
- Plant Biology
- Microbial Ecology
Background:
- Mutualistic interactions are critical drivers of community dynamics, comparable to antagonistic ones like competition and predation.
- Resource mutualisms, particularly nitrogen-fixing rhizobia, can profoundly influence plant community structure and function.
- Nutrient-limited ecosystems may amplify the effects of mutualists on diversity and composition.
Purpose of the Study:
- To experimentally investigate how the mutualism between nitrogen-fixing rhizobia and legumes affects plant diversity and community composition.
- To assess the impact of rhizobia across a nitrogen gradient on early-assembling mesocosm communities.
- To understand the broader ecosystem consequences of this symbiosis on diversity, composition, and productivity.
Main Methods:
- Experimental manipulation of rhizobia presence in mesocosms with identical initial species composition.
- Application of a nitrogen gradient to simulate varying nutrient availability.
- Assessment of alpha-diversity, community composition, beta-diversity, inorganic nitrogen, and productivity post-harvest.
Main Results:
- Rhizobia presence decreased plant community diversity and increased community convergence (reduced beta-diversity).
- Community composition was significantly altered, with increased competitive dominance of the legume host, Chamaecrista fasciculata.
- Total community productivity increased, with varied positive and negative responses observed in non-leguminous species.
Conclusions:
- Rhizobia act as keystone mutualists, significantly reducing plant diversity by promoting legume dominance.
- These findings underscore the importance of symbiotic interactions in shaping terrestrial plant communities.
- Understanding mutualisms is essential for predicting plant community responses to environmental changes, especially in nutrient-poor conditions.
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