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Abstract When plants colonize new habitats, the novel interactions they form with new mutualists or enemies can immediately affect plant performance. These novel interactions also may provoke rapid evolutionary responses and can be ideal scenarios for investigating how species interactions influence plant evolution.To explore how mutualists influence the evolution of colonizing plant populations, we capitalized on an experiment in which two former agricultural fields were seeded with identical prairie seed mixes in 2010. Six years later, we compared how populations of the legumeChamaecrista fasciculatafrom these sites and their original (shared) source population responded to nitrogen‐fixing rhizobia from the restoration sites in a greenhouse reciprocal cross‐inoculation experiment.We found that the two populations differed both from their original source population and from each other in the benefits they derive from rhizobia, and that one population has evolved reduced allocation to rhizobia (i.e. forms fewer rhizobium‐housing nodules).Synthesis. Our results suggest that these plant populations have evolved different ways of interacting with rhizobia, potentially in response to differences in rhizobium quality between sites. Our study illustrates how microbial mutualists may shape plant evolution in new environments and highlights how variation in microbial mutualists potentially may select for different evolutionary strategies in plant hosts.
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Legume life history interacts with land use degradation of rhizobia: Implications for restoration success
Abstract Restoration of soil microbial communities, and microbial mutualists in particular, is increasingly recognized as critical for the successful restoration of grassland plant communities. Although the positive effects of restoring arbuscular mycorrhizal fungi during the restoration of these systems have been well documented, less is known about the potential importance of nitrogen‐fixing rhizobium bacteria, which associate with legume plant species that comprise an essential part of grassland plant communities, to restoration outcomes. In a series of greenhouse and field experiments, we examined the effects of disturbance on rhizobium communities, how plant interactions with these mutualists changed with disturbance, and whether rhizobia can be used to enhance the establishment of desirable native legume species in degraded grasslands. We found that agricultural disturbance alters rhizobium communities in ways that affect the growth and survival of legume species. Native legume species derived more benefit from interacting with rhizobia than did non‐native species, regardless of rhizobia disturbance history. Additionally, slow‐growing, long‐lived legume species received more benefits from associating with rhizobia from undisturbed native grasslands than from associating with rhizobia from more disturbed sites. Together, this suggests that native rhizobia may be key to enhancing the restoration success of legumes in disturbed habitats.
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- PAR ID:
- 10584794
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecological Applications
- Volume:
- 35
- Issue:
- 3
- ISSN:
- 1051-0761
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Native legumes are functionally important members of grasslands, but their reintroduction into degraded systems is limited by strong establishment filters. One of these establishment filters might be rhizobia limitation, where legume seedlings are unable to find suitable rhizobia symbionts in grasslands targeted for restoration. To test links between rhizobial inoculation and legume demographic parameters in a grassland restoration context, we evaluated how inoculation with rhizobia altered survival and seed production of a native annual legume (Chamaecrista fasciculata) inoculated with rhizobia and transplanted into a restored prairie. Small mammal herbivory was an important filter affecting survival ofC. fasciculatatransplants, with inoculated plants 81% more likely to be grazed than uninoculated plants. Despite this heavy grazing, plants inoculated with rhizobia survived transplantation 71% more often and, as a result, produced 82% more flowers, experienced 73% more visits by pollinators, and on average produced 220% more seeds. Our results indicate that although herbivory may also shape legume population establishment, at least in some years in some places, rhizobia could alterC. fasciculatainteractions with both herbivores and pollinators and improve population establishment.more » « less
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Summary Many plant species simultaneously interact with multiple symbionts, which can, but do not always, generate synergistic benefits for their host. We ask if plant life history (i.e. annual vs perennial) can play an important role in the outcomes of the tripartite symbiosis of legumes, arbuscular mycorrhizal fungi (AMF), and rhizobia.We performed a meta‐analysis of 88 studies examining outcomes of legume–AMF–rhizobia interactions on plant and microbial growth.Perennial legumes associating with AMF and rhizobia grew larger than expected based on their response to either symbiont alone (i.e. their response to co‐inoculation was synergistic). By contrast, annual legume growth with co‐inoculation did not differ from additive expectations. AMF and rhizobia differentially increased phosphorus (P) and nitrogen (N) tissue concentration. Rhizobium nodulation increased with mycorrhizal fungi inoculation, but mycorrhizal fungi colonization did not increase with rhizobium inoculation. Microbial responses to co‐infection were significantly correlated with synergisms in plant growth.Our work supports a balanced plant stoichiometry mechanism for synergistic benefits. We find that synergisms are in part driven by reinvestment in complementary symbionts, and that time‐lags in realizing benefits of reinvestment may limit synergisms in annuals. Optimization of microbiome composition to maximize synergisms may be critical to productivity, particularly for perennial legumes.more » « less
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