1
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Dixit T. A synthesis of coevolution across levels of biological organization. Evolution 2024; 78:211-220. [PMID: 38085659 DOI: 10.1093/evolut/qpad082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 04/16/2023] [Accepted: 04/28/2023] [Indexed: 02/03/2024]
Abstract
In evolutionary ecology, coevolution is typically defined as reciprocal evolution of interacting species. However, outside the context of interacting species, the term "coevolution" is also used at levels of biological organization within species (e.g., between males and females, between cells, and between genes or proteins). Furthermore, although evolution is typically defined as "genetic change over time", coevolution need not involve genetic changes in the interacting parties, since cultures can also evolve. In this review, I propose that coevolution be defined more broadly as "reciprocal adaptive evolution at any level of biological organisation". The classification of reciprocal evolution at all levels of biological organization as coevolution would maintain consistency in terminology. More importantly, the broader definition should facilitate greater integration of coevolution research across disciplines. For example, principles usually discussed only in the context of coevolution between species or coevolution between genes (e.g., tight and diffuse coevolution, and compensatory coevolution, respectively) could be more readily applied to new fields. The application of coevolutionary principles to new contexts could also provide benefits to society, for instance in deducing the dynamics of coevolution between cancer cells and cells of the human immune system.
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Affiliation(s)
- Tanmay Dixit
- Department of Zoology, University of Cambridge, Cambridge, United Kingdom
- DST-NRF Centre of Excellence at the FitzPatrick Institute of African Ornithology, University of Cape Town, Rondebosch, Cape Town, South Africa
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2
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Yoder JB, Dang A, MacGregor C, Plaza M. Plant‐associate interactions and diversification across trophic levels. Evol Lett 2022; 6:375-389. [PMID: 36254257 PMCID: PMC9554764 DOI: 10.1002/evl3.296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 08/27/2022] [Indexed: 11/11/2022] Open
Abstract
Interactions between species are widely understood to have promoted the diversification of life on Earth, but how interactions spur the formation of new species remains unclear. Interacting species often become locally adapted to each other, but they may also be subject to shared dispersal limitations and environmental conditions. Moreover, theory predicts that different kinds of interactions have different effects on diversification. To better understand how species interactions promote diversification, we compiled population genetic studies of host plants and intimately associated herbivores, parasites, and mutualists. We used Bayesian multiple regressions and the BEDASSLE modeling framework to test whether host and associate population structures were correlated over and above the potentially confounding effects of geography and shared environmental variation. We found that associates' population structure often paralleled their hosts' population structure, and that this effect is robust to accounting for geographic distance and climate. Associate genetic structure was significantly explained by plant genetic structure somewhat more often in antagonistic interactions than in mutualistic ones. This aligns with a key prediction of coevolutionary theory that antagonistic interactions promote diversity through local adaptation of antagonists to hosts, while mutualistic interactions more often promote diversity via the effect of hosts' geographic distribution on mutualists' dispersal.
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Affiliation(s)
- Jeremy B. Yoder
- Department of Biology California State University Northridge Northridge CA 91330 USA
| | - Albert Dang
- Department of Biology California State University Northridge Northridge CA 91330 USA
| | - Caitlin MacGregor
- Department of Biology California State University Northridge Northridge CA 91330 USA
| | - Mikhail Plaza
- Program in Plant Biology and Conservation Northwestern University Evanston IL 60208 USA
- Negaunee Institute for Plant Conservation Science and Action Chicago Botanic Garden Glencoe IL 60035 USA
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3
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Batstone RT, Burghardt LT, Heath KD. Phenotypic and genomic signatures of interspecies cooperation and conflict in naturally occurring isolates of a model plant symbiont. Proc Biol Sci 2022; 289:20220477. [PMID: 35858063 PMCID: PMC9277234 DOI: 10.1098/rspb.2022.0477] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Given the need to predict the outcomes of (co)evolution in host-associated microbiomes, whether microbial and host fitnesses tend to trade-off, generating conflict, remains a pressing question. Examining the relationships between host and microbe fitness proxies at both the phenotypic and genomic levels can illuminate the mechanisms underlying interspecies cooperation and conflict. We examined naturally occurring genetic variation in 191 strains of the model microbial symbiont Sinorhizobium meliloti, paired with each of two host Medicago truncatula genotypes in single- or multi-strain experiments to determine how multiple proxies of microbial and host fitness were related to one another and test key predictions about mutualism evolution at the genomic scale, while also addressing the challenge of measuring microbial fitness. We found little evidence for interspecies fitness conflict; loci tended to have concordant effects on both microbe and host fitnesses, even in environments with multiple co-occurring strains. Our results emphasize the importance of quantifying microbial relative fitness for understanding microbiome evolution and thus harnessing microbiomes to improve host fitness. Additionally, we find that mutualistic coevolution between hosts and microbes acts to maintain, rather than erode, genetic diversity, potentially explaining why variation in mutualism traits persists in nature.
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Affiliation(s)
- Rebecca T. Batstone
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, IL 61801, USA
| | - Liana T. Burghardt
- Department of Plant Science, The Pennsylvania State University, 103 Tyson Building, University Park, PA, 16802 USA
| | - Katy D. Heath
- Department of Plant Biology, University of Illinois at Urbana-Champaign, 286 Morrill Hall, 505 South Goodwin Avenue, Urbana, IL 61801, USA
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4
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Epstein B, Burghardt LT, Heath KD, Grillo MA, Kostanecki A, Hämälä T, Young ND, Tiffin P. Combining GWAS and population genomic analyses to characterize coevolution in a legume-rhizobia symbiosis. Mol Ecol 2022. [PMID: 35793264 DOI: 10.1111/mec.16602] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/03/2022] [Accepted: 07/04/2022] [Indexed: 11/28/2022]
Abstract
The mutualism between legumes and rhizobia is clearly the product of past coevolution. However, the nature of ongoing evolution between these partners is less clear. To characterize the nature of recent coevolution between legumes and rhizobia, we used population genomic analysis to characterize selection on functionally annotated symbiosis genes as well as on symbiosis gene candidates identified through a two-species association analysis. For the association analysis, we inoculated each of 202 accessions of the legume host Medicago truncatula with a community of 88 Sinorhizobia (Ensifer) meliloti strains. Multistrain inoculation, which better reflects the ecological reality of rhizobial selection in nature than single-strain inoculation, allows strains to compete for nodulation opportunities and host resources and for hosts to preferentially form nodules and provide resources to some strains. We found extensive host by symbiont, that is, genotype-by-genotype, effects on rhizobial fitness and some annotated rhizobial genes bear signatures of recent positive selection. However, neither genes responsible for this variation nor annotated host symbiosis genes are enriched for signatures of either positive or balancing selection. This result suggests that stabilizing selection dominates selection acting on symbiotic traits and that variation in these traits is under mutation-selection balance. Consistent with the lack of positive selection acting on host genes, we found that among-host variation in growth was similar whether plants were grown with rhizobia or N-fertilizer, suggesting that the symbiosis may not be a major driver of variation in plant growth in multistrain contexts.
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Affiliation(s)
- Brendan Epstein
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Liana T Burghardt
- Department of Plant Sciences, The University of Pennsylvania, University Park, Pennsylvania, USA
| | - Katy D Heath
- Department of Plant Biology, University of Illinois, Urbana, Illinois, USA.,Carl R. Woese Institute for Genomic Biology, University of Illinois, Urbana, Illinois, USA
| | - Michael A Grillo
- Department of Biology, Loyola University Chicago, Chicago, Illinois, USA
| | - Adam Kostanecki
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Tuomas Hämälä
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA.,School of Life Sciences, University of Nottingham, Nottingham, UK
| | - Nevin D Young
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA.,Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota, USA
| | - Peter Tiffin
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
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5
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Amandine C, Ebert D, Stukenbrock E, Rodríguez de la Vega RC, Tiffin P, Croll D, Tellier A. Unraveling coevolutionary dynamics using ecological genomics. Trends Genet 2022; 38:1003-1012. [PMID: 35715278 DOI: 10.1016/j.tig.2022.05.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 05/08/2022] [Accepted: 05/10/2022] [Indexed: 11/27/2022]
Abstract
Coevolutionary interactions, from the delicate co-dependency in mutualistic interactions to the antagonistic relationship of hosts and parasites, are a ubiquitous driver of adaptation. Surprisingly, little is known about the genomic processes underlying coevolution in an ecological context. However, species comprise genetically differentiated populations that interact with temporally variable abiotic and biotic environments. We discuss the recent advances in coevolutionary theory and genomics as well as shortcomings, to identify coevolving genes that take into account this spatial and temporal variability of coevolution, and propose a practical guide to understand the dynamic of coevolution using an ecological genomics lens.
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Affiliation(s)
- Cornille Amandine
- Université Paris Saclay, INRAE, CNRS, AgroParisTech, GQE - Le Moulon, 91190 Gif-sur-Yvette, France.
| | - Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
| | - Eva Stukenbrock
- Max Planck Institute for Terrestrial Microbiology, Max Planck Research Group, Fungal Biodiversity, Marburg, Germany
| | | | - Peter Tiffin
- Department of Plant and Microbial Biology, 250 Biological Sciences, 1445 Gortner Ave., University of Minnesota, Saint Paul, MN 55108, USA
| | - Daniel Croll
- Laboratory of Evolutionary Genetics, Institute of Biology, University of Neuchâtel, 2000 Neuchâtel, Switzerland.
| | - Aurélien Tellier
- Population Genetics, Department of Life Science Systems, Technical University of Munich, Liesel-Beckman-Str. 2, 85354 Freising, Germany.
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6
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Myers KN, Conn D, Brown AMV. Essential Amino Acid Enrichment and Positive Selection Highlight Endosymbiont's Role in a Global Virus-Vectoring Pest. mSystems 2021; 6:e01048-20. [PMID: 33531407 PMCID: PMC7857533 DOI: 10.1128/msystems.01048-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 01/05/2021] [Indexed: 12/20/2022] Open
Abstract
Host-associated microbes display remarkable convergence in genome repertoire resulting from selection to supplement missing host functions. Nutritional supplementation has been proposed in the verrucomicrobial endosymbiont Xiphinematobacter sp., which lives within a globally widespread group of plant-parasitic nematodes that vector damaging nepoviruses to plants. Only one genome sequence has been published from this symbiont, leaving unanswered questions about its diversity, host range, role, and selective pressures within its hosts. Because its hosts are exceptionally resistant to culturing, this symbiont is best studied through advanced genomic approaches. To analyze the role of Xiphinematobacter sp. in its host, sequencing was performed on nematode communities, and then genomes were extracted for comparative genomics, gene ontology enrichment tests, polymorphism analysis, de Bruijn-based genome-wide association studies, and tests of pathway- and site-specific selection on genes predicted play a role in the symbiosis. Results showed a closely clustered set of Xiphinematobacter isolates with reduced genomes of ∼917 kbp, for which a new species was proposed. Symbionts shared only 2.3% of genes with outgroup Verrucomicrobia, but comparative analyses showed high conservation of all 10 essential amino acid (EAA) biosynthesis pathways plus several vitamin pathways. These findings were supported by gene ontology enrichment tests and high polymorphisms in these pathways compared with background. Genome-wide association analysis confirmed high between-species fixation of alleles with significant functional enrichment for EAA and thiamine synthesis. Strong positive selection was detected on sites within these pathways, despite several being under increased purifying selection. Together, these results suggest that supplementation of EAAs missing in the host diet may drive this widespread symbiosis.IMPORTANCE Xiphinematobacter spp. are distinctly evolved intracellular symbionts in the phylum Verrucomicrobia, which includes the important human gut-associated microbe Akkermansia muciniphila and many highly abundant free-living soil microbes. Like Akkermansia sp., Xiphinematobacter sp. is obligately associated with the gut of its hosts, which in this case consists of a group of plant-parasitic nematodes that are among the top 10 most destructive species to global agriculture, by vectoring plant viruses. This study examined the hypothesis that the key to this symbiont's stable evolutionary association with its host is through provisioning nutrients that its host cannot make that may be lacking in the nematode's plant phloem diet, such as essential amino acids and several vitamins. The significance of our research is in demonstrating, using population genomics, the signatures of selective pressure on these hypothesized roles to ultimately learn how this independently evolved symbiont functionally mirrors symbionts of phloem-feeding insects.
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Affiliation(s)
- Kaitlyn N Myers
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, USA
| | - Daniel Conn
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, USA
| | - Amanda M V Brown
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, USA
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7
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Vidal MC, Segraves KA. Coevolved mutualists experience fluctuating costs and benefits over time. Evolution 2021; 75:219-230. [PMID: 33368192 DOI: 10.1111/evo.14155] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 12/07/2020] [Accepted: 12/20/2020] [Indexed: 01/08/2023]
Abstract
Understanding how mutualisms persist over time requires investigations of how mutualist species coevolve and adapt to the interaction. In particular, the key factors in the evolution of mutualisms are the costs and benefits mutualists experience during the interaction. Here, we used a yeast nutritional mutualism to test how mutualists coevolve and adapt in an obligate mutualism. We allowed two yeast mutualists to evolve together for 15 weeks (about 150 generations), and then we tested if the mutualists had coevolved using time-shift assays. We also examined two mutualistic traits associated with the costs and benefits: resource use efficiency and commodity production. We found that the mutualists quickly coevolved. Furthermore, the changes in benefits and costs were nonlinear and varied with evolutionary changes occurring in the mutualist partner. One mutualist initially evolved to reduce mutualistic commodity production and increase efficiency in mutualistic resource use; however, this negatively affected its mutualist partner that evolved reduced commodity production and resource use efficiency. As a result, the former increased commodity production, resulting in an increase in benefits for its partner. The quick, nonlinear, and asynchronous evolution of yeast mutualists closely resembles antagonistic coevolutionary patterns, supporting the view that mutualisms should be considered as reciprocal exploitation.
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Affiliation(s)
- Mayra C Vidal
- Department of Biology, Syracuse University, Syracuse, New York, 13244.,Biology Department, University of Massachusetts Boston, Boston, Massachusetts, 02125
| | - Kari A Segraves
- Department of Biology, Syracuse University, Syracuse, New York, 13244
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8
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Genome-Wide Identification of the CrRLK1L Subfamily and Comparative Analysis of Its Role in the Legume-Rhizobia Symbiosis. Genes (Basel) 2020; 11:genes11070793. [PMID: 32674446 PMCID: PMC7397338 DOI: 10.3390/genes11070793] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 07/07/2020] [Accepted: 07/09/2020] [Indexed: 12/12/2022] Open
Abstract
The plant receptor-like-kinase subfamily CrRLK1L has been widely studied, and CrRLK1Ls have been described as crucial regulators in many processes in Arabidopsis thaliana (L.), Heynh. Little is known, however, about the functions of these proteins in other plant species, including potential roles in symbiotic nodulation. We performed a phylogenetic analysis of CrRLK1L subfamily receptors of 57 different plant species and identified 1050 CrRLK1L proteins, clustered into 11 clades. This analysis revealed that the CrRLK1L subfamily probably arose in plants during the transition from chlorophytes to embryophytes and has undergone several duplication events during its evolution. Among the CrRLK1Ls of legumes and A. thaliana, protein structure, gene structure, and expression patterns were highly conserved. Some legume CrRLK1L genes were active in nodules. A detailed analysis of eight nodule-expressed genes in Phaseolus vulgaris L. showed that these genes were differentially expressed in roots at different stages of the symbiotic process. These data suggest that CrRLK1Ls are both conserved and underwent diversification in a wide group of plants, and shed light on the roles of these genes in legume–rhizobia symbiosis.
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9
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Younginger BS, Friesen ML. Connecting signals and benefits through partner choice in plant-microbe interactions. FEMS Microbiol Lett 2020; 366:5626345. [PMID: 31730203 DOI: 10.1093/femsle/fnz217] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 10/17/2019] [Indexed: 12/20/2022] Open
Abstract
Stabilizing mechanisms in plant-microbe symbioses are critical to maintaining beneficial functions, with two main classes: host sanctions and partner choice. Sanctions are currently presumed to be more effective and widespread, based on the idea that microbes rapidly evolve cheating while retaining signals matching cooperative strains. However, hosts that effectively discriminate among a pool of compatible symbionts would gain a significant fitness advantage. Using the well-characterized legume-rhizobium symbiosis as a model, we evaluate the evidence for partner choice in the context of the growing field of genomics. Empirical studies that rely upon bacteria varying only in nitrogen-fixation ability ignore host-symbiont signaling and frequently conclude that partner choice is not a robust stabilizing mechanism. Here, we argue that partner choice is an overlooked mechanism of mutualism stability and emphasize that plants need not use the microbial services provided a priori to discriminate among suitable partners. Additionally, we present a model that shows that partner choice signaling increases symbiont and host fitness in the absence of sanctions. Finally, we call for a renewed focus on elucidating the signaling mechanisms that are critical to partner choice while further aiming to understand their evolutionary dynamics in nature.
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Affiliation(s)
- Brett S Younginger
- Department of Plant Pathology, Washington State University, PO Box 646430, 345 Johnson Hall, Pullman, WA 99164, USA
| | - Maren L Friesen
- Department of Plant Pathology, Washington State University, PO Box 646430, 345 Johnson Hall, Pullman, WA 99164, USA.,Department of Crop and Soil Sciences, Washington State University, PO Box 646420, 115 Johnson Hall, Pullman, WA 99164, USA
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10
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Bamba M, Kawaguchi YW, Tsuchimatsu T. Plant adaptation and speciation studied by population genomic approaches. Dev Growth Differ 2018; 61:12-24. [DOI: 10.1111/dgd.12578] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 10/22/2018] [Accepted: 10/22/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Masaru Bamba
- Department of Biology (Frontier Science Program); Graduate School of Science and Engineering; Chiba University; Chiba Japan
| | - Yawako W. Kawaguchi
- Department of Biology (Frontier Science Program); Graduate School of Science and Engineering; Chiba University; Chiba Japan
| | - Takashi Tsuchimatsu
- Department of Biology; Graduate School of Science; Chiba University; Chiba Japan
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11
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Andersen JC, Mills NJ. Comparative genetics of invasive populations of walnut aphid, Chromaphis juglandicola, and its introduced parasitoid, Trioxys pallidus, in California. Ecol Evol 2018; 8:801-811. [PMID: 29321915 PMCID: PMC5756880 DOI: 10.1002/ece3.3667] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 10/13/2017] [Accepted: 10/27/2017] [Indexed: 01/08/2023] Open
Abstract
Coevolution may be an important component of the sustainability of importation biological control, but how frequently introduced natural enemies coevolve with their target pests is unclear. Here we explore whether comparative population genetics of the invasive walnut aphid, Chromaphis juglandicola, and its introduced parasitoid, Trioxys pallidus, provide insights into the localized breakdown of biological control services in walnut orchards in California. We found that sampled populations of C. juglandicola exhibited higher estimates of genetic differentiation (FST) than co-occurring populations of T. pallidus. In contrast, estimates of both the inbreeding coefficient (GIS) and contemporary gene flow were higher for T. pallidus than for C. juglandicola. We also found evidence of reciprocal outlier loci in some locations, but none showed significant signatures of selection. Synthesis and applications. Understanding the importance of coevolutionary interactions for the sustainability of biological control remains an important and understudied component of biological control research. Given the observed differences in gene flow and genetic differentiation among populations of T. pallidus and C. juglandicola, we suspect that temporary local disruption of biological control services may occur more frequently than expected while remaining stable at broader regional scales. Further research that combines genomewide single nucleotide polymorphism genotyping with measurements of phenotypic traits is needed to provide more conclusive evidence of whether the occurrence of outlier loci that display significant signatures of selection can be interpreted as evidence of the presence of a geographic mosaic of coevolution in this system.
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Affiliation(s)
- Jeremy C. Andersen
- Department of Environmental Science Policy and ManagementUniversity of California BerkeleyBerkeleyCAUSA
| | - Nicholas J. Mills
- Department of Environmental Science Policy and ManagementUniversity of California BerkeleyBerkeleyCAUSA
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12
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Hillesland KL. Evolution on the bright side of life: microorganisms and the evolution of mutualism. Ann N Y Acad Sci 2017; 1422:88-103. [PMID: 29194650 DOI: 10.1111/nyas.13515] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/05/2017] [Accepted: 09/11/2017] [Indexed: 01/15/2023]
Abstract
Mutualistic interactions, where two interacting species have a net beneficial effect on each other's fitness, play a crucial role in the survival and evolution of many species. Despite substantial empirical and theoretical work in past decades, the impact of these interactions on natural selection is not fully understood. In addition, mutualisms between microorganisms have been largely ignored, even though they are ecologically important and can be used as tools to bridge the gap between theory and empirical work. Here, I describe two problems with our current understanding of natural selection in mutualism and highlight the properties of microbial mutualisms that could help solve them. One problem is that bias and methodological problems have limited our understanding of the variety of mechanisms by which species may adapt to mutualism. Another problem is that it is rare for experiments testing coevolution in mutualism to address whether each species has adapted to evolutionary changes in its partner. These problems can be addressed with genome resequencing and time-shift experiments, techniques that are easier to perform in microorganisms. In addition, microbial mutualisms may inspire novel insights and hypotheses about natural selection in mutualism.
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13
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Yoder JB, Tiffin P. Sanctions, Partner Recognition, and Variation in Mutualism. Am Nat 2017; 190:491-505. [DOI: 10.1086/693472] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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14
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Westhoek A, Field E, Rehling F, Mulley G, Webb I, Poole PS, Turnbull LA. Policing the legume-Rhizobium symbiosis: a critical test of partner choice. Sci Rep 2017; 7:1419. [PMID: 28469244 PMCID: PMC5431162 DOI: 10.1038/s41598-017-01634-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 04/03/2017] [Indexed: 11/29/2022] Open
Abstract
In legume-Rhizobium symbioses, specialised soil bacteria fix atmospheric nitrogen in return for carbon. However, ineffective strains can arise, making discrimination essential. Discrimination can occur via partner choice, where legumes prevent ineffective strains from entering, or via sanctioning, where plants provide fewer resources. Several studies have inferred that legumes exercise partner choice, but the rhizobia compared were not otherwise isogenic. To test when and how plants discriminate ineffective strains we developed sets of fixing and non-fixing strains that differed only in the expression of nifH - essential for nitrogen fixation - and could be visualised using marker genes. We show that the plant is unable to select against the non-fixing strain at the point of entry, but that non-fixing nodules are sanctioned. We also used the technique to characterise mixed nodules (containing both a fixing and a non-fixing strain), whose frequency could be predicted using a simple diffusion model. We discuss that sanctioning is likely to evolve in preference to partner choice in any symbiosis where partner quality cannot be adequately assessed until goods or services are actively exchanged.
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Affiliation(s)
- Annet Westhoek
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
- Systems Biology Doctoral Training Centre, University of Oxford, Oxford, OX1 3RQ, UK
| | - Elsa Field
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Finn Rehling
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
- Department of Ecology, Philipps-University Marburg, Marburg, D-35043, Germany
| | - Geraldine Mulley
- School of Biological Sciences, University of Reading, Reading, RG6 6AJ, UK
| | - Isabel Webb
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
| | - Philip S Poole
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK.
| | - Lindsay A Turnbull
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK.
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15
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Yoder JB, Leebens-Mack J. The evolutionary ecology of "mutual services" in the 21st century. AMERICAN JOURNAL OF BOTANY 2016; 103:1712-1716. [PMID: 27793857 DOI: 10.3732/ajb.1600367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 10/13/2016] [Indexed: 06/06/2023]
Affiliation(s)
- Jeremy B Yoder
- Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4 Canada
| | - James Leebens-Mack
- Department of Plant Biology, University of Georgia, Athens, Georgia 30602-7271 USA
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