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Agarwal R, Althoff DM. Extreme specificity in obligate mutualism-A role for competition? Ecol Evol 2024; 14:e11628. [PMID: 38911491 PMCID: PMC11190587 DOI: 10.1002/ece3.11628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 05/31/2024] [Accepted: 06/10/2024] [Indexed: 06/25/2024] Open
Abstract
Obligate mutualisms, reciprocally obligate beneficial interactions, are some of the most important mutualisms on the planet, providing the basis for the evolution of the eukaryotic cell, the formation and persistence of terrestrial ecosystems and the establishment and expansion of coral reefs. In addition, these mutualisms can also lead to the diversification of interacting partner species. Accompanying this diversification is a general pattern of a high degree of specificity among interacting partner species. A survey of obligate mutualisms demonstrates that greater than half of these systems have only one or two mutualist species on each side of the interaction. This is in stark contrast to facultative mutualisms that can have dozens of interacting mutualist species. We posit that the high degree of specificity in obligate mutualisms is driven by competition within obligate mutualist guilds that limits species richness. Competition may be particularly potent in these mutualisms because mutualistic partners are totally dependent on each other's fitness gains, which may fuel interspecific competition. Theory and the limited number of empirical studies testing for the role of competition in determining specificity suggest that competition may be an important force that fuels the high degree of specificity. Further empirical research is needed to dissect the relative roles of trait complementarity, mutualism regulation, and competition among mutualist guild members in determining mutualism specificity at local scales.
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Affiliation(s)
- Renuka Agarwal
- Department of BiologySyracuse UniversitySyracuseNew YorkUSA
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Hale KRS, Maes DP, Valdovinos FS. Simple mechanisms of plant reproductive benefits yield different dynamics in pollination and seed dispersal mutualisms. Am Nat 2022; 200:202-216. [DOI: 10.1086/720204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Hale KRS, Valdovinos FS. Ecological theory of mutualism: Robust patterns of stability and thresholds in two-species population models. Ecol Evol 2021; 11:17651-17671. [PMID: 35003630 PMCID: PMC8717353 DOI: 10.1002/ece3.8453] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 11/29/2021] [Indexed: 11/08/2022] Open
Abstract
Mutualisms are ubiquitous in nature, provide important ecosystem services, and involve many species of interest for conservation. Theoretical progress on the population dynamics of mutualistic interactions, however, comparatively lagged behind that of trophic and competitive interactions, leading to the impression that ecologists still lack a generalized framework to investigate the population dynamics of mutualisms. Yet, over the last 90 years, abundant theoretical work has accumulated, ranging from abstract to detailed. Here, we review and synthesize historical models of two-species mutualisms. We find that population dynamics of mutualisms are qualitatively robust across derivations, including levels of detail, types of benefit, and inspiring systems. Specifically, mutualisms tend to exhibit stable coexistence at high density and destabilizing thresholds at low density. These dynamics emerge when benefits of mutualism saturate, whether due to intrinsic or extrinsic density dependence in intraspecific processes, interspecific processes, or both. We distinguish between thresholds resulting from Allee effects, low partner density, and high partner density, and their mathematical and conceptual causes. Our synthesis suggests that there exists a robust population dynamic theory of mutualism that can make general predictions.
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Affiliation(s)
- Kayla R. S. Hale
- Department of Ecology and Evolutionary BiologyUniversity of MichiganAnn ArborMichiganUSA
| | - Fernanda S. Valdovinos
- Department of Environmental Science and PolicyUniversity of CaliforniaDavisCaliforniaUSA
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Johnson CA. How mutualisms influence the coexistence of competing species. Ecology 2021; 102:e03346. [PMID: 33742453 DOI: 10.1002/ecy.3346] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 02/01/2021] [Accepted: 02/22/2021] [Indexed: 11/09/2022]
Abstract
Mutualisms are ubiquitous in nature and are thought to play important roles in the maintenance of biodiversity. For biodiversity to be maintained, however, species must coexist in the face of competitive exclusion. Chesson's coexistence theory provides a mechanistic framework for evaluating coexistence, yet mutualisms are conspicuously absent from coexistence theory and there are no comparable frameworks for evaluating how mutualisms affect the coexistence of competiting species. To address this conceptual gap, I develop theory predicting how multitrophic mutualisms mediate the coexistence of species competing for mutualistic commodities and other limiting resources using the niche and fitness difference concepts of coexistence theory. I demonstrate that failing to account for mutualisms can lead to erroneous conclusions. For example, species might appear to coexist on resources alone, when the simultaneous incorporation of mutualisms actually drives competitive exclusion, or competitive exclusion might occur under resource competition, when in fact, the incorporation of mutualisms generates coexistence. Existing coexistence theory cannot therefore be applied to mutualisms without explicitly considering the underlying biology of the interactions. By discussing how the metrics derived from coexistence theory can be quantified empirically, I show how this theory can be operationalized to evaluate the coexistence consequences of mutualism in natural communities.
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Affiliation(s)
- Christopher A Johnson
- Department of Ecology and Evolutionary Biology, Princeton University, 106A Guyot Hall, Princeton, New Jersey, 08544, USA.,Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH) Zürich, Universitäetstrasse 16, Zürich, 8092, Switzerland
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5
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Johnson CA, Bronstein JL. Coexistence and competitive exclusion in mutualism. Ecology 2019; 100:e02708. [DOI: 10.1002/ecy.2708] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 01/29/2019] [Accepted: 03/11/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Christopher A. Johnson
- Department of Ecology and Evolutionary Biology University of Arizona P.O. Box 210088 Tucson Arizona 85721 USA
- Center for Adaptation to a Changing Environment Institute of Integrative Biology ETH Zürich Universitätstrasse 16 Zürich 8092 Switzerland
| | - Judith L. Bronstein
- Department of Ecology and Evolutionary Biology University of Arizona P.O. Box 210088 Tucson Arizona 85721 USA
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Sun Z, Koffel T, Stump SM, Grimaud GM, Klausmeier CA. Microbial cross-feeding promotes multiple stable states and species coexistence, but also susceptibility to cheaters. J Theor Biol 2019; 465:63-77. [DOI: 10.1016/j.jtbi.2019.01.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 12/07/2018] [Accepted: 01/08/2019] [Indexed: 01/22/2023]
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Pauw A, Johnson CM. Mutualism between co-occurring plant species in South Africa's Mediterranean climate heathland is mediated by birds. PLANT BIOLOGY (STUTTGART, GERMANY) 2018; 20 Suppl 1:224-230. [PMID: 28960844 DOI: 10.1111/plb.12635] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 09/21/2017] [Indexed: 06/07/2023]
Abstract
Interactions among plant species via pollinators vary from competitive to mutualistic and can influence the probability of stable coexistence of plant species. We aimed to determine the nature of the interaction via flower visitors between Leucospermum conocarpodendron and Mimetes fimbriifolius, two shrubs in the Proteaceae that share many ecological traits and coexist on the Cape Peninsula, South Africa. To assess the extent of pollinator sharing we analysed nectar properties and recorded the pollinator fauna, their behaviour and contribution to seed set. To test for competition via interspecific pollen transfer, we recorded the movement patterns of pollinators and quantified pollen loads. To determine the effect of co-flowering on visitation rates we recorded visits in stands that varied in the density of the two species. We found that the species produce similar rewards and share pollinating Cape Sugarbirds (Promerops cafer). Interspecific pollen transfer is avoided by placing pollen on different parts of the bird. Both species are visited by nectar-thieving Orange-breasted Sunbirds (Anthobaphes violacea). Insects and autonomous self-pollination contributed little to seed set. Pollinator visits increased with conspecific density in both species, and the slope of the increase was steepest in the presence of high densities of the co-occurring plant species. Nectar thief visits also increased with conspecific density in both species, but the slope declined with increasing density of the co-occurring species. Co-occurrence enhanced pollinator visits and alleviated nectar robbing in both plant species, consistent with mutualisms. Mutualism within a trophic level is unusual, but may help to explain the stable coexistence of ecologically similar species.
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Affiliation(s)
- A Pauw
- Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa
| | - C M Johnson
- Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa
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9
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Safe sites of pollen placement: a conflict of interest between plants and bees? Oecologia 2017; 186:163-171. [DOI: 10.1007/s00442-017-3999-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 11/03/2017] [Indexed: 10/18/2022]
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Farasin J, Andres J, Casiot C, Barbe V, Faerber J, Halter D, Heintz D, Koechler S, Lièvremont D, Lugan R, Marchal M, Plewniak F, Seby F, Bertin PN, Arsène-Ploetze F. Thiomonas sp. CB2 is able to degrade urea and promote toxic metal precipitation in acid mine drainage waters supplemented with urea. Front Microbiol 2015; 6:993. [PMID: 26441922 PMCID: PMC4585258 DOI: 10.3389/fmicb.2015.00993] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Accepted: 09/07/2015] [Indexed: 11/13/2022] Open
Abstract
The acid mine drainage (AMD) in Carnoulès (France) is characterized by the presence of toxic metals such as arsenic. Several bacterial strains belonging to the Thiomonas genus, which were isolated from this AMD, are able to withstand these conditions. Their genomes carry several genomic islands (GEIs), which are known to be potentially advantageous in some particular ecological niches. This study focused on the role of the “urea island” present in the Thiomonas CB2 strain, which carry the genes involved in urea degradation processes. First, genomic comparisons showed that the genome of Thiomonas sp. CB2, which is able to degrade urea, contains a urea genomic island which is incomplete in the genome of other strains showing no urease activity. The urease activity of Thiomonas sp. CB2 enabled this bacterium to maintain a neutral pH in cell cultures in vitro and prevented the occurrence of cell death during the growth of the bacterium in a chemically defined medium. In AMD water supplemented with urea, the degradation of urea promotes iron, aluminum and arsenic precipitation. Our data show that ureC was expressed in situ, which suggests that the ability to degrade urea may be expressed in some Thiomonas strains in AMD, and that this urease activity may contribute to their survival in contaminated environments.
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Affiliation(s)
- Julien Farasin
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
| | - Jérémy Andres
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
| | - Corinne Casiot
- Laboratoire Hydrosciences Montpellier, UMR 5569, Centre National de la Recherche Scientifique-UM I, UM II, IRD, Université Montpellier 2, CCMSE Montpellier, France
| | - Valérie Barbe
- Laboratoire de Biologie Moléculaire Pour l'Etude des Génomes, CEA-IG-Genoscope Evry, France
| | - Jacques Faerber
- Institut de Physique et de Chimie des Matériaux de Strasbourg, Université de Strasbourg, CNRS UMR 7504 Strasbourg, France
| | - David Halter
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
| | - Dimitri Heintz
- Plateforme Métabolomique, UPR2357, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire des Plantes, Institut de Botanique Strasbourg, France
| | - Sandrine Koechler
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
| | - Didier Lièvremont
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
| | - Raphael Lugan
- Plateforme Métabolomique, UPR2357, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire des Plantes, Institut de Botanique Strasbourg, France
| | - Marie Marchal
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
| | - Frédéric Plewniak
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
| | | | - Philippe N Bertin
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
| | - Florence Arsène-Ploetze
- Laboratoire Génétique Moléculaire, Génomique et Microbiologie, UMR7156, Université de Strasbourg - Centre National de la Recherche Scientifique, Institut de Botanique Strasbourg, France
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Revilla TA. Numerical responses in resource-based mutualisms: A time scale approach. J Theor Biol 2015; 378:39-46. [DOI: 10.1016/j.jtbi.2015.04.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 04/09/2015] [Indexed: 10/23/2022]
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Lee CT. Inherent demographic stability in mutualist-resource-exploiter interactions. Am Nat 2015; 185:551-61. [PMID: 25811088 DOI: 10.1086/680228] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Core principles of ecological theory predict that, in the absence of other factors, mutualisms should experience destabilizing positive feedback and should be vulnerable to extinction through competitive exclusion by exploiter species. Many effective stabilizing mechanisms address one issue or the other, and many turn upon additional features. Using an explicitly demographic approach, I show that indirect, demography-mediated interactions between mutualists and exploiters can enable mutualist-exploiter coexistence, which in turn can stabilize the abundances of mutualists, exploiters, and their shared resources. This occurs because of the distinct resource demographic responses that are inherent to interaction with mutualistic and exploitative partners and can occur in long-lasting, exclusive interactions, such as protection mutualisms, as well as in apparently very different, short-lived mutualistic interactions, such as pollination. The key necessary factor-demographic response to interspecific interaction-is common in nature. Some demographic structure is also necessary and is generated through interspecific interaction in long-lasting associations; it is also very common in natural populations. Thus, the explicitly demographic and multispecies approach taken here constitutes a potentially promising single explanation for the apparent stability of mutualism in a wide range of natural systems.
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Affiliation(s)
- Charlotte T Lee
- Department of Biology, Duke University, Durham, North Carolina 27708
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Revilla TA, Encinas–Viso F. Dynamical transitions in a pollination-herbivory interaction: a conflict between mutualism and antagonism. PLoS One 2015; 10:e0117964. [PMID: 25700003 PMCID: PMC4336290 DOI: 10.1371/journal.pone.0117964] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 01/06/2015] [Indexed: 11/23/2022] Open
Abstract
Plant-pollinator associations are often seen as purely mutualistic, while in reality they can be more complex. Indeed they may also display a diverse array of antagonistic interactions, such as competition and victim–exploiter interactions. In some cases mutualistic and antagonistic interactions are carried-out by the same species but at different life-stages. As a consequence, population structure affects the balance of inter-specific associations, a topic that is receiving increased attention. In this paper, we developed a model that captures the basic features of the interaction between a flowering plant and an insect with a larval stage that feeds on the plant’s vegetative tissues (e.g. leaves) and an adult pollinator stage. Our model is able to display a rich set of dynamics, the most remarkable of which involves victim–exploiter oscillations that allow plants to attain abundances above their carrying capacities and the periodic alternation between states dominated by mutualism or antagonism. Our study indicates that changes in the insect’s life cycle can modify the balance between mutualism and antagonism, causing important qualitative changes in the interaction dynamics. These changes in the life cycle could be caused by a variety of external drivers, such as temperature, plant nutrients, pesticides and changes in the diet of adult pollinators.
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Affiliation(s)
- Tomás A. Revilla
- Centre for Biodiversity Theory and Modelling, Station d’Ecologie Expérimentale du Centre National de la Recherche Scientifique à Moulis, Moulis, France
- * E-mail:
| | - Francisco Encinas–Viso
- Community and Conservation Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, Groningen, The Netherlands
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García-Algarra J, Galeano J, Pastor JM, Iriondo JM, Ramasco JJ. Rethinking the logistic approach for population dynamics of mutualistic interactions. J Theor Biol 2014; 363:332-43. [PMID: 25173080 DOI: 10.1016/j.jtbi.2014.08.039] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 07/18/2014] [Accepted: 08/20/2014] [Indexed: 10/24/2022]
Abstract
Mutualistic communities have an internal structure that makes them resilient to external perturbations. Late research has focused on their stability and the topology of the relations between the different organisms to explain the reasons of the system robustness. Much less attention has been invested in analyzing the systems dynamics. The main population models in use are modifications of the r-K formulation of logistic equation with additional terms to account for the benefits produced by the interspecific interactions. These models have shortcomings as the so-called r-K formulation diverges under some conditions. In this work, we introduce a model for population dynamics under mutualism that preserves the original logistic formulation. It is mathematically simpler than the widely used type II models, although it shows similar complexity in terms of fixed points and stability of the dynamics. We perform an analytical stability analysis and numerical simulations to study the model behavior in general interaction scenarios including tests of the resilience of its dynamics under external perturbations. Despite its simplicity, our results indicate that the model dynamics shows an important richness that can be used to gain further insights in the dynamics of mutualistic communities.
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Affiliation(s)
| | - Javier Galeano
- Complex System Group, Universidad Politécnica de Madrid, 28040 Madrid, Spain; Dep. Ciencia y Tecnología Aplicadas a la I.T. Agrícola, E.U.I.T. Agrícola, Universidad Politécnica de Madrid, 28040 Madrid, Spain.
| | - Juan Manuel Pastor
- Complex System Group, Universidad Politécnica de Madrid, 28040 Madrid, Spain; Dep. Ciencia y Tecnología Aplicadas a la I.T. Agrícola, E.U.I.T. Agrícola, Universidad Politécnica de Madrid, 28040 Madrid, Spain
| | - José María Iriondo
- Área de Biodiversidad y Conservación, Dept. Biología y Geología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain
| | - José J Ramasco
- Instituto de Física Interdisciplinar y Sistemas Complejos IFISC (CSIC-UIB), Campus UIB, 07122 Palma de Mallorca, Spain
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