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Ecosystem engineers activate mycorrhizal mutualism in salt marshes

Authors

  • Pedro Daleo,

    Corresponding author
    1. Departamento de Biología (FCEyN), UNMdP, CC 573 Correo Central, B7600WAG, Mar del Plata, Rivadavia 1917, 1033, Buenos Aires, Argentina
    2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
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  • Eugenia Fanjul,

    1. Departamento de Biología (FCEyN), UNMdP, CC 573 Correo Central, B7600WAG, Mar del Plata, Rivadavia 1917, 1033, Buenos Aires, Argentina
    2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
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  • Agustina Mendez Casariego,

    1. Departamento de Biología (FCEyN), UNMdP, CC 573 Correo Central, B7600WAG, Mar del Plata, Rivadavia 1917, 1033, Buenos Aires, Argentina
    2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
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  • Brian R. Silliman,

    1. Department of Zoology, University of Florida, Gainesville, FL 32611, USA
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  • Mark D. Bertness,

    1. Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
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  • Oscar Iribarne

    1. Departamento de Biología (FCEyN), UNMdP, CC 573 Correo Central, B7600WAG, Mar del Plata, Rivadavia 1917, 1033, Buenos Aires, Argentina
    2. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
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* E-mail: pdaleo@mdp.edu.ar

Abstract

Theory predicts that ecosystem engineers should have their most dramatic effects when they enable species, through habitat amelioration, to live in zones where physical and biological conditions would otherwise suppress or limit them. Mutualisms between mycorrhizal fungi and plants are key determinants of productivity and biodiversity in most terrestrial systems, but are thought to be unimportant in wetlands because anoxic sediments exclude fungal symbionts. Our field surveys revealed arbuscular mycorrhizal associations on salt marsh plant roots, but only in the presence of crabs that oxygenate soils as a by-product of burrowing. Field experiments demonstrate that fungal colonization is dependent on crab burrowing and responsible for nearly 35% of plant growth. These results highlight ecosystem engineers as ecological linchpins that can activate and maintain key mutualisms between species. Our findings align salt marshes with other important biogenic habitats whose productivity is reliant on mutualisms between the primary foundation species and micro-organisms.

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