title: Trade-offs in an ant-plant-fungus mutualism.
abstract: Species engaged in multiple, simultaneous mutualisms are subject to trade-offs in their mutualistic investment if the traits involved in each interaction are overlapping, which can lead to conflicts and affect the longevity of these associations. We investigate this issue via a tripartite mutualism involving an ant plant, two competing ant species and a fungus the ants cultivate to build galleries under the stems of their host plant to capture insect prey. The use of the galleries represents an innovative prey capture strategy compared with the more typical strategy of foraging on leaves. However, because of a limited worker force in their colonies, the prey capture behaviour of the ants results in a trade-off between plant protection (i.e. the ants patrol the foliage and attack intruders including herbivores) and ambushing prey in the galleries, which has a cascading effect on the fitness of all of the partners. The quantification of partners' traits and effects showed that the two ant species differed in their mutualistic investment. Less investment in the galleries (i.e. in fungal cultivation) translated into more benefits for the plant in terms of less herbivory and higher growth rates and vice versa. However, the greater vegetative growth of the plants did not produce a positive fitness effect for the better mutualistic ant species in terms of colony size and production of sexuals nor was the mutualist compensated by the wider dispersal of its queens. As a consequence, although the better ant mutualist is the one that provides more benefits to its host plant, its lower host-plant exploitation does not give this ant species a competitive advantage. The local coexistence of the ant species is thus fleeting and should eventually lead to the exclusion of the less competitive species.
authors.affiliation: CNRS, UMR Ecologie des Forêts de Guyane, AgroParisTech, CIRAD, INRA, Université de Guyane, Université des Antilles, Campus Agronomique, BP 316, 97379 Kourou Cedex, France jerome.orivel@ecofog.gf.
authors.forename: Jérôme
authors.identifier: http://orcid.org/0000-0002-5636-3228
authors.initials: J
authors.lastname: Orivel
authors.affiliation: UMR Evolution et Diversité Biologique, Université de Toulouse, 118 Route de Narbonne, 31062 Toulouse Cedex 9, France.
authors.forename: Pierre-Jean
authors.initials: PJ
authors.lastname: Malé
authors.affiliation: CNRS, UMR Ecologie des Forêts de Guyane, AgroParisTech, CIRAD, INRA, Université de Guyane, Université des Antilles, Campus Agronomique, BP 316, 97379 Kourou Cedex, France.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Lauth
authors.affiliation: CNRS, UMR Ecologie des Forêts de Guyane, AgroParisTech, CIRAD, INRA, Université de Guyane, Université des Antilles, Campus Agronomique, BP 316, 97379 Kourou Cedex, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Roux
authors.affiliation: CNRS, UMR Ecologie des Forêts de Guyane, AgroParisTech, CIRAD, INRA, Université de Guyane, Université des Antilles, Campus Agronomique, BP 316, 97379 Kourou Cedex, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Petitclerc
authors.affiliation: CNRS, UMR Ecologie des Forêts de Guyane, AgroParisTech, CIRAD, INRA, Université de Guyane, Université des Antilles, Campus Agronomique, BP 316, 97379 Kourou Cedex, France.|Ecolab, Université de Toulouse, CNRS, INPT, UPS, 118 Route de Narbonne, 31062 Toulouse Cedex 9, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Dejean
authors.affiliation: CNRS, UMR Ecologie des Forêts de Guyane, AgroParisTech, CIRAD, INRA, Université de Guyane, Université des Antilles, Campus Agronomique, BP 316, 97379 Kourou Cedex, France.|IRD, UMR AMAP (botAnique et Modélisation de l'Architecture des Plantes et des Végétations), Boulevard de la Lironde, TA A-51/PS2, 34398 Montpellier Cedex 5, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Leroy
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology*; D005616:French Guiana; D005658:Fungi / Q000502:physiology*; D060434:Herbivory; D010944:Plants; D013559:Symbiosis
keywords: Hirtella; allomerus; ant–plant–fungus interaction; dispersal; mutualism; species coexistence