Reproductive system, social organization, human disturbance and ecological dominance in native populations of the little fire ant, Wasmannia auropunctata

Authors

  • JULIEN FOUCAUD,

    1. INRA, UMR CBGP (INRA/IRD/Cirad/Montpellier SupAgro), Campus international de Baillarguet, CS 30016, F-34988 Montferrier-sur-Lez cedex, France
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    • Present address: Laboratoire Évolution, Génomes et Spéciation, CNRS, UPR 9034, 91198 Gif-sur-Yvette Cedex, France.

  • JÉRÔME ORIVEL,

    1. Laboratoire Evolution et Diversité Biologique, UMR-CNRS 5174, Université Toulouse III, 118 route de Narbonne, 31062 Toulouse cedex 4, France
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  • DENIS FOURNIER,

    1. INRA, UMR CBGP (INRA/IRD/Cirad/Montpellier SupAgro), Campus international de Baillarguet, CS 30016, F-34988 Montferrier-sur-Lez cedex, France
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    • **

      Present address: Evolutionary Biology and Ecology – CP 160/12, Université Libre de Bruxelles, 50 av. F.D. Roosevelt, 1050 Brussels, Belgium.

  • JACQUES H. C. DELABIE,

    1. Laboratório de Mirmecologia, CEPEC-CEPLAC & UESC, CP 7, 45600-000 Itabuna, Bahia, Brazil
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  • ANNE LOISEAU,

    1. INRA, UMR CBGP (INRA/IRD/Cirad/Montpellier SupAgro), Campus international de Baillarguet, CS 30016, F-34988 Montferrier-sur-Lez cedex, France
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  • JULIEN LE BRETON,

    1. Laboratoire Evolution et Diversité Biologique, UMR-CNRS 5174, Université Toulouse III, 118 route de Narbonne, 31062 Toulouse cedex 4, France
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  • PHILIPPE CERDAN,

    1. Laboratoire Environnement de Petit Saut (HYDRECO), BP 823, 97388 Kourou cedex, France
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  • ARNAUD ESTOUP

    1. INRA, UMR CBGP (INRA/IRD/Cirad/Montpellier SupAgro), Campus international de Baillarguet, CS 30016, F-34988 Montferrier-sur-Lez cedex, France
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Julien Foucaud, Fax: (33) 1 69 82 37 36; E-mail: julien.foucaud@legs.cnrs-gif.fr

Abstract

The invasive ant species Wasmannia auropunctata displays both ecologically dominant and non-dominant populations within its native range. Three factors could theoretically explain the ecological dominance of some native populations of W. auropunctata: (i) its clonal reproductive system, through demographic and/or adaptive advantages; (ii) its unicolonial social organization, through lower intraspecific and efficient interspecific competition; (iii) the human disturbance of its native range, through the modification of biotic and abiotic environmental conditions. We used microsatellite markers and behavioural tests to uncover the reproductive modes and social organization of dominant and non-dominant native populations in natural and human-modified habitats. Microsatellite and mtDNA data indicated that dominant and non-dominant native populations (supercolonies as determined by aggression tests) of W. auropunctata did not belong to different evolutionary units. We found that the reproductive system and the social organization are neither necessary nor sufficient to explain W. auropunctata ecological dominance. Dominance rather seems to be set off by unknown ecological factors altered by human activities, as all dominant populations were recorded in human-modified habitats. The clonal reproductive system found in some populations of W. auropunctata may however indirectly contribute to its ecological dominance by allowing the species to expand its environmental niche, through the fixation over time of specific combinations of divergent male and female genotypes. Unicoloniality may rather promote the range expansion of already dominant populations than actually trigger ecological dominance. The W. auropunctata model illustrates the strong impact of human disturbance on species’ ecological features and the adaptive potential of clonal reproductive systems.

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