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The worldwide expansion of the Argentine ant

Authors

  • Valérie Vogel,

    Corresponding author
    1. Department of Ecology and Evolution, University of Lausanne, Biophore, CH-1015 Lausanne, Switzerland
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    • These authors contributed equally to the work.

  • Jes S. Pedersen,

    1. Department of Ecology and Evolution, University of Lausanne, Biophore, CH-1015 Lausanne, Switzerland
    2. Centre for Social Evolution, Department of Biology, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark
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    • These authors contributed equally to the work.

  • Tatiana Giraud,

    1. Department of Ecology and Evolution, University of Lausanne, Biophore, CH-1015 Lausanne, Switzerland
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    • Present address: Ecologie, Systématique et Evolution, Bâtiment 362, Université Paris-Sud, F-91405 Orsay cedex, France.

  • Michael J. B. Krieger,

    1. Department of Ecology and Evolution, University of Lausanne, Biophore, CH-1015 Lausanne, Switzerland
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    • Present address: Swiss Federal Institute of Technology Zurich, 8092 Zurich, Switzerland.

  • Laurent Keller

    1. Department of Ecology and Evolution, University of Lausanne, Biophore, CH-1015 Lausanne, Switzerland
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Valérie Vogel, Service of Hospital Preventive Medicine, IMU 05-510, CHUV, CH-1011 Lausanne, Switzerland.
E-mail: valerie.vogel@chuv.ch

Abstract

Aim  The aim of this study was to determine the number of successful establishments of the invasive Argentine ant outside native range and to see whether introduced supercolonies have resulted from single or multiple introductions. We also compared the genetic diversity of native versus introduced supercolonies to assess the size of the propagules (i.e. the number of founding individuals) at the origin of the introduced supercolonies.

Location  Global.

Methods  We used mitochondrial DNA (mtDNA) markers and microsatellite loci to study 39 supercolonies of the Argentine ant Linepithema humile covering both the native (n = 25) and introduced range (n = 14).

Results  Data from three mitochondrial genes and 13 nuclear microsatellites suggest that the introduced supercolonies studied originated from at least seven founding events out of the native area in Argentina (primary introductions). The distribution of mtDNA haplotypes also suggests that supercolonies in the introduced range each derive from a single source supercolony and that one of these source supercolonies has been particularly successful, being the basis of many introduced populations spread across the world. Comparison of the genetic diversity of supercolonies based on the five most diverse loci also revealed that native and introduced supercolonies have greatly overlapping ranges of diversity, although the genetic diversity is on average less in introduced than in native supercolonies.

Main conclusions  Both primary introductions (from the native range) and secondary introductions (from sites with established invasive supercolonies) were important in the global expansion of the Argentine ant. In combination with the similar social organization of colonies in the native and introduced range, this indicates that invasiveness did not evolve recently as a unique and historically contingent event (e.g. reduction of genetic diversity) in this species. Rather, native L. humile supercolonies have characteristics that make them pre-adapted to invade new – and in particular disturbed – habitats when given the opportunity. These results have important implications with regard to possible strategies to be used to control invasive ants.

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