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Investigation of the population genetic structure and mating system in the ant Pheidole pallidula

Authors

  • Denis Fournier,

    Corresponding author
    1. Department of Animal Biology, Unit of Animal Communities CP 160/12, Free University of Brussels (ULB), Avenue F.D. Roosevelt, 50, B-1050 Brussels, Belgium,
    2. Laboratory of Evolutionary Genetics, Free University of Brussels (ULB), Institute of Molecular Biology and Medicine, B-6041 Gosselies, Belgium
      Denis Fournier. Fax: + 32 (0)2650.24.45; E-mail: Denis.Fournier@ulb.ac.be
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  • Serge Aron,

    1. Department of Animal Biology, Unit of Animal Communities CP 160/12, Free University of Brussels (ULB), Avenue F.D. Roosevelt, 50, B-1050 Brussels, Belgium,
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  • Michel C. Milinkovitch

    1. Laboratory of Evolutionary Genetics, Free University of Brussels (ULB), Institute of Molecular Biology and Medicine, B-6041 Gosselies, Belgium
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Denis Fournier. Fax: + 32 (0)2650.24.45; E-mail: Denis.Fournier@ulb.ac.be

Abstract

The origin of eusociality in haplo-diploid organisms such as Hymenoptera has been mostly explained by kin selection. However, several studies have uncovered decreased relatedness values within colonies, resulting primarily from multiple queen matings (polyandry) and/or from the presence of more than one functional queen (polygyny). Here, we report on the use of microsatellite data for the investigation of sociogenetic parameters, such as relatedness, and levels of polygyny and polyandry, in the ant Pheidole pallidula. We demonstrate, through analysis of mother–offspring combinations and the use of direct sperm typing, that each queen is inseminated by a single male. The inbreeding coefficient within colonies and the levels of relatedness between the queens and their mate are not significantly different from zero, indicating that matings occur between unrelated individuals. Analyses of worker genotypes demonstrate that 38% of the colonies are polygynous with 2–4 functional queens, and suggest the existence of reproductive skew, i.e. unequal respective contribution of queens to reproduction. Finally, our analyses indicate that colonies are genetically differentiated and form a population exhibiting significant isolation-by-distance, suggesting that some colonies originate through budding.

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