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The evolution of intermediate castration virulence and ant coexistence in a spatially structured environment

Authors

  • András Szilágyi,

    1. Department of Plant Taxonomy and Ecology, Eötvös University, Pázmány Péter sétány 1C, H-1117 Budapest, Hungary
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  • István Scheuring,

    1. Research Group of Theoretical Biology and Ecology, Department of Plant Taxonomy and Ecology, Eötvös University and HAS, Pázmány Péter sétány 1C, H-1117 Budapest, Hungary
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  • David P. Edwards,

    1. School of Biological Sciences, University of East Anglia, Norwich NR47TJ, UK
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  • Jerome Orivel,

    1. Laboratoire Evolution et Diversité Biologique, UMR-CNRS 5174, Université Toulouse III, 118 route de Narbonne, 31062 Toulouse cedex 9, France
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  • Douglas W. Yu

    Corresponding author
    1. School of Biological Sciences, University of East Anglia, Norwich NR47TJ, UK
    2. Ecology, Conservation, and Environment Center (ECEC), State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Science, Kunming, Yunnan 650223 China
      E-mail: dougwyu@gmail.com
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E-mail: dougwyu@gmail.com

Abstract

Ecology Letters (2009) 12: 1306–1316

Abstract

Theory suggests that spatial structuring should select for intermediate levels of virulence in parasites, but empirical tests are rare and have never been conducted with castration (sterilizing) parasites. To test this theory in a natural landscape, we construct a spatially explicit model of the symbiosis between the ant-plant Cordia nodosa and its two, protecting ant symbionts, Allomerus and Azteca. Allomerus is also a castration parasite, preventing fruiting to increase colony fecundity. Limiting the dispersal of Allomerus and host plant selects for intermediate castration virulence. Increasing the frequency of the mutualist, Azteca, selects for higher castration virulence in Allomerus, because seeds from Azteca-inhabited plants are a public good that Allomerus exploits. These results are consistent with field observations and, to our knowledge, provide the first empirical evidence supporting the hypothesis that spatial structure can reduce castration virulence and the first such evidence in a natural landscape for either mortality or castration virulence.

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