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Tri-trophic interactions affect density dependence of seed fate in a tropical forest palm

Authors

  • Marco D. Visser,

    Corresponding author
    1. Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon, Republic of Panama
    2. Forest Ecology and Forest Management Group, Wageningen University and Research Centre, Wageningen, The Netherlands
    3. Department of Experimental Plant Ecology, Institute for Water and Wetland Research, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
      E-mail:m.visser@science.ru.nl
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  • Helene C. Muller-Landau,

    1. Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon, Republic of Panama
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  • S. Joseph Wright,

    1. Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon, Republic of Panama
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  • Gemma Rutten,

    1. Institute of Plant Sciences, University of Bern, Altenbergrain 21 CH-3013, Bern, Switzerland
    2. Community and Conservation Ecology Group, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands
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  • Patrick A. Jansen

    1. Smithsonian Tropical Research Institute, Box 0843-03092, Balboa, Ancon, Republic of Panama
    2. Forest Ecology and Forest Management Group, Wageningen University and Research Centre, Wageningen, The Netherlands
    3. Community and Conservation Ecology Group, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands
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E-mail:m.visser@science.ru.nl

Abstract

Ecology Letters (2011) 14: 1093–1100

Abstract

Natural enemies, especially host-specific enemies, are hypothesised to facilitate the coexistence of plant species by disproportionately inflicting more damage at increasing host abundance. However, few studies have assessed such Janzen–Connell mechanisms on a scale relevant for coexistence and no study has evaluated potential top-down influences on the specialized pests. We quantified seed predation by specialist invertebrates and generalist vertebrates, as well as larval predation on these invertebrates, for the Neotropical palm Attalea butyracea across ten 4-ha plots spanning 20-fold variation in palm density. As palm density increased, seed attack by bruchid beetles increased, whereas seed predation by rodents held constant. But because rodent predation on bruchid larvae increased disproportionately with increasing palm density, bruchid emergence rates and total seed predation by rodents and bruchids combined were both density-independent. Our results demonstrate that top-down effects can limit the potential of host-specific insects to induce negative-density dependence in plant populations.

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