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<p>Insect pests invading an ecosystem typically face various forces regulating their population growth and spread. While the resources they feed on and their natural enemies have ‘bottom-up’ and ‘top-down’ effects on insect invasion success, other native species, more distant in the local trophic network, can have indirect effects on the ecosystem’s susceptibility to invasion. Resolving the mechanisms underlying these naturally occurring indirect interactions and their impact on invasion dynamics is a key challenge toward risk assessment and environmental management. In this contribution, we investigated how indirect interactions with several native species contribute to variations in <i>Dryocosmus kuriphilus</i> infestation level in 24 natural chestnut tree populations of the French Eastern Pyrenees. This invasive gall-forming hymenopteran parasite cultivated and wild <i>Castanea sativa</i> stands, and its hymenopteran parasitoid, <i>Torymus sinensis</i>, is globally used as a control agent. We combined ecological, molecular and statistical approaches to investigate the effects of <i>Quercus pubescens</i>, <i>Fagus sylvatica</i> and the parasitic fungus <i>Cryphonectria parasitica</i> on the pest invasion potential and biological control. The integration of these empirically supported effects into a specifically designed <i>D. kuriphilus–T. sinensis</i> dynamical model showed that the dilution effect exerted by <i>Q. pubescens</i> on <i>D. kuriphilus</i> oviposition rate (<i>effect i</i>) typically dominates the amplification of chestnut trees detection induced by <i>C. parasitica</i> infection (<i>effect ii</i>). Meanwhile, galls formed on <i>Q. pubescens</i> could significantly reduce the pest invasion potential through the production of native parasitoids (<i>effect iii</i>) and by providing alternative hosts for the introduced control agent <i>T. sinensis</i> (<i>effect iv</i>).</p>

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An integrative field and modelling study of the bottom-up, top-down and indirect effects of native species on invasive insects and their biological control: the case of the worldwide chestnut tree pest, Dryocosmus kuriphilus, in the French Eastern Pyrenees

  • 期刊论文

  • 发表日期：

    2026年4月22日

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  • Jean-Loup Zitoun,
  • Raphaël Rousseau,
  • Sébastien Gourbière

摘要

Insect pests invading an ecosystem typically face various forces regulating their population growth and spread. While the resources they feed on and their natural enemies have ‘bottom-up’ and ‘top-down’ effects on insect invasion success, other native species, more distant in the local trophic network, can have indirect effects on the ecosystem’s susceptibility to invasion. Resolving the mechanisms underlying these naturally occurring indirect interactions and their impact on invasion dynamics is a key challenge toward risk assessment and environmental management. In this contribution, we investigated how indirect interactions with several native species contribute to variations in Dryocosmus kuriphilus infestation level in 24 natural chestnut tree populations of the French Eastern Pyrenees. This invasive gall-forming hymenopteran parasite cultivated and wild Castanea sativa stands, and its hymenopteran parasitoid, Torymus sinensis, is globally used as a control agent. We combined ecological, molecular and statistical approaches to investigate the effects of Quercus pubescens, Fagus sylvatica and the parasitic fungus Cryphonectria parasitica on the pest invasion potential and biological control. The integration of these empirically supported effects into a specifically designed D. kuriphilus–T. sinensis dynamical model showed that the dilution effect exerted by Q. pubescens on D. kuriphilus oviposition rate (effect i) typically dominates the amplification of chestnut trees detection induced by C. parasitica infection (effect ii). Meanwhile, galls formed on Q. pubescens could significantly reduce the pest invasion potential through the production of native parasitoids (effect iii) and by providing alternative hosts for the introduced control agent T. sinensis (effect iv).