Testing the stress-gradient hypothesis with aquatic detritivorous invertebrates: insights for biodiversity-ecosystem functioning research

Authors

  • V. Fugère,

    Corresponding author
    1. Department of Biology, McGill University, 1205 Ave. Docteur Penfield, Montreal, Quebec H3A 1B1, Canada
      Correspondence author. E-mail: vincent.fugere@mail.mcgill.ca
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  • P. Andino,

    1. Pontificia Universidad Católica del Ecuador, Facultad de Ciencias Exactas y Naturales, Laboratorio de Entomología, Quito, Ecuador
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  • R. Espinosa,

    1. Pontificia Universidad Católica del Ecuador, Facultad de Ciencias Exactas y Naturales, Laboratorio de Entomología, Quito, Ecuador
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  • F. Anthelme,

    1. Pontificia Universidad Católica del Ecuador, Facultad de Ciencias Exactas y Naturales, Laboratorio de Entomología, Quito, Ecuador
    2. Institut de Recherche pour le Développement (IRD), UMR AMAP, CIRAD, TA A51/PS2, 34398 Montpellier Cedex 5, France
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  • D. Jacobsen,

    1. Freshwater Biological Section, Biology Department, University of Copenhagen, Helsingørsgade 51, DK-3400 Hillerød, Denmark
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  • O. Dangles

    1. Pontificia Universidad Católica del Ecuador, Facultad de Ciencias Exactas y Naturales, Laboratorio de Entomología, Quito, Ecuador
    2. Institut de Recherche pour le Développement (IRD), UR 072, LEGS-CNRS, UPR 9034, CNRS 91198 Gif-sur Yvette Cedex, France and Université Paris-Sud 11, 91405 Orsay Cedex, France
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Correspondence author. E-mail: vincent.fugere@mail.mcgill.ca

Summary

1. The stress-gradient hypothesis (SGH) states that environmental stress modulates species interactions, causing a shift from negative interactions to net positive interactions with increasing stress.

2. Potentially, this modulation of species interactions could in turn influence biodiversity-ecosystem function (B-EF) relationships along stress gradients. Although the SGH has been extensively discussed in plant community ecology in the past two decades, it has received little attention from animal ecologists.

3. To explore whether the SGH could be applied to animal communities, we conducted a litter decomposition experiment with aquatic detritivorous invertebrates in which we manipulated litter quality and measured species interactions along this resource quality gradient. Litter quality was manipulated by presenting detritivores with leaves of plant species varying in specific leaf area and decomposition rate in streams.

4. We found a switch from negative to neutral interactions with increasing resource quality stress, in line with the SGH. However, by re-examining other published results with aquatic detritivores from the perspective of the SGH, we found that a diversity of patterns seem to characterize detritivore interactions along stress gradients.

5. Although the basic pattern proposed by the SGH may not apply to animal systems in general, we show that aquatic detritivore interactions do change along stress gradients, which underlines the importance of incorporating environmental stressors more explicitly in B-EF research.

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