Species richness–decomposition relationships depend on species dominance


  • Olivier Dangles,

    Corresponding author
    1. Institut de Recherche en Biologie de l'Insecte, IRBI UMR CNRS 6035, Faculté des Sciences and Techniques, Parc de Grandmont, F-37200 Tours, France
      E-mail: olivier.dangles@univ-tours.fr
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  • Björn Malmqvist

    1. Department of Ecology and Environmental Science, Umeå University, SE-90187 Umeå, Sweden
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E-mail: olivier.dangles@univ-tours.fr


Human disturbances both decrease the number of species in ecosystems and change their relative abundances. Here we present field evidence demonstrating that shifts in species abundances can have effects on ecosystem functioning that are as great as those from shifts in species richness. We investigated spatial and temporal variability of leaf decomposition rates and community metrics of leaf-eating invertebrates (shredders) in streams. The shredder community composition dramatically influenced the diversity–function relationship; decomposition was much higher for a given species richness at sites with high species dominance than at sites where dominance was low. Decomposition rates also markedly depended on the identity of the dominant species. Further, dominance effects on decomposition varied seasonally and the number of species required for maintaining decomposition increased with increasing evenness. These findings reveal important but less obvious aspects of the biodiversity–ecosystem functioning relationship.