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Food resources and vegetation structure mediate climatic effects on species richness of birds

Authors

  • Stefan W. Ferger,

    Corresponding author
    1. Biodiversity and Climate Research Centre (BiK-F), Frankfurt am Main, Germany
    2. Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, Germany
    • Correspondence: Stefan W. Ferger, Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, Frankfurt am Main 60325, Germany.

      E-mail: stefan.ferger@yahoo.de

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  • Matthias Schleuning,

    1. Biodiversity and Climate Research Centre (BiK-F), Frankfurt am Main, Germany
    2. Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, Germany
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  • Andreas Hemp,

    1. Department of Plant Systematics, University of Bayreuth, Bayreuth, Germany
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  • Kim M. Howell,

    1. Department of Zoology and Wildlife Conservation, University of Dar es Salaam, Dar es Salaam, Tanzania
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  • Katrin Böhning-Gaese

    1. Biodiversity and Climate Research Centre (BiK-F), Frankfurt am Main, Germany
    2. Senckenberg Gesellschaft für Naturforschung, Frankfurt am Main, Germany
    3. Institute for Ecology, Evolution and Diversity, Goethe University, Frankfurt am Main, Germany
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  • Editor: Christy McCain

Abstract

Aim

Climate is widely recognized as a major predictor of species richness patterns along large-scale environmental gradients. Nevertheless, the mechanisms by which climate influences species richness are still a matter of debate. We disentangle whether climate influences species richness of birds directly via physiological limitations or indirectly via vegetation structure or the availability of food resources.

Location

Mount Kilimanjaro, Tanzania.

Methods

We recorded bird species richness along an elevational gradient from 870 to 4550 m a.s.l. We quantified local climatic conditions, vegetation structure and the availability of food resources, and applied path analysis to disentangle their direct and indirect effects on species richness of all birds, frugivores and insectivores.

Results

Overall, we recorded 2945 individuals from 114 bird species. Species richness of all birds was closely correlated with temperature, vegetation structure and invertebrate biomass and both direct and indirect (via vegetation structure and availability of food resources) climatic effects were important for the diversity of the whole, trophically heterogeneous bird community. The species richness of insectivorous birds was linked to vegetation structure and invertebrate biomass, while the richness of frugivores was strongly associated with fruit abundance. Climatic factors influenced bird species richness of both avian feeding guilds exclusively indirectly via vegetation structure and availability of food resources.

Main conclusions

We reveal the importance of trophic interactions for generating species richness patterns along large-scale environmental gradients. Our results challenge the general assumption that temperature and water availability influence species richness mostly directly, and underscore the importance of vegetation structure and the availability of food resources as principal mediators of climatic effects on species richness patterns on macroecological scales.

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