Continental-scale variability in browser diversity is a major driver of diversity patterns in acacias across Africa

Authors

  • Michelle Greve,

    Corresponding author
    1. Ecoinformatics & Biodiversity Group, Department of Bioscience, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark
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  • Anne M. Lykke,

    1. Terrestrial Ecology, Department of Bioscience, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark
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  • Christopher W. Fagg,

    1. Herbário UB e Faculdade de Ceilândia, Instituto de Ciências Biológicas bloco 9, 1o piso, Universidade de Brasília – Campus Darcy Ribeiro Asa Norte – Brasilia-DF – 70910-900, Brazil
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  • Jan Bogaert,

    1. Gembloux Agro-Bio Tech, Unité Biodiversité et Paysage, Université de Liège, Passage des Déportés, 2 B-5030 Gembloux, Belgium
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  • Ib Friis,

    1. Natural History Museum of Denmark, University of Copenhagen, Gothersgade 130, 1123 København K, Denmark
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  • Rob Marchant,

    1. York Institute of Tropical Ecosystem Dynamics and Centre for Integration of Research, Conservation and Learning (CIRCLE), Environment Department, University of York, York YO10 5DD, UK
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  • Andrew R. Marshall,

    1. York Institute of Tropical Ecosystem Dynamics and Centre for Integration of Research, Conservation and Learning (CIRCLE), Environment Department, University of York, York YO10 5DD, UK
    2. Flamingo Land Ltd., Kirby Misperton, North Yorkshire YO17 6UX, UK
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  • Joël Ndayishimiye,

    1. Service d’Ecologie du Paysage et Systèmes de Production Végétale, Université Libre de Bruxelles, 50 Avenue F.D. Roosevelt, CP 169, B-1050 Bruxelles, Belgium
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  • Brody S. Sandel,

    1. Ecoinformatics & Biodiversity Group, Department of Bioscience, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark
    2. Center for Massive Data Algorithmics (MADALGO), Department of Computer Science, Aarhus University, Aabogade 34, DK-8200 Aarhus N, Denmark
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  • Christopher Sandom,

    1. Ecoinformatics & Biodiversity Group, Department of Bioscience, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark
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  • Marco Schmidt,

    1. Institute for Ecology, Evolution and Diversity, Goethe University, Siesmayerstr. 70, 60323 Frankfurt, Germany
    2. Biodiversity and Climate Research Centre (BiK-F) and Department of Botany and Molecular Evolution, Research Institute Senckenberg, Senckenberganlage 25, 60325 Frankfurt, Germany
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  • Jonathan R. Timberlake,

    1. Herbarium, Library, Art and Archives, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
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  • Jan J. Wieringa,

    1. Netherlands Centre for Biodiversity Naturalis (section NHN), Herbarium Vadense, Biosystematics Group, Wageningen University, General Foulkesweg 37, 6703 BL Wageningen, The Netherlands
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  • Georg Zizka,

    1. Institute for Ecology, Evolution and Diversity, Goethe University, Siesmayerstr. 70, 60323 Frankfurt, Germany
    2. Biodiversity and Climate Research Centre (BiK-F) and Department of Botany and Molecular Evolution, Research Institute Senckenberg, Senckenberganlage 25, 60325 Frankfurt, Germany
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  • Jens-Christian Svenning

    1. Ecoinformatics & Biodiversity Group, Department of Bioscience, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark
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Correspondence author: E-mail: michelle_greve@yahoo.com

Summary

1. It has been proposed that, across broad spatial scales, climatic factors are the main drivers of ecological patterns, while biotic factors are mainly important at local spatial scales. However, few tests of the effect of biotic interactions on broad-scale patterns have been conducted; conclusions about the scale-dependence of the importance of biotic interactions thus seem premature.

2. We developed an extensive database of locality records of one of Africa’s most conspicuous groups, the acacias (the genera Senegalia and Vachellia), and used species distribution models (SDMs) to estimate the distribution of all African acacias.

3. African acacias are particularly well adapted against mammalian herbivory; therefore, we hypothesized that browser diversity could be an important driver of acacia richness. Species richness maps for the two genera were created from SDM-generated maps. Ordinary least square (OLS) regressions and, to consider spatial autocorrelation, simultaneous autoregressive (SAR) analyses were used to model richness of the two genera in relation to mammalian browser richness, current environment (including climate), and climate history since the Last Glacial Maximum (LGM). We used variation partitioning to determine what percentage of variation could be explained by these three groups of factors.

4. Both genera showed centres of richness in East Africa and the Limpopo Basin of southern Africa. Browser richness was the best explanatory variable for richness of both genera. Environmental factors explained negligible variation in the richness of Senegalia, but some variation in Vachellia. For both genera, the residuals of the species richness model of one genus also explained much variation in the richness of the other genus, indicating that common factors not considered in the richness analyses here may additionally be driving the richness of both genera.

5. Mechanisms that could generate a correlation between browser and acacia richness are proposed, and differences in the determinants of richness patterns of Senegalia and Vachellia discussed in the light of the two genera’s history of colonization of Africa.

6.Synthesis. This is the first study that demonstrates that consumer diversity can influence richness patterns at continental scales and demonstrates that biotic factors can drive richness even at broad spatial scales.

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