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Midpoint attractors and species richness: Modelling the interaction between environmental drivers and geometric constraints |
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| Authors: | Robert K Colwell Nicholas J Gotelli Louise A Ashton Jan Beck Gunnar Brehm Tom M Fayle Konrad Fiedler Matthew L Forister Michael Kessler Roger L Kitching Petr Klimes Jürgen Kluge John T Longino Sarah C Maunsell Christy M McCain Jimmy Moses Sarah Noben Katerina Sam Legi Sam Arthur M Shapiro Xiangping Wang Vojtech Novotny |
| Affiliation: | 1. Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, USA;2. Departmento de Ecologia, Universidade Federal de Goiás, Goiania, GO, Brasil;3. University of Colorado Museum of Natural History, Boulder, CO, USA;4. Department of Biology, University of Vermont, Burlington, VT, USA;5. Environmental Futures Research Institute, Griffith University, Nathan, Qld, Australia;6. Life Sciences Department, Natural History Museum, London, UK;7. Department of Environmental Science (Biogeography), University of Basel, Basel, Switzerland;8. Phyletisches Museum, Friedrich‐Schiller Universit?t, Jena, Germany;9. Institute of Entomology, Biology Centre of the Czech Academy of Sciences and Faculty of Science, University of South Bohemia, ?eské Budějovice, Czech Republic;10. Forest Ecology and Conservation Group, Imperial College London, Berkshire, UK;11. Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah, Sabah, Malaysia;12. Department of Botany & Biodiversity Research, University of Vienna, Vienna, Austria;13. Program in Ecology, Evolution, and Conservation Biology, Department of Biology, University of Nevada, Reno, NV, 89557, USA;14. Institute of Systematic Botany, University of Zurich, Zurich, Switzerland;15. Department of Geography, University of Marburg, Marburg, Germany;16. Department of Biology, University of Utah, Salt Lake City, UT, USA;17. Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA;18. New Guinea Binatang Research Center, Madang, Papua New Guinea;19. School of Natural and Physical Sciences, University of Papua New Guinea, National Capital District, Papua New Guinea;20. Center for Population Biology, University of California, Davis, CA, USA;21. College of Forestry, Beijing Forestry University, Beijing, China |
| Abstract: | We introduce a novel framework for conceptualising, quantifying and unifying discordant patterns of species richness along geographical gradients. While not itself explicitly mechanistic, this approach offers a path towards understanding mechanisms. In this study, we focused on the diverse patterns of species richness on mountainsides. We conjectured that elevational range midpoints of species may be drawn towards a single midpoint attractor – a unimodal gradient of environmental favourability. The midpoint attractor interacts with geometric constraints imposed by sea level and the mountaintop to produce taxon‐specific patterns of species richness. We developed a Bayesian simulation model to estimate the location and strength of the midpoint attractor from species occurrence data sampled along mountainsides. We also constructed midpoint predictor models to test whether environmental variables could directly account for the observed patterns of species range midpoints. We challenged these models with 16 elevational data sets, comprising 4500 species of insects, vertebrates and plants. The midpoint predictor models generally failed to predict the pattern of species midpoints. In contrast, the midpoint attractor model closely reproduced empirical spatial patterns of species richness and range midpoints. Gradients of environmental favourability, subject to geometric constraints, may parsimoniously account for elevational and other patterns of species richness. |
| Keywords: | Bayesian model Biogeography elevational gradients geometric constraints mid‐domain effect midpoint predictor model stochastic model truncated niche |
