Global Variation in Woodpecker Species Richness Shaped by Tree
Journal of Biogeography (J. Biogeogr.) (2017) 44, 1824–1835 ORIGINAL Global variation in woodpecker species ARTICLE richness shaped by tree availability † † Sigrid Kistrup Ilsøe1, , W. Daniel Kissling2, ,* , Jon Fjeldsa3, Brody Sandel4 and Jens-Christian Svenning1 1Section for Ecoinformatics and Biodiversity, ABSTRACT Department of Bioscience, Aarhus University, Aim Species richness patterns are generally thought to be determined by abi- DK-8000 Aarhus C, Denmark, 2Institute for otic variables at broad spatial scales, with biotic factors being only important Biodiversity and Ecosystem Dynamics (IBED), University of Amsterdam, 1090 GE at fine spatial scales. However, many organism groups depend intimately on Amsterdam, The Netherlands, 3Center for other organisms, raising questions about this generalization. As an example, Macroecology, Evolution and Climate at woodpeckers (Picidae) are closely associated with trees and woody habitats Natural History Museum of Denmark, because of multiple morphological and ecological specializations. In this study, University of Copenhagen, DK-1350 we test whether this strong biotic association causes woodpecker diversity to be Copenhagen K, Denmark, 4Department of closely linked to tree availability at a global scale. Biology, Santa Clara University, Santa Clara, Location Global. CA 95057, USA Methods We used spatial and non-spatial regressions to test for relationships between broad-scale woodpecker species richness and predictor variables describing current and deep-time availability of trees, current climate, Quater- nary climate change, human impact, topographical heterogeneity and biogeo- graphical region. We further used structural equation models to test for direct and indirect effects of predictor variables. Results There was a strong positive relationship between woodpecker species richness and current tree cover and annual precipitation, respectively.
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