Numerous studies have shown reduced performance in plants that are surrounded by neighbours of the same species1,2, a phenomenon known as conspecific negative density dependence (CNDD)3. A long-held ecological hypothesis posits that CNDD is more pronounced in tropical than in temperate forests4,5, which increases community stabilization, species coexistence and the diversity of local tree species6,7. Previous analyses supporting such a latitudinal gradient in CNDD8,9 have suffered from methodological limitations related to the use of static data10-12. Here we present a comprehensive assessment of latitudinal CNDD patterns using dynamic mortality data to estimate species-site-specific CNDD across 23 sites. Averaged across species, we found that stabilizing CNDD was present at all except one site, but that average stabilizing CNDD was not stronger toward the tropics. However, in tropical tree communities, rare and intermediate abundant species experienced stronger stabilizing CNDD than did common species. This pattern was absent in temperate forests, which suggests that CNDD influences species abundances more strongly in tropical forests than it does in temperate ones13. We also found that interspecific variation in CNDD, which might attenuate its stabilizing effect on species diversity14,15, was high but not significantly different across latitudes. Although the consequences of these patterns for latitudinal diversity gradients are difficult to evaluate, we speculate that a more effective regulation of population abundances could translate into greater stabilization of tropical tree communities and thus contribute to the high local diversity of tropical forests.

Bayreuth Center of Ecology and Environmental Research University of Bayreuth Bayreuth Germany

Cofrin Center for Biodiversity Department of Biology University of Wisconsin Green Bay Green Bay WI USA

Conservation Ecology Center Smithsonian's National Zoo and Conservation Biology Institute Front Royal VA USA

Departamento de Ciencias Forestales Universidad Nacional de Colombia Sede Medellín Medellín Colombia

Department of Biological Sciences National Sun Yat sen University Kaohsiung Taiwan

Department of Biological Sciences National University of Singapore Singapore Singapore

Department of Biology Indiana University Bloomington IN USA

Department of Biology University of Wisconsin Green Bay Green Bay WI USA

Department of Botany and Plant Pathology Oregon State University Corvallis OR USA

Department of Ecology and Evolutionary Biology Tulane University New Orleans LA USA

Department of Ecology and Evolutionary Biology University of California Los Angeles Los Angeles CA USA

Department of Ecology Evolution and Environmental Biology Columbia University New York NY USA

Department of Ecology University of São Paulo São Paulo Brazil

Department of Environmental Science University of Puerto Rico Rio Piedras USA

Department of Forest Biology Faculty of Forestry Kasetsart University Bangkok Thailand

Department of Forest Ecology Silva Tarouca Research Institute Brno Czech Republic

Department of Forest Management University of Montana Missoula MT USA

Department of Natural Resources and Environmental Studies National Donghwa University Hualien Taiwan

Department of Plant Science University of Buea Buea Cameroon

Department of Science and Technology Uva Wellassa University Badulla Sri Lanka

Department of Wildland Resources Utah State University Logan UT USA

Ecosystem Analysis and Simulation Lab University of Bayreuth Bayreuth Germany

Environmental Change Institute School of Geography and the Environment University of Oxford Oxford UK

Environmental Studies Department University of California Santa Cruz Santa Cruz CA USA

Forest Global Earth Observatory Smithsonian Tropical Research Institute Panama City Panama

Forest Global Earth Observatory Smithsonian Tropical Research Institute Washington DC USA

Forest Research Institute Malaysia Kepong Malaysia

Global Earth Observatory Smithsonian Tropical Research Institute Washington DC USA

Graduate School of Science Osaka Metropolitan University Osaka Japan

Institute of Environmental Sciences Leiden University Leiden The Netherlands

Institute of Molecular Biosciences Mahidol University Nakhon Pathom Thailand

Instituto Amazónico de Investigaciones Científicas Sinchi Bogotá Colombia

Instituto de Investigación de Recursos Biológicos Alexander von Humboldt Bogotá Colombia

National Biobank of Thailand National Science and Technology Development Agency Bangkok Thailand

Sarawak Forest Department Kuching Malaysia

School of Forest Fisheries and Geomatics Sciences University of Florida Gainesville FL USA

School of the Environment Washington State University Pullman WA USA

School of the Environment Yale University New Haven CT USA

Smithsonian Environmental Research Center Edgewater MD USA

Smithsonian Tropical Research Institute Panama City Panama

Thai Long Term Forest Ecological Research Project Department of Forest Biology Faculty of Forestry Kasetsart University Bangkok Thailand

Theoretical Ecology University of Regensburg Regensburg Germany

UK Centre for Ecology and Hydrology Bush Estate Penicuik UK

University of Kisangani Kisangani Congo

Wilderness Institute University of Montana Missoula MT USA

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