The relationship between levels of dominance and species richness is highly contentious, especially in ant communities. The dominance-impoverishment rule states that high levels of dominance only occur in species-poor communities, but there appear to be many cases of high levels of dominance in highly diverse communities. The extent to which dominant species limit local richness through competitive exclusion remains unclear, but such exclusion appears more apparent for non-native rather than native dominant species. Here we perform the first global analysis of the relationship between behavioral dominance and species richness. We used data from 1,293 local assemblages of ground-dwelling ants distributed across five continents to document the generality of the dominance-impoverishment rule, and to identify the biotic and abiotic conditions under which it does and does not apply. We found that the behavioral dominance-diversity relationship varies greatly, and depends on whether dominant species are native or non-native, whether dominance is considered as occurrence or relative abundance, and on variation in mean annual temperature. There were declines in diversity with increasing dominance in invaded communities, but diversity increased with increasing dominance in native communities. These patterns occur along the global temperature gradient. However, positive and negative relationships are strongest in the hottest sites. We also found that climate regulates the degree of behavioral dominance, but differently from how it shapes species richness. Our findings imply that, despite strong competitive interactions among ants, competitive exclusion is not a major driver of local richness in native ant communities. Although the dominance-impoverishment rule applies to invaded communities, we propose an alternative dominance-diversification rule for native communities.

Appalachian Lab University of Maryland Center for Environmental Science Frostburg Maryland

Biodiversity Coordination National Institute for Amazonian Research Manaus AM Brazil

Biodiversity Monitoring and Assessment Royal Belgian Institute of Natural Sciences Brussels Belgium

Biology Centre of the Czech Academy of Sciences Institute of Entomology and Faculty of Science University of South Bohemia České Budějovice Czech Republic

Biology Department Lawrence University Appleton Wisconsin

Center for Macroecology Evolution and Climate Natural History Museum of Denmark University of Copenhagen Copenhagen Denmark

Centre for Invasion Biology Department of Zoology and Entomology University of Pretoria Pretoria South Africa

College of Science and Engineering James Cook University Cairns Queensland Australia

CREAF Cerdanyola del Vallès Catalunya Spain

Departamento de Biologia Universidade Federal do Amazonas Manaus Brazil

Department of Applied Ecology North Carolina State University Raleigh North Carolina

Department of Biogeography University of Bayreuth Bayreuth Germany

Department of Biology Lake Forest College Lake Forest Illinois

Department of Chemistry Life Sciences and Environmental Sustainability University of Parma Parma Italy

Department of Earth Ocean and Ecological Sciences University of Liverpool Liverpool UK

Department of Ecology Evolution and the Environment La Trobe University Melbourne Vic Australia

Department of Environment and Agriculture Curtin University Perth WA Australia

Department of Environmental Science University of Girona Girona Spain

Department of Experimental Diabetology Nuthetal Germany

Division of Tropical Ecology and Animal Biodiversity Department of Botany and Biodiversity Research University of Vienna Vienna Austria

Environmental Program Rubenstein School of Environment and Natural Resources University of Vermont Burlington Vermont

Environmental Studies Department University of California Santa Cruz California

Estación Biológica de Doñana CSIC Sevilla Spain

Institute of Insect Biology University François Rabelais of Tours Tours France

Instituto de Biologia Universidade Federal de Uberlândia Uberlândia MG Brazil

Instituto de Ciencias Biológicas Escuela Politécnicamenk Nacional Quito Ecuador

IPÊ Instituto de Pesquisas Ecológicas Nazaré Paulista SP Brasil

ITZ Ecology and Evolution TiHo Hannover Hannover Germany

National Laboratory for Ecological Analysis and Synthesis ENES UNAM Michoacan Mexico

New Guinea Binatang Research Center Madang Papua New Guinea

Research Institute for the Environment and Livelihoods Charles Darwin University Casuarina NT Australia

School of Biological Sciences The University of Hong Kong Hong Kong SAR

School of Biological Sciences University of WA Perth WA Australia

School of Life Sciences University of KwaZulu Natal Pietermaritzburg South Africa

Science and Technology for Amazonian Resources Graduate Program Institute of Exact Sciences and Technology Itacoatiara AM Brazil

Société d'Histoire Naturelle Alcide d'Orbigny Aubière France

Tropical Ecosystems Research Centre CSIRO Winnellie NT Australia

Univ Autònoma Barcelona Cerdanyola del Vallès Catalunya Spain

University of Florida Entomology and Nematology Department Gainesville Florida

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