Eric W. Seabloom, University of Minnesota
Elizabeth T. Borer, University of Minnesota
Yvonne M. Buckley, University of Queensland
Elsa E. Cleland, University of California, San Diego
Kendi F. Davies, University of Colorado at Boulder
Jennifer Firn, Queensland University of Technology
W. Stanley Harpole, Iowa State UniversityFollow
Yann Hautier, University of Zurich
Eric Lind, University of Minnesota
Andrew S. MacDougall, University of Guelph
John L. Orrock, University of Wisconsin–Madison
Suzanne M. Prober, CSIRO Ecosystem Sciences
Peter B. Adler, Utah State University
Juan Alberti, Instituto de Investigaciones Marinas y Costeras
T. Michael Anderson, Wake Forest University
Jonathan D. Bakker, University of Washington
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Dana Blumenthal, USDA Agricultural Research Service
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Maria Caldeira, Technical University of Lisbon
Chengjin Chu, Lanzhou University
Michael J. Crawley, Imperial College London
Pedro Daleo, Instituto de Investigaciones Marinas y Costeras
Ellen I. Damschen, University of Wisconsin–Madison
Carla M. D'Antonio, University of California, Santa Barbara
Nicole M. DeCrappeo, United States Geological Survey
Chris R. Dickman, University of Sydney
Guozhen Du, Lanzhou University
Philip A. Fay, USDA-ARS Grassland Soil and Water Research Lab
Paul N. Frater, Iowa State University
Daniel S. Gruner, University of Maryland
Nicole Hagenah, University of KwaZulu-Natal
Andrew Hector, University of Zurich
Aveliina Helm, University of Tartu
Helmut Hillebrand, Carl-von-Ossietzky University
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Oscar Iribarne, Instituto de Investigaciones Marinas y Costeras
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Adam Kay, University of St. Thomas
Kevin P. Kirkman, University of KwaZulu-Natal
Julia A. Klein, Colorado State University - Fort Collins
Johannes M. H. Knops, University of Nebraska–Lincoln
Kimberly J. La Pierre, Yale University
Laura M. Ladwig, University of New Mexico - Main Campus
John G. Lambrinos, Oregon State University
Andrew D. B. Leakey, University of Illinois
Qi Li, Chinese Academy of Sciences
Wei Li, Southwest Forestry University
Rebecca L. McCulley, University of Kentucky
Brett A. Melbourne, University of Colorado at Boulder
Charles E. Mitchell, University of North Carolina at Chapel Hill
Joslin L. Moore, University of Melbourne
John Morgan, La Trobe University
Brent D. Mortensen, Iowa State UniversityFollow
Lydia R. O'Halloran, Oregon State University
Meelis Partel, University of Tartu
Jesus Pascual, Instituto de Investigaciones Marinas y Costeras
David A. Pyke, U.S. Geological Survey Forest and Rangeland Ecosystem Science Center
Anita C. Risch, Swiss Federal Institute for Forest, Snow and Landscape Research
Roberto Salguero-Gomez, The University of Queensland
Mahesh Sankaran, National Centre for Biological Sciences
Martin Schuetz, Swiss Federal Institute for Forest, Snow and Landscape Research
Anna Simonsen, University of Toronto
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Carly J. Stevens, Lancaster University
Lauren Sullivan, Iowa State UniversityFollow
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Louie Yang, University of California - Davis

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Global Change Biology



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Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species' relative abundance will more rapidly advance our understanding of invasions.


This article is from Global Change Biology 19 (2013): 3677, doi:10.1111/gcb.12370


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