Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?
- Department of Ecology, Evolution, and Behavior, University of MN, St. Paul MN 55108 USA
- ARC Centre of Excellence for Environmental Decisions, School of Biological Sciences, The University of Queensland, Brisbane Queensland 4072 Australia
- Ecology, Behavior & Evolution Section, University of California, San Diego La Jolla CA 92093 USA
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder CO 80309 USA
- Queensland University of Technology, Biogeosciences, Brisbane Queensland 4000 Australia
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames IA 50011 USA
- Department of Ecology, Evolution, and Behavior, University of MN, St. Paul MN 55108 USA; Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190 CH-8057 Zurich Switzerland
- Department of Integrative Biology, University of Guelph, Guelph Ontario N1G 2W1 Canada
- Department of Zoology, University of Wisconsin, Madison WI 53706 USA
- CSIRO Ecosystem Sciences, Private Bag 5 Wembley WA 6913 Australia
- Department of Wildland Resources and the Ecology Center, Utah State University, Logan UT 84322 USA
- Instituto de Investigaciones Marinas y Costeras (UNMdP-CONICET), Mar del Plata Argentina
- Department of Biology, Wake Forest University, Winston-Salem NC 27109 USA
- School of Environmental and Forest Sciences, University of Washington, Seattle WA 98195-4115 USA
- Rangeland Resources Research Unit, USDA Agricultural Research Service, Fort Collins CO 80526 USA
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins CO 80523 USA
- Department of Plant Biology, Michigan State University, East Lansing MI 48824 USA
- Centro de Estudos Florestais, Instituto Superior de Agronomia, Technical University of Lisbon, Lisbon Portugal
- School of Life Sciences, Lanzhou University, Lanzhou 730000 China
- Department of Biology, Imperial College London, Silwood Park Ascot SL5 7PY UK
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara CA 93106 USA
- U.S. Geological Survey Forest and Rangeland Ecosystem Science Center, Corvallis OR 97331 USA
- Desert Ecology Research Group, School of Biological Sciences, University of Sydney, Sydney NSW 2006 Australia
- USDA-ARS Grassland Soil and Water Research Lab, Temple TX 76502 USA
- Department of Entomology, University of Maryland, College Park MD 20742 USA
- School of Life Sciences, University of KwaZulu-Natal, Scottsville Pietermaritzburg 3209 South Africa; Department of Ecology, Evolutionary Biology, Yale University, New Haven CT 06520 USA
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190 CH-8057 Zurich Switzerland
- Institute of Ecology and Earth Sciences, University of Tartu, Tartu Estonia
- Institute for Chemistry and Biology of the Marine Environment, Carl-von-Ossietzky University, Wilhelmshaven Germany
- INSTAAR, University of Colorado, Boulder CO 80309-0450 USA
- USDA-ARS Agroecosystem Management Research Unit, Lincoln NE 68583 USA
- Biology Department, University of St. Thomas, Saint Paul MN 55105 USA
- School of Life Sciences, University of KwaZulu-Natal, Scottsville Pietermaritzburg 3209 South Africa
- Department Forest, Rangeland & Watershed Stewardship, Colorado State University, Fort Collins CO 80523-1472 USA
- School of Biological Sciences, University of Nebraska, Lincoln NE 68588 USA
- Department of Ecology, Evolutionary Biology, Yale University, New Haven CT 06520 USA
- Department of Biology, University of New Mexico, Albuquerque NM 87103 USA
- Department of Horticulture, Oregon State University, Corvallis OR 97331 USA
- Department of Plant Biology and Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana IL 61801 USA
- Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810008 Qinghai China
- Yunnan Academy of Biodiversity, Southwest Forestry University, Kunming 650224 China
- Department of Plant & Soil Sciences, University of Kentucky, Lexington KY 40546 USA
- Department of Biology, University of North Carolina, Chapel Hill NC 27599 USA
- Australian Research Centre for Urban Ecology, Melbourne, c/o School of Botany, University of Melbourne, Melbourne Victoria 3010 Australia
- Department of Botany, La Trobe University, Bundoora 3086 Victoria Australia
- Department of Zoology, Oregon State University, Corvallis OR 97331 USA
- Swiss Federal Institute for Forest, Snow and Landscape Research, 8903 Birmensdorf Switzerland
- National Centre for Biological Sciences, GKVK Campus, Bellary Road Bangalore 560065 India
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto ON M5S 3B2 Canada
- Department of Biology, Colorado State University, Fort Collins CO 80523 USA
- Lancaster Environment Center, Lancaster University, Lancaster LA1 4YQ UK
- Biodiversity Research Centre, University of British Columbia, Vancouver V6T 1Z4 Canada
- Department of Biology, Duke University, Durham NC 27708 USA
- Department of Entomology, University of California, Davis CA 95616 USA
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.
- Research Organization:
- USDA Forest Service-Savannah River, New Ellenton, SC (United States)
- Sponsoring Organization:
- USDOE; USDOE Office of Environmental Management (EM), Project Management (EM-50)
- Contributing Organization:
- USDA Forest Service-Savannah River
- DOE Contract Number:
- AI09-00SR22188
- OSTI ID:
- 1126900
- Report Number(s):
- 13-08-P; na
- Journal Information:
- Global Change Biology, Vol. 19, Issue 12; ISSN 1354-1013
- Publisher:
- Wiley
- Country of Publication:
- United States
- Language:
- English
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