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Pan et al . claim that our results actually support a strong linear positive relationship between productivity and richness, whereas Fridley et al . contend that the data support a strong humped relationship. These responses illustrate how preoccupation with bivariate patterns distracts from a deeper understanding of the multivariate mechanisms that control these important ecosystem properties.

Many ecosystems worldwide are dominated by introduced plant species, leading to loss of biodiversity and ecosystem function. A common but rarely tested assumption is that these plants are more abundant in introduced vs. native communities, because ecological or evolutionary-based shifts in populations underlie invasion success. Here, data for 26 herbaceous species at 39 sites, within eight countries, revealed that species abundances were similar at native (home) and introduced (away) sites – grass species were generally abundant home and away, while forbs were low in abundance, but more abundant at home. Sites with six or more of these species had similar community abundance hierarchies, suggesting that suites of introduced species are assembling similarly on different continents. Overall, we found that substantial changes to populations are not necessarily a pre-condition for invasion success and that increases in species abundance are unusual. Instead, abundance at home predicts abundance away, a potentially useful additional criterion for biosecurity programmes.

The Kalahari Transect (KT) is an International Geosphere–Biosphere Programme mega-transect designed to examine hydrological and ecological patterns and processes throughout the savannas of southern Africa. The KT traverses a precipitation gradient ranging from ∼920 mm rain/year in the north to ∼260 mm rain/year in the south. Previous research shows a positive correlation between canopy cover and precipitation suggesting a water limitation on productivity. However, there has been minimal research on other possible sources of limitations, such as soil Nitrogen (N) and/or Phosphorus (P). We used a factorial in-situ experimental design to test for increased aboveground grass production (measured as peak season standing stock) under elevated soil P and P + N levels. Four sites along the KT precipitation gradient were used in this study: Mongu (Zambia), Pandamatenga (Botswana), Ghanzi (Botswana) and Tshane (Botswana). Soils at each site were amended with N and P fertilizers during the dry season. We extracted soil samples during the following growing season to analyze for plant available soil P. Vegetation samples were harvested from which we measured foliar P and aboveground grass biomass production. We saw differences in foliar P at the treatment and site level but not for the interaction between treatment and site. There were individual effects from site on biomass but not for any interactions with nutrient treatments. Despite higher levels of foliar P, we did not detect an increase in aboveground biomass. This may be explained by luxury uptake or allocation to belowground resources.

Savannas cover about 20% of the Earth’s land area and 50% of Africa. As an indispensable component of savanna, grasses play an important role in these ecosystems. A better understanding of grass productivity and its controlling factors in savanna ecosystems could therefore be a key to understand the functioning of savannas and predict savanna responses to future climatic changes. In this study, a stable isotope fertilization experiment was conducted to determine how factors limiting grass production in savannas differ across regional climate gradients. The study was conducted on the geomorphically homogenous Kalahari Transect (KT), which offers an ideal setting to study nutrient and vegetation dynamics independently of confounding soil effects. The results show that the grasses assimilated the added fertilizer at all the sites but they did not respond to nitrogen fertilization for both dry and wet years, and at both dry and wet ends of the Transect. Although prior studies have proposed a switch between water and nitrogen limitations between arid and mesic savannas, our results suggest that nitrogen availability may not limit grass productivity across the whole KT. Thus, although the traditional classifications as nutrient poor (broad-leaf) and nutrient rich (fine-leaf) savanna ecosystems may still be useful, it does not necessarily imply the existence of nitrogen limitation in the nutrient poor area; in fact, it is more likely that the herbaceous species found in the more humid sites (nutrient poor sites) are already adapted to lower nitrogen availability.

Exotic species dominate many communities; however the functional significance of species' biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands., It remains unclear whether exotic and native species are functionally different. Using a global grassland experiment, Seabloom et al. show that native and exotic species respond differently to two globally pervasive environmental changes, addition of mineral nutrients and alteration of herbivore density.

Human alterations to nutrient cycles and herbivore communities are affecting global biodiversity dramatically. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light. © 2014 Macmillan Publishers Limited. Fil: Borer, Elizabeth. University of Minnesota; Estados Unidos Fil: Seabloom, Eric. University of Minnesota; Estados Unidos Fil: Gruner, Daniel. University of Maryland; Estados Unidos Fil: Harpole, Stanley. Iowa State University; Estados Unidos Fil: Hillebrand, Helmut. Carl-von- Ossietzky University; Alemania Fil: Lind, Eric M.. University of Minnesota; Estados Unidos Fil: Adler, Peter B.. Utah State University; Estados Unidos Fil: Alberti, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Anderson, Michael. Wake Forest University; Estados Unidos Fil: Bakker, Jonathan D.. University of Washington; Estados Unidos Fil: Biederman, Lori. Iowa State University; Estados Unidos Fil: Blumenthal, Dana. United States Department of Agriculture. Agricultural Research Service; Estados Unidos Fil: Brown, Cynthia S.. State University of Colorado - Fort Collins; Estados Unidos Fil: Brudvig, Lars A.. University of Minnesota; Estados Unidos Fil: Buckley, Yvonne M.. The University Of Queensland; Australia Fil: Cadotte, Marc. University of Toronto Scarborough; Canadá Fil: Chu, Chengjin. Lanzhou University; China Fil: Cleland, Elsa. University of California; Estados Unidos Fil: Crawley, Michael. Imperial College at Silwood Park; Reino Unido Fil: Daleo, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Damschen, Ellen. University of Wisconsin; Estados Unidos Fil: Davies, Kendi. State University of Colorado - Fort Collins; Estados Unidos Fil: DeCrappeo, Nicole. Forest and Rangeland Ecosystem Science Center; Estados Unidos Fil: Du, Guozhen. Lanzhou University; Estados Unidos Fil: Firn, Jennifer. Queensland University of Technology; Australia Fil: Hautier, Yann. University of Minnesota; Estados Unidos Fil: Heckman, Robert. University of North Carolina at Chapel Hill; Estados Unidos Fil: Hector, Andy. University of Oxford; Reino Unido Fil: Hillerislambers, Janneke. University of Washington; Estados Unidos Fil: Iribarne, Oscar Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Klein, Julia. State University of Colorado - Fort Collins; Estados Unidos Fil: Knops, Johannes M. H.. University of Nebraska; Estados Unidos Fil: La Pierre, Kimberly. University of California; Estados Unidos Fil: Leakey, Andrew D. B.. University of Illinois at Urbana-Champaign; Estados Unidos Fil: Li, Wei. Iowa State University; Estados Unidos Fil: MacDougall, Andrew S.. University of Guelph; Canadá Fil: McCulley, Rebecca. University Of Kentucky; Estados Unidos Fil: Melbourne, Brett. State University of Colorado - Fort Collins; Estados Unidos Fil: Mitchell, Charles. University of North Carolina at Chapel Hill; Estados Unidos Fil: Moore, Joslin. University of Melbourne; Australia Fil: Mortensen, Brent. Iowa State University; Estados Unidos Fil: O'Halloran, Lydia. Oregon State University; Estados Unidos Fil: Orrock, John. University of Wisconsin; Estados Unidos Fil: Pascual, Jesus Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Prober, Suzanne. CSIRO Ecosystem Sciences; Australia Fil: Pyke, David. Forest and Rangeland Ecosystem Science Center; Canadá Fil: Risch, Anita. Swiss Federal Institute For Forest, Snow And Landscape Research; Suiza Fil: Schuetz, Martin. Swiss Federal Institute For Forest, Snow And Landscape Research; Suiza Fil: Smith, Melinda D.. State University of Colorado - Fort Collins; Estados Unidos Fil: Stevens, Carly. Lancaster University; Reino Unido Fil: Sullivan, Lauren. Iowa State University; Estados Unidos Fil: Williams, Ryan. Iowa State University; Estados Unidos Fil: Wragg, Peter. University of Minnesota; Estados Unidos Fil: Yang, Louie. University of California; Estados Unidos

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. 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. Fil: Seabloom, Eric W.. University of Minnesota; Estados Unidos Fil: Borer, Elizabeth T.. University of Minnesota; Estados Unidos Fil: Buckley, Yvonne. The University Of Queensland; Australia Fil: Cleland, Elsa E.. University of California, San Diego; Estados Unidos Fil: Kendi, Davies. State University of Colorado Boulder; Estados Unidos Fil: Firn, Jennifer. Queensland University of Technology. Brisbane; Australia Fil: Hartpole, Stanley W.. Iowa State University; Estados Unidos Fil: Hautier, Yann. University of Zurich; Suiza Fil: Lind, Eric. Universidad de Minnesota; Estados Unidos Fil: MacDougall, Andrew. University of Guelph; Canadá Fil: Orrock, John L.. University of Wisconsin; Estados Unidos Fil: Prober, Suzanne M.. CSIRO Ecosystem Sciences; Australia Fil: Adler, Peter. Utah State University; Estados Unidos Fil: Alberti, Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Anderson, T. Michael. Wake Forest University; Estados Unidos Fil: Bakker, Jonathan D.. University of Washington; Estados Unidos Fil: Biederman, Lori A.. Iowa State University; Estados Unidos Fil: Blumenthal, Dana. Rangeland Resources Research Unit; Estados Unidos Fil: Browns, Cynthia S.. State University of Colorado - Fort Collins; Estados Unidos Fil: Brudvig, Lars A.. Michigan State University; Estados Unidos Fil: Caldeira, Maria. Technical University of Lisbon; Portugal Fil: Chu, Chengjin. Lanzhou University; China Fil: Crawley, Michel. Imperial College London; Reino Unido Fil: Daleo, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Damschen, Ellen I.. University of Wisconsin; Estados Unidos Fil: D'antonio, Carla. University of California; Estados Unidos Fil: Decrappeo, Nicole. Geological Survey Forest and Rangeland Ecosystem Science Center; Estados Unidos Fil: Dickman, Chris. University of Sydney; Australia Fil: Du, Guozhen. Lanzhou University; China Fil: Fay, Philip. Grassland Soil and Water Research Lab; Estados Unidos Fil: Frater, Paul. Iowa State University; Estados Unidos Fil: Gruner, Daniel S.. University of Queensland; Australia Fil: Hagenah, Nicole. University of KwaZulu-Natal; Sudáfrica Fil: Hector, Andrew. University of Zurich; Suiza Fil: Helm, Avellina. University Of Tartu.; Estonia Fil: Hillebrand, Helmut. Carl-von-Ossietzky University; Alemania Fil: Hofmockel, Kirsten. Iowa State University; Estados Unidos Fil: Humphries, Hope. State University of Colorado - Fort Collins; Estados Unidos Fil: Iribarne, Oscar Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Jin, Virginia L.. Agroecosystem Management Research Unit; Estados Unidos Fil: Kay, Adam. University of St. Thomas; Estados Unidos Fil: Kirkman, Kevin. University of KwaZulu-Natal; Estonia Fil: Klein, Julia. State University of Colorado - Fort Collins; Estados Unidos Fil: Knops, Johannes M. H.. University Of Nebraska; Estados Unidos Fil: La Pierre, Kimberly. Yale University; Estados Unidos Fil: Ladwig, Laura M.. University Of New Mexico; Estados Unidos Fil: Lambrinos, John G.. Oregon State University; Estados Unidos Fil: Leakey, Andrew. University of Illinois at Urbana-Champaign; Estados Unidos Fil: Li, Qi. Northwest Institute of Plateau Biology, Chinese Academy of Sciences; China Fil: Li, Wei. Southwest Forestry University; China Fil: McCulley, Rebecca. University Of Kentucky; Estados Unidos Fil: Melbourne, Brett. State University of Colorado Boulder; Estados Unidos Fil: Mitchell, Charles. University of North Carolina; Estados Unidos Fil: Moore, Joslin. Australian Research Centre for Urban Ecology; Australia Fil: Morgan, John. La Trobe University; Australia Fil: Mortensen, Brent. Iowa State University; Estados Unidos Fil: O'Halloran, Lydia. Oregon State University; Estados Unidos Fil: Pärtel, Meelis. University Of Tartu.; Estonia Fil: Pascual, Jesus Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Pyke, David A.. University of California; Estados Unidos Fil: Risch, Anita. Swiss Federal Institute For Forest, Snow And Landscape Research; Suiza Fil: Salguero Goméz, Roberto. The University Of Queensland; Australia Fil: Sankaran, Mahesh. National Centre for Biological Sciences; India Fil: Schuetz, Martin. Swiss Federal Institute For Forest, Snow And Landscape Research; Suiza Fil: Simonsen, Anna. University of Toronto; Canadá Fil: Smith, Melinda. State University of Colorado - Fort Collins; Estados Unidos Fil: Stevens, Carly. Lancaster Environment Center; Canadá Fil: Sullivan, Lauren. Iowa State University; Estados Unidos Fil: Wardle, Glenda M.. University of Sydney; Australia Fil: Wolkovich, Elizabeth M.. University of British Columbia; Canadá Fil: Wragg, Peter D.. The University Of Queensland; Australia Fil: Wright, Justin. University of Duke; Estados Unidos Fil: Yang, Louie. University of California; Estados Unidos

Studies of experimental grassland communities1,2,3,4,5,6,7 have demonstrated that plant diversity can stabilize productivity through species asynchrony, in which decreases in the biomass of some species are compensated for by increases in others1,2. However, it remains unknown whether these findings are relevant to natural ecosystems, especially those for which species diversity is threatened by anthropogenic global change8,9,10,11. Here we analyse diversity–stability relationships from 41 grasslands on five continents and examine how these relationships are affected by chronic fertilization, one of the strongest drivers of species loss globally8. Unmanipulated communities with more species had greater species asynchrony, resulting in more stable biomass production, generalizing a result from biodiversity experiments to real-world grasslands. However, fertilization weakened the positive effect of diversity on stability. Contrary to expectations, this was not due to species loss after eutrophication but rather to an increase in the temporal variation of productivity in combination with a decrease in species asynchrony in diverse communities. Our results demonstrate separate and synergistic effects of diversity and eutrophication on stability, emphasizing the need to understand how drivers of global change interactively affect the reliable provisioning of ecosystem services in real-world systems. Fil: Hautier, Yann. University of Minnesota; Estados Unidos. Universitat Zurich; Suiza Fil: Seabloom, Eric. University of Minnesota; Estados Unidos Fil: Borer, Elizabeth T. University of Minnesota; Estados Unidos Fil: Adler, Peter. State University of Utah; Estados Unidos Fil: Harpole, E. Stanley. University of Iowa; Estados Unidos Fil: Hillebrand, Helmut. University Oldenburg; Alemania Fil: Lind, Eric M.. University of Minnesota; Estados Unidos Fil: McDougall, Andrew S.. University of Guelph; Canadá Fil: Stevens, Carly J.. Lancaster University; Reino Unido Fil: Bakker, Jonathan D. University of Washington; Estados Unidos Fil: Buckley, Yvonne M.. University of Queensland; Australia. Trinity College Dublin; Irlanda Fil: Chu, Chengjin. Lanzhou University; China Fil: Collins, Scott L.. University Of New Mexico; Estados Unidos Fil: Daleo, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Damschen, Ellen I.. University of Wisconsin; Estados Unidos Fil: Davies, Kendi F.. State University of Colorado Boulder; Estados Unidos Fil: Fay, Philip A.. United States Department of Agriculture Agricultural Research Service; Estados Unidos Fil: Frin, Jennifer. Queensland University of Technology; Australia Fil: Gruner, Daniel S.. University of Maryland; Estados Unidos Fil: Jin, Virginia L.. United States Department of Agriculture Agricultural Research Service; Estados Unidos Fil: Klein, Julia A.. State University of Colorado - Fort Collins; Estados Unidos Fil: Knops, Johannes M. H.. University Of Nebraska; Estados Unidos Fil: La Pierre, Kimberly J.. University of California at Berkeley; Estados Unidos Fil: Li, Wei. Southwest Forestry University; China Fil: McCulley, Rebecca L.. University Of Kentucky; Estados Unidos Fil: Melbourne, Brett A.. State University of Colorado - Fort Collins; Estados Unidos Fil: Moore, Joslin L.. University of Melbourne; Australia. Monash University; Australia Fil: O'Halloran, Lydia R.. Oregon State University; Estados Unidos Fil: Prober, Suzanne M.. CSIRO Ecosystem Sciences; Australia Fil: Risch, Anita C.. Swiss Federal Institute for Forest; Suiza Fil: Sankaran, Mahesh. University of Leeds; Reino Unido. National Centre for Biological Sciences; India Fil: Schuetz, Martin. Swiss Federal Institute for Forest; Suiza Fil: Hector, Andy. University of Oxford; Reino Unido

Based on regional-scale studies, aboveground production and litter decomposition are thought to positively covary, because they are driven by shared biotic and climatic factors. Until now we have been unable to test whether production and decomposition are generally coupled across climatically dissimilar regions, because we lacked replicated data collected within a single vegetation type across multiple regions, obfuscating the drivers and generality of the association between production and decomposition. Furthermore, our understanding of the relationships between production and decomposition rests heavily on separate meta-analyses of each response, because no studies have simultaneously measured production and the accumulation or decomposition of litter using consistent methods at globally relevant scales. Here, we use a multi-country grassland dataset collected using a standardized protocol to show that live plant biomass (an estimate of aboveground net primary production) and litter disappearance (represented by mass loss of aboveground litter) do not strongly covary. Live biomass and litter disappearance varied at different spatial scales. There was substantial variation in live biomass among continents, sites and plots whereas among continent differences accounted for most of the variation in litter disappearance rates. Although there were strong associations among aboveground biomass, litter disappearance and climatic factors in some regions (e.g. U.S. Great Plains), these relationships were inconsistent within and among the regions represented by this study. These results highlight the importance of replication among regions and continents when characterizing the correlations between ecosystem processes and interpreting their global-scale implications for carbon flux. We must exercise caution in parameterizing litter decomposition and aboveground production in future regional and global carbon models as their relationship is complex.

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters(-2)) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.

Many ecosystems worldwide are dominated by introduced plant species, leading to loss of biodiversity and ecosystem function. A common but rarely tested assumption is that these plants are more abundant in introduced vs. native communities, because ecological or evolutionary-based shifts in populations underlie invasion success. Here, data for 26 herbaceous species at 39 sites, within eight countries, revealed that species abundances were similar at native (home) and introduced (away) sites - grass species were generally abundant home and away, while forbs were low in abundance, but more abundant at home. Sites with six or more of these species had similar community abundance hierarchies, suggesting that suites of introduced species are assembling similarly on different continents. Overall, we found that substantial changes to populations are not necessarily a pre-condition for invasion success and that increases in species abundance are unusual. Instead, abundance at home predicts abundance away, a potentially useful additional criterion for biosecurity programmes.