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.
Bibliographical noteFunding Information:
This work was generated using data from the Nutrient Network (http://nutnet.org) experiment, funded at the site scale by individual researchers. Coordination and data management have been supported by funding to E. Borer and E. Seabloom from the National Science Foundation Research Coordination Network (NSF-DEB-1042132), Long Term Ecological Research (NSF-DEB-1234162 to Cedar Creek LTER) programs and the Institute on the Environment (DG-0001-13). We also thank the Minnesota Supercomputer Institute for hosting project data. Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.