title: Multiple mechanisms enable invasive species to suppress native species.
abstract: OBJECTIVE
  Invasive plants represent a significant threat to ecosystem biodiversity. To decrease the impacts of invasive species, a major scientific undertaking of the last few decades has been aimed at understanding the mechanisms that drive invasive plant success. Most studies and theories have focused on a single mechanism for predicting the success of invasive plants and therefore cannot provide insight as to the relative importance of multiple interactions in predicting invasive species' success.
  
  
  METHODS
  We examine four mechanisms that potentially contribute to the success of invasive velvetgrass Holcus lanatus: direct competition, indirect competition mediated by mammalian herbivores, interference competition via allelopathy, and indirect competition mediated by changes in the soil community. Using a combination of field and greenhouse approaches, we focus on the effects of H. lanatus on a common species in California coastal prairies, Erigeron glaucus, where the invasion is most intense.
  
  
  RESULTS
  We found that H. lanatus had the strongest effects on E. glaucus via direct competition, but it also influenced the soil community in ways that feed back to negatively influence E. glaucus and other native species after H. lanatus removal.
  
  
  CONCLUSIONS
  This approach provided evidence for multiple mechanisms contributing to negative effects of invasive species, and it identified when particular strategies were most likely to be important. These mechanisms can be applied to eradication of H. lanatus and conservation of California coastal prairie systems, and they illustrate the utility of an integrated set of experiments for determining the potential mechanisms of invasive species' success.
authors: Section of Evolution and Ecology, 2320 Storer Hall, One Shields Ave, University of California, Davis, Davis, California 95615, USA. alibenne@bio.indiana.edu
authors: Alison E
authors: AE
authors: Bennett
authors: Meredith
authors: M
authors: Thomsen
authors: Sharon Y
authors: SY
authors: Strauss
mesh_terms: D000704:Analysis of Variance; D018533:Biomass; D049919:Erigeron / Q000254:growth & development*; D018525:Germination / Q000502:physiology; D031752:Holcus / Q000254:growth & development*; D058865:Introduced Species; D036226:Seedlings / Q000254:growth & development; D012987:Soil
chemical_list: D012987:Soil