Joint effects of nutrient addition and enemy exclusion on exotic plant success.

Journal Article (Journal Article)

Worldwide, ecosystems are increasingly dominated by exotic plant species, a shift hypothesized to result from numerous ecological factors. Two of these, increased resource availability and enemy release, may act in concert to increase exotic success in plant communities (Resource-Enemy Release Hypothesis, R-ERH). To test this, we manipulated the availability of soil nutrients and access of vertebrate herbivores, insect herbivores, and fungal pathogens to intact grassland communities containing both native and exotic species. Our results supported both conditions necessary for R-ERH. First, exotics were less damaged than natives, experiencing less foliar damage (insect herbivory and fungal disease) than native species, particularly in communities where soil nutrients were added. Second, fertilization increased foliar damage on native species, but not exotic species. As well as fulfilling both conditions for R-ERH, these results demonstrate the importance of considering the effects of resource availability when testing for enemy release. When both conditions are fulfilled, R-ERH predicts that increasing resource availability will increase exotic abundance only in the presence of enemies. Our results fully supported this prediction for vertebrate herbivores: fertilization increased exotic cover only in communities exposed to vertebrate herbivores. Additionally, the prediction was partially supported for insect herbivores and fungal pathogens, excluding these enemies reduced exotic cover as predicted, but inconsistent with R-ERH, this effect occurred only in unfertilized communities. These results highlight the need to consider the influence of multiple enemy guilds on community processes like exotic plant invasions. Moreover, this study experimentally demonstrates that resource availability and natural enemies can jointly influence exotic success in plant communities.

Full Text

Duke Authors

Cited Authors

  • Heckman, RW; Wright, JP; Mitchell, CE

Published Date

  • December 2016

Published In

Volume / Issue

  • 97 / 12

Start / End Page

  • 3337 - 3345

PubMed ID

  • 27911999

Electronic International Standard Serial Number (EISSN)

  • 1939-9170

International Standard Serial Number (ISSN)

  • 0012-9658

Digital Object Identifier (DOI)

  • 10.1002/ecy.1585


  • eng