Document: JON-3-82-9

Species diversity and biological invasions: Relating local process to community pattern.

LEVINE, J.M.*

University of California, Berkeley, CA 94720 USA ¹

Abstract:
Concerns over biodiversity loss and the impacts of exotic species on natural ecosystems have rekindled interest in the relationship between species diversity and community susceptibility to biological invasions. I investigated both the community-wide patterns of diversity and invasion, and the intrinsic neighborhood scale effects of diversity in a California riparian system. In a survey of a 7 km stretch of the South Fork Eel River plant community, I found that the three most common exotic plants more frequently invaded diverse versus species poor areas. Yet a direct in situ manipulation of local diversity showed that the intrinsic effects of diversity are to enhance invasion resistance in this system. This apparent contradiction is resolved by recognizing that neighborhood scale effects of diversity can be overwhelmed by ecological factors spatially covarying with diversity at community wide scales. An additional seed addition experiment suggested that for this system, seed supply drives patterns of diversity and invasion. Results suggest that species loss at small scales may reduce invasion resistance. Yet at community-wide scales, the overwhelming effects of ecological factors spatially covarying with diversity, such as propagule supply, cause the most diverse natural communities to be most susceptible to invasion.

Keywords: Species diversity, exotic species, invasions

This abstract is being presented at: 9:00 AM in session:
Oral Session #2: Conservation Ecology.