Document: MAR-3-82-24

Ecological and geographic patterns of impact in invaded communities: A meta-analysis.

WONHAM, M.J.* ¹, K.GOODELL ², B.VON HOLLE ³ and I.M.PARKER ⁴

University of Washington, Seattle, WA 98195 USA ¹
State University of New York, Stony Brook, NY USA ²
University of Tennessee, Knoxville, TN USA ³
University of California, Santa Cruz, CA USA ⁴

Abstract:
Charles Elton suggested that the success of introduced species varied with the latitude, degree of isolation (islands vs. continents), and degree of anthropogenic disturbance of the recipient community. We conducted a metaanalysis to test these, and other, ecological predictions about patterns of impact (as opposed to success) of introduced species. We quantitatively synthesized results from 90 field studies that provided 618 different measures of impact of plant, insect, marine invertebrate, or fish invaders. We divided response variables into impacts at the individual, population, community or ecosystem levels, expressed as the response ratio (lnRR). Both latitude and the level of anthropogenic disturbance affected patterns of invasion impact. Population level impacts of fish, insect, and marine invertebrate invaders increased at higher latitudes. Individual, but not population level impacts of plants also increased with latitiude. For all taxa and levels together, there was no significant trend in impact with latitude. Population level impacts of plant invaders were greater in undisturbed communities than in disturbed communities. In contrast, individual level impacts of all invaders together were higher in disturbed communities. For all other taxa and levels, the magnitude of impact did not differ between disturbed and undisturbed communities. We found no difference between islands and continents in the magnitude of invasion impacts for any taxon or any level. The time elapsed between the onset of the invasion and the beginning of the study affected the magnitude of invader impact. The sooner a study began, the higher the measured impacts for all taxa and levels together. Population level impacts of plants and marine invaders were also higher in earlier studies. In contrast, population level impacts of fish increased with the time since invasion. Impacts were marginally significantly higher on native than on alien response species, for insect invaders at the population level. Impacts of invaders on native versus alien response species did not differ for all taxa and levels considered together. These patterns of invasion impact warrant future investigation of the mechanisms that drive them.

Keywords: global patterns, introduced species, community response

This abstract is being presented at: 11:15 AM in session:
Oral Session #56: Metapopulation Analysis.