The colonization of native phytophagous insects in North America by exotic parasitoids |
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Authors: | Bradford A Hawkins Paul C Marino |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA e-mail: bhawkins@uci.edu, US;(2) Department of Biology, University of Charleston, South Carolina, Charleston, SC 29424, USA, US |
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Abstract: | Classical biological control could have a major environmental cost if introduced natural enemies colonize and disrupt native
systems. Although quantifying these impacts is difficult for systems already colonized by natural enemies, the a priori condition
for such impacts can be evaluated based on the extent to which exotics have acquired native hosts. We use native host records
for exotic parasitoids introduced into North America for biological control to document the number of exotic species that
have been recorded from at least one native insect species. We also evaluate the ability of six biological and ecological
variables to predict whether or not a parasitoid will move onto natives. Sixteen percent of 313 parasitoid species introduced
against holometabolous pests are known from natives. Further, the likelihood that a parasitoid had colonized native hosts
was largely unpredictable with respect to the independent variables. We conclude that given the quality of the data available
either now or in the foreseeable future, coupled with inherent stochasticity in host shifts by parasitoids, there are no rules
of thumb to assist biological control workers in evaluating if an introduced parasitoid will colonize native insect communities.
Received: 2 July 1997 / Accepted: 3 August 1997 |
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Keywords: | Biological control Parasitoids Exotics Introductions Environmental impact |
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