Acknowledgments

The authors appreciate the assistance by the following individuals: R.E. Aston, D. Boozer, J.C. Britton, G.R. Buckingham, D.K. Camp, F.T. Campbell, J.T. Carlton, T. Champeau, W.R. Courtenay, Jr., D. Fox, J.H. Frank, J.B. Gratzek, J. Krummich, R. Mann, S. McKinney, D.W. Mitchell, C.R. Mock, F. Morrelo, W.B. Robertson, Jr., C.R. Robins, D.C. Schmitz, P.L. Shafland, C.J. Sindermann, K. Steidinger, H. Tiebolt, III, C. Watson, T. Webber, R.G. Westbrooks, and P. Zajicek for technical guidance and information on the present status of the nonindigenous species; V. Blazer, K. Brown, V.J. Catrow, E.A. Chornesky, G. B. Edwards, S.K. Gross, J.P. Jennings, D. Johnson, M. Meyers, R.A. Peoples, A. Rosenfield, P.N. Windle, and D.P. Wojcik for assistance in identifying sources of information and references; S.L. Bostick, J.R. McCann and D.A. Renegar for technical assistance and preparation of the manuscript.