events. Any other pathways in which past events can be reconstructed should be equally valuable for study. We anticipate that the study of the evolution of invasiveness should be able to provide answers for why invasiveness occurs in some cases and does not occur in others.
We thank V. Symonds, K. Gallagher, and N. Sherman for discussions early in the development of the manuscript and also thank the following for their comments on draft versions of the manuscript: R. Abbott, D. Crawford, J. Hamrick, I. Parker, L. Rieseberg, A. Snow, P. Soltis, and R. Whitkus. We are grateful for feedback from the 1998 Ecological Genetics Group Meeting and the first workshop of the Collaboratory on the Population Biology of Invasive Species (funded by a grant from the National Science Foundation through a grant to the University of California at Irvine). This work was supported by funding from a University of California Competitive grant (1997–980069) and an Environmental Protection Agency grant (R-826102–01-0) to N.C.E., and by National Science Foundation Grants 9973734 to K.A.S. and 9322795 to K.A.S. and C. D'Antonio.
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