With the growing awareness of the biological (Noss et al.
1995; Schmitz and Simberloff 1997, Simberloff 2000),
economic (US Congress, Office of Technology Assessment
1993; Pimentel et al. 2000), and social (Asher and
Spurrier 1998) impacts of weed invasions, there has been
increasing interest in what makes a plant species invasive
(Blossey and Notzold 1995; Rejmanek 1995; Blossey
1996; Crawley et al. 1996; Rejmanek and Richardson
1996; Williamson and Fitter 1996; Daehler 1998; Willis et
al. 1999; Mack et al. 2000; Siemann and Rogers 2001,
2003; Keane and Crawley 2002; Shea and Chesson 2002;
Wolfe 2002) and predicting the identity of potential
invasive plants (Daehler and Strong 1993; Mack 1996;
Rejmanek 1996; Reichard and Hamilton 1997;Williamson
1999; Randall and Hoshovsky 2000; Kolar and Lodge
2001; Pysek 2001).