Potential Valuable Ecological Functions of Nonindigenous Plants

Recent popular and technical literature on nonindigenous (NI) plants is rife with examples of species run amok in natural and managed ecosystems. In North America, for example, conspicuous, well-established NI species like garlic mustard (Alliaria petiolata) Japanese honeysuckle (Lonicera japonica) kudzu (Pueraria montana) purple loosestrife (Lythrum salicaria) and multiflora rose (Rosa multiflora) among others, have gained considerable notoriety because of their demonstrated or presumed ability to alter the structure and function of ecosystems (Sawyers 1989; Vitousek 1990; Williams CE 1993b, 1996; Williams T 1994). Yet not all NI plants in a region are invasive pests and not all systems are equally invasible, even by the most aggressive NI species (Brothers and Spingarn 1992; Fox and Fox 1986; Hiebert 1990; Langdon and Johnson 1994; Myers 1983; Robertson et al. 1994; Vitousek 1990; Westman 1990a; Williams CE 1993a, 1993c, 1996). Moreover, in a few specific instances, NI plants may be of ecological value in some systems, playing important structural and functional roles in recovery after disturbance or as surrogates for extirpated indigenous (IN) species (Bowler 1992; De Pietri 1992; Henry 1992, 1993; Lovejoy 1985; Lugo 1988; Whelan and Dilger 1992).