PARENT SESSION
Session #21: Current status of knowledge on invasive species: Theory and practice. Organized by: R. C. Anderson and W. R. Perry.
Thursday, August 9, 2001. Madison Ballroom B
Predicting communities vulnerable to plant invasions.
Mack, Richard1, 1
ABSTRACT- Predicting the vulnerability of communities to plant naturalizations and invasions has proven to be challenging. The extreme differences among species in their opportunities for immigration to potential new ranges and the substantial differences in the total number of species in each biome greatly confounds gauges of community vulnerability based on species numbers and species diversity. The number of occurrences of even crudely-defined "similar climates" world-wide is a related complication; immigrant species do not always become naturalized in habitats with climates putatively similar to the climate in their native range. Nevertheless, some patterns are emerging in the quest for solutions. Geographically isolated sites usually support taxonomically isolated native floras as well, and these sites now often support very large naturalized floras. The native plants in such isolated areas may occupy roles from which they may be readily displaced by immigrants. Such geographic isolation, of course, influences the evolution of all other forms of life. For example, native grazers, predators and parasites may all lack any means to attack immigrant species. The likelihood of attack correlates roughly with the taxonomic relatedness of immigrants to native plants in the new range; immigrants without even familial representatives among the natives may avoid any substantial interaction with native predators, grazers and parasites. Thus, such immigrants appear to have a higher likelihood of naturalization compared with immigrants with native congeners. Many exceptions nevertheless occur. Predicting community vulnerability will require much better understanding of the taxonomic relatedness of native and immigrant species than has been heretofore envisioned.
KEY WORDS: invaders, immigrants, naturalization, invasions