Community Level Consequences of a Biological Invasion : Effects of a Non-native Vine on Three Plant Communities

Biological invasions by non-native species are a global phenomenon that have the capacity to dramatically alter native communities and ecosystems. Despite the alarming rate and scale of these Invasions, surprisingly few studies have explored the effects of exotic plant species on the communities they invade. This shortage is particularly troubling because land managers require such information to prioritize control activities and address future challenges. In this study, I investigated the influence of cape-ivy (Delairea odorata; Asteraceae), a non-native vine from South Africa, on the species richness, diversity and composition of three coastal plant communities in northern California. Using both experimental and non-experimental methods. this research demonstrated that plots invaded by cape-ivy contained significantly fewer plant species and exhibited lower species diversity than plots lacking cape-iv~. These effects were consistent across three different habitat types -coastal scrub, Willow riparian and alder riparian. Invasion by cape-ivy also significantly reduced the abundance and richness of seedlings in all three habitat types. These results indicate that cape-ivy has had significant negative impacts on three divergent plant communities, and that control of this invasive plant should be a major priority for land managers