COMMUNITY INVASIBILITY AND ITS INFLUENCING FACTORS

The extent to which a community was invaded by alien species is often evaluated by invasibility, which can be affected by the mortality of exotic species, climate, the properties of the native species, the level of disturbance, and the ecosystem's resistance to invasion. Comparison of invasibility between communities or regions is usually based on the number and richness of exotic species, but neither index acts as a good criterion because each often represents a single aspect of the dynamic process in communities. Using a simple model describing the number of exotic species we show that invasibility is hardly comparable between regions because of intricate controlling factors, which include the invasion process, the properties of the invasive species, and the resistance to invasion of native species and the local community. We also introduce several important concepts in invasion ecology such as invasibility, invasion potential and propagule pressure.