Invasive Species Mechanisms

Propagule Pressure

• If the number of introductions exceed the “threshold” that herbivores can control than successful invasion occurs

Empty Niche Hypothesis

• Exotics can be successful in a new community accessing resources not being utilized by local species

Invasion Meltdown hypothesis

• Increasing number of exotic species facilitate additional invasions

Natural Enemies Hypothesis

• Natural enemies supports plants in their native range and it is the escape from these enemies allowing exotics populations to explode

Biotic resistance hypothesis

• Exotics fail to establish and spread due to negative interactions between the introduced species and the native biota