Which communities are more vulnerable to invasion by outside plants and animals?
Tropical evergreen forests
Oceanic island communities
Islands are generally lacking in species richness, trophic complexity, and functional diversity as compared to other mainland ecosystems. The result of this is low biotic resistance to invasion and many empty niches available for exploitation. The residents of such communities are incapable of dealing with predators, herbivores, and strong competitors. Thus, the invaders tend to be much more successful on oceanic islands and their impacts tend to be much stronger, which results in the extinctions and restructuring of communities.
So, the correct answer is 'Oceanic island communities'