What is an Exotic Species?
The National Park Service defines native species as all species that have occurred, now occur, or may occur as a result of natural processes on lands designated as units of the national park system. Native plants evolve within their own ecological niche in concert with other native plants. Biodiversity exists when species are constrained in their growth by natural factors so that they can't overrun neighboring species. Natural growth restraints include competition with other native species, diseases, feeding by insects and other animals, climate, etc.