Final answer:
A tree island is typically a tropical hardwood hammock, an 'island' of hardwood trees found in ecosystems like the Everglades. This term is specific to Florida and the Caribbean. Tropical rainforests are often chosen as the basis for ecological preserves due to their high biodiversity and multiple niches.
Step-by-step explanation:
In the context of ecosystems and biodiversity, a tree island refers to small patches of forested land that appear as 'islands' within a different type of ecosystem. Among the options provided, tropical hardwood hammock fits this description. It is an ecological term specific to Florida and the Caribbean, referring to a stand of hardwood trees that form an ecological 'island' within a more contrasting ecosystem, such as a wetland or grassland. This type of hammock is often found in areas like the Everglades, where they are slightly elevated compared to the surrounding marshes or wetlands, and provide a rich, biodiverse habitat for a variety of species.
When considering which ecosystem forms the basis of a new ecological preserve designed to host a variety of niches and species, islands or tropical rain forests are often prime candidates. Both tend to have high levels of biodiversity and can foster multiple ecological niches within a limited space. However, the tropical rainforest, in particular, is known for its incredible biodiversity and variety of habitats within a compact area, making it a strong foundation for preserve design.