Final answer:
The statement is true; the South American mainland and the Caribbean islands have distinct ecological niches and species due to evolutionary processes of isolation and adaptation, resulting in different morphologies, especially among anoles.
Step-by-step explanation:
The statement that the South American mainland has very different ecological niches than the Caribbean islands, and mainland anoles have very different morphologies is true. This diversity is largely due to the evolutionary processes of isolation and adaptation in these different environments. For instance, the Caribbean islands are known for their high number of endemic species, which have evolved due to their separation from mainland ancestors. This is in contrast to the various biomes of the South American mainland, such as the tropical wet forest, that support a different array of plant and animal life.
Furthermore, studies have shown that South American temperate plants are more closely related to South American tropical plants than to temperate plants found in Europe, signifying the influence of regional continuity and shared ecological and evolutionary history. The biogeographic realms also highlight the differences in biodiversity; the Neotropics, which include South America, is considered one of the most biodiverse regions, particularly in terms of amphibians, reptiles, birds, and mammals.
In summary, different ecological conditions, geological history, and evolutionary paths have led to a distinct range of species and morphologies on the South American mainland compared to those found on the Caribbean islands, underscoring the truth of the statement.