Islands are incredible breeding grounds for evolution. A huge number of new, rare, and exotic species are not just found on islands — they’re created by them.
The birth of new species is fueled by islands because they, due to their isolated nature, break off small groups of a larger species and encourage it to mutate. In genetics, this effect is called the founder effect, and it occurs whenever a small population is isolated.
One or two members of that small population may carry a unique mutation or trait. Normally, that mutation would get lost in a large population and wouldn’t persist — but on an island, there may only be a couple other members of that species, and so the mutation is far more likely to get passed on.