What are the predictions of the island biogeography theory?

The Island Biogeography Theory (IBT) is an ecological theory that predicts how the size and distance between islands influence the number of species on them. According to IBT, the larger an island and the closer it is to the mainland, the more species it will be able to support. Furthermore, IBT states that species diversity on an island is determined by the balance between immigration (the arrival of species to settle on the island) and extinction (the death of species that cannot survive on the island), and that this balance is determined by the size and distance of the island from the mainland.