You identify five endemic species of mammals living on an island a short distance from the mainland. You also identify each species' closest relative on the mainland. Two alternatives exist to explain this group of species: Hypothesis

1. The ancestors of the current island species dispersed from the mainland to the island and subsequently diverged on the island (dispersal). Hypothesis
2. The island was originally part of the mainland but a rise in sea level resulted in its being cut off, with the result that the mammals on the island diverged from the ones on the mainland (vicariance).