Remote oceanic islands are characterized as having disharmonic biota, meaning th

This pattern stems from the random nature of the ancestral colonization of those islands. Successfully colonizing a remote island is rare, but in the vastness of time such events occur regularly. Precisely what groups make it is a matter of chance, but some have a far greater likelihood than others. Flying animals, for example, are more likely colonists than large or sensitive terrestrial animals (and in fact no native mammals or amphibians are found on the remotest islands). Since the colonization process is random, each island system experiences a unique colonization history. Thus, each will have its own complement of taxa from continental areas, which, depending on the timing of ancestral colonization and the available niches, will spread and diversify to different degrees on each.