Neoendemic And Paleoendemic Islands

Neoendemics typically form on isolated islands that have been created de novo and have abundant empty ecological space into which those few colonists can diversify. Besides Hawaii, other volcanic archipelagoes, including the Marquesas, Societies, and Galapagos in the Pacific and the Canaries in the Atlantic, have provided ideal conditions for the formation of neoendemics. However, species can also form on fragment islands, formed as a mass of land has broken away from a larger continental region. Examples of such islands include some of the Caribbean islands, and the islands of New Zealand and Madagascar. As these islands, formed upon losing connection with a continental source, become more isolated, gene flow between island and continental populations may become insufficient to overcome genetic divergence. Unlike volcanic islands that form in isolation, starting without any species and accumulating species through time, fragment islands are usually ecologically saturated at the time of separation and tend to lose species through ecological time, a process termed relaxation. Over evolutionary time, the species on these islands may change through relictualization, with the formation of paleoendemics, usually without adaptive radiation.

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