Endemism is the restriction of a biological taxon's native distribution to a specified geographic region. A species can be endemic to one island, an archipelago or a continent; the region must be stated. Presence within a region is insufficient: the defining point is that its native range does not extend elsewhere at the stated scale.
The Seychelles warbler supplies a useful scale comparison. The research team's account identifies it as endemic to the Seychelles and describes conservation species translocations from the remnant Cousin Island population to other islands within the archipelago. Establishing populations on several Seychelles islands is compatible with endemism to the Seychelles; it is incompatible with describing its range as confined to Cousin Island alone.[ref]
Seychelles Warbler Project overview. Research team's introductory species account and translocation history; destinations include Aride, Cousine, Denis and Fregate.
Charles Darwin used island distributions as evidence in biogeography. In the first edition of On the Origin of Species by Charles Darwin, he explained endemic forms as those found nowhere else and compared affinities of island organisms with nearby mainland organisms. His Galápagos and Cape Verde comparisons connected geographic barriers and colonization with evolutionary modification.[ref]
On the Origin of Species by Charles Darwin. First edition (1859), chapter XII, p. 390 definition; pp. 398–403 island affinities and differences.
Endemism is a pattern to explain, not a complete explanation of origin. A restricted range may reflect local speciation, limits to dispersal, or survival after extinction elsewhere. Nor does endemism by itself imply rarity or low local density: a common organism can be geographically restricted. This is the geographic use of the term; epidemiological endemicity concerns a different kind of persistence.
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Endemism refers to the ecological phenomenon where a species is native to and restricted to a specific geographic area. This area can range from a particular country or region to an island or even smaller locations, such as a single mountain or habitat. Endemic species are not found naturally anywhere else outside of that designated area. Endemism is often used to describe plants and animals, and it can arise due to various factors, including geographic isolation, evolutionary processes, and environmental conditions specific to a region.