Endemism



Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation, county or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. The extreme opposite of endemism is cosmopolitan distribution.

Overview
Physical, climatic, and biological factors can contribute to endemism. The orange-breasted sunbird is exclusively found in the fynbos vegetation zone of southwestern South Africa. The glacier bear is found only in limited places in Southeast Alaska. Political factors can play a part if a species is protected, or actively hunted, in one jurisdiction but not another.

There are two subcategories of endemism – paleoendemism and neoendemism. Paleoendemism refers to a species that was formerly widespread but is now restricted to a smaller area. Neoendemism refers to a species that has recently arisen such as a species that has diverged and become reproductively isolated, or one that has formed following hybridization and is now classified as a separate species. This is a common process in plants, especially those that exhibit polyploidy.

Endemic types or species are especially likely to develop on biologically isolated areas such as islands because of their geographical isolation. This includes remote island groups, such as Hawaii, the Galápagos Islands, and Socotra, biologically isolated but not island areas such as the highlands of Ethiopia, or large bodies of water like Lake Baikal.

Endemics can easily become endangered or extinct if their restricted habitat changes, particularly but not only due to human actions, including the introduction of new organisms. There were millions of both Bermuda Petrels and "Bermuda cedars" (actually junipers) in Bermuda when it was settled at the start of the seventeenth century. By the end of the century, the petrels were thought extinct. Cedars, already ravaged by centuries of shipbuilding, were driven nearly to extinction in the twentieth century by the introduction of a parasite. Bermuda petrels and cedars, although not actually extinct, are very rare today, as are other species endemic to Bermuda.

Ecoregions with high endemism
According to the World Wildlife Fund, the following ecoregions have the highest percentage of endemic plants:


 * Fynbos (South Africa)
 * Hawaiian tropical dry forests (United States)
 * Hawaiian tropical rainforests (United States)
 * Kwongan heathlands (Australia)
 * Madagascar dry deciduous forests (Madagascar)
 * Madagascar lowland forests (Madagascar)
 * New Caledonia dry forests (New Caledonia)
 * New Caledonia rain forests (New Caledonia)
 * Sierra Madre de Oaxaca pine-oak forests (Mexico)
 * Sierra Madre del Sur pine-oak forests (Mexico)
 * Luzon montane rainforests (Philippines)
 * Luzon rainforests (Philippines)
 * Luzon tropical pine forests (Philippines)
 * Mindanao montane rain forests (Philippines)
 * Mindanao-Eastern Visayas rain forests (Philippines)
 * Palawan rain forests (Philippines)

Threats to highly endemistic regions
Some of the principal causes of habitat degradation and loss in these ecosystems are:


 * Agriculture
 * Urban growth
 * Surface mining
 * Mining of oil, metals and minerals
 * Large scale logging operations
 * Slash-and-burn techniques employed by some cultures.