Endemism is the state of a
An endemic species can also be referred to as an endemism or in scientific literature as an endemite. For example Cytisus aeolicus is an endemite of the Italian flora. Adzharia renschi was once believed to be an endemite of the Caucasus, but it was later discovered to be a non-indigenous species from South America belonging to a different genus.Some endemics are restricted to very small ranges. Tahina spectabilis for example is native to only 12 acres (4.8 hectares) and the tiny waterlily Nymphaea thermarum was native to a single thermal mudhole in Ruwanda of a few square yards (a few square meters)
The extreme opposite of an endemic species is one with a cosmopolitan distribution, having a global or widespread range.
A rare alternative term for a species that is endemic is "precinctive", which applies to species (and other taxonomic levels) that are restricted to a defined geographical area. Other terms that sometimes are used interchangeably, but less often, include autochthonal, autochthonic, and indigenous, however, these terms do not reflect the status of a species that specifically belongs only to a determined place.
History of the concept
The word endemic is from
The more uncommon term 'precinctive' has been used by some
Endemism in general excludes examples kept by humans in
Endemism is caused by historical and ecological factors.
The stability of a region's climate and habitat through time may also contribute to high rates of endemism (especially
Microorganisms were traditionally not believed to form endemics. The hypothesis 'everything is everywhere', first stated in Dutch by Lourens G.M. Baas Becking in 1934, describes the theory that the distribution of organisms smaller than 2mm is cosmopolitan where habitats occur that support their growth.
The first subcategories were first introduced by Claude P. E. Favager and Juliette Contandriopoulis in 1961: schizoendemics, apoendemics and patroendemics.
Paleoendemism refers to species that were formerly widespread but are now restricted to a smaller area.
Paleoendemism is more or less synonymous with the concept of a '
Schizoendemics, apoendemics and patroendemics can all be classified as types of neoendemics. Schizoendemics arise from a wider distributed taxon that has become reproductively isolated without becoming (potentially) genetically isolated – a schizoendemic has the same
Pseudoendemics are taxa that have possibly recently evolved from a mutation. Holoendemics is a concept introduced by Richardson in 1978 to describe taxa that have remained endemic to a restricted distribution for a very long time.
In a 2000 paper, Myers and de Grave further attempted to redefine the concept. In their view, everything is endemic, even cosmopolitan species are endemic to Earth, and earlier definitions restricting endemics to specific locations are wrong. Thus the subdivisions neoendemics and paleoendemics are without merit regarding the study of distributions, because these concepts consider that an endemic has a distribution limited to one place. Instead, they propose four different categories: holoendemics, euryendemics, stenoendemics and rhoendemics. In their scheme cryptoendemics and euendemics are further subdivisions of rhoendemics. In their view, a holoendemic is a cosmopolitan species. Stenoendemics, also known as local endemics,
Isolated islands commonly develop a number of endemics. Many species and other higher taxonomic groups exist in very small terrestrial or aquatic islands, which restrict their distribution. The Devil's Hole pupfish, Cyprinodon diabolis, has its whole native population restricted to a spring that is 20 x 3 meters, in Nevada's Mojave Desert. This 'aquatic island' is connected to an underground basin; however, the population present in the pool remains isolated.
Other areas very similar to the Galapagos Islands of the Pacific Ocean exist and foster high rates of endemism. The Socotra Archipelago of Yemen, located in the Indian Ocean, has seen a new endemic species of parasitic leech, Myxobdella socotrensis, appear. This species is restricted to freshwater springs, where it may attach to and feed upon native crabs.
Mountains can be seen as '
Volcanoes also tend to harbor a number of endemic species. Plants on volcanoes tend to fill a specialized ecological niche, with a very restrictive range, due to the unique environmental characteristics. The Kula Volcano, one of the fourteen volcanoes in Turkey, is home to 13 endemic species of plants.
Endemics might more easily become
The concept of finding endemic species that occur in the same region to designate 'endemism hotspots' was first proposed by Paul Müller in a 1973 book. According to him, this is only possible where 1.) the taxonomy of the species in question is not in dispute; 2.) the species distribution is accurately known; and 3.) the species have relatively small distributional ranges.
In a 2000 article, Myers et al. used the standard of having more than 0.5% of the world's plant species being endemic to the region to designate 25 geographical areas of the world as 'biodiversity hotspots'.
In response to the above, the
Other scientists have argued that endemism is not an appropriate measure of biodiversity, because the levels of threat or biodiversity are not actually correlated to areas of high endemism. When using bird species as an example, it was found that only 2.5% of biodiversity hotspots correlate with endemism and the threatened nature of a geographic region.
Other conservation efforts for endemics include keeping captive and semi-captive populations in zoological parks and botanical gardens. These methods are ex situ ("off-site") conservation methods. The use of such methods may not only offer refuge and protection for individuals of declining or vulnerable populations, but it may also allow biologists valuable opportunities to research them as well.
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I use the word precinctive in the sense of 'confined to the area under discussion' ... 'precinctive forms' means those forms that are confined to the area specified.
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- The dictionary definition of endemicat Wiktionary