Endemism

The orange-breasted sunbird (Nectarinia violacea) is exclusively found in fynbos vegetation.

Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, nation, country 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. Another term for a species that is endemic, is precinctive - which applies to species (and subspecific categories) that are restricted to a defined geographical area.

Etymology

The word endemic entered the English language in the 17th century. It comes from the New Latin word endēmicus, which is the latinisation of the Greek word endēmos, meaning "native." Endēmos is formed of the words en, "in," and dēmos, "the people."^[1]

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.

Origin of the term precinctive

Precinctive seems to have been coined by eminent biogeographer and systematist David Sharp when he was discussing the Hawaiian fauna.^[2] He stated: “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.” That definition excludes artificial confinement of examples by humans in far-off botanical gardens or zoological parks.

Sharp coined the word precinctive because he objected to use of the word ‘endemic’ for such use, writing that “I use the word precinctive in preference to endemic or peculiar – both of which are in common use – in the sense of confined to the area under discussion. The word endemic has been objected to on the grounds that its definition does not indicate geographical restriction and that it is actually used in medicine to signify constant, but not necessarily exclusive presence in a locality.”

Sharp’s criticism of use of the word ‘endemic’ in the biogeographic sense was valid. When the word endemic was first used in English (from French, and originally spelled ‘endemique’ and given as the antonym of ‘epidemique’^[3]) it dealt with populations of human pathogens. Later the spelling was changed to ‘endemick’ but the subject still was epidemiology and the prevalence of pathogens, not geographic restriction.^[4] Biogeography is a discipline distinct from ecology.^[5] The ecological use of ‘endemic’ became expanded to plant pathogens and plants and animals, and is exemplified by Southwood and Comins: “The change from epidemic to endemic level may occur because…”^[6] and by Price “When the effect of enemies is disrupted or environmental conditions become particularly favorable for reproduction, the population escapes the stabilizing influence of enemies … and increases to epidemic proportions … However, shortage of food and disease may lead to massive mortality and low natality causing the population to crash to … endemic levels.”^[7] In ecology, endemic is the antonym of epidemic. It applies to populations of any kind of organism in which very high densities can alternate with very low ones.

Most biologists ignored Sharp’s coining of the word precinctive, and continued ‘thundering down the wrong track’ in using the late 19th century use of ‘endemic’ in a biogeographic sense instead of its original ecological sense. The result is that there are two major uses of the word ‘endemic’: (1) its original ecological sense (epidemiology and population dynamics, dating back to the early 17th century), and (2) its biogeographic sense dating back to the late 19th century. A third meaning arose when some 20th century writers began to confuse the term ‘indigenous’ with the biogeographic concept of ‘endemic’.

Some of the subsequent uses of the word precinctive can be found in Sharp, D. and Scott, H. 1908,^[8] Cockerell, T.D.A. 1914,^[9] MacCaughey, V. 1916,^[10] Bequaert, J. 1921 ^[11] and 1940,^[12] Gressitt, J.L. 1960,^[13] Snelling, R.R. 1966,^[14] Mackerras, I.M. 1970,^[15] Liebherr, J.K. 1997,^[16] Whitehead, D.R. and Ball, G.E. 1997,^[17] McCoy, E.D. and Mushinsky, H.R. 1999,^[18] Bossart, J.L. and Carlton, C.E. 2002,^[19] Majka, C.G. and Sikes, D.S. 2009,^[20] and Hughes, M.A., Shin, K., Eickwort, J. and Smith, J.A. 2012.^[21]

Precinctivity

Precinctivity (a noun) is the condition of being restricted to a specified geographical area. Apparently first used by MacCaughey in 1917. It is the equivalent of the unfortunate word ‘endemism’, which was based on the misappropriated word ‘endemic’ in its biogeographical sense.^[22]

Precinction

Precinction (a noun) is the condition of being restricted to a geographical area. Perhaps first used by Frank and McCoy (based on a word that had been used in English in 1730 meaning girdled about) who apparently failed to notice the earlier use of ‘precinctivity’ by MacCaughey 1917 in the botanical literature.^[23][24]

Ecoregions with high endemism/precinctivity

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

• Fynbos (South Africa)^[25]
• Hawaiian tropical dry forests (United States)^[26]
• Hawaiian tropical rainforests (United States)^[27]
• Kwongan heathlands (Australia)^[28]
• Madagascar dry deciduous forests (Madagascar)^[29]
• Madagascar lowland forests (Madagascar)^[30]
• New Caledonia dry forests (New Caledonia)^[31]
• New Caledonia rain forests (New Caledonia)^[32]
• Sierra Madre de Oaxaca pine-oak forests (Mexico)^[33]
• Sierra Madre del Sur pine-oak forests (Mexico)^[34]
• Luzon montane rainforests (Philippines)^[35]
• Luzon rainforests (Philippines)^[36]
• Luzon tropical pine forests (Philippines)^[37]
• Mindanao montane rain forests (Philippines)^[38]
• Mindanao-Eastern Visayas rain forests (Philippines)^[39]
• Palawan rain forests (Philippines)^[40]

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^[41][42]
• Slash-and-burn techniques employed by some cultures.

See also

• Native plant

References

Further reading

• Juan J. Morrone (1994). "On the Identification of Areas of Endemism". Systematic Biology 43 (3): 438–441. doi:10.1093/sysbio/43.3.438. 
• CDL Orme, RG Davies, M Burgess, F Eigenbrod, et al. (18 August 2005). "Global hotspots of species richness are not congruent with endemism or threat". Nature 436 (7053): 1016–9. doi:10.1038/nature03850. PMID 16107848. 
• JT Kerr (October 1997). "Species Richness, Endemism, and the Choice of Areas for Conservation". Conservation Biology 11 (55): 1094–1100. doi:10.1046/j.1523-1739.1997.96089.x. JSTOR 2387391.