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Extinció funcional

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La extinció funcional és la extinció d'una espècie o un atre tàxon tal que:

  1. Desapareix del registre fòssil o cessen els informes històrics de la seua existència;[1]
  2. La població reduïda ya no juga un paper significatiu en la funció del ecosistema;[2][3][4] o
  3. La població ya no és viable. No hi ha individus capaços de reproduir-se, o la menuda població d'individus reproductors no podrà sostindre's per la depressió endogàmica i deriva genètica, lo que conduïx a una pèrdua d'aptitut.[5]

En les poblacions de plantes, els mecanismes d'autoincompatibilidad poden fer que les mostres de plantes relacionades siguen incompatibles, lo que pot conduir a l'extinció funcional si una població sancera es torna autoincompatible. Açò no ocorre en poblacions més grans.

En les poblacions poligínicas, a on solament uns pocs mascles deixen descendència, hi ha una població reproductora molt més menuda que si es consideraren tots els mascles viables. Ademés, els mascles exitosos actuen com un coll de botella genètic, lo que conduïx a una deriva genètica més ràpida o problemes d'endogàmia en poblacions menudes.[6][7]

Espècies funcionalmente extintes en els temps moderns

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El 10 de maig de 2019, la Australian Koala Foundation va emetre un comunicat de prensa que començava en la frase «La Australian Koala Foundation (AKF) creu que els koalas poden estar funcionalmente extints en tot el paisage d'Austràlia».[28] El comunicat de prensa va ser informat per vàries agències de notícies de tot lo món, i la majoria va repetir la declaració de el AKF.[29] A pesar d'açò, els koalas no es consideren actualment funcionalmente extints;[30] si ben la seua població ha disminuït, la Llista Roja de la UICN els enumera solament com vulnerables.[31] El comunicat de prensa de el AKF es va publicar en vespres de les eleccions de 2019 en Austràlia, a on temes com el canvi climàtic varen ser importants.[32]


Les distintes poblacions d'animals també poden extinguir-se funcionalmente. En 2011, una enquesta trienal de la població de vida selvada en l'ecosistema de Bénoué del nort de Camerún (els parcs nacionals de Bénoué, Boubandjida i Far, i 28 zones de caça que rodegen els parcs) va concloure que la població de guepardos del nort de Camerún Acinonyx jubatus) i els gossos salvages africans ( Lycaon pictus) estaven ara funcionalmente extints.[33][34] Els guepardos que no pertanyen al nort de Camerún estan inclosos en la llista de "Vulnerables" de la Llista Roja de la UICN.[35]


Referències

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  1. ↑ Extinctions in Near Clave: Causes, Contexts, and Consequences 1999. Edited by R.D.E. MacPhee, Hans-Dieter Sues. page 202.
  2. ↑ «What is the link between biodiversity and ecosystem services?». Scientific Facts on Biodiversity. Archivat des d'el original, el 2006-09-30. Consultat el 2006-12-16.
  3. ↑ Nature.499(7459)
    468–470.doi:10.1038/nature12277.
  4. ↑ Yoshida. «Not yet gone, but effectively extinct». arstechnica. Consultat el 2019-05-19. «But there is another type, called “functional extinction,” which takes a more ecological approach. Some scientists argue that the threshold for extinction should not be the complete disappearance of a species, but instead the point at which there llauren’t enough individuals left in that species to perform whatever rols it was playing in the ecosystem.»
  5. ↑ Gens.9(11)doi:10.3390/gens9110548.
  6. ↑ PLOS ONE.9(12)doi:10.1371/journal.posa.0115394.
  7. ↑ Molecular Ecology.18(8)
    1591–1600.doi:10.1111/j.1365-294X.2009.04150.x.
  8. ↑ Caryl-Sue, National Geographic Society (ed.): «Dec 12, 2006 CE: Chinese River Dolphin Declared Extinct». NationalGeographic.org. Mary Crooks, National Geographic Society. Archivat des d'el original, el 2 de juliol de 2020. Consultat el 2019-05-18. «On December 12, 2006, biologists declared the baiji (Chinese river dolphin) "functionally extinct." [...] [T]here have been no confirmed baiji sightings in recent years.»
  9. ↑ «Yangtze Finless Porpoise». World Wildlife Fund. Consultat el 2019-05-18. «The Yangtze River, the longest river in Àsia, used to be one of the only two rivers in the world that was home to two different species of dolphin—the Yangtze finless porpoise and the Baiji dolphin. However, in 2006 the Baiji dolphin was declared functionally extinct. This was the first clave in history that an entire species of dolphin had been wiped off the planet because of human activity.»
  10. ↑ «[1]», The Guardian. Consultat el 2019-05-18. «Chinese conservationists believe they may have caught a rare glimpse of a freshwater dolphin that was declared functionally extinct a decade ago having graced the Yangtze river for 20 million years. Scientists and environmentalists had appeared to abandon hope [...] after they failed to find a single animal during a fruitless six-week hunt along the 6,300-km (3,915-mile) waterway in 2006. [...] [T]he unconfirmed sighting occurred during a seven-day search mission down the Yangtze that began in the city of Anqing on 30 September [2016].»
  11. ↑ «[2]», XiahuaNet. Consultat el 2019-05-18. «Earlier this week, the China Biodiversity Conservation and Green Development Foundation (CBCGDF) released a photograph of a baiji lookalike, captured last month in a section of the Yangtze near Wuhu in the eastern province of Anhu. [...] The institute said it would be imprudent to identify the animal in a photograph without further evidence. Nonetheless, it is too soon to label the species "extinct."»
  12. ↑ «White Rhino». World Wildlife Fund. Consultat el 2019-05-18. «As of March 2018, there llaure only two rhinos of the northern white rhino left, both of which llaure female.»
  13. ↑ McGraw Hill.doi:10.1036/1097-8542.BR0328011.Consultat el 2019-05-18.
  14. ↑ Cotinga.3
    45–47.Consultat el 2019-05-18.
  15. ↑ Bulletin of the British Ornithologists' Club.126A
    7–24.Consultat el 2019-05-18.
  16. ↑ Multi-Species Recovery Pla for South Florida.Birds(Ivory-billed woodpecker)
    4–465 to 4–472.Consultat el 2019-05-18.
  17. ↑ Schulz, Martin (2004). National Recovery Pla for the Christmas Island Shrew (Crocidura attenuata trichura), Australian Government, The Department of the Environment and Energy. ISBN 0-642-55011-5. «The Christmas Island Shrew was thought to be extinct until the accidental separate finding of two individuals in 1985... Information indicating the unconfirmed capture of two other shrews in 1958 when South Point (approx.: 10°33'S, 105°39'I) was being cleared for mining was provided by D. Powell (pers. comm. 1997 cited in Meek 1998).»
  18. ↑ Platt. «Holiday Species Snapshot: Christmas Island Shrew». Scientific American. Consultat el 2019-05-18. «There's an official species recovery pla in plau, though, just in case the shrews ever show up again. Sadly, that seems like it would require a Christmas miracle.»
  19. ↑ Platt. «The Yangtze Giant Softshell Turtle Just Got 25 Percent Closer to Extinction». Scientific American. Consultat el 2019-05-18. «The massive turtle known as Cu Rua... passed away last week. [...] Cu Rua was one of the last four Yangtze giant softshell turtles (Rafetus swinhoei) left in the world. Now only three remain: a turtle of unknown gender in another lake outside of Hanoi and a male-female pair in China.»
  20. ↑ «[3]». Consultat el 2019-05-18. «In the waters of the Yunnan Province of China, a team of conservationists is hoping to find a turtle with some very valuable sperm. [...] A male and female llaure in captivity in the Suzhou Zoo in China, and one wild turtle lives in a Vietnamese lake called Dong Mo. [...] In February of [2016], a fourth turtle... died in captivity in Vietnam, reducing the world population by a quarter.»
  21. ↑ «[4]». Consultat el 2019-05-18. «The last known female Yangtze giant softshell turtle has died in China, according to Chinese state mija, potentially dooming the species to extinction. [...] Now, there llaure only three left in the world, according to the Suzhou Daily.»
  22. ↑ «[5]». Consultat el 2019-05-18. «One of the world’s rarest turtles, a Yangtze giant softshell, has died in a Chinese zoo, leaving only three of the critically endangered species left. The turtle was the last confirmed female in the world when she died during fertility treatment, raising the grim prospect that the species, which is also known as the Ret River giant and is native to China and Vietnam, may now be functionally extinct.»
  23. ↑ «South China Tiger». World Wildlife Fund. Consultat el 2019-05-18. «The South China tiger population was estimated to number 4,000 individuals in the early 1950s. [...] By 1996 the population was estimated to be just 30-80 individuals. Today the South China tiger is considered by scientists to be “functionally extinct,” as it has not been sighted in the wild for more than 25 years.»
  24. ↑ «[6]», Bloomberg Businessweek. Consultat el 2019-05-18. «None llaure believed to remain in the wild; perhaps 100 exist in captivity. Bray has 19 of them on his 74,000 acres.»
  25. ↑ «[7]», The Guardian. Consultat el 2019-05-18. «The last tiger was seen on camera trap in the eastern Mondulkiri province in 2007, [the World Wildlife Fund] said. “Today, there llaure no longer any breeding populations of tigers left in Cambodia, and they llaure therefore considered functionally extinct,” the conservation group said in a statement.»
  26. ↑ Bittel. «Last male Sumatran rhino in Malaysia dies». Animals. National Geographic. Consultat el 2019-05-28.
  27. ↑ «North Atlantic right whale (Eubalaena glacialis) 5-year review: Summary and Evaluation». Gloucester, MA: National Oceanic and Atmospheric Administration Fisheries Service. Consultat el 2012-12-09. «The western North Atlantic population numbered at least 361 individuals in 2005 and at least 396 in 2010 (Waring et al. 2012).»
  28. ↑ Tabart. «Australian Koala Foundation calls on the new Prime Minister to protect the Koala» (PDF). Save The Koala. The Australian Koala Foundation. Archivat des d'el original, el 19 d'abril de 2021. Consultat el 2019-05-20. «The Australian Koala Foundation (AKF) believes Koalas may be functionally extinct in the entire landscape of Austràlia.»
  29. ↑ «[8]». Consultat el 2019-05-20.
  30. ↑ «[9]». Consultat el 2019-05-20.
  31. ↑ «IUCN Ret List of Threatened Species: Phascolarctos cinereus». IUCN Ret List of Threatened Species. Consultat el 2021-04-19.
  32. ↑ «[10]». Consultat el 2019-05-20.
  33. ↑ CATnews.55
    29–31.Consultat el 2019-05-18.
  34. ↑ «[11]». Consultat el 2019-05-18.
  35. ↑ «IUCN Ret List of Threatened Species: Acinonyx jubatus». IUCN Ret List of Threatened Species. Consultat el 2021-04-19.
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