Editing Extinction (section)

=== Genetic pollution ===
{{Main|Genetic pollution}}
Extinction sometimes results for species evolved to specific ecologies<ref>{{cite journal |last=Mooney |first=H.A. |author2=Cleland, E.E. |year=2001 |title=The evolutionary impact of invasive species |journal=[[Proceedings of the National Academy of Sciences|PNAS]] |volume=98 |issue=10 |pages=5446–5451 |doi=10.1073/pnas.091093398 |pmid=11344292 |pmc=33232 |bibcode=2001PNAS...98.5446M |doi-access=free}}</ref> that are subjected to [[genetic pollution]]—i.e., uncontrolled [[Hybrid (biology)|hybridization]], [[introgression]] and genetic swamping that lead to homogenization or [[Fitness (biology)|out-competition]] from the introduced ([[Heterosis|or hybrid]]) species.<ref>{{cite web |url=http://www.nativeseednetwork.org/article_view?id=13 |title=Glossary: definitions from the following publication: Aubry, C., R. Shoal and V. Erickson. 2005. Grass cultivars: their origins, development, and use on national forests and grasslands in the Pacific Northwest. USDA Forest Service. 44 pages, plus appendices.; Native Seed Network (NSN), Institute for Applied Ecology, 563 SW Jefferson Ave, Corvallis, OR 97333, USA |archive-url=https://web.archive.org/web/20060222092651/http://www.nativeseednetwork.org/article_view?id=13 |archive-date=22 February 2006 |url-status=dead}}</ref> Endemic populations can face such extinctions when new populations are imported or [[selective breeding|selectively bred]] by people, or when habitat modification brings previously isolated species into contact. Extinction is likeliest for [[rare species]] coming into contact with more abundant ones;<ref name="RareEucalypts"/> [[interbreeding]] can swamp the rarer gene pool and create hybrids, depleting the purebred gene pool (for example, the endangered [[wild water buffalo]] is most threatened with extinction by genetic pollution from [[Water buffalo|the abundant domestic water buffalo]]). Such extinctions are not always apparent from [[morphology (biology)|morphological]] (non-genetic) observations. Some degree of [[gene flow]] is a normal evolutionary process; nevertheless, hybridization (with or without introgression) threatens rare species' existence.<ref>{{cite journal |title=Extinction by Hybridization and Introgression |first1=J.M. |last1=Rhymer |first2=D. |last2=Simberloff |journal=Annual Review of Ecology and Systematics |date=November 1996 |volume=27 |issue=1 |pages=83–109 |doi=10.1146/annurev.ecolsys.27.1.83 |publisher=Annual Reviews |quote=Introduced species, in turn, are seen as competing with or preying on native species or destroying their habitat. Introduces species (or [[subspecies]]), however, can generate another kind of extinction, a genetic extinction by hybridization and introgression with native flora and fauna |jstor=2097230 |bibcode=1996AnRES..27...83R}}</ref><ref>{{cite book |title=Genetic pollution from farm forestry using eucalypt species and hybrids : a report for the RIRDC/L&WA/FWPRDC Joint Venture Agroforestry Program |first1=Brad M. |last1=Potts |others=Robert C. Barbour, Andrew B. Hingston |date=September 2001 |isbn=978-0-642-58336-9 |publisher=Australian Government, Rural Industrial Research and Development Corporation}}</ref>

The gene pool of a [[species]] or a [[population]] is the variety of genetic information in its living members. A large gene pool (extensive [[genetic diversity]]) is associated with robust populations that can survive bouts of intense [[Selection (biology)|selection]]. Meanwhile, low genetic diversity (see [[inbreeding]] and [[population bottlenecks]]) reduces the range of adaptions possible.<ref>
{{cite web |url=http://adl.brs.gov.au/data/warehouse/brsShop/data/12858_10_1_3.pdf |title=Genetic diversity |page=104 |year=2003 |access-date=2010-05-30 |quote=In other words, greater genetic diversity can offer greater resilience. In order to maintain the capacity of our forests to [[adaption|adapt]] to future changes, therefore, genetic diversity must be preserved |url-status=dead |archive-url=https://web.archive.org/web/20110313092336/http://adl.brs.gov.au/data/warehouse/brsShop/data/12858_10_1_3.pdf |archive-date=2011-03-13}}</ref> Replacing native with alien genes narrows genetic diversity within the original population,<ref name="RareEucalypts">
{{cite web |url=http://adl.brs.gov.au/data/warehouse/brsShop/data/12858_10_1_3.pdf |title=Australia's state of the forests report |page=107 |year=2003 |url-status=dead |archive-url=https://web.archive.org/web/20110313092336/http://adl.brs.gov.au/data/warehouse/brsShop/data/12858_10_1_3.pdf |archive-date=2011-03-13}}</ref><ref>{{cite journal |last1=Lindenmayer |first1=D. B. |last2=Hobbs |first2=R. J. |last3=Salt |first3=D. |title=Plantation forests and biodiversity conservation |journal=Australian Forestry |date=January 2003 |volume=66 |issue=1 |pages=62–66 |doi=10.1080/00049158.2003.10674891 |bibcode=2003AuFor..66...62L |s2cid=53968395 |url=https://researchrepository.murdoch.edu.au/id/eprint/4637/1/plantation_forests.pdf |access-date=9 February 2022 |archive-date=17 February 2022 |archive-url=https://web.archive.org/web/20220217143102/https://researchrepository.murdoch.edu.au/id/eprint/4637/1/plantation_forests.pdf |url-status=live}}</ref> thereby increasing the chance of extinction.