Editing Hybrid (biology) (section)

==Human influence==

===Anthropogenic hybridization===

Hybridization is greatly influenced by human impact on the environment,<ref name="A2001">{{cite journal |last1=Allendorf |first1=Fred W. |last2=Leary |first2=R. F. |last3=Spruell |first3=P. |last4=Wenburg |first4=J. K. |title=The problems with hybrids: setting conservation guidelines |journal=Trends in Ecology & Evolution |date=2001 |volume=16 |issue=11 |pages=613–622|doi=10.1016/S0169-5347(01)02290-X}}</ref> through effects such as [[habitat fragmentation]] and species introductions.<ref>{{cite journal |last1=Ehrlich |first1=Paul |author-link=Paul Ehrlich |first2=John |last2=Holdren |title=Impact of population Growth |journal=Science |date=26 March 1971 |volume=171 |pages=1212–1216 |doi=10.1126/science.171.3977.1212 |issue=3977 |pmid=5545198|bibcode=1971Sci...171.1212E}}</ref> Such impacts make it difficult to [[conservation genetics|conserve the genetics]] of populations undergoing [[introgression|introgressive hybridization]]. Humans have introduced species worldwide to environments for a long time, both intentionally for purposes such as [[biological control]], and unintentionally, as with accidental escapes of individuals. Introductions can drastically affect populations, including through hybridization.<ref name="A2007" /><ref>{{Cite journal |last1=Vitousek |first1=Peter M. |last2=D'Antonio |first2=Carla M. |last3=Loope |first3=Lloyd L. |last4=Rejmánek |first4=Marcel |last5=Westbrooks |first5=Randy |date=1997 |title=Introduced Species: A Significant Component of Human-Caused Global Change |url=https://www.jstor.org/stable/24054520 |journal=New Zealand Journal of Ecology |volume=21 |issue=1 |pages=1–16 |jstor=24054520 |issn=0110-6465}}</ref>

===Management===
[[File:Aquilegia pubescens-formosa hybrid-swarm flowers close.jpg|thumb|Examples of hybrid flowers from [[hybrid swarm]]s of ''[[Aquilegia pubescens]]'' and ''[[Aquilegia formosa]]'']]

There is a kind of continuum with three semi-distinct categories dealing with anthropogenic hybridization: hybridization without introgression, hybridization with widespread introgression (backcrossing with one of the parent species), and [[hybrid swarm]]s (highly variable populations with much interbreeding as well as backcrossing with the parent species). Depending on where a population falls along this continuum, the management plans for that population will change. Hybridization is currently an area of great discussion within [[wildlife management]] and habitat management. [[Global warming|Global climate change]] is creating other changes such as difference in population distributions which are indirect causes for an increase in anthropogenic hybridization.<ref name="A2001" />

Conservationists disagree on when is the proper time to give up on a population that is becoming a hybrid swarm, or to try and save the still existing pure individuals. Once a population becomes a complete mixture, the goal becomes to conserve those hybrids to avoid their loss. Conservationists treat each case on its merits, depending on detecting hybrids within the population. It is nearly impossible to formulate a uniform hybridization policy, because hybridization can occur beneficially when it occurs "naturally", and when hybrid swarms are the only remaining evidence of prior species, they need to be conserved as well.<ref name="A2001" />

===Genetic mixing and extinction===
{{Main|Genetic pollution}}
{{further|Genetic mixing|Introgression}}

Regionally developed [[ecotype]]s can be threatened with [[extinction]] when new alleles or genes are introduced that alter that ecotype. This is sometimes called genetic mixing.<ref>{{cite journal |last1=Mooney |first1=H. A. |last2=Cleland |first2=E. E. |date=2001 |title=The evolutionary impact of invasive species |journal=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> Hybridization and introgression, which can happen in natural and hybrid populations, of new genetic material can lead to the replacement of local [[genotypes]] if the hybrids are more [[Fitness (biology)|fit]] and have breeding advantages over the indigenous ecotype or species. These hybridization events can result from the introduction of non-native genotypes by humans or through habitat modification, bringing previously isolated species into contact. Genetic mixing can be especially detrimental for rare species in isolated habitats, ultimately affecting the population to such a degree that none of the originally genetically distinct population remains.<ref>{{cite journal |last1=Rhymer |first1=J. M. |last2=Simberloff |first2=D. |date=1996 |title=Extinction by Hybridization and Introgression |journal=Annual Review of Ecology and Systematics |volume=27 |issue=1 |pages=83–109 |doi=10.1146/annurev.ecolsys.27.1.83|bibcode=1996AnRES..27...83R }}</ref><ref>{{cite book |last1=Potts |first1=Brad M. |last2=Barbour |first2=Robert C. |last3=Hingston |first3=Andrew B. |date=2001 |url= http://www.rirdc.gov.au/reports/AFT/01-114.pdf |title=Genetic Pollution from Farm Forestry using eucalypt species and hybrids:A report for RIRDC/L&WA/FWPRDC Joint Venture Agroforestry Program |archive-url= https://web.archive.org/web/20040102175403/http://www.rirdc.gov.au/reports/AFT/01-114.pdf |archive-date=2 January 2004 |publisher=Rural Industrial Research and Development Corporation, Australian Government |id=RIRDC Publication No. 01/114; RIRDC Project No CPF - 3A |isbn=9780642583369 |issn=1440-6845}}</ref>

===Effect on biodiversity and food security===
[[File:Irrigation1.jpg|thumb|The [[Green Revolution]] of the 20th century relied on hybridization to create [[high-yielding varieties]], along with increased reliance on inputs of [[fertilizer]]s, [[pesticide]]s, and [[irrigation]].<ref>{{cite journal |last=Farmer |first=B. H. |date=1986 |title=Perspectives on the 'Green Revolution' in South Asia |journal=Modern Asian Studies |volume=20 |issue=1 |pages=175–199 |doi=10.1017/s0026749x00013627|s2cid=145626108}}</ref>]]
{{Main|Biodiversity|Food security}}

In agriculture and [[animal husbandry]], the [[Green Revolution]]'s use of conventional hybridization increased yields by breeding [[high-yielding varieties]]. The replacement of locally indigenous breeds, compounded with unintentional cross-pollination and crossbreeding (genetic mixing), has reduced the gene pools of various wild and indigenous breeds resulting in the loss of [[genetic diversity]].<ref>[http://www.farmedia.org/bulletins/bulletin28.html "Genetic Pollution: The Great Genetic Scandal"] Devinder Sharma {{webarchive |url= https://web.archive.org/web/20090518120050/http://www.farmedia.org/bulletins/bulletin28.html |date=18 May 2009}}; Bulletin 28</ref> Since the indigenous breeds are often well-adapted to local extremes in climate and have immunity to local pathogens, this can be a significant genetic erosion of the gene pool for future breeding. Therefore, commercial plant geneticists strive to breed "widely adapted" cultivars to counteract this tendency.<ref>Troyer, A. Forrest. ''Breeding Widely Adapted Cultivars: Examples from Maize.'' Encyclopedia of Plant and Crop Science, 27 February 2004.</ref>