Editing Gene flow (section)

== Examples ==
[[File:Marineiguana03.jpg|thumb|[[Marine iguana]] of the [[Galapagos Islands]] evolved via allopatric speciation, through limited gene flow and geographic isolation.]]While gene flow can greatly enhance the fitness of a population, it can also have negative consequences depending on the population and the environment in which they reside. The effects of gene flow are context-dependent.

* '''Fragmented Population:''' fragmented landscapes such as the [[Galápagos Islands|Galapagos Islands]] are an ideal place for [[adaptive radiation]] to occur as a result of differing geography. [[Darwin's finches]] likely experienced allopatric speciation in some part due to differing geography, but that does not explain why we see so many different kinds of finches on the same island. This is due to adaptive radiation, or the evolution of varying traits in light of competition for resources. Gene flow moves in the direction of what resources are abundant at a given time.<ref>{{Cite journal| vauthors  = Grant PR, Grant BR |s2cid=36303685|date=2002-04-26 |title=Unpredictable Evolution in a 30-Year Study of Darwin's Finches |journal=Science | volume=296 |issue=5568|pages=707–711 |doi=10.1126/science.1070315 |pmid=11976447|bibcode=2002Sci...296..707G}}</ref>  
* '''Island Population:''' The [[marine iguana]] is an endemic species of the Galapagos Islands, but it evolved from a mainland ancestor of land iguana. Due to geographic isolation gene flow between the two species was limited and differing environments caused the marine iguana to evolve in order to adapt to the island environment. For instance, they are the only iguana that has evolved the ability to swim.
* '''Human Populations:''' In Europe ''Homo sapiens'' interbred with [[Neanderthal]]s resulting in gene flow between these populations.<ref>{{cite journal | vauthors = Prüfer K, Racimo F, Patterson N, Jay F, Sankararaman S, Sawyer S, Heinze A, Renaud G, Sudmant PH, de Filippo C, Li H, Mallick S, Dannemann M, Fu Q, Kircher M, Kuhlwilm M, Lachmann M, Meyer M, Ongyerth M, Siebauer M, Theunert C, Tandon A, Moorjani P, Pickrell J, Mullikin JC, Vohr SH, Green RE, Hellmann I, Johnson PL, Blanche H, Cann H, Kitzman JO, Shendure J, Eichler EE, Lein ES, Bakken TE, Golovanova LV, Doronichev VB, Shunkov MV, Derevianko AP, Viola B, Slatkin M, Reich D, Kelso J, Pääbo S | display-authors = 6 | title = The complete genome sequence of a Neanderthal from the Altai Mountains | journal = Nature | volume = 505 | issue = 7481 | pages = 43–9 | date = January 2014 | pmid = 24352235 | doi = 10.1038/nature12886 | url= | pmc = 4031459 | bibcode = 2014Natur.505...43P }}</ref> This gene flow has resulted in Neanderthal alleles in modern European population.<ref>{{cite journal | vauthors = Jagoda E, Lawson DJ, Wall JD, Lambert D, Muller C, Westaway M, Leavesley M, Capellini TD, Mirazón Lahr M, Gerbault P, Thomas MG, Migliano AB, Willerslev E, Metspalu M, Pagani L | display-authors = 6 | title = Disentangling Immediate Adaptive Introgression from Selection on Standing Introgressed Variation in Humans | journal = Molecular Biology and Evolution | volume = 35 | issue = 3 | pages = 623–630 | date = March 2018 | pmid = 29220488 | pmc = 5850494 | doi = 10.1093/molbev/msx314 }}</ref>  Two theories exist for the [[human evolution]] throughout the world. The first is known as the multiregional model in which modern human variation is seen as a product of radiation of ''[[Homo erectus]]'' out of Africa after which local differentiation led to the establishment of regional population as we see them now.<ref>{{cite book | vauthors = Tobias PV, Strong V, White W |title=Hominid Evolution: Past, Present, and Future : Proceedings of the Taung Diamond Jubilee International Symposium, Johannesburg and Mmabatho, Southern Africa, 27th January-4th February 1985 |date=1985 |publisher=A.R. Liss |isbn=978-0-8451-4202-8 }}{{page needed|date=February 2020}}</ref><ref name=pmid3125610>{{cite journal | vauthors = Stringer CB, Andrews P | title = Genetic and fossil evidence for the origin of modern humans | journal = Science | volume = 239 | issue = 4845 | pages = 1263–8 | date = March 1988 | pmid = 3125610 | doi = 10.1126/science.3125610 | bibcode = 1988Sci...239.1263S | jstor = 1700885 }}</ref> Gene flow plays an important role in maintaining a grade of similarities and preventing speciation. In contrast the single origin theory assumes that there was a common ancestral population originating in Africa of ''[[Homo sapiens]]'' which already displayed the anatomical characteristics we see today.  This theory minimizes the amount of parallel evolution that is needed.<ref name=pmid3125610/>
* '''Butterflies:''' Comparisons between sympatric and allopatric populations of&nbsp;''[[Heliconius melpomene]]'',&nbsp;''H. cydno'', and&nbsp;''H. timareta''&nbsp;revealed a genome-wide trend of increased shared variation in sympatry, indicative of pervasive interspecific gene flow.<ref>{{cite journal | vauthors = Martin SH, Dasmahapatra KK, Nadeau NJ, Salazar C, Walters JR, Simpson F, Blaxter M, Manica A, Mallet J, Jiggins CD | display-authors = 6 | title = Genome-wide evidence for speciation with gene flow in Heliconius butterflies | journal = Genome Research | volume = 23 | issue = 11 | pages = 1817–28 | date = November 2013 | pmid = 24045163 | pmc = 3814882 | doi = 10.1101/gr.159426.113 }}</ref>&nbsp;
* '''Human-mediated gene flow:''' The captive genetic management of [[threatened species]] is the only way in which humans attempt to induce gene flow in ex situ situation. One example is the [[giant panda]] which is part of an international breeding program in which genetic materials are shared between zoological organizations in order to increase genetic diversity in the small populations. As a result of low reproductive success, artificial insemination with fresh/frozen-thawed sperm was developed which increased cub survival rate. A 2014 study found that high levels of genetic diversity and low levels of inbreeding were estimated in the breeding centers.<ref>{{cite journal | vauthors = Shan L, Hu Y, Zhu L, Yan L, Wang C, Li D, Jin X, Zhang C, Wei F | display-authors = 6 | title = Large-scale genetic survey provides insights into the captive management and reintroduction of giant pandas | journal = Molecular Biology and Evolution | volume = 31 | issue = 10 | pages = 2663–71 | date = October 2014 | pmid = 25015646 | doi = 10.1093/molbev/msu210 | doi-access = free }}</ref>
* '''Plants:''' Two populations of [[Erythranthe|monkeyflowers]] were found to use different pollinators (bees and hummingbirds) that limited gene flow, resulting in genetic isolation, eventually producing two different species, ''[[Mimulus lewisii]]'' and ''[[Mimulus cardinalis]]'' .<ref>{{cite journal | vauthors = Schemske DW, Bradshaw HD | title = Pollinator preference and the evolution of floral traits in monkeyflowers (Mimulus) | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 96 | issue = 21 | pages = 11910–5 | date = October 1999 | pmid = 10518550 | pmc = 18386 | doi = 10.1073/pnas.96.21.11910 | bibcode = 1999PNAS...9611910S | doi-access = free }}</ref>
* '''Sika deer:''' Sika deer were introduced into Western Europe, and they reproduce easily with the native red deer. This translocation of Sika deer has led to introgression and there are no longer "pure" red deer in the region, and all can be classified as hybrids.<ref>Storfer, Andrew. "Gene Flow and Endangered Species Translocations: a Topic Revisited." ''Elsevier'', Center for Ecology, Evolution and Behavior and T.H. Morgan School of Biological Sciences, May 1998.</ref>
* '''Bobwhite quail:''' Bobwhite quail were translocated from the southern part of the United States to Ontario in order to increase population numbers and game for hunting. The hybrids that resulted from this translocation was less fit than the native population and were not adapted to survive the Northern Winters.<ref>{{cite journal |last1=Storfer |first1=Andrew |title=Gene flow and endangered species translocations: a topic revisited |journal=Biological Conservation |date=February 1999 |volume=87 |issue=2 |pages=173–180 |doi=10.1016/S0006-3207(98)00066-4 |bibcode=1999BCons..87..173S }}</ref>