Editing Founder effect (section)

{{short description|Effect in population genetics}}
{{for|the concept in organizations|Founder's syndrome}}
[[File:Founder effect.svg|thumb|upright=1.5|Founder effect: The original population (left) could give rise to different founder populations (right).]]

In [[population genetics]], the '''founder effect''' is the loss of [[genetic variation]] that occurs when a new [[population]] is established by a very small number of individuals from a larger population. It was first fully outlined by [[Ernst Mayr]] in 1942,<ref>{{cite journal |pmid=15280221 |pmc=1470966 |url=http://www.genetics.org/cgi/pmidlookup?view=long&pmid=15280221 |year=2004 |last1=Provine |first1=W. B. |author-link=Will Provine |title=Ernst Mayr: Genetics and speciation |journal=Genetics |volume=167 |issue=3 |pages=1041–6 |doi=10.1093/genetics/167.3.1041 }}</ref> using existing theoretical work by those such as [[Sewall Wright]].<ref>{{cite journal |pmid=6777243 |pmc=1214177 |url=http://www.genetics.org/cgi/pmidlookup?view=long&pmid=6777243 |year=1980 |last1=Templeton |first1=A. R. |title=The theory of speciation via the founder principle |journal=Genetics |volume=94 |issue=4 |pages=1011–38 |doi=10.1093/genetics/94.4.1011 }}</ref> As a result of the loss of genetic variation, the new population may be distinctively different, both [[genotype|genotypically]] and [[phenotype|phenotypically]], from the parent population from which it is derived. In extreme cases, the founder effect is thought to lead to the [[speciation]] and subsequent [[evolution]] of new species.<ref>{{cite journal | vauthors = Joly E | title = The existence of species rests on a metastable equilibrium between inbreeding and outbreeding. An essay on the close relationship between speciation, inbreeding and recessive mutations | journal = Biology Direct | volume = 6 | pages = 62 | date = December 2011 | pmid = 22152499 | pmc = 3275546 | doi = 10.1186/1745-6150-6-62 | doi-access = free }}</ref>

In the figure shown, the original population has nearly equal numbers of blue and red individuals. The three smaller founder populations show that one or the other color may predominate (founder effect), due to random sampling  of the original population. A [[population bottleneck]] may also cause a founder effect, though it is not strictly a new population.

The founder effect occurs when a small group of migrants—not genetically representative of the population from which they came—establish in a new area.<ref>{{cite book |first1=Leland |last1=Hartwell |first2=Leroy |last2=Hood |first3=Michael |last3=Goldberg |first4=Ann E. |last4=Reynolds |first5=Lee |last5=Silver |first6=Ruth C |last6=Veres |year=2004 |title=Genetics: From Genes to Genomes |url=https://archive.org/details/genetics00 |url-access=registration |page=[https://archive.org/details/genetics00/page/241 241] |publisher=McGraw-Hill Higher Education |isbn=978-0-07-121468-1}}</ref><ref>{{cite book |first1=Peter H. |last1=Raven |first2=Ray F. |last2=Evert |first3=Susan E. |last3=Eichhorn |year=1999 |title=Biology of Plants |page=241 |publisher=W H Freeman and Company}}</ref> In addition to founder effects, the new population is often [[small population size|very small]], so it shows increased sensitivity to [[genetic drift]], an increase in [[inbreeding]], and relatively low [[genetic variation]].