Editing Allee effect (section)

=== Genetic mechanisms ===
Declines in population size can result in a loss of genetic diversity, and owing to [[genetic diversity|genetic variation]]'s role in the evolutionary potential of a species, this could in turn result in an observable Allee effect. As a species' population becomes smaller, its gene pool will be reduced in size as well. One possible outcome from this [[population bottleneck|genetic bottleneck]] is a reduction in fitness of the species through the process of [[genetic drift]], as well as [[inbreeding depression]].<ref>{{Cite journal |author =Frankham R |s2cid=6088451 |year=1996 |title=Relationship of genetic variation to population size in wildlife- a review |journal=Conservation Biology |volume=10 |pages=1500–1508 |doi=10.1046/j.1523-1739.1996.10061500.x |issue=6|bibcode=1996ConBi..10.1500F }}</ref> This overall fitness decrease of a species is caused by an accumulation of [[Mutation#Harmful mutations|deleterious mutations]] throughout the population. Genetic variation within a species could range from beneficial to detrimental. Nevertheless, in a smaller sized gene pool, there is a higher chance of a stochastic event in which deleterious alleles become fixed ([[genetic drift]]). While evolutionary theory states that expressed deleterious alleles should be purged through natural selection, purging would be most efficient only at eliminating alleles that are highly detrimental or harmful. Mildly deleterious alleles such as those that act later in life would be less likely to be removed by natural selection, and conversely, newly acquired beneficial mutations are more likely to be lost by random chance in smaller genetic pools than larger ones.<ref name=book1 /><ref>{{Cite book |last=Gillespie |first=J. H. |year=2004 |title=Population genetics: a concise guide |publisher=Johns Hopkins University Press |location=Baltimore, Maryland, USA |isbn=0-8018-8008-4 }}</ref>

Although the long-term population persistence of several species with low genetic variation has recently prompted debate on the generality of inbreeding depression, there are various empirical evidences for genetic Allee effects.<ref>{{Cite journal |author =Reed DH |year=2010 |title=Albatrosses, eagles and newts, Oh My!: exceptions to the prevailing paradigm concerning genetic diversity and population viability? |journal=Animal Conservation |volume=13 |pages=448–457 |doi=10.1111/j.1469-1795.2010.00353.x |issue=5|doi-access=free |bibcode=2010AnCon..13..448R }}</ref> One such case was observed in the endangered [[Florida panther]] (''Puma concolor coryi''). The Florida panther experienced a genetic bottleneck in the early 1990s where the population was reduced to ≈25 adult individuals. This reduction in genetic diversity was correlated with defects that include lower sperm quality, abnormal testosterone levels, cowlicks, and kinked tails.<ref>{{Cite journal |year=2010 |title=Genetic restoration of the Florida panther |journal=Science |volume=329 |pages=1641–1645 |bibcode=2010Sci...329.1641J |last1=Johnson|first1=WE|last2=Onorato |first2=DP|last3=Roelke |first3=MW|last4=Land |first4=ED|last5=Cunningham |first5=M|last6=Belden |first6=RC|last7=McBride |first7=R|last8=Jansen |first8=D|last9=Lotz |first9=M|s2cid=206527881 |display-authors=8|doi=10.1126/science.1192891 |pmid=20929847 |issue=5999|pmc=6993177 }}</ref> In response, a genetic rescue plan was put in motion and several female pumas from Texas were introduced into the Florida population. This action quickly led to the reduction in the prevalence of the defects previously associated with inbreeding depression. Although the timescale for this inbreeding depression is larger than of those more immediate Allee effects, it has significant implications on the long-term persistence of a species.