Editing Population bottleneck (section)

===Other animals===
{| class="wikitable" style="float:right; margin:1em 0 1em 1em"
|-
! Year !! American<br />bison (est)
|-
| Before 1492
|align="right"| 60,000,000
|-
| 1890
|align="right"| 750
|-
| 2000
|align="right"| 360,000
|}

[[European bison]], also called wisent ''(Bison bonasus),'' faced extinction in the early 20th century. The animals living today are all descended from 12 individuals and they have extremely low genetic variation, which may be beginning to affect the reproductive ability of bulls.<ref>{{cite journal |doi=10.1007/s10344-005-0081-4 |title=Low level of genetic variability in European bisons (''Bison bonasus'') from the Bialowieza National Park in Poland |journal=European Journal of Wildlife Research |volume=51 |issue=2 |pages=84–7 |year=2005 |last1=Luenser |first1=K. |last2=Fickel |first2=J. |last3=Lehnen |first3=A. |last4=Speck |first4=S. |last5=Ludwig |first5=A.|bibcode=2005EJWR...51...84L |s2cid=34102378 }}</ref>

The population of [[American bison]] ''(Bison bison)'' fell due to overhunting, nearly leading to extinction around the year 1890, though it has since begun to recover (see table).

[[Image:Northern Elephant Seal, San Simeon2.jpg|thumb|left|250px| Overhunting pushed the [[northern elephant seal]] to the brink of extinction by the late 19th century. Although they have made a comeback, the genetic variation within the population remains very low.]]

A classic example of a population bottleneck is that of the [[northern elephant seal]], whose population fell to about 30 in the 1890s. Although it now numbers in the hundreds of thousands, the potential for bottlenecks within colonies remains. Dominant bulls are able to mate with the largest number of females—sometimes as many as 100. With so much of a colony's offspring descended from just one dominant male, genetic diversity is limited, making the species more vulnerable to diseases and genetic mutations. 

The [[golden hamster]] is a similarly bottlenecked species, with the vast majority of domesticated hamsters descended from a single litter found in the [[Syrian desert]] around 1930, and very few wild golden hamsters remain.

An extreme example of a population bottleneck is the New Zealand [[black robin]], of which every specimen today is a descendant of a single female, called Old Blue. The Black Robin population is still recovering from its low point of only five individuals in 1980.

The [[genome]] of the [[giant panda]] shows evidence of a severe bottleneck about 43,000 years ago.<ref>{{cite journal |doi=10.1351/pac200274040575 |title=Genetic diversity and conservation of endangered animal species |journal=Pure and Applied Chemistry |volume=74 |issue=4 |pages=575–84 |year=2002 |last1=Zhang |first1=Ya-Ping |last2=Wang |first2=Xiao-xia |last3=Ryder |first3=Oliver A. |last4=Li |first4=Hai-Peng |last5=Zhang |first5=He-Ming |last6=Yong |first6=Yange |last7=Wang |first7=Peng-yan|s2cid=13945117 |url=http://www.degruyter.com/downloadpdf/j/pac.2002.74.issue-4/pac200274040575/pac200274040575.xml |doi-access=free }}</ref> There is also evidence of at least one primate species, the [[golden snub-nosed monkey]], that also suffered from a bottleneck around this time. An unknown environmental event is suspected to have caused the bottlenecks observed in both of these species. The bottlenecks likely caused the low [[genetic diversity]] observed in both species.

Other facts can sometimes be inferred from an observed population bottleneck. Among the [[Galápagos Islands]] [[Galápagos tortoise|giant tortoises]]—themselves a prime example of a bottleneck—the comparatively large population on the slopes of the [[Alcedo Volcano|Alcedo volcano]] is significantly less diverse than four other tortoise populations on the same island. DNA analyses date the bottleneck to around 88,000 years before present ([[Before Present|YBP]]).<ref>{{cite journal |vauthors=Beheregaray LB, Ciofi C, Geist D, Gibbs JP, Caccone A, Powell JR |title=Genes record a prehistoric volcano eruption in the Galápagos |journal=Science |volume=302 |issue=5642 |pages=75 |date=October 2003  |pmid=14526072 |doi=10.1126/science.1087486|s2cid=39102858 }}</ref> About 100,000 YBP the [[volcano]] erupted violently, deeply burying much of the tortoise habitat in pumice and ash.

Another example can be seen in the [[greater prairie chicken]]s, which were prevalent in North America until the 20th century. In [[Illinois]] alone, the number of greater prairie chickens plummeted from over 100 million in 1900 to about 46 in 1998.<ref name=":1">{{Cite journal |last1=Mussmann |first1=S. M. |last2=Douglas |first2=M. R. |last3=Anthonysamy |first3=W. J. B. |last4=Davis |first4=M. A. |last5=Simpson |first5=S. A. |last6=Louis |first6=W. |last7=Douglas |first7=M. E. |date=February 2017 |title=Genetic rescue, the greater prairie chicken and the problem of conservation reliance in the Anthropocene |journal=Royal Society Open Science |language=en |volume=4 |issue=2 |pages=160736 |doi=10.1098/rsos.160736 |issn=2054-5703 |pmc=5367285 |pmid=28386428|bibcode=2017RSOS....460736M }}</ref> These declines in population were the result of hunting and [[habitat destruction]], but the random consequences have also caused a great loss in species diversity. DNA analysis comparing the birds from 1990 and mid-century shows a steep genetic decline in recent decades. Management of the greater prairie chickens now includes [[genetic rescue]] efforts including translocation of prairie chickens between [[Lek mating|lek]]s to increase each population's genetic diversity.<ref name=":1" /> 

Population bottlenecking poses a major threat to the stability of species populations as well. ''[[Papilio homerus]]'' is the largest butterfly in the Americas and is endangered according to the [[International Union for Conservation of Nature|IUCN]]. The disappearance of a central population poses a major threat of population bottleneck. The remaining two populations are now geographically isolated and the populations face an unstable future with limited remaining opportunity for gene flow.<ref>{{Cite journal|last1=Lehnert|first1=Matthew S.|last2=Kramer|first2=Valerie R.|last3=Rawlins|first3=John E.|last4=Verdecia|first4=Vanessa|last5=Daniels|first5=Jaret C.|date=2017-07-10|title=Jamaica's Critically Endangered Butterfly: A Review of the Biology and Conservation Status of the Homerus Swallowtail (Papilio (Pterourus) homerus Fabricius)|journal=Insects|language=en|volume=8|issue=3|pages=68|doi=10.3390/insects8030068|pmid=28698508|pmc=5620688|doi-access=free}}</ref>

Genetic bottlenecks exist in [[cheetah]]s.<ref>{{cite journal | pmc=46261 | pmid=8475057 | volume=90 |issue = 8| title=Dating the genetic bottleneck of the African cheetah. | date=Apr 1993 | journal=Proc Natl Acad Sci U S A | pages=3172–6 | doi=10.1073/pnas.90.8.3172|last1 = Menotti-Raymond|first1 = M.|last2 = O'Brien|first2 = S. J.| bibcode=1993PNAS...90.3172M | doi-access=free }}</ref><ref>{{cite journal|last1=O'Brien|first1=S.|last2=Roelke|first2=M.|last3=Marker|first3=L|last4=Newman|first4=A|last5=Winkler|first5=C.|last6=Meltzer|first6=D|last7=Colly|first7=L|last8=Evermann|first8=J.|last9=Bush|first9=M|last10=Wildt|first10=D.|title=Genetic basis for species vulnerability in the cheetah|journal=Science|volume=227|issue=4693|date=March 22, 1985|pages=1428–1434|doi=10.1126/science.2983425|pmid=2983425|bibcode=1985Sci...227.1428O|url=http://bio150.chass.utoronto.ca/labs/cool-links/lab5/OBrien_et_al_1985_lab_5.pdf|archive-url=https://web.archive.org/web/20060507232241/http://bio150.chass.utoronto.ca/labs/cool-links/lab5/OBrien_et_al_1985_lab_5.pdf|archive-date=2006-05-07}}</ref>