Editing Habitat fragmentation (section)

==== Gene Flow and Inbreeding ====
[[Gene flow]] occurs when individuals of the same species exchange genetic information through reproduction. Populations can maintain genetic diversity through [[Animal migration|migration]]. When a habitat becomes fragmented and reduced in area, gene flow and migration are typically reduced. Fewer individuals will migrate into the remaining fragments, and small disconnected populations that may have once been part of a single large population will become reproductively isolated. Scientific evidence that gene flow is reduced due to fragmentation depends on the study species. While trees that have long-range pollination and dispersal mechanisms may not experience reduced gene flow following fragmentation,<ref>{{cite journal |last1=Kramer |first1=Andrea T. |last2=Ison |first2=Jennifer L. |last3=Ashley |first3=Mary V. |last4=Howe |first4=Henry F. |title=The Paradox of Forest Fragmentation Genetics |journal=Conservation Biology |date=August 2008 |volume=22 |issue=4 |pages=878–885 |doi=10.1111/j.1523-1739.2008.00944.x |pmid=18544089|bibcode=2008ConBi..22..878K |s2cid=1665248 }}</ref> most species are at risk of reduced gene flow following habitat fragmentation.<ref name="Lienert2004" />

Reduced gene flow, and reproductive isolation can result in [[inbreeding]] between related individuals. Inbreeding does not always result in negative fitness consequences, but when inbreeding is associated with fitness reduction it is called [[inbreeding depression]]. Inbreeding becomes of increasing concern as the level of [[homozygosity]] increases, facilitating the expression of deleterious alleles that reduce the fitness. Habitat fragmentation can lead to inbreeding depression for many species due to reduced gene flow.<ref name="Pavolva2017">{{cite journal |last1=Pavlova |first1=Alexandra |last2=Beheregaray |first2=Luciano B. |last3=Coleman |first3=Rhys |last4=Gilligan |first4=Dean |last5=Harrisson |first5=Katherine A. |last6=Ingram |first6=Brett A. |last7=Kearns |first7=Joanne |last8=Lamb |first8=Annika M. |last9=Lintermans |first9=Mark |last10=Lyon |first10=Jarod |last11=Nguyen |first11=Thuy T. T. |last12=Sasaki |first12=Minami |last13=Tonkin |first13=Zeb |last14=Yen |first14=Jian D. L. |last15=Sunnucks |first15=Paul |title=Severe consequences of habitat fragmentation on genetic diversity of an endangered Australian freshwater fish: A call for assisted gene flow |journal=Evolutionary Applications |date=July 2017 |volume=10 |issue=6 |pages=531–550 |doi=10.1111/eva.12484 |pmid=28616062 |pmc=5469170|bibcode=2017EvApp..10..531P }}</ref><ref>{{cite journal |last1=Wang |first1=W |last2=Qiao |first2=Y |last3=Li |first3=S |last4=Pan |first4=W |last5=Yao |first5=M |title=Low genetic diversity and strong population structure shaped by anthropogenic habitat fragmentation in a critically endangered primate, Trachypithecus leucocephalus |journal=Heredity |date=15 February 2017 |volume=118 |issue=6 |pages=542–553 |doi=10.1038/hdy.2017.2 |pmid=28198816 |pmc=5436025|bibcode=2017Hered.118..542W }}</ref> Inbreeding depression is associated with conservation risks, like local extinction.<ref>{{Cite journal|last1=Hedrick|first1=Philip W.|last2=Kalinowski|first2=Steven T.|date=November 2000|title=Inbreeding Depression in Conservation Biology|journal=Annual Review of Ecology and Systematics|language=en|volume=31|issue=1|pages=139–162|doi=10.1146/annurev.ecolsys.31.1.139|bibcode=2000AnRES..31..139H |issn=0066-4162}}</ref>