Editing Speciation (section)

=== Parapatric ===
{{Main|Parapatric speciation}}

In parapatric speciation, there is only partial separation of the zones of two diverging populations afforded by geography; individuals of each species may come in contact or cross habitats from time to time, but reduced fitness of the [[Zygosity|heterozygote]] leads to selection for behaviours or mechanisms that prevent their [[Hybrid (biology)|interbreeding]]. Parapatric speciation is modelled on continuous variation within a "single", connected habitat acting as a source of natural selection rather than the effects of isolation of habitats produced in peripatric and allopatric speciation.<ref>{{Cite web|url=https://www.nature.com/scitable/knowledge/library/speciation-the-origin-of-new-species-26230527/|title=Speciation: The Origin of New Species {{!}} Learn Science at Scitable|website=Nature |language=en|access-date=2020-02-16}}</ref>

Parapatric speciation may be associated with differential landscape-dependent [[Selection (biology)|selection]]. Even if there is a [[gene flow]] between two populations, strong differential selection may impede assimilation and different species may eventually develop.<ref>{{harvnb|Endler|1977}}</ref> Habitat differences may be more important in the development of reproductive isolation than the isolation time. Caucasian rock lizards ''[[Darevskia]] rudis'', ''D. valentini'' and ''D. portschinskii'' all [[hybrid (biology)|hybrid]]ize with each other in their [[hybrid zone]]; however, hybridization is stronger between ''D. portschinskii'' and ''D. rudis'', which separated earlier but live in similar habitats than between ''D. valentini'' and two other species, which separated later but live in climatically different habitats.<ref>{{cite journal |last1=Tarkhnishvili |first1=David |last2=Murtskhvaladze |first2=Marine |last3=Gavashelishvili |first3=Alexander |date=August 2013 |title=Speciation in Caucasian lizards: climatic dissimilarity of the habitats is more important than isolation time |journal=[[Biological Journal of the Linnean Society]] |volume=109 |issue=4 |pages=876–892 |doi=10.1111/bij.12092|doi-access=free }}</ref>

Ecologists refer to{{clarify|date=May 2018<!--what is being claimed here?-->}} parapatric and peripatric speciation in terms of [[ecological niche]]s. A niche must be available in order for a new species to be successful. [[Ring species]] such as ''[[gull|Larus]]'' gulls have been claimed to illustrate speciation in progress, though the situation may be more complex.<ref name=Liebers>{{cite journal |last1=Liebers |first1=Dorit |last2=Knijff |first2=Peter de |last3=Helbig |first3=Andreas J. |title=The herring gull complex is not a ring species |journal=Proc Biol Sci |date=2004 |volume=271 |issue=1542 |pages=893–901 |doi=10.1098/rspb.2004.2679 |pmc=1691675 |pmid=15255043}}<!--nor Herring Gull--></ref> The grass ''[[Anthoxanthum odoratum]]'' may be starting parapatric speciation in areas of mine contamination.<ref>{{cite web |title=Parapatric speciation |url=http://evolution.berkeley.edu/evolibrary/article/_0/speciationmodes_04 |publisher=University of California Berkeley |access-date=3 April 2017}}</ref>