Editing Sympatric speciation (section)

===History===
{{further|Modern synthesis (20th century)}}

The German evolutionary biologist Ernst Mayr argued in the 1940s that speciation cannot occur without geographic, and thus reproductive, isolation.<ref name="Mayr 1947"/> He stated that gene flow is the inevitable result of sympatry, which is known to squelch genetic differentiation between populations. Thus, a physical barrier must be present, he believed, at least temporarily, in order for a new biological species to arise.<ref name="Mallet et al 2009">{{cite journal |doi=10.1111/j.1420-9101.2009.01816.x |title=Space, sympatry and speciation |year=2009 |last1=Mallet |first1=J. |last2=Meyer |first2=A. |last3=Nosil |first3=P. |last4=Feder |first4=J. L. |journal=Journal of Evolutionary Biology |volume=22 |issue=11 |pages=2332–41 |pmid=19732264|s2cid=9722101 |url=https://kops.uni-konstanz.de/bitstream/123456789/8588/1/space_sympatry_and_speciation.pdf |doi-access=free }}</ref> This hypothesis is the source of much controversy around the possibility of sympatric speciation. Mayr's hypothesis was popular and consequently quite influential, but is now widely disputed.<ref name="Jiggins 2006">{{cite journal |doi=10.1016/j.cub.2006.03.077 |title=Sympatric Speciation: Why the Controversy? |year=2006 |last1=Jiggins |first1=Chris D. |journal=Current Biology |volume=16 |issue=9 |pages=R333–4 |pmid=16682343|s2cid=16947323 |doi-access=free |bibcode=2006CBio...16.R333J }}</ref>

The first to propose what is now the most pervasive hypothesis on how sympatric speciation may occur was [[John Maynard Smith]], in 1966. He came up with the idea of disruptive selection. He figured that if two ecological niches are occupied by a single species, diverging selection between the two niches could eventually cause [[reproductive isolation]].<ref>{{cite journal |first=J. Maynard |last=Smith |year=1966 |title=Sympatric Speciation |journal=The American Naturalist |volume=100 |issue=916 |pages=637–50 |jstor=2459301 |doi=10.1086/282457|bibcode=1966ANat..100..637S |s2cid=222329634 }}</ref> By adapting to have the highest possible fitness in the distinct niches, two species may emerge from one even if they remain in the same area, and even if they are mating randomly.<ref name="Kondrashov & Kondrashov 1999"/>