Editing Sympatric speciation (section)

==Evidence==
Sympatric speciation events are quite common in plants, which are prone to acquiring multiple [[Homologous chromosome|homologous]] sets of [[chromosomes]], resulting in [[polyploidy]]. The polyploid offspring occupy the same environment as the parent plants (hence sympatry), but are reproductively isolated.

A number of models have been proposed for alternative modes of sympatric speciation. The most popular, which invokes the [[disruptive selection]] model, was first put forward by [[John Maynard Smith]] in 1966.<ref>{{cite journal|title= Sympatric Speciation |author= John Maynard Smith |journal= American Naturalist |volume=100 | issue = 916 |year=1966 |pages=637–50 |jstor=2459301 |doi=10.1086/282457|bibcode= 1966ANat..100..637S |s2cid= 222329634 }}</ref> Maynard Smith suggested that [[homozygote|homozygous]] individuals may, under particular environmental conditions, have a greater fitness than those with [[allele]]s [[heterozygote|heterozygous]] for a certain trait. Under the mechanism of [[natural selection]], therefore, homozygosity would be favoured over heterozygosity, eventually leading to speciation. Sympatric divergence could also result from the [[sexual conflict]].<ref>[[Thierry Lodé]] ''La guerre des sexes chez les animaux'' Eds O Jacob, Paris, 2006{{page needed|date=November 2013}}</ref>

Disruption may also occur in multiple-gene traits. The [[Darwin's finches|medium ground finch]] (''Geospiza fortis'') is showing gene pool divergence in a population on [[Santa Cruz Island (Galapagos)|Santa Cruz Island]]. Beak morphology conforms to two different size ideals, while intermediate individuals are selected against. Some characteristics (termed [[magic trait]]s) such as beak morphology may drive speciation because they also affect mating signals. In this case, different beak [[phenotype]]s may result in different [[bird call]]s, providing a barrier to exchange between the gene pools.<ref>{{cite journal |doi=10.1098/rspb.2007.0224 |title=Reproductive isolation of sympatric morphs in a population of Darwin's finches |year=2007 |last1=Huber |first1=S. K |last2=Leon |first2=L. F. D. |last3=Hendry |first3=A. P |last4=Bermingham |first4=E. |last5=Podos |first5=J. |journal=Proceedings of the Royal Society B: Biological Sciences |volume=274 |issue=1619 |pages=1709–14 |pmid=17504742 |pmc=2493575}}</ref>

A somewhat analogous system has been reported in horseshoe bats, in which echolocation call frequency appears to be a magic trait. In these bats, the constant frequency component of the call not only determines prey size but may also function in aspects of social communication. Work from one species, the [[large-eared horseshoe bat]] (''Rhinolophus philippinensis''), shows that abrupt changes in call frequency among sympatric morphs is correlated with reproductive isolation.<ref>{{cite journal |doi=10.1038/nature02487 |title=Harmonic-hopping in Wallacea's bats |year=2004 |last1=Kingston |first1=Tigga |last2=Rossiter |first2=Stephen J. |journal=Nature |volume=429 |issue=6992 |pages=654–7 |pmid=15190351|bibcode=2004Natur.429..654K |s2cid=4422561 }}</ref> A further well-studied circumstance of sympatric speciation is when insects feed on more than one species of [[Host (biology)|host plant]]. In this case insects become specialized as they struggle to overcome the various plants' [[Antipredator adaptation|defense mechanisms]]. (Drès and Mallet, 2002)<ref>Begon, Townsend, Harper: ''Ecology – From individuals to ecosystems'', 4th ed., p.10</ref>

''Rhagoletis pomonella'', the [[apple maggot]], may be currently undergoing sympatric or, more precisely, heteropatric (see [[heteropatry]]) speciation. The apple feeding race of this species appears to have spontaneously emerged from the [[Crataegus|hawthorn]] feeding race in the 1800–1850 AD time frame, after apples were first introduced into [[North America]]. The apple feeding race does not now normally feed on [[Crataegus|hawthorn]]s, and the hawthorn feeding race does not now normally feed on apples. This may be an early step towards the emergence of a new species.<ref>{{cite journal |last1=Feder |first1=Jeffrey L. |last2=Chilcote |first2=Charles A. |last3=Bush |first3=Guy L. |year=1988 |title=Genetic differentiation between sympatric host races of the apple maggot fly ''Rhagoletis pomonella'' |url=https://www.nature.com/articles/336061a0 |journal=Nature |volume=336 |issue=6194 |pages=61–64 |bibcode=1988Natur.336...61F |doi=10.1038/336061a0 |s2cid=4318103 |hdl-access=free |hdl=2027.42/62806}}</ref><ref>{{cite journal |last1=McPheron |first1=Bruce A. |last2=Smith |first2=D. Courtney |last3=Berlocher |first3=Stewart H. |year=1988 |title=Genetic differences between host races of ''Rhagoletis pomonella'' |journal=Nature |volume=336 |issue=6194 |pages=64–66 |bibcode=1988Natur.336...64M |doi=10.1038/336064a0 |s2cid=4264026}}</ref><ref>{{cite journal |last1=Smith |first1=D. Courtney |year=1988 |title=Heritable divergence of ''Rhagoletis pomonella'' host races by seasonal asynchrony |journal=Nature |volume=336 |issue=6194 |pages=66–67 |bibcode=1988Natur.336...66S |doi=10.1038/336066a0 |s2cid=4371982}}</ref> 

Some parasitic ants may have evolved via sympatric speciation.<ref>{{cite journal|last1=Rabeling|first1=Christian|last2=Schultz|first2=Ted R.|last3=Pierce|first3=Naomi E.|last4=Bacci Jr|first4=Maurício|title=A Social Parasite Evolved Reproductive Isolation from Its Fungus-Growing Ant Host in Sympatry|journal=[[Current Biology]]|date=August 2014|doi=10.1016/j.cub.2014.07.048|pmid=25155509|volume=24|issue=17|pages=2047–2052|doi-access=free|bibcode=2014CBio...24.2047R }}</ref> Isolated and relatively homogeneous habitats such as crater lakes and islands are among the best geographical settings in which to demonstrate sympatric speciation. For example, [[Amphilophus|Nicaragua crater lake cichlid fishes]] include nine described species and dozens of undescribed species that have evolved by sympatric speciation.<ref>{{cite journal |doi=10.1016/j.ympev.2010.05.015 |title=Not a simple case – A first comprehensive phylogenetic hypothesis for the Midas cichlid complex in Nicaragua (Teleostei: Cichlidae: Amphilophus) |year=2010 |last1=Geiger |first1=Matthias F. |last2=McCrary |first2=Jeffrey K. |last3=Schliewen |first3=Ulrich K. |journal=Molecular Phylogenetics and Evolution |volume=56 |issue=3 |pages=1011–24 |pmid=20580847|bibcode=2010MolPE..56.1011G }}</ref><ref>{{cite journal |doi=10.1038/nature04325 |title=Sympatric speciation in Nicaraguan crater lake cichlid fish |year=2006 |last1=Barluenga |first1=Marta |last2=Stölting |first2=Kai N. |last3=Salzburger |first3=Walter |last4=Muschick |first4=Moritz |last5=Meyer |first5=Axel |journal=Nature |volume=439 |issue=7077 |pages=719–23 |pmid=16467837|bibcode=2006Natur.439..719B |s2cid=3165729 |url=https://kops.uni-konstanz.de/bitstream/123456789/6577/1/sympatric_speciation_in_nicaraguan_crater_lake_cichlid_fish_2006.pdf }}</ref> ''[[Monostroma]] latissimum'', a marine green algae, also shows sympatric speciation in southwest Japanese islands. Although [[panmictic]], the molecular phylogenetics using nuclear introns revealed staggering diversification of population.<ref>{{cite journal | last1 = Bast | first1 = F. | last2 = Kubota | first2 = S. | last3 = Okuda | first3 = K. | year = 2014 | title = Phylogeographic Assessment of Panmictic Monostroma Species from Kuroshio Coast, Japan Reveals Sympatric Speciation | journal = Journal of Applied Phycology | volume =  27| issue = 4| pages =  1725–1735| doi = 10.1007/s10811-014-0452-x | s2cid = 17236629 }}</ref>

African [[cichlid]]s also offer some evidence for sympatric speciation. They show a large amount of diversity in the [[African Great Lakes]]. Many studies point to sexual selection as a way of maintaining reproductive isolation. Female choice with regards to male coloration is one of the more studied modes of sexual selection in African cichlids. Female choice is present in cichlids because the female does much of the work in raising the offspring, while the male has little energy input in the offspring. She exerts sensory bias when picking males by choosing those that have colors similar to her or those that are the most colorful.<ref>{{cite journal | last1 = Allender | first1 = C.J. | last2 = Seehausen | first2 = O. | last3 = Knight | first3 = M.E. | last4 = Turner | first4 = G.F. | last5 = Macleen | first5 = N. | year = 2003 | title = Divergent selection during speciation of the Lake Malawi cichlid fishes inferred from parallel radiations in nuptial coloration | journal = PNAS | volume = 100 | issue = 24| pages = 14074–14079 | doi=10.1073/pnas.2332665100 | pmid=14614144 | pmc=283548| bibcode = 2003PNAS..10014074A | doi-access = free }}</ref><ref>{{cite journal | last1 = Egger | first1 = B. | last2 = Mattersdorfer | first2 = K. | last3 = Sefc | first3 = K.M. | year = 2009 | title = Variable discrimination and asymmetric preferences in laboratory tests of reproductive isolation between cichlid colour morphs | journal = Journal of Evolutionary Biology | volume = 23 | issue = 2| pages = 433–439 | doi=10.1111/j.1420-9101.2009.01906.x| pmid = 20002244 | s2cid = 6533055 }}</ref><ref>{{cite journal | last1 = Selz | first1 = O.M. | last2 = Pierotti | first2 = M.E.R. | last3 = Mann | first3 = M.E. | last4 = Schmid | first4 = C. | last5 = Seehausen | first5 = O. | year = 2014 | title = Female preference for male color is necessary and sufficient for assortative mating in 2 cichlid sister species | journal = Behavioral Ecology | volume = 25 | issue = 3| pages = 612–626 | doi=10.1093/beheco/aru024| doi-access = free }}</ref> This helps maintain sympatric speciation within the lakes. Cichlids also use acoustic reproductive communication. The male cichlid quivers as a ritualistic display for the female which produces a certain number of pulses and pulse period. Female choice for good genes and sensory bias is one of the deciding factors in this case, selecting for calls that are within her species and that give the best fitness advantage to increase the survivability of the offspring.<ref>{{cite journal | last1 = Amorim | first1 = M.C.P. | last2 = Simóes | first2 = J.M. | last3 = Fonseca | first3 = P.J. | last4 = Turners | first4 = G.F. | year = 2008 | title = Species differences in courtship acoustic signals among five Lake Malawi cichlid species (Pseudotropheus spp.) | journal = J. Fish Biol. | volume = 72 | issue = 6| pages = 1355–1368 | doi=10.1111/j.1095-8649.2008.01802.x| bibcode = 2008JFBio..72.1355A | hdl = 10400.12/1391 | hdl-access = free }}</ref><ref>{{cite journal | last1 = Maruska | first1 = K.P. | last2 = Ung | first2 = U.S. | last3 = Fernald | first3 = R.D. | year = 2012 | title = The African Cichlid Fish Astatotilapia burtoni Uses Acoustic Communication for Reproduction: Sound Production, Hearing, and Behavioral Significance | journal = PLOS ONE | volume = 7 | issue = 5| page = e37612 | doi=10.1371/journal.pone.0037612 | pmid=22624055 | pmc=3356291| bibcode = 2012PLoSO...737612M | doi-access = free }}</ref> Male-male competition is a form of intrasexual selection and also has an effect on speciation in African cichlids. Ritualistic fighting among males establishes which males are going to be more successful in mating. This is important in sympatric speciation because species with similar males may be competing for the same females. There may be a fitness advantage for one phenotype that could allow one species to invade another.<ref>{{cite journal | last1 = Seehausen | first1 = O. | last2 = Schulter | first2 = D. | year = 2004 | title = Male-male competition and nuptial-colour displacement as a diversifying force in Lake Victoria cichlid fishes | journal = Proc. R. Soc. Lond. | volume = 241 | issue = 1546| pages = 1345–1353 | doi = 10.1098/rspb.2004.2737 | pmid = 15306332 | pmc = 1691729 }}</ref><ref>{{cite journal | last1 = Dijkstra | first1 = P.D. | last2 = Seehausen | first2 = O. | last3 = Groothuis | first3 = T.G.G. | year = 2005 | title = Direct male-male competition can facilitate invasion of new colour types in Lake Victoria cichlids | journal = Behav. Ecol. Sociobiol. | volume = 58 | issue = 2| pages = 136–143 | doi=10.1007/s00265-005-0919-5| bibcode = 2005BEcoS..58..136D | s2cid = 22364262 | url = https://boris.unibe.ch/49522/ }}</ref> Studies show this effect in species that are genetically similar, have the capability to interbreed, and show phenotypic color variation. Ecological character displacement is another means for sympatric speciation. Within each lake there are different niches that a species could occupy. For example, different diets and depth of the water could help to maintain isolation between species in the same lake.

[[Allochronic speciation|Allochrony]] offers some empirical evidence that sympatric speciation has taken place, as many examples exist of recently diverged ([[sister taxon|sister taxa]]) allochronic species. A case of ongoing sympatric divergence due to allochrony might be found in the marine insect [[Clunio marinus]].<ref>{{Cite journal|last1=Kaiser|first1=Tobias S.|last2=Haeseler|first2=Arndt von|last3=Tessmar-Raible|first3=Kristin|last4=Heckel|first4=David G.|date=2021|title=Timing strains of the marine insect Clunio marinus diverged and persist with gene flow|journal=Molecular Ecology|language=en|volume=30|issue=5|pages=1264–1280|doi=10.1111/mec.15791|pmid=33410230|issn=1365-294X|doi-access=free|bibcode=2021MolEc..30.1264K |hdl=21.11116/0000-0007-AC55-8|hdl-access=free}}</ref>

A rare example of sympatric speciation in animals is the divergence of "resident" and "transient" [[orca]] forms in the northeast Pacific.<ref>{{cite journal |doi=10.1093/jhered/89.2.121 |title=Low genetic variation among killer whales (''Orcinus orca'') in the eastern North Pacific and genetic differentiation between foraging specialists |year=1998 |last1=Hoelzel |first1=A. R. |last2=Dahlheim |first2=M. |last3=Stern |first3=S. J. |journal=Journal of Heredity |volume=89 |issue=2 |pages=121–8 |pmid=9542159|doi-access=free }}</ref> Resident and transient orcas inhabit the same waters, but avoid each other and do not interbreed. The two forms hunt different prey species and have different diets, vocal behaviour, and social structures. Some divergences between species could also result from contrasts in microhabitats. A population bottleneck occurred around 200,000 years ago greatly reducing the population size at the time as well as the variance of genes which allowed several ecotypes to emerge afterwards.<ref>{{cite journal|doi=10.1101/gr.102954.109 | volume=20 | issue=7 | title=Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species | journal=Genome Research | pages=908–916 | pmid=20413674 | pmc=2892092 | year=2010 | last1 = Morin | first1 = PA | last2 = Archer | first2 = FI | last3 = Foote | first3 = AD | last4 = Vilstrup | first4 = J | last5 = Allen | first5 = EE | last6 = Wade | first6 = P | last7 = Durban | first7 = J | last8 = Parsons | first8 = K | last9 = Pitman | first9 = R | last10 = Li | first10 = L | last11 = Bouffard | first11 = P | last12 = Abel Nielsen | first12 = SC | last13 = Rasmussen | first13 = M | last14 = Willerslev | first14 = E | last15 = Gilbert | first15 = MT | last16 = Harkins | first16 = T}}</ref>

The [[European polecat]] (''Mustela putorius'') exhibited a rare dark phenotype similar to the European [[mink]] (''Mustela lutreola'') phenotype, which is directly influenced by peculiarities of forest brooks.<ref>{{cite journal |doi=10.1046/j.1420-9101.2001.00275.x |title=Genetic divergence without spatial isolation in polecat Mustela putorius populations |year=2001 |last1=Lodé |first1=T. |journal=Journal of Evolutionary Biology |volume=14 |issue=2 |pages=228–36|s2cid=83203438 |doi-access=free }}</ref>