Editing Speciation (section)

=== Sympatric ===
{{Main|Sympatric speciation}}
[[File:Pundamilia (Haplochromis) nyererei male.jpg|thumb|left|[[Cichlid]]s such as ''[[Haplochromis nyererei]]'' diversified by [[sympatric speciation]] in the [[Rift Valley lakes]].]]

Sympatric speciation is the formation of two or more descendant species from a single ancestral species all occupying the same geographic location.

Often-cited examples of sympatric speciation are found in insects that become dependent on different [[Host (biology)|host]] plants in the same area.<ref name="rhagoletis1">{{cite journal |last1=Feder |first1=Jeffrey L. |author2=Xianfa Xie |last3=Rull |first3=Juan |last4=Velez |first4=Sebastian |last5=Forbes |first5=Andrew |last6=Leung |first6=Brian |last7=Dambroski |first7=Hattie |last8=Filchak |first8=Kenneth E. |last9=Aluja |first9=Martin |display-authors=3 |date=May 3, 2005 |title=Mayr, Dobzhansky, and Bush and the complexities of sympatric speciation in ''Rhagoletis'' |journal=PNAS |volume=102 |issue=Suppl 1 |pages=6573–6580 |doi=10.1073/pnas.0502099102 |pmc=1131876 |pmid=15851672 |bibcode=2005PNAS..102.6573F |doi-access=free }}</ref><ref name=hostplant1>{{cite journal |last1=Berlocher |first1=Stewart H. |last2=Feder |first2=Jeffrey L. |date=January 2002 |title=Sympatric Speciation in Phytophagous Insects: Moving Beyond Controversy? |journal=Annual Review of Entomology |volume=47 |pages=773–815 |doi=10.1146/annurev.ento.47.091201.145312 |pmid=11729091|s2cid=9677456 }}</ref>

The best known example of sympatric speciation is that of the [[cichlid]]s of [[East Africa]] inhabiting the [[Rift Valley lakes]], particularly [[Lake Victoria]], [[Lake Malawi]] and [[Lake Tanganyika]]. There are over 800 described species, and according to estimates, there could be well over 1,600 species in the region. Their evolution is cited as an example of both [[natural selection|natural]] and [[sexual selection]].<ref>{{cite journal |last1=Machado |first1=Heather E. |last2=Pollen |first2=Alexander A. |last3=Hofmann |first3=Hans A. |last4=Renn |first4=Suzy C. P. |display-authors=3 |date=December 2009 |title=Interspecific profiling of gene expression informed by comparative genomic hybridization: A review and a novel approach in African cichlid fishes |journal=[[Integrative and Comparative Biology]] |volume=49 |issue=6 |pages=644–659 |doi=10.1093/icb/icp080 |pmid=21665847|doi-access=free }}</ref><ref>{{cite journal |last1=Fan |first1=Shaohua |last2=Elmer |first2=Kathryn R. |last3=Meyer |first3=Axel |author-link3=Axel Meyer |date=February 5, 2012 |title=Genomics of adaptation and speciation in cichlid fishes: recent advances and analyses in African and Neotropical lineages |journal=[[Philosophical Transactions of the Royal Society B]]  |volume=367 |issue=1587 |pages=385–394 |doi=10.1098/rstb.2011.0247 |pmc=3233715 |pmid=22201168}}</ref> A 2008 study suggests that sympatric speciation has occurred in [[Tennessee cave salamander]]s.<ref>{{cite journal |last1=Niemiller |first1=Matthew L. |last2=Fitzpatrick |first2=Benjamin M. |last3=Miller |first3=Brian T. |date=May 2008 |title=Recent divergence with gene flow in Tennessee cave salamanders (Plethodontidae: ''Gyrinophilus'') inferred from gene genealogies |journal=[[Molecular Ecology]] |volume=17 |issue=9 |pages=2258–2275 |doi=10.1111/j.1365-294X.2008.03750.x |pmid=18410292|s2cid=20761880 |doi-access=free |bibcode=2008MolEc..17.2258N }}</ref> Sympatric speciation driven by ecological factors may also account for the extraordinary diversity of crustaceans living in the depths of Siberia's [[Lake Baikal]].<ref>{{cite journal |last1=Martens |first1=Koen |title=Speciation in ancient lakes |journal=Trends in Ecology & Evolution |date=May 1997 |volume=12 |issue=5 |pages=177–182 |doi=10.1016/S0169-5347(97)01039-2|pmid=21238028 |bibcode=1997TEcoE..12..177M }}</ref>

Budding speciation has been proposed as a particular form of sympatric speciation, whereby small groups of individuals become progressively more isolated from the ancestral stock by breeding preferentially with one another. This type of speciation would be driven by the conjunction of various advantages of inbreeding such as the expression of advantageous recessive phenotypes, reducing the recombination load, and reducing the cost of sex.<ref>{{cite journal |last1=Joly |first1=E. |title=The existence of species rests on a metastable equilibrium between inbreeding and outbreeding. An essay on the close relationship between speciation, inbreeding and recessive mutations |journal=Biology Direct |date=9 December 2011 |volume=6 |page=62 |pmid=22152499 |doi=10.1186/1745-6150-6-62|pmc=3275546 |doi-access=free }}</ref>

[[File:Rhagoletis pomonella.jpg|thumb|''[[Rhagoletis pomonella]]'', the hawthorn fly, appears to be in the process of sympatric speciation.]]

The hawthorn fly (''[[Rhagoletis pomonella]]''), also known as the apple maggot fly, appears to be undergoing sympatric speciation.<ref>{{cite journal |last1=Feder |first1=Jeffrey L. |last2=Roethele |first2=Joseph B. |last3=Filchak |first3=Kenneth |last4=Niedbalski |first4=Julie |last5=Romero-Severson |first5=Jeanne |display-authors=3 |date=March 2003 |title=Evidence for inversion polymorphism related to sympatric host race formation in the apple maggot fly, ''Rhagoletis pomonella'' |url=http://www.genetics.org/content/163/3/939.long |journal=[[Genetics (journal)|Genetics]]  |volume=163 |issue=3 |pages=939–953 |doi=10.1093/genetics/163.3.939 |pmc=1462491 |pmid=12663534 |access-date=2015-09-07}}</ref> Different populations of hawthorn fly feed on different fruits. A distinct population emerged in North America in the 19th century some time after [[apple]]s, a non-native species, were introduced. This apple-feeding population normally feeds only on apples and not on the historically preferred fruit of [[Crataegus|hawthorns]]. The current hawthorn feeding population does not normally feed on apples. Some evidence, such as that six out of thirteen [[Alloenzyme|allozyme]] loci are different, that hawthorn flies mature later in the season and take longer to mature than apple flies; and that there is little evidence of interbreeding (researchers have documented a 4–6% hybridization rate) suggests that sympatric speciation is occurring.<ref>{{cite journal |last1=Berlocher |first1=Stewart H. |last2=Bush |first2=Guy L. |date=June 1982 |title=An electrophoretic analysis of Rhagoletis (Diptera: Tephritidae) phylogeny |journal=[[Systematic Zoology]] |volume=31 |issue=2 |pages=136–155 |doi=10.2307/2413033 |jstor=2413033}}</ref>