Editing Cladogenesis (section)

{{short description|Evolutionary splitting of a parent species into two distinct species, forming a clade}}
[[File:Hawaje-NoRedLine.jpg|thumb|right|260px|An example of cladogenesis today is the [[Hawaiian Islands|Hawaiian archipelago]], to which stray organisms traveled across the ocean via ocean currents and winds. Most of the species on the islands are not found anywhere else on Earth due to evolutionary divergence.]]

'''Cladogenesis''' is an [[evolution]]ary splitting of a parent [[species]] into two distinct species, forming a [[clade]].<ref name=Gould&Eldredge1977>{{cite journal | last1=Gould | first1=Stephen Jay | last2=Eldredge | first2=Niles | year=1977 | title=Punctuated equilibria: the tempo and mode of evolution reconsidered | url=http://www.nileseldredge.com/pdf_files/Punctuated_Equilibria_Gould_Eldredge_1977.pdf | journal=Paleobiology | volume=3 | issue=2 | pages=115–151 [145] | doi=10.1017/s0094837300005224 | access-date=2015-04-03 | archive-date=2014-06-24 | archive-url=https://web.archive.org/web/20140624060126/http://www.nileseldredge.com/pdf_files/Punctuated_Equilibria_Gould_Eldredge_1977.pdf | url-status=dead }}</ref>

This event usually occurs when a few organisms end up in [[Allopatric speciation|new, often distant areas]] or when environmental changes cause several extinctions, opening up ecological niches for the survivors and causing [[population bottleneck]]s and [[founder effect]]s changing [[allele frequency|allele frequencies]] of diverging populations compared to their ancestral population. The events that cause these species to originally separate from each other over distant areas may still allow both of the species to have equal chances of surviving, reproducing, and even evolving to better suit their environments while still being two distinct species due to subsequent [[natural selection]], [[mutation]]s and [[genetic drift]].<ref>{{cite journal | last1=Strotz | first1=LC | last2=Allen | first2=AP | year=2013 | title=Assessing the role of cladogenesis in macroevolution by integrating fossil and molecular evidence | journal=PNAS | volume=110 | issue=8| pages=2904–9 |doi=10.1073/pnas.1208302110 | pmid=23378632 | pmc=3581934| bibcode=2013PNAS..110.2904S | doi-access=free }}</ref>

Cladogenesis is in contrast to [[anagenesis]], in which an ancestral [[species]] gradually accumulates change, and eventually, when enough is accumulated, the species is sufficiently distinct and different enough from its original starting form that it can be labeled as a new form - a new species. With anagenesis, the lineage in a [[phylogenetic tree]] does not split.

To determine whether a speciation event is cladogenesis or anagenesis, researchers may use simulation, [[evidence]] from fossils, molecular evidence from the DNA of different living species, or modelling. It has however been debated whether the distinction between cladogenesis and anagenesis is necessary at all in evolutionary theory.<ref>{{cite journal | last1=Vaux | first1=F | last2=Trewick | first2=SA | last3=Morgan-Richards | first3=M | year=2016 | title=Lineages, splits and divergence challenge whether the terms anagenesis and cladogenesis are necessary | journal=Biological Journal of the Linnean Society | volume=117 | issue=2| pages=165–176 |doi=10.1111/bij.12665| doi-access=free }}</ref><ref>{{cite journal |doi=10.1111/bij.12885 |title=Species, lineages, splitting, and divergence: why we still need 'anagenesis' and 'cladogenesis' |journal=Biological Journal of the Linnean Society |volume=120 |issue=2 |pages=474–479 |year=2017 |last1=Allmon |first1=Warren|doi-access=free }}</ref><ref>{{cite journal |doi=10.1111/bij.12872 |title=Speciation through the looking-glass |journal=Biological Journal of the Linnean Society |volume=120 |issue=2 |pages=480–488 |year=2017 |last1=Vaux |first1=Felix |last2=Trewick |first2=Steven A. |last3=Morgan-Richards |first3=Mary |doi-access=free }}</ref>