View source for Divergent evolution

{{short description|Accumulation of differences between closely related species populations, leading to speciation}}

[[File:Darwin's finches.jpeg|right|thumb|[[Darwin's finches]] are a clear and famous example of divergent evolution, in which an ancestral species [[adaptive radiation|radiates]] into a number of descendant species with both similar and different traits.]]
{{Evolutionary biology}}

'''Divergent evolution''' or '''divergent selection''' is the accumulation of differences between closely related populations within a [[species]], sometimes leading to [[speciation]]. Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in [[allopatric speciation|allopatric]] or [[peripatric speciation]]) and experience different [[Natural selection|selective pressures]] that cause [[adaptation]]s. After many generations and continual evolution, the populations become [[reproductive isolation|less able to interbreed]] with one another.<ref>{{cite web |url=http://evolution.berkeley.edu/evolibrary/article/speciationmodes_05 |title=Sympatric speciation |access-date=2 February 2016}}</ref> The American naturalist [[J. T. Gulick]] (1832–1923) was the first to use the term "divergent evolution", with its use becoming widespread in modern evolutionary literature.<ref name="Gulick">{{closed access}} {{cite journal |last=Gulick |first=John T. |author-link=J. T. Gulick |date=September 1888 |title=Divergent Evolution through Cumulative Segregation |url=https://books.google.com/books?id=cNQUAAAAYAAJ&q=editions:HARVARD32044106309446 |journal=Journal of the Linnean Society of London, Zoology |volume=20 |issue=120 |pages=189–274 |doi=10.1111/j.1096-3642.1888.tb01445.x |access-date=26 September 2011 |doi-access=free}} {{subscription required}}</ref> Examples of divergence in nature are the [[adaptive radiation]] of the [[Darwin's finches|finches]] of the [[Galapagos|Galápagos]], changes in [[Mobbing (animal behavior)|mobbing]] behavior of the [[kittiwake]], and the evolution of the modern-day dog from the wolf.

The term can also be applied in [[molecular evolution]], such as to [[protein]]s that derive from [[homology (biology)|homologous]] genes. Both orthologous genes (resulting from a speciation event) and paralogous genes (resulting from [[gene duplication]]) can illustrate divergent evolution. Through [[gene duplication]], it is possible for divergent evolution to occur between two genes within a species. Similarities between species that have diverged are due to their common origin, so such similarities are homologies.<ref>{{Citation |last1=Zuckerkandl |first1=EMILE |title=Evolutionary Divergence and Convergence in Proteins |date=1965-01-01 |work=Evolving Genes and Proteins |pages=97–166 |editor-last=Bryson |editor-first=Vernon |url=https://www.sciencedirect.com/science/article/pii/B9781483227344500176 |access-date=2024-03-24 |publisher=Academic Press |isbn=978-1-4832-2734-4 |last2=Pauling |first2=LINUS |editor2-last=Vogel |editor2-first=Henry J.}}</ref>

== Causes ==
Animals undergo divergent evolution for a number of reasons linked to changes in environmental or social pressures. This could include changes in the environment, such access to food and shelter.<ref name=":0">{{Cite web |last1=Clark |first1=Mary Ann |last2=Douglas |first2=Matthew |last3=Choi |first3=Jung |date=2018-03-28 |title=18.1 Understanding Evolution - Biology 2e {{!}} OpenStax |url=https://openstax.org/books/biology-2e/pages/18-1-understanding-evolution |access-date=2024-03-24 |website=openstax.org |language=English}}</ref> It could also result from changes in predators, such as new adaptations, an increase or decrease in number of active predators, or the introduction of new predators.<ref>{{Cite journal |last1=Johnson |first1=Jerald B. |last2=Belk |first2=Mark C. |date=2020-10-31 |title=Predators as Agents of Selection and Diversification |journal=Diversity |language=en |volume=12 |issue=11 |pages=415 |doi=10.3390/d12110415 |doi-access=free |issn=1424-2818}}</ref> Divergent evolution can also be a result of mating pressures such as increased competition for mates or [[selective breeding]] by humans.<ref>{{Cite web |title=Artificial selection |url=https://evolution.berkeley.edu/lines-of-evidence/artificial-selection/ |access-date=2024-03-24 |website=evolution.berkeley.edu}}</ref>

== Distinctions ==
Divergent evolution is a type of evolution and is distinct from [[convergent evolution]] and [[parallel evolution]], although it does share similarities with the other types of [[evolution]].<ref>{{Cite web |date=2018-07-13 |title=18.5G: Convergent Evolution |url=https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/18%3A_Evolution_and_the_Origin_of_Species/18.05%3A_Evidence_of_Evolution/18.5G%3A_Convergent_Evolution |access-date=2024-03-24 |website=Biology LibreTexts |language=en}}</ref>

=== Divergent versus convergent evolution ===
[[Convergent evolution]] is the development of analogous structures that occurs in different species as a result of those two species facing similar environmental pressures and adapting in similar ways. It differs from divergent evolution as the species involved do not descend from a closely related common ancestor and the traits accumulated are similar.<ref name=":0" /> An example of convergent evolution is the development of flight in birds, bats, and insects, all of which are not closely related but share analogous structures allowing for flight.<ref>{{Cite book |last=Alexander |first=David E. |url=https://books.google.com/books?id=H6xUCgAAQBAJ&pg=PT28 |title=On the Wing: Insects, Pterosaurs, Birds, Bats and the Evolution of Animal Flight |date=2015-09-02 |publisher=Oxford University Press |isbn=978-0-19-999679-7 |language=en}}</ref>

=== Divergent versus parallel evolution ===
[[Parallel evolution]] is the development of a similar trait in species descending from a common ancestor. It is comparable to divergent evolution in that the species are descend from a common ancestor, but the traits accumulated are similar due to similar environmental pressures while in divergent evolution the traits accumulated are different.<ref>{{Cite journal |last=Pearce |first=Trevor |date=2012-06-01 |title=Convergence and Parallelism in Evolution: A Neo-Gouldian Account |url=https://www.journals.uchicago.edu/doi/10.1093/bjps/axr046 |journal=The British Journal for the Philosophy of Science |language=en |volume=63 |issue=2 |pages=429–448 |doi=10.1093/bjps/axr046 |issn=0007-0882|url-access=subscription }}</ref> An example of parallel evolution is that certain arboreal frog species, 'flying' frogs, in both Old World families and New World families, have developed the ability of gliding flight. They have "enlarged hands and feet, full webbing between all fingers and toes, lateral skin flaps on the arms and legs, and reduced weight per snout-vent length".<ref>{{cite journal|last=Emerson|first=S.B.|author2=M.A.R. Koehl|author2-link = M. A. R. Koehl|title=The interaction of behavioral and morphological change in the evolution of a novel locomotor type: 'Flying' frogs.|journal=Evolution|year=1990|volume=44|issue=8|pages=1931–1946|doi=10.2307/2409604|jstor=2409604|pmid=28564439}}</ref>

== Darwin's finches ==
One of the first recorded examples of divergent evolution is the case of [[Darwin's Finches]]. During Darwin's travels to the [[Galápagos Islands]], he discovered several different species of finch, living on the different islands. Darwin observed that the finches had different beaks specialized for that species of finches' diet.<ref>{{Cite book |last1=Desmond |first1=Adrian J. |title=Darwin |last2=Moore |first2=James R. |date=1991 |publisher=Joseph |isbn=978-0-7181-3430-3 |edition=1. publ |location=London}}</ref> Some finches had short beaks for eating nuts and seeds, other finches had long thin beaks for eating insects, and others had beaks specialized for eating cacti and other plants.<ref>{{Cite book |last=Grant |first=Peter R. |title=Ecology and evolution of Darwin's finches |date=1999 |publisher=Princeton University Press |isbn=978-0-691-04865-9 |location=Princeton, N.J}}</ref> He concluded that the finches evolved from a shared common ancestor that lived on the islands, and due to [[geographic isolation]], evolved to fill the particular niche on each of the islands.<ref>{{Cite book |last1=Grant |first1=Peter R. |url=https://www.worldcat.org/title/ocm82673670 |title=How and why species multiply: the radiation of Darwin's finches |last2=Grant |first2=B. Rosemary |date=2008 |publisher=Princeton University Press |isbn=978-0-691-13360-7 |series=Princeton series in evolutionary biology |location=Princeton |oclc=ocm82673670}}</ref> This is supported by modern day [[genomic sequencing]].<ref>{{Cite journal |last1=Lamichhaney |first1=Sangeet |last2=Berglund |first2=Jonas |last3=Almén |first3=Markus Sällman |last4=Maqbool |first4=Khurram |last5=Grabherr |first5=Manfred |last6=Martinez-Barrio |first6=Alvaro |last7=Promerová |first7=Marta |last8=Rubin |first8=Carl-Johan |last9=Wang |first9=Chao |last10=Zamani |first10=Neda |last11=Grant |first11=B. Rosemary |last12=Grant |first12=Peter R. |last13=Webster |first13=Matthew T. |last14=Andersson |first14=Leif |date=2015-02-11 |title=Evolution of Darwin's finches and their beaks revealed by genome sequencing |url=https://www.nature.com/articles/nature14181 |journal=Nature |language=en |volume=518 |issue=7539 |pages=371–375 |doi=10.1038/nature14181 |pmid=25686609 |bibcode=2015Natur.518..371L |issn=1476-4687|url-access=subscription }}</ref>

==Divergent evolution in dogs==
Another example of divergent evolution is the [[origin of the domestic dog]] and the modern [[wolf]], who both shared a common ancestor.<ref>{{Cite journal |last=Vila |first=C. |date=1999-01-01 |title=Phylogenetic relationships, evolution, and genetic diversity of the domestic dog |url=https://academic.oup.com/jhered/article-lookup/doi/10.1093/jhered/90.1.71 |journal=Journal of Heredity |volume=90 |issue=1 |pages=71–77 |doi=10.1093/jhered/90.1.71|pmid=9987908 }}</ref> Comparing the anatomy of dogs and wolves supports this claim as they have similar body shape, skull size, and limb formation.<ref>{{Cite journal |last=Honeycutt |first=Rodney L |date=2010-03-09 |title=Unraveling the mysteries of dog evolution |journal=BMC Biology |volume=8 |pages=20 |doi=10.1186/1741-7007-8-20 |doi-access=free |issn=1741-7007 |pmc=2841097 |pmid=20214797}}</ref> This is even more obvious in some species of dogs, such as [[malamute]]s and [[Husky|huskies]], who appear even more physically and behaviorally similar.<ref>{{Cite journal |last1=Freedman |first1=Adam H. |last2=Lohmueller |first2=Kirk E. |last3=Wayne |first3=Robert K. |date=2016-11-01 |title=Evolutionary History, Selective Sweeps, and Deleterious Variation in the Dog |url=https://www.annualreviews.org/doi/10.1146/annurev-ecolsys-121415-032155 |journal=Annual Review of Ecology, Evolution, and Systematics |language=en |volume=47 |issue=1 |pages=73–96 |doi=10.1146/annurev-ecolsys-121415-032155 |issn=1543-592X|url-access=subscription }}</ref> There is a divergent genomic sequence of the [[mitochondrial DNA]] of wolves and dogs dated to over 100,000 years ago, which further supports the theory that dogs and wolves have diverged from shared ancestry.<ref>{{Cite journal |last1=Vilà |first1=C. |last2=Savolainen |first2=P. |last3=Maldonado |first3=J. E. |last4=Amorim |first4=I. R. |last5=Rice |first5=J. E. |last6=Honeycutt |first6=R. L. |last7=Crandall |first7=K. A. |last8=Lundeberg |first8=J. |last9=Wayne |first9=R. K. |date=1997-06-13 |title=Multiple and ancient origins of the domestic dog |url=https://pubmed.ncbi.nlm.nih.gov/9180076/ |journal=Science |volume=276 |issue=5319 |pages=1687–1689 |doi=10.1126/science.276.5319.1687 |issn=0036-8075 |pmid=9180076}}</ref>

== Divergent evolution in kittiwakes ==
Another example of divergent evolution is the behavioral changes in the [[kittiwake]] as opposed to other species of [[gull]]s. Ancestorial and other modern-day species of gulls exhibit a [[Mobbing (animal behavior)|mobbing]] behavior in order to protect their young due the nesting at ground-level where they are susceptible to predators.<ref>{{cite book |last=Alcock |first=John |title=Animal Behavior: An Evolutionary Approach, Tenth Edition |year=2013 |pages=101–109}}</ref> As a result of migration and environmental changes, the kittiwake nest solely on cliff faces. As a result, their young are protected from predatory reptiles, mammals, and birds who struggle with the climb and cliff-face weather conditions, and they do not exhibit this mobbing behavior.<ref>{{cite journal |last=Cullen |first=Esther |date=April 2008 |title=Adaptations in the kittiwake to cliff-nesting |journal=Ibis |volume=99 |issue=2 |pages=275–302 |doi=10.1111/j.1474-919x.1957.tb01950.x}}</ref>

== Divergent evolution in cacti ==
Another example of divergent evolution is the split forming the [[Cactaceae]] family approximately dated in the late Miocene. Due to increase in arid climates, following the [[Eocene–Oligocene extinction event|Eocene–Oligocene]] event, these ancestral plants evolved to survive in the new climates.<ref>{{Cite journal |last1=Hernández-Hernández |first1=Tania |last2=Brown |first2=Joseph W. |last3=Schlumpberger |first3=Boris O. |last4=Eguiarte |first4=Luis E. |last5=Magallón |first5=Susana |date=June 2014 |title=Beyond aridification: multiple explanations for the elevated diversification of cacti in the New World Succulent Biome |url=https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.12752 |journal=New Phytologist |language=en |volume=202 |issue=4 |pages=1382–1397 |doi=10.1111/nph.12752 |pmid=24611540 |issn=0028-646X|hdl=2027.42/106989 |hdl-access=free }}</ref> Cacti evolved to have [[areole]]s, [[Succulent plant|succulent]] [[Plant stem|stems]], and some have light leaves, with the ability to store water for up to months.<ref>{{Cite web |title= |url=http://web.mac.com/redifiori/Russell_Di_Fiori/Phylogenetics_files/Edwards_Donoghue2006.pdf |access-date=2024-03-25 |archive-url=https://web.archive.org/web/20120213193904/http://web.mac.com/redifiori/Russell_Di_Fiori/Phylogenetics_files/Edwards_Donoghue2006.pdf |archive-date=2012-02-13 }}</ref> The plants they diverged from either went extinct leaving little in the fossil record or migrated surviving in less arid climates.<ref>{{Cite journal |last1=Arakaki |first1=Mónica |last2=Christin |first2=Pascal-Antoine |last3=Nyffeler |first3=Reto |last4=Lendel |first4=Anita |last5=Eggli |first5=Urs |last6=Ogburn |first6=R. Matthew |last7=Spriggs |first7=Elizabeth |last8=Moore |first8=Michael J. |last9=Edwards |first9=Erika J. |date=2011-05-17 |title=Contemporaneous and recent radiations of the world's major succulent plant lineages |journal=Proceedings of the National Academy of Sciences |language=en |volume=108 |issue=20 |pages=8379–8384 |doi=10.1073/pnas.1100628108 |doi-access=free |issn=0027-8424 |pmc=3100969 |pmid=21536881|bibcode=2011PNAS..108.8379A }}</ref>

== See also ==
* [[Cladistics]]
* [[Contingency (evolutionary biology)]]
* [[Devolution (biology)|Devolution]]
* [[Chronospecies]]

== References ==
{{reflist|30em}}

==Further reading==
* {{cite book |title=Improbable Destinies: Fate, Chance, and the Future of Evolution |author=Jonathan B. Losos |year=2017 |publisher=Riverhead Books |isbn=978-0399184925 }}

{{evo ecol}}

[[Category:Evolutionary biology]]
[[Category:Evolution of animals]]