Editing Ecotype (section)

== Ecotype and speciation ==
{{Cquote
| quote = Just as sunlight can appear as a dim crack in the sky before clouds part, the coarse boundaries of ecotypes may appear as a separation of principle[sic] component clusters before speciation.
| author = David B. Lowry
| source = Ecotypes and the controversy over stages in the formation of new species, Biological Journal of the Linnean Society.
| width = 40
| float = Right
}}
The birth of the term 'ecotype' originally came from early interest in understanding speciation.<ref name=dbl/> Darwin argued that species evolved through natural selection from variations within population which he termed as 'varieties'. <ref>{{Cite web |date=2022-11-18 |title=Species and varieties |url=https://www.darwinproject.ac.uk/commentary/life-sciences/species-and-varieties |access-date=2024-10-18 |website=Darwin Correspondence Project |language=en}}</ref> Later on, through a series of experiments, Turresson studied the effect of the environment on heritable plant variation and came up with the term 'ecotype' to denote differences between groups occupying distinct habitats.<ref name="G."/> This, he argued, was a genotypical response of plants to habitat type and it denotes a first step toward isolating reproductive barriers that facilitate the emergence of 'species' via divergence and, ultimately, genetic isolation.<ref name="G."/><ref>{{Cite journal |last1=Johannesson |first1=Kerstin |last2=Panova |first2=Marina |last3=Kemppainen |first3=Petri |last4=André |first4=Carl |last5=Rolán-Alvarez |first5=Emilio |last6=Butlin |first6=Roger K. |date=2010-06-12 |title=Repeated evolution of reproductive isolation in a marine snail: unveiling mechanisms of speciation |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |language=en |volume=365 |issue=1547 |pages=1735–1747 |doi=10.1098/rstb.2009.0256 |pmid=20439278 |issn=0962-8436|pmc=2871885 }}</ref><ref>{{Cite journal |last1=Rieseberg |first1=Loren H. |last2=Willis |first2=John H. |date=2007-08-17 |title=Plant Speciation |journal=Science |language=en |volume=317 |issue=5840 |pages=910–914 |doi=10.1126/science.1137729 |issn=0036-8075 |pmc=2442920 |pmid=17702935|bibcode=2007Sci...317..910R }}</ref> In his 1923 paper, Turesson states that variation among species in a population is not random, rather, it is driven by environmental selection pressure.<ref name=gt2>{{Cite journal |last=Turesson |first=Göte |date=2010-07-09 |title=The Plant Species in Relation to Habitat and Climate: Contributions to the Knowledge of Genecological Units |journal=Hereditas |language=en |volume=6 |issue=2 |pages=147–236 |doi=10.1111/j.1601-5223.1925.tb03139.x|doi-access=free }}</ref> For example, the maturity of ''Trifolium subterraneum'', a clover which was found to correlate to moisture condition; when sown in low rainfall areas of Adelaide after a few years the population would consist of genotypes that produced seeds early in the season (early genotype), however in higher rainfall areas the clover population would shift to mid-season genotypes, differences among population of ''Trifolium subterraneum'' is in response to the selective action of the habitat.<ref name=":1">{{Cite journal |last=Gregor |first=J. W. |date=January 1944 |title=THE ECOTYPE |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.1944.tb00299.x |journal=Biological Reviews |language=en |volume=19 |issue=1 |pages=20–30 |doi=10.1111/j.1469-185X.1944.tb00299.x |issn=1464-7931|url-access=subscription }}</ref> These adaptive differences were hereditary and would emerge in response to specific environmental conditions.<ref>{{Cite journal |date=1946-08-01 |title=Trifolium Subterraneum Linn. in Australia: an Autecological Study |url=https://www.nature.com/articles/158176a0 |journal=Nature |language=en |volume=158 |issue=4005 |pages=176–177 |doi=10.1038/158176a0 |bibcode=1946Natur.158..176. |issn=1476-4687}}</ref> Heritable differences is a key feature in ecotypic variation.<ref>{{Cite journal |last=Turesson |first=Göte |date=2010-07-09 |title=The Species and the Variety as Ecological Units |journal=Hereditas |language=en |volume=3 |issue=1 |pages=100–113 |doi=10.1111/j.1601-5223.1922.tb02727.x|doi-access=free }}</ref> Ecotypic variation is as a result of particular environmental trends.<ref name=":1" /> Individuals, which are able to survive and reproduce successfully pass on their genes to the next generation and establish a population best adapted to the local environment. <ref>{{Cite web |title=Ecotypes |url=https://www2.nau.edu/~gaud/bio300w/ecotype.htm |access-date=2024-10-29 |website=www2.nau.edu}}</ref> Ecotypic variation is therefore described to have a genetic base, and are brought about by interactions between an individual's genes and the environment. <ref>{{Cite journal |last1=Stronen |first1=Astrid V. |last2=Norman |first2=Anita J. |last3=Vander Wal |first3=Eric |last4=Paquet |first4=Paul C. |date=2022-01-19 |title=The relevance of genetic structure in ecotype designation and conservation management |journal=Evolutionary Applications |language=en |volume=15 |issue=2 |pages=185–202 |doi=10.1111/eva.13339 |issn=1752-4571 |pmc=8867706 |pmid=35233242|bibcode=2022EvApp..15..185S }}</ref> An example of ecotype formation that lead to reproductive isolation and ultimately speciation can be found in the small sea snail periwinkle, [[Littorina saxatilis]]. <ref>{{Cite journal |last=Johannesson |first=Kerstin |date=2009-01-01 |title=Inverting the null-hypothesis of speciation: a marine snail perspective |url=https://link.springer.com/article/10.1007/s10682-007-9225-1 |journal=Evolutionary Ecology |language=en |volume=23 |issue=1 |pages=5–16 |doi=10.1007/s10682-007-9225-1 |bibcode=2009EvEco..23....5J |issn=1573-8477|url-access=subscription }}</ref> It is distributes across different habitats such as lagoons, salt marshes and rocky shores the range of distribution is from Portugal to Novaya Zemlaya and Svalbard and from North Carolina to Greenland.<ref name=":3">{{Cite journal |date=November 1996 |title=D.G. Reid Systematics and evolution of Littorina. x, 463p. London: The Ray Society, 1996. (Volume 164 of the series). |url=http://dx.doi.org/10.1017/s002531540004114x |journal=Journal of the Marine Biological Association of the United Kingdom |volume=76 |issue=4 |pages=1119 |doi=10.1017/s002531540004114x |bibcode=1996JMBUK..76T1119. |issn=0025-3154|url-access=subscription }}</ref> The polymorphic snail species have different heritable features such as size and shape depending on the habitat they occupy e.g. bare cliffs, boulders and barnacle belts.<ref name=":3" /> Phenotypic evolution in these snails can be strongly attributed to different ecological factors present in their habitats. For example, in coastal regions of Sweden, Spain and UK, ''Littorina saxatilis'' posses different shell shape in response to predation by crabs or waves surges. <ref name=":4">{{Cite journal |last1=Johannesson |first1=Kerstin |last2=Panova |first2=Marina |last3=Kemppainen |first3=Petri |last4=André |first4=Carl |last5=Rolán-Alvarez |first5=Emilio |last6=Butlin |first6=Roger K. |date=2010-06-12 |title=Repeated evolution of reproductive isolation in a marine snail: unveiling mechanisms of speciation |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume=365 |issue=1547 |pages=1735–1747 |doi=10.1098/rstb.2009.0256 |issn=1471-2970 |pmc=2871885 |pmid=20439278}}</ref> Predation by crabs, also called crab crushing, gives rise to snails with wary behavior having large and thick shells which can easily retract and avoid predation. Wave-surfs on the other hand, select for smaller sized snails with large apertures to increase grip and bold behavior.<ref name=":4" /> All this provide the basis for the emergence of different snail ecotypes. Snail ecotypes on the basis of morphology and behavior pass these characteristic on to their offspring.<ref>{{Cite journal |last=Janson |first=K. |date=February 1987 |title=Genetic drift in small and recently founded populations of the marine snail Littorina Saxatilis |url=https://www.nature.com/articles/hdy19875 |journal=Heredity |language=en |volume=58 |issue=1 |pages=31–37 |doi=10.1038/hdy.1987.5 |issn=1365-2540}}</ref>