User:Noah Kilonzo/sandbox
Terminology
[edit]Ecotypes are closely related to morphs or polymorphisms which is defined as the existence of distinct phenotypes among members of the same species[1]. Another term closely related is genetic polymorphism; and it is when species of the same population display variation in a specific DNA sequence, i.e. as a result of having more than one allele in a gene's locus.[2]. In order to be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population (whose members can all potentially interbreed).[3] Polymorphism is actively and steadily maintained in populations of species by natural selection (most famously sexual dimorphism in humans) in contrast to transient polymorphisms where conditions in a habitat change in such a way that a "form" is being replaced completely by another.
In fact, Begon, Townsend, and Harper assert that
| “ | There is not always clear distinction between local ecotypes and genetic polymorphisms. | ” |
The notions "form" and "ecotype" may appear to correspond to a static phenomenon, however; this is not always the case. Evolution occurs continuously both in time and space, so that two ecotypes or forms may qualify as distinct species in only a few generations. Begon, Townsend, and Harper use an illuminating analogy on this:
| “ | ... the origin of a species, whether allopatric or sympatric, is a process, not an event. For the formation of a new species, like the boiling of an egg, there is some freedom to argue about when it is completed. | ” |
Thus ecotypes and morphs can be thought of as precursory steps of potential speciation.[4]
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- ^ Wiens, John J. (1999-11). "Polymorphism in Systematics and Comparative Biology". Annual Review of Ecology and Systematics. 30 (1): 327–362. doi:10.1146/annurev.ecolsys.30.1.327. ISSN 0066-4162.
{{cite journal}}: Check date values in:|date=(help) - ^ "Polymorphism". www.genome.gov. Retrieved 2024-10-12.
- ^ "Genetic polymorphism". Proceedings of the Royal Society of London. Series B. Biological Sciences. 164 (995): 350–361. 1966-03-22. doi:10.1098/rspb.1966.0037. ISSN 0080-4649.
- ^ Lowry, David B. (June 2012). "Ecotypes and the controversy over stages in the formation of new species". Biological Journal of the Linnean Society. 106 (2): 241–257. doi:10.1111/j.1095-8312.2012.01867.x.
Ecotype and Speciation
[edit]| “ | 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 component clusters before speciation. | ” |
| — David B. Lowry, Ecotypes and the controversy over stages in the formation of new species, Biological Journal of the Linnean Society, Volume 106, Issue 2, June 2012. | ||
The birth of the term 'ecotype' originally came from early interest in understanding speciation[1]. Darwin argued that species evolved through natural selection from variations within population which he termed as 'varieties'. [2] 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. [3] 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.[3][4][5] In his 1923 paper, Turesson states that variation among species in a population is not random, rather, it is driven by environmental selection pressure.[6] 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.[7] These adaptive differences were hereditary and would emerge in response to specific environmental conditions.[8] Heritable differences is a key feature in ecotypic variation.[9] Ecotypic variation is as a result of particular environmental trends.[7] Inidividuals, 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. [10] Ecotypic variation is therefore described to have a genetic base, and are brought about by interactions between an individual's genes and the environment. [11] An example of ecotype formation that lead to reproductive isolation and ultimately speciation can be found in the small sea snail periwinkle, Littorina saxatilis. [12] It is ditributes across different habitats such as lagoons, salt marshes and rocky shores the rande of distribution is from Portugal to Novaya Zemlaya and Svalbard and from North Carolina to Greenland.[13] The polymoprhic snail species posses different heritable features such as size and shape depending on the habitat they occupy e.g. bare cliffs, boulders and barnalcle belts.[13] 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. [14] Predation by crabs, also called crab crushing, gives rise to snails with wary behaviour having large and thick shells which can easily retract and avoid predation. Wave-surfs select for smaller sized snails with large apertures to increase grip and bold behaviour.[14] All this provide the basis for the emergence of different snail ecotypes. Snail ecotypes on the basis of morphology and behaviour pass these characteristic on to their offspring.[15]
- ^ Cite error: The named reference
:0was invoked but never defined (see the help page). - ^ "Species and varieties". Darwin Correspondence Project. 2022-11-18. Retrieved 2024-10-18.
- ^ a b Turesson, GöTe (2010-07-09). "THE GENOTYPICAL RESPONSE OF THE PLANT SPECIES TO THE HABITAT". Hereditas. 3 (3): 211–350. doi:10.1111/j.1601-5223.1922.tb02734.x.
- ^ Johannesson, Kerstin; Panova, Marina; Kemppainen, Petri; André, Carl; Rolán-Alvarez, Emilio; Butlin, Roger K. (2010-06-12). "Repeated evolution of reproductive isolation in a marine snail: unveiling mechanisms of speciation". Philosophical Transactions of the Royal Society B: Biological Sciences. 365 (1547): 1735–1747. doi:10.1098/rstb.2009.0256. ISSN 0962-8436.
- ^ Rieseberg, Loren H.; Willis, John H. (2007-08-17). "Plant Speciation". Science. 317 (5840): 910–914. doi:10.1126/science.1137729. ISSN 0036-8075. PMC 2442920. PMID 17702935.
{{cite journal}}: CS1 maint: PMC format (link) - ^ Turesson, GöTE (2010-07-09). "THE PLANT SPECIES IN RELATION TO HABITAT AND CLIMATE: CONTRIBUTIONS TO THE KNOWLEDGE OF GENECOLOGICAL UNITS". Hereditas. 6 (2): 147–236. doi:10.1111/j.1601-5223.1925.tb03139.x.
- ^ a b Gregor, J. W. (1944-01). "THE ECOTYPE". Biological Reviews. 19 (1): 20–30. doi:10.1111/j.1469-185X.1944.tb00299.x. ISSN 1464-7931.
{{cite journal}}: Check date values in:|date=(help) - ^ "Trifolium Subterraneum Linn. in Australia: an Autecological Study". Nature. 158 (4005): 176–177. 1946-08-01. doi:10.1038/158176a0. ISSN 1476-4687.
- ^ Turesson, GöTe (2010-07-09). "THE SPECIES AND THE VARIETY AS ECOLOGICAL UNITS". Hereditas. 3 (1): 100–113. doi:10.1111/j.1601-5223.1922.tb02727.x.
- ^ "Ecotypes". www2.nau.edu. Retrieved 2024-10-29.
- ^ Stronen, Astrid V.; Norman, Anita J.; Vander Wal, Eric; Paquet, Paul C. (2022-01-19). "The relevance of genetic structure in ecotype designation and conservation management". Evolutionary Applications. 15 (2): 185–202. doi:10.1111/eva.13339. ISSN 1752-4571. PMC 8867706. PMID 35233242.
{{cite journal}}: CS1 maint: PMC format (link) - ^ Johannesson, Kerstin (2009-01-01). "Inverting the null-hypothesis of speciation: a marine snail perspective". Evolutionary Ecology. 23 (1): 5–16. doi:10.1007/s10682-007-9225-1. ISSN 1573-8477.
- ^ a b "D.G. Reid Systematics and evolution of Littorina. x, 463p. London: The Ray Society, 1996. (Volume 164 of the series)". Journal of the Marine Biological Association of the United Kingdom. 76 (4): 1119–1119. 1996-11. doi:10.1017/s002531540004114x. ISSN 0025-3154.
{{cite journal}}: Check date values in:|date=(help) - ^ a b Johannesson, Kerstin; Panova, Marina; Kemppainen, Petri; André, Carl; Rolán-Alvarez, Emilio; Butlin, Roger K. (2010-06-12). "Repeated evolution of reproductive isolation in a marine snail: unveiling mechanisms of speciation". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 365 (1547): 1735–1747. doi:10.1098/rstb.2009.0256. ISSN 1471-2970. PMC 2871885. PMID 20439278.
- ^ Janson, K. (1987-02). "Genetic drift in small and recently founded populations of the marine snail Littorina Saxatilis". Heredity. 58 (1): 31–37. doi:10.1038/hdy.1987.5. ISSN 1365-2540.
{{cite journal}}: Check date values in:|date=(help)