In biology, a taxon (back-formation from taxonomy; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion. If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping.
Initial attempts at classifying and ordering organisms (plants and animals) were set forth in Carl Linnaeus's system in Systema Naturae, 10th edition (1758),[1] as well as an unpublished work by Bernard and Antoine Laurent de Jussieu. The idea of a unit-based system of biological classification was first made widely available in 1805 in the introduction of Jean-Baptiste Lamarck's Flore françoise, and Augustin Pyramus de Candolle's Principes élémentaires de botanique. Lamarck set out a system for the "natural classification" of plants. Since then, systematists continue to construct accurate classifications encompassing the diversity of life; today, a "good" or "useful" taxon is commonly taken to be one that reflects evolutionary relationships.[note 1]
Many modern systematists, such as advocates of phylogenetic nomenclature, use cladistic methods that require taxa to be monophyletic (all descendants of some ancestor). Their basic unit, therefore, the clade is equivalent to the taxon, assuming that taxa should reflect evolutionary relationships. Similarly, among those contemporary taxonomists working with the traditional Linnean (binomial) nomenclature, few propose taxa they know to be paraphyletic.[2] An example of a long-established taxon that is not also a clade is the classReptilia, the reptiles; birds and mammals are the descendants of animals traditionally classed as reptiles, but neither are included in the Reptilia (birds are traditionally placed in the class Aves, and mammals in the class Mammalia).[3]
The term taxon was first used in 1926 by Adolf Meyer-Abich for animal groups, as a back-formation from the word taxonomy; the word taxonomy had been coined a century before from the Greek components τάξις (taxis, meaning arrangement) and -νομία (-nomia meaning method).[4][5] For plants, it was proposed by Herman Johannes Lam in 1948, and it was adopted at the VII International Botanical Congress, held in 1950.[6]
A taxonomic unit, whether named or not: i.e. a population, or group of populations of organisms which are usually inferred to be phylogenetically related and which have characters in common which differentiate (q.v.) the unit (e.g. a geographic population, a genus, a family, an order) from other such units. A taxon encompasses all included taxa of lower rank (q.v.) and individual organisms. [...]"
A taxon can be assigned a taxonomic rank, usually (but not necessarily) when it is given a formal name.
"Phylum" applies formally to any biological domain, but traditionally it was always used for animals, whereas "division" was traditionally often used for plants, fungi, etc.
A prefix is used to indicate a ranking of lesser importance. The prefix super- indicates a rank above, the prefix sub- indicates a rank below. In zoology, the prefix infra- indicates a rank below sub-. For instance, among the additional ranks of class are superclass, subclass and infraclass.
Rank is relative, and restricted to a particular systematic schema. For example, liverworts have been grouped, in various systems of classification, as a family, order, class, or division (phylum). The use of a narrow set of ranks is challenged by users of cladistics; for example, the mere 10 ranks traditionally used between animal families (governed by the International Code of Zoological Nomenclature (ICZN)) and animal phyla (usually the highest relevant rank in taxonomic work) often cannot adequately represent the evolutionary history as more about a lineage's phylogeny becomes known.
In addition, the class rank is quite often not an evolutionary but a phenetic or paraphyletic group and as opposed to those ranks governed by the ICZN (family-level, genus-level and species-level taxa), can usually not be made monophyletic by exchanging the taxa contained therein. This has given rise to phylogenetic taxonomy and the ongoing development of the PhyloCode, which has been proposed as a new alternative to replace Linnean classification and govern the application of names to clades. Many cladists do not see any need to depart from traditional nomenclature as governed by the ICZN, International Code of Nomenclature for algae, fungi, and plants, etc.
^This is not considered as mandatory, however, as indicated by terms for non-monophyletic groupings ("invertebrates", "conifers", "fish", etc).
References
^Quammen, David (June 2007). "A Passion for Order". National Geographic Magazine. Retrieved 27 April 2013.
^de Queiroz, K & J Gauthier (1990). "Phylogeny as a Central Principle in Taxonomy: Phylogenetic Definitions of Taxon Names" (PDF). Systematic Zoology. 39 (4): 307–322. doi:10.2307/2992353. JSTOR 2992353.
^Romer, A. S. (1970) [1949]. The Vertebrate Body (4th <-- ed.). W.B. Saunders. pp. -->.
^Sylvain Adnet; Brigitte Senut; Thierry Tortosa; Romain Amiot, Julien Claude, Sébastien Clausen, Anne-Laure Decombeix, Vincent Fernandez, Grégoire Métais, Brigitte Meyer-Berthaud, Serge Muller (25 September 2013). Principes de paléontologie. Dunod. p. 122. ISBN978-2-10-070313-5. La taxinomie s'enrichit avec l'invenition du mot «taxon» par Adolf Meyer-Abich, naturaliste allemand, dans sa Logik der morphologie, im Rahmen einer Logik der gesamten Biologie (1926) [Translation: Taxonomy is enriched by the invention of the word "taxon" by Adolf Meyer-Abich, German naturalist, in his Logik der morphologie, im Rahmen einer Logik der gesamten Biologie (1926).]{{cite book}}: CS1 maint: multiple names: authors list (link)
^Meyer-Abich, Adolf (1926). Logik der Morphologie im Rahmen einer Logik der gesamten Biologie. Springer-Verlag. p. 127. ISBN978-3-642-50733-5.
^Naik, V. N. (1984). Taxonomy of Angiosperms. Tata McGraw Hill, New Delhi, p. 2.
^ICZN (1999) International Code of Zoological Nomenclature. Glossary 2005-01-03 at the Wayback Machine. International Commission on Zoological Nomenclature.
External links
The dictionary definition of taxon at Wiktionary
January 31, 2023
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For the journal see Taxon journal For other uses see Taxa disambiguation In biology a taxon back formation from taxonomy plural taxa is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit Although neither is required a taxon is usually known by a particular name and given a particular ranking especially if and when it is accepted or becomes established It is very common however for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion If a taxon is given a formal scientific name its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping African elephants form the genus Loxodonta a widely accepted taxon Initial attempts at classifying and ordering organisms plants and animals were set forth in Carl Linnaeus s system in Systema Naturae 10th edition 1758 1 as well as an unpublished work by Bernard and Antoine Laurent de Jussieu The idea of a unit based system of biological classification was first made widely available in 1805 in the introduction of Jean Baptiste Lamarck s Flore francoise and Augustin Pyramus de Candolle s Principes elementaires de botanique Lamarck set out a system for the natural classification of plants Since then systematists continue to construct accurate classifications encompassing the diversity of life today a good or useful taxon is commonly taken to be one that reflects evolutionary relationships note 1 Many modern systematists such as advocates of phylogenetic nomenclature use cladistic methods that require taxa to be monophyletic all descendants of some ancestor Their basic unit therefore the clade is equivalent to the taxon assuming that taxa should reflect evolutionary relationships Similarly among those contemporary taxonomists working with the traditional Linnean binomial nomenclature few propose taxa they know to be paraphyletic 2 An example of a long established taxon that is not also a clade is the class Reptilia the reptiles birds and mammals are the descendants of animals traditionally classed as reptiles but neither are included in the Reptilia birds are traditionally placed in the class Aves and mammals in the class Mammalia 3 Contents 1 History 2 Definition 3 Ranks 4 See also 5 Notes 6 References 7 External linksHistory EditThe term taxon was first used in 1926 by Adolf Meyer Abich for animal groups as a back formation from the word taxonomy the word taxonomy had been coined a century before from the Greek components ta3is taxis meaning arrangement and nomia nomia meaning method 4 5 For plants it was proposed by Herman Johannes Lam in 1948 and it was adopted at the VII International Botanical Congress held in 1950 6 Definition EditThe glossary of the International Code of Zoological Nomenclature 1999 defines 7 a taxon pl taxa n A taxonomic unit whether named or not i e a population or group of populations of organisms which are usually inferred to be phylogenetically related and which have characters in common which differentiate q v the unit e g a geographic population a genus a family an order from other such units A taxon encompasses all included taxa of lower rank q v and individual organisms dd Ranks Edit The hierarchy of biological classification s eight major taxonomic ranks Intermediate minor rankings are not shown A taxon can be assigned a taxonomic rank usually but not necessarily when it is given a formal name Phylum applies formally to any biological domain but traditionally it was always used for animals whereas division was traditionally often used for plants fungi etc A prefix is used to indicate a ranking of lesser importance The prefix super indicates a rank above the prefix sub indicates a rank below In zoology the prefix infra indicates a rank below sub For instance among the additional ranks of class are superclass subclass and infraclass Rank is relative and restricted to a particular systematic schema For example liverworts have been grouped in various systems of classification as a family order class or division phylum The use of a narrow set of ranks is challenged by users of cladistics for example the mere 10 ranks traditionally used between animal families governed by the International Code of Zoological Nomenclature ICZN and animal phyla usually the highest relevant rank in taxonomic work often cannot adequately represent the evolutionary history as more about a lineage s phylogeny becomes known In addition the class rank is quite often not an evolutionary but a phenetic or paraphyletic group and as opposed to those ranks governed by the ICZN family level genus level and species level taxa can usually not be made monophyletic by exchanging the taxa contained therein This has given rise to phylogenetic taxonomy and the ongoing development of the PhyloCode which has been proposed as a new alternative to replace Linnean classification and govern the application of names to clades Many cladists do not see any need to depart from traditional nomenclature as governed by the ICZN International Code of Nomenclature for algae fungi and plants etc See also Edit Biology portalABCD Schema Alpha taxonomy Chresonym Cladistics Folk taxonomy Ichnotaxon International Code of Nomenclature for algae fungi and plants International Code of Zoological Nomenclature ICZN List of taxa named by anagrams Rank botany Rank zoology Segregate taxonomy Virus classificationNotes Edit This is not considered as mandatory however as indicated by terms for non monophyletic groupings invertebrates conifers fish etc References Edit Quammen David June 2007 A Passion for Order National Geographic Magazine Retrieved 27 April 2013 de Queiroz K amp J Gauthier 1990 Phylogeny as a Central Principle in Taxonomy Phylogenetic Definitions of Taxon Names PDF Systematic Zoology 39 4 307 322 doi 10 2307 2992353 JSTOR 2992353 Romer A S 1970 1949 The Vertebrate Body 4th lt ed W B Saunders pp gt Sylvain Adnet Brigitte Senut Thierry Tortosa Romain Amiot Julien Claude Sebastien Clausen Anne Laure Decombeix Vincent Fernandez Gregoire Metais Brigitte Meyer Berthaud Serge Muller 25 September 2013 Principes de paleontologie Dunod p 122 ISBN 978 2 10 070313 5 La taxinomie s enrichit avec l invenition du mot taxon par Adolf Meyer Abich naturaliste allemand dans sa Logik der morphologie im Rahmen einer Logik der gesamten Biologie 1926 Translation Taxonomy is enriched by the invention of the word taxon by Adolf Meyer Abich German naturalist in his Logik der morphologie im Rahmen einer Logik der gesamten Biologie 1926 a href Template Cite book html title Template Cite book cite book a CS1 maint multiple names authors list link Meyer Abich Adolf 1926 Logik der Morphologie im Rahmen einer Logik der gesamten Biologie Springer Verlag p 127 ISBN 978 3 642 50733 5 Naik V N 1984 Taxonomy of Angiosperms Tata McGraw Hill New Delhi p 2 ICZN 1999 International Code of Zoological Nomenclature Glossary Archived 2005 01 03 at the Wayback Machine International Commission on Zoological Nomenclature External links Edit The dictionary definition of taxon at Wiktionary Retrieved from https en wikipedia org w index php title Taxon amp oldid 1132569858, wikipedia, wiki, book, books, library,
