In biology , a taxon ( back-formation from taxonomy ; pl. : 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, especially in the context of rank-based (" Linnaean ") nomenclature (much less so under phylogenetic nomenclature ). 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.
18-980: See text Senecioneae is the largest tribe of the Asteraceae , or the sunflower family, comprising over 150 genera and over 3,500 species. Almost one-third of the species in this tribe are placed in the genus Senecio . Its members exhibit probably the widest possible range of form to be found in the entire plant kingdom, and include annuals , minute creeping alpines , herbaceous and evergreen perennials , shrubs , climbers , succulents , trees , and semi- aquatic plants . Plants in this tribe are responsible for more livestock poisonings than all other plants combined. Its members usually contain liver and kidney toxic and carcinogenic unsaturated pyrrolizidine alkaloids in Senecio and furanoeremophilanes in Tetradymia . A number of species are well known in horticulture . Since
36-457: A tribe is a taxonomic rank above genus , but below family and subfamily . It is sometimes subdivided into subtribes . By convention, all taxa ranked above species are capitalized, including both tribe and subtribe. In zoology , the standard ending for the name of a zoological tribe is "-ini". Examples include the tribes Caprini (goat-antelopes), Hominini (hominins), Bombini (bumblebees), and Thunnini (tunas). The tribe Hominini
54-520: A better taxonomy than treating the variation patterns as infrageneric taxa is yet unclear. A respectable case can be made for maintaining Senecio as a broad concept, at least until revisionary studies at the species level are carried out and the results subjected to critical analyses. Most genera that have been removed from the Senecioneae in the broadest sense have come to rest within the Liabeae or within
72-694: A broadly circumscribed Heliantheae (e.g., allies in the Arnicinae , Chaenactidinae , or Madiinae ; Haploesthes in the Flaveriinae ; and Raillardella and allies in the Madiinae ). Additional information may be found in B. G. Baldwin et al. (2002), H. Robinson (1981), B. Nordenstam (1977–1978) and K. Bremer (1994). Senecioneae genera recognized by the Global Compositae Database as of October 2022: Tribe (biology) In biology ,
90-408: Is divided into subtribes by some scientists; subtribe Hominina then comprises "humans". The standard ending for the name of a zoological subtribe is "-ina". In botany , the standard ending for the name of a botanical tribe is "-eae". Examples include the tribes Acalypheae and Hyacintheae . The tribe Hyacintheae is divided into subtribes, including the subtribe Massoniinae. The standard ending for
108-545: Is included in the Reptilia (birds are traditionally placed in the class Aves , and mammals in the class Mammalia ). 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 ( táxis ), meaning "arrangement", and νόμος ( nómos ), meaning " method ". For plants, it
126-500: 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
144-463: 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 . 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
162-463: The decades as genera and groups of genera have been moved in and out, as was the case for Arnica , Liabum , Munnozia , Schistocarpha , etc. which have since then been excluded. Of the several potential causes for this constant redefinition the greatest is probably that little is known about its intergeneric relationships or a lack of phylogenetic understanding enhanced by the other problems of conflicting clues from morphological characters,
180-476: The fairly sophisticated folk taxonomies. Much later, Aristotle, and later still, European scientists, like Magnol , Tournefort and Carl Linnaeus 's system in Systema Naturae , 10th edition (1758), , as well as an unpublished work by Bernard and Antoine Laurent de Jussieu , contributed to this field. The idea of a unit-based system of biological classification was first made widely available in 1805 in
198-466: 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
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#1733093000532216-682: 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 . Many modern systematists, such as advocates of phylogenetic nomenclature , use cladistic methods that require taxa to be monophyletic (all descendants of some ancestor). Therefore, their basic unit,
234-415: The large size of the tribe, the absence of a precise delimitation or circumscription of Senecio and the naturalness of these assemblages combined with the imprecise boundaries of the different species themselves. Many segregate genera have been recognized in recent studies, often with circumscriptions derived from selected representative species. Whether the recognition of numerous segregate genera provides
252-457: The name of a botanical subtribe is "-inae". In bacteriology , the form of tribe names is as in botany, e.g., Pseudomonadeae, based on the genus name Pseudomonas . An unfamiliar taxonomic rank cannot necessarily be identified as a tribe merely by the presence of one of the standard suffixes: Accordingly, working within animals alone, subfamily -inae , tribe -ini, and subtribe -ina are unique suffixes to their specific taxonomic ranks. At
270-490: The other extreme, working within algae alone, -eae suffixes class -phyceae , suborder -ineae , family -aceae , subfamily -oideae , and tribe -eae . The longer suffixes themselves suffixed with -eae must first be eliminated before recognizing an unfamiliar -eae designation as belonging to rank tribe. Taxa Initial attempts at classifying and ordering organisms (plants and animals) were presumably set forth in prehistoric times by hunter-gatherers, as suggested by
288-452: The time of Bentham , the "premier systematic botanist of the nineteenth century", considerable efforts have been made to classify and understand the striking morphological diversity in the Senecioneae. The traditional view of the tribe has been that of one huge genus Senecio plus many other genera which exhibit varying degrees of distinctiveness. Circumscription and delimitation of the tribe have experienced expansions and contractions over
306-420: 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
324-543: Was proposed by Herman Johannes Lam in 1948, and it was adopted at the VII International Botanical Congress , held in 1950. The glossary of the International Code of Zoological Nomenclature (1999) defines a 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
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