Genus ( / ˈ dʒ iː n ə s / ; pl. : genera / ˈ dʒ ɛ n ər ə / ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses . In binomial nomenclature , the genus name forms the first part of the binomial species name for each species within the genus.
43-639: 10–24; see text Cercis / ˈ s ɜːr s ɪ s / is a genus of about 10 species in the subfamily Cercidoideae of the pea family Fabaceae . It contains small deciduous trees or large shrubs commonly known as redbuds in the USA. They are characterised by simple, rounded to heart-shaped leaves and pinkish-red flowers borne in the early spring on bare leafless shoots, on both branches and trunk (" cauliflory "). The genus contains ten species, native to warm temperate regions of North America, southern Europe, western and central Asia, and China. Cercis
86-415: A branching main axis. Examples of racemes occur on mustard ( genus Brassica ) and radish (genus Raphanus ) plants. A spike is an unbranched, indeterminate inflorescence, similar to a raceme, but bearing sessile flowers (sessile flowers are attached directly, without stalks). Examples occur on Malabar nut ( Justicia adhatoda ) and chaff flowers (genus Achyranthes ). A spikelet can refer to
129-477: A clade that is sister to a clade formed by Colorado Plateau and eastern North American clades. Molecular dating suggests a divergence time among these three clades of at least 12 million years. These clades were also inferred from a distance-based analysis of Cercis in the United States with isozyme data as reported in an unpublished Ph.D. dissertation (Ballenger 1992). On the basis of these studies, Cercis
172-407: A genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of
215-651: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as
258-628: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,
301-439: A mixed salad or made into fritters with a flavor described as an agreeably acidic bite. The tree was frequently figured in the 16th and 17th-century herbals. It is said to be the tree from which Judas Iscariot hanged himself after betraying Christ, but the name may also derive from "Judea's tree", after the region encompassing Israel and Palestine where the tree is commonplace. A smaller Eastern American woodland understory tree,
344-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for
387-406: A shoot, in this case one bearing the flowers. In indeterminate inflorescence-like racemes, the oldest flowers grow close to the base and new flowers are produced as the shoot grows in height, with no predetermined growth limit. A plant that flowers on a showy raceme may have this reflected in its scientific name, e.g. the species Actaea racemosa . A compound raceme, also called a panicle , has
430-499: A small spike, although it primarily refers to the ultimate flower cluster unit in grasses ( family Poaceae ) and sedges (family Cyperaceae ), in which case the stalk supporting the cluster becomes the pedicel. A true spikelet comprises one or more florets enclosed by two glumes (sterile bracts ), with flowers and glumes arranged in two opposite rows along the spikelet. Examples occur on rice (species Oryza sativa ) and wheat (genus Triticum ), both grasses. An ament or catkin
473-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;
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#1732773289080516-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and
559-602: Is derived from the Greek word κερκις ( kerkis ) meaning "weaver's shuttle", which was applied by Theophrastus to C. siliquastrum due to the resemblance of the dry seed pod to a loom shuttle. Cercis species are used as food plants by the larvae of some Lepidoptera species including mouse moth and Automeris io (both recorded on eastern redbud ). The bark of C. chinensis has been used in Chinese medicine as an antiseptic. Cercis fossils have been found that date to
602-612: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms
645-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,
688-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with
731-502: Is treated as comprising three species, with the Colorado Plateau and all Arizona specimens recognized as C. orbiculata , distinct from C. occidentalis from California and C. canadensis from eastern North America. This delimitation of species will also be employed for the treatment of the genus for Flora of North America (Ballenger and Vincent, in preparation). The chain-flowered redbud ( Cercis racemosa ) from western China
774-446: Is unusual in the genus in having its flowers in pendulous 10 cm (4 in) racemes , as in a Laburnum, rather than short clusters. The wood is medium weight, somewhat brittle, of light tan color with a noticeably large heartwood area of darker brown, tinged with red. The wood has attractive figuring and is used in wood turning , for making decorative items and in the production of wood veneer . Genus The composition of
817-412: Is very similar to a spike or raceme "but with subtending bracts so conspicuous as to conceal the flowers until pollination, as in the pussy–willow , alder , [and] birch ...". These are sometimes called amentaceous plants . A spadix is a form of spike in which the florets are densely crowded along a fleshy axis and enclosed by one or more large, brightly–colored bracts called spathes . Usually
860-564: The Eocene . Cercis comprises the following species: The Judas tree ( Cercis siliquastrum ) is 10–15 m tall tree native to the south of Europe and southwest Asia. It is found in Iberia, southern France, Italy, Bulgaria, Greece, and Asia Minor, and forms a low tree with a flat spreading head. In early spring it is covered with a profusion of magenta flowers which appear before the leaves. The flowers are edible and are sometimes eaten in
903-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to
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#1732773289080946-824: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;
989-419: The nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,
1032-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,
1075-455: The base and new flowers are produced as the shoot grows in height, with no predetermined growth limit. Examples of racemes occur on mustard ( genus Brassica ), radish (genus Raphanus ), and orchid (genus Phalaenopsis ) plants. A raceme or racemoid is an unbranched, indeterminate type of inflorescence bearing pedicellate flowers (flowers having short floral stalks called pedicels ) along its axis. In botany , an axis means
1118-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of
1161-545: The eastern redbud, Cercis canadensis , is common from southernmost Canada to Piedmont, Alabama, and East Texas. It differs from C. siliquastrum in its pointed leaves and slightly smaller size (rarely over 12 m tall). The flowers are also used in salads and for making pickled relish, while the inner bark of twigs gives a mustard-yellow dye. It is commonly grown as an ornamental. The related western redbud, Cercis occidentalis , ranges from California east to Utah primarily in foothill regions. Its leaves are more rounded at
1204-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this
1247-737: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,
1290-533: The justification was cursory and not definitive. Morphometric studies of North American Cercis indicate that, although morphological variation is strongly correlated with geography across North America, considerable overlap in flower, fruit, and leaf characters limit their use for taxon delimitation. In contrast to morphology, molecular phylogenetic analyses recover three geographically well-defined clades within North America, with California Cercis forming
1333-633: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,
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1376-427: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Raceme A raceme ( / r eɪ ˈ s iː m , r ə -/ ) or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to
1419-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus
1462-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this
1505-541: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for
1548-470: The same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but the French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or
1591-408: The scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of a species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in
1634-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,
1677-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being
1720-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for
1763-691: The tip than the relatively heart-shaped leaves of the eastern redbud. The tree often forms multi-trunked colonies that are covered in bright pink flowers in early spring (February - March). White-flowered variants are in cultivation. It buds only once a year. The species of Cercis in North America form a clade . Hopkins (1942) established a two-species system for North America which is still widely recognized. Alternatively, based on an exploratory morphometric analysis, Isely (1975) inferred up to six separate entities (“phases”). Barneby (1989) recognized only one continental species and treated all of western North American Cercis as C. canadensis var. orbiculata , but
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1806-576: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up
1849-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in
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