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Different types pf taxa
Different types pf taxa bearing unique binomial name. Source: Author

Binomial Nomenclature: Two Term Naming System

“How strange and chaotic life it become if it were possible to abandon the use of names for the identification of everything we see, make, or handle. The acquisition and dissemination of knowledge would become impossible, and the business of the world could not go on.”-Macself in Johnson, 1971

A word or set of words by which a person or thing is known, addressed, or referred to. And Nomenclature means the devising or choosing of names for things, especially in a science or other discipline. Man has always been a nomenclaturist; he has used names for plants, animals, and objects; he has categorized plants, animals, and objects with or without special terminology and systems. “Centuries ago each plant was known by a long, descriptive sentence, which was unwieldy, to say the least. Then Caspar Bauhin (1560-1624) devised a plan of adopting two names only for each plant. But it was not until the great Swedish naturalist, Linnaeus (1707-1778), undertook the task of methodically naming and classifying the whole living world ‘from buffaloes to buttercups’ that the dual name system became permanently established. Since the publication of “Species Plantarum” by Linnaeus in 1753, the forming of names in Latin for international use has been a fundamental task for botanists or taxonomists.

Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process.

Binomial nomenclature (‘two-term naming system’), also called binary nomenclature, is a formal system of naming system. Two parts of a name use Latin word. The first part of the name is generic name- identifies the genus to which the species belongs, the second part of the name is the specific name or specific epithet- identifies the species within the genus.

History

Nomenclature of a flower plant
Crepe-myrtle. Source: Author

Botanical nomenclature has a long history, going back beyond the period when the Latin language was scientific language all over the UK. The principal Latin writer on botany was Pliny the Elder (23-79 AD). Leonhart Fuchs, a German physician and botanist, is often considered the originator of Latin names for the rapidly increasing number of plants known to science.

The Bauhins, in particular Caspar Bauhin (1560–1624), took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. He was a Swiss botanist whose Pinax theatri botanici (1623) described thousands of plants and classified them in a manner that draws comparisons to the later binomial nomenclature of Linnaeus.

Carl Linnaeus (1707–1778), a Swedish botanist, invented the modern system of binomial nomenclature. His famous books named Genera plantarum (1737), Species plantarum (1753) introduced binominal nomenclature.

Difference between taxonomy and nomenclature

Taxonomy is the scientific study of describing, identifying, naming and classifying a living organism based on its character. And nomenclature is the section of taxonomy concerned with naming taxa as well as with the application of existing taxon names in the context of subsequently proposed taxonomies. A taxonomist always care about a taxa to describe, identify and to give it proper classification. Naming a taxa is only a part of taxonomy.

What is ICBN or ICN?

ICBN- International Code of Botanical Nomenclature. The ICBN is the set of rules and recommendations dealing with the formal botanical names that are given to plants. Its intent is that each taxonomic group (‘taxon’, plural ‘taxa’) of plants has only one correct name that is accepted worldwide.

ICBN is the set of rules and recommendations for naming the plants, fungi and a few other groups of organisms. The name was changed from ICBN to ICN in July 2011 at the International Botanical Congress in Melbourne. Botany requires a precise and simple system of nomenclature used by botanists in all country, dealing on the one hand with the terms which denote the ranks of taxonomic groups or units, and on the other hand with the scientific names which are applied to the individual taxonomic groups’ plants.

History of ICBN

  • It was Linnaeus who proposed the elementary rules of naming plants first in 1737 in his Critica botanica and then in 1751 in Philosophia Botanica.
  • Elementary rules were framed to serve as a guide to botanists. Later in 1813, A.P. de Candolle in his Theories elementary de la botanique gave a detailed set of rules regarding plant nomenclature.
  • It was then that Alphonse de Candolle, son of A.P. de Candolle convened an assembly of botanists of several countries to present a new set of rules. Candolle convened the First International Botanical Congress held at Paris in 1867.
  • Subsequent meetings of the International Botanical Congress were held in 1892 (Rochester Code), 1905 (Vienna Code), 1907 (American Code) and 1910, but a general agreement regarding the internationally acceptable rules of plant nomenclature was reached in 1930 at the IBC meeting at Cambridge where for the first time in botanical history, a code of nomenclature came into being that was international in function as well as in name.
  • This code is called the International Code of Botanical Nomenclature (ICBN). The modifications or amendments as suggested by the International Botanical Congress at the subsequent meetings have been incorporated in the ICBN on a regular basis.
  • The ICBN sets the formal starting date of plant nomenclature at 1 May 1753, the publication of Species Plantarum by Linnaeus.

Division I. 6 principles

  • Principle I: Botanical nomenclature is independent of zoological and bacteriological nomenclature. The Code applies equally to names of taxonomic groups treated as plants whether or not these groups were originally so treated
  • Principle II: The application of names of taxonomic groups is determined by means of nomenclatural types.
  • Principle IlI: The nomenclature of a taxonomic group is based upon priority of publication.
  • Principle IV: Each taxonomic group with a particular circumscription, position, and rank can bear only one correct name, the earliest that is in accordance with the Rules, except in specified cases.
  • Principle V: Scientific names of taxonomic groups are treated as Latin regardless of their derivation.
  • Principle VI: The Rules of nomenclature are retroactive unless expressly limited.
    Main Rules of Nomenclature of Plants The following points highlight the eight main rules of nomenclature. The rules are:
  1.  Nomenclatural Type
  2.  Rule of Priority
  3.  Names of Taxa
  4.  Effective and Valid Publication
  5.  Retention of Specific and Infra-specific Epithets
  6.  Rejection of Names
  7.  Splitting of a Genus
  8.  Synonym and Basionym.

Rule 1: Nomenclatural Type

Nomenclature of flower plant
Sulfur cosmos. Source: Author

The nomenclatural type is that constituent element (a specimen, or a description or a figure) of a taxon to which the name is permanently attached. This need not be the most typical or representative element but is the original material on which the description of the taxon is based.
Following kinds of types are recognize

  1. Holotype: Specimen or other element designated by the author or used by him as the nomenclatural type.
  2. Isotype: This is a duplicate of the holotype.
  3. Syntype: When more than one specimen are cited by the author without mentioning which is the holotype, each specimen is designated as a Syntype.
  4. Paratype: Specimens cited along with the holotype are designated as Paratype.
  5. Lectotype: This is a substitute of the holotype when that is lost and is to be selected from the isotypes. When no holotype was designated by the author a specimen from the original material is selected to be the Lectotype.
  6. Neotype: When all original materials are missing a Neotype is selected from other materials.
  7. Topotype: Specimen of a species collected at the same locality as the holotype.

Rule 2: Rule of Priority

  • In the case of a family or a taxon below the rank of a family the earliest legitimate name should be considered as valid (or correct). For this purpose 1st May 1753 is taken as the earliest date for all plants excepting the Fungi, some Algae, and the Musci other than the Sphagnaceae.
  • This means the names appecaring in Linnaeus’s Species Plantarum are the earliest names for the purpose of consideration of the Rule of Priority; those published earlier are not to be given priority.

Rule 3: Names of Taxa

  • The name of a species is a binary combination consisting of the name of the genus followed by a single specific epithet. The name of a genus is a substantive in the singular number. The specific epithet is an adjective and is of the same gender generic name, or is a noun in apposition to the generic name. The specific epithet must not exactly repeat t as the generic name.
  •  The name of an infra-specific taxon is a combination of the name of a species and an infra-specific epithet connected by a term denoting its rank. The name of a genus or of taxa of higher rank is spelt with a capital initial letter.
  •  All specific and infra-specific epithets should be written with a small initial letter. Formerly it was the custom to spell the epithets with a capital initial letter where the epithets were derived from the names of persons, or were vernacular names, or were former generic names. This is not followed at present.
  •  The name of a family is derived from the name of the genus which is the type for the family. The name of a subfamily, a tribe or a sub-tribe is derived from the name of the type-genus belonging to that subfamily, tribe or sub-tribe.
  •  Endings of the names of taxa above the rank of genus should be in the manner noted below:
    • Order –“ales” (e.g. Rosales)
    •  Suborder –“ineae” (e.g. Rosineae)
    •  Family -“aceac (e.g. Rosaceae)
    •  Subfamily -oideae” (eg Rosoideae )
    •  Tribe –“eac”
    •  Subtribe- “inae”
    •  A few family-names although not complying with the above rules are treated as valid because of long usage as such.

These are noted below with their alternative names:

  • Palmae (Arecaceae from Areca)
  • Gramineae (Poaceae from Poa)
  • Cruciferae (Brassicaceae from Brassica)
  • Leguminosae (Fabaceae from Faba)
  • Guttiferae (Clusiaceao from Clusia)
  • Umbelliferae (Apiaceae from Apium)
  • Labiatae (Lamiaceae front Lamium)
  •  Compositae (Asteraceae from Aster).

Rule 4: Effective and Valid Publication

  • Any printed matter when widely circulated is regarded as effectively published. It is sufficient, if the printed matter is distributed at least to the botanical institutions with libraries accessible to botanists generally. The date of effective publication is the date on which the printed matter became available.
  • Valid publication of a name of new taxon is necessary to have it effectively published, to have correct form and to be accompanied by a description or diagnosis or a reference to a previously published description. For the name of a new taxon to be valid it is necessary that the description or the diagnosis should be in Latin.
  • Those published earlier to 1st Jan, 1935 are considered valid even if the description or diagnosis were not in Latin. In the case of Algae the date has been fixed as 1st Jan. 1958 instead of 1st Jan. 1935, In the case of recent Algae, the Latin description or diagnosis of a new taxon must be accompanied by an illustration or figure.
  • Publication of a new name of the rank of family or below on or after 1st January, 1958 is not considered valid if the type is not indicated.
  • The name of a taxon below the rank of a genus is not validly published unless the name of the genus or species to which it is assigned is validly published.
  • He who first validly published the name of a taxon is the author of that name. It is necessary to cite the name of the author after the name of the taxon.

Rule 5: Retention of Specific and Infra-specific Epithets

  • When a species is transferred to another genus without change of rank, the specific epithet must be retained. If the name of a genus is changed being illegitimate, the binary combinations for all the species under that genus should be changed also and in doing so the new generic name should be used retaining the older specific epithets.
  • This rule applies equally to infra-specific taxa. A specific epithet is not illegitimate merely because it was originally published under an illegitimate generic name; it is to be taken into consideration for purpose of priority.

Rule 6: Rejection of Names

  • A name is to be rejected if it is used in different senses and for that reason has become a source of error. A name is to be rejected if it is based on a type consisting of two or more entirely discordant elements. A name is to be rejected also if it is based on a monstrosity.

Rule 7: Splitting of a Genus

  • When a genus is divided into 2 or more genera the original generic name must be retained for one of the smaller genera which includes the type species of the undivided genus. This rule applies equally to cases of division of species.

Rule 8: Synonym and Basionym

  • All names of a taxon other than the valid names are synonyms of that taxon.
  •  Basionym means original name on which a new name is based. The author atation of the new species should be included and the authors of basionym should be in parenthesis. eg Tea originally named by Linnaeus as Thea sinmss L. Later Sweet noticed that the genus Thea was not really different from Camellia and He renamed all Theas as Camellias. Thea sinensis became as Camellia sinensis (L.) Sweet, He had to keep the specific epithet the same as original name (Basionym) for that species given by Linnaeus.

Importance of nomenclature

Nomenclature of flower plant
Garden Nasturtium. Source: Author

Why use this relatively complicated system of names? Supposedly Latin names are so long and unpronounceable. Why not use common names? Benson (1962) states very succinctly why vernacular or common names cannot replace scientific names.

  1. Names in common language are ordinarily applicable in only a single language; they are not universal.
  2.  In most parts of the world relatively few species have c or vernacular names in any language.
  3. Common names are applied indiscriminately to genera, species or varieties.
  4. Often two or more unrelated plants are known by the same name, and frequently even in one language a single species may have two to several common names applied either in the same or different localities.

The system of nomenclature has been standardized in a code so that communication about plants, plant parts, and plant products is based on a name acceptable the world over for commercial as well as scientific purposes. This work since (presumably) one kind of plant may not have more than one correct name and no two kinds of plants may have the same name. The scientific name is communication symbol for plant knowledge and use everywhere.


Reference

  • Vascular plant systematics by Albert E. Radford.
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About Sabiha Alam Shifa

Currently studying in 2nd year at Department of Botany, University of Dhaka. Interested in researching about plants. Love to investigate. E-mail: sabihaalam-2019617121@bot.du.ac.bd Minimum monthly resolution- Publish (1), Revise (1), Share (1)

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