Binomial Nomenclature Of Plants

Binomial Nomenclature 

Plant Nomenclature:

The assignment of scientific names to plants is called Nomenclature. Name is one of the most important ways of identifying an object. Names maybe common, proper, abstract or collective.

Our choice of names for individuals is generally arbitrary, however, it imbibes a great influence of language, religion, culture and tradition. Since due to wide application and influence on human affairs, the process of naming requires an international accepted terminology and names, so that our work maybe meaningful and comprehensive one to all concerned.

Common Names:

Plants are innumerable and all the plants do not have common names and those which have their names are misleading. One plant may have different common names depending upon the language. Common names are frequently local and not well recorded and confusion results by not knowing exactly to what plants they apply. Many plants, because of their utility in one way or the other, have Common or Vernacular or Local Names. Widely distributed plants have a large number of common names, e.g., Pansy (Viola tricolor) is most grown in European and American gardens and has about 50 common English Names.

In multilingual countries, almost all the useful plants have local names that vary from language to language and even from dialect to dialect. For example, Mango (Mangifera indica) is known by over 50 different names. Therefore, the common have limited usage and proved ineffective for wider use throughout the country or world. Also the common names are misleading and inadequate as these are neither universal nor methodical. Since many plants are so much alike in appearance that they are not clearly distinguished and many are so inconspicuous that they are not most often mentioned, many species therefore have no common names.

Disadvantages of Common Names:

Botanists prefer Latinized scientific names instead of common names as common names pose a number of problems, such as:

  1. Common or Vernacular names are not universal and may be applied in a single language, e.g., in Pakistan, the common name for Habiscus esculentus is “Bhimdi” whereas in England it is Lady’s finger.
  2. The common names usually do not provide information indicating the generic and family relationship.
  3. If a plant is well known, it may have a dozen or more common names. For example, Chrysanthemum lecanthemum is called daisy, white daisy, ox-eye daisy, shasta daisy or white weed.
  4. Sometimes two or more plants may have the same common names e.g., Sida (Malvaceae) is called ironweed in Goergia but in Midwest, Veronica (Compositae) is known as ironweed.
  5. Many species, especially are universal and are recognized throughout the world.

Scientific Names:

The assignment of scientific names to plants is called Nomenclature. It involves principles governed by rules developed and adopted by the International Botanical Congresses. The ultimate goal of this precise system id to provide one correct name for each taxon. Although the classification schemes may change with time, the scientific names of plants are relatively stable. The plants retain its name although the family or higher taxonomic categories are changed. The botanists agreed that scientific names should be in Latin, because this language is not being used in any country or nation at present and at one time it was widely used language of European countries and a lot of literature has been available in Latin. Latin names were mostly taken from common names used in ancient Cireece and Rome. For the sake of precision, the names were supplemented by adjectives. A single name thus used was followed by one or many adjectives. This gave rise to names composed of three or more words. These names are called Polynomials, for example, the name Salix Pitmila angustifolia was used for a species of Willow. The use of polynomials remained in practice till 1753 when Linnaeus substituted polynomials with Binomial format and used it in his book Species Plantarum. This two words format made naming more convenient and provided a readily expandable system.

Today all plants names, are of Latin origin or have a Latinized spelling and are treated as Latin regardless of their origin.

Composition of Scientific Names:

The Genus Name and the Specific Epithet together form a Binomial, called the Species Name. A complete scientific name of white oak is Quercus alba L. The genus is Quercu, the specific epithet is alba and the author citation Linnaeus (L).

Generic Name:

The generic name is a singular Latinized noun or a word treated as a noun. It is always written with an initial capital letter. After a generic name has been spelled out at least once, it may be abbreviated by using the initial capital letter, for example, Q for Quercus. Generic name may not consist of two words unless they are joined with a hyphen. The name may be taken from any resource or it may commemorate some person of distinction, for example, genera such as Linnae for Linnaeus.

Specific Epithets:

The specific epithet is often an adjective illustrating a distinguishing feature of the species. It may be from any source, and may honour a person or may be derived from an old common name or may even be composed arbitrarily. Specific epithets consisting of two words are joined with the help of a hyphen, for example, Capsella bursa-pectoris. All specific epithets are written with a small initial letter, but capital letter may be used when epithets are derived from a person’s name, from former generic names or from common names.

Author:

The name of the person or persons following the genus and specific epithet indicates the author’s name. The author’s citation is a source of historical information regarding name of the plant. The author citation maybe abbreviated, e.g., “L” for Linnaeus. If a species is described by two authors, the name of the author who described first will be placed in parathensis, for example, Veronica acaulis (Walter) Gleason. In this case, Walter supplied the specific epithet whereas Gleason transferred the species to the genus Veronica.

Rules of Nomenclature:

The increase number of plants known to the botanists in the 18th century required the development of order and stability in plant nomenclature. The first rules of naming plants were proposed by Linnaeus in 1737 and again in 1751. In the latter part of the 18th century priority or the use of the oldest name, was recognized as the basis of the nomenclature. But certain botanists created confusion by deviating from the principle. A. P. de Candolle set forth a detailed set of rules on the process of naming the plants. Later on these rules were made basis of International Code of Botanical Nomenclature, many plants were assigned two or more names by accident so a complex synonymy developed. Therefore, need for a standardized botanical nomenclature was felt. In 1866, a group of eminent taxonomists met in London to solve the problem and authorized A. P. de Candolle to formulate rules of botanical nomenclature. In August 1867, first International Botanical Congress was held in Paris and set of rules developed by A. P. de Candolle was adopted with a slight revision and was termed as Paris Code. Practical applications of these rules revealed some deficiencies and need to modify the rules arose. Botanical congresses were held in 1892, 1905, 1907 to resolve the nomenclatural problem and establish internationally accepted rules. A general agreement was reached in International Botanical Congress of 1930. Subsequent congresses have been held on a regular basis and have offered only minor modification in the rules. Development and changes in the code are often discussed in the journal Taxon, published by international association of Plant Taxonomy.

Digest of Rules of Nomenclature:

Today botanists throughout the world use the international Code of Botanical Nomenclature, which is written in English, French and German. The present code consists of 6 Principles, 75 Rules, 57 Recommendations and a number of notes and examples. A digest of principles, rules and recommendations is as below:

  1. Botanical nomenclature is independent of Zoological nomenclature but the name of the plant must not be rejected merely because it is identical with the name of an animal, e.g., Cecropia refers to a moth and to a large genus of tropical trees in the family
  2. The applications of names of taxonomic groups is determined by means of nomenclature Types, i.e., the specimen associated with each species name.
  3. The nomenclature of a taxonomic group is based upon the Priority of Publication, i.e., the correct name is the earliest validly and effectively published name that conforms to the rules.

Effective Publication:

The name must be published in a book or a periodical which is distributed to botanical centers throughout the world in indelible form.

Valid Publication:

A Validly Published name of taxon is accompanied by the description of the taxon and a reference to a previously validly published description. The description should include points in which the taxon differs from its allies, figures with details of structure and if the taxon is a parasite, the host should be indicated.

The first validly published name of species or a taxon becomes its valid name and first validly published name has precedence over names of same rank published later. If other names are subsequently published for the same taxon, they shall become Synonyms or Invalid Names. The starting point for such a system of priority was agreed to be Linnaeus “Species Plantarum” published on May 1, 1753.

  1. Scientific names of taxonomic groups are treated as Latin i.e., the generic name and the specific epithet may be from Latin or Latinised. The generic name should start with a capital initial letter and the specific epithet with a small initial letter. The words which cannot be readily adopted to the Latin tongue should be avoided. Similarly, the names should not be dedicated to a person quite unconnected with
  2. Retention, Choice & Rejection of Names:

If in a binomial, the specific epithet repeats the generic name, e.g., Malus malus (previous binomial for apple), it is known as Tautonym. Apple was considered closely related to pear (Pyrus communis) and was therefore, placed in the same genus under the name Pyruss malus. Later on it was found that it belongs to the genus Malus. The new combination becomes Malus malus, a tautonym. The tautonymy is banned in Botany, therefore, a new specific epithet pumila was assigned to it. The valid scientific name for apple is Malus pumila.

  • Two species with same specific epithet cannot occur in the same genus. If this happens, they are called The earliest valid name will be retained and the later will become Synonym.
  • When a species is described in one genus and later transferred to another genus, the specific epithet, if legitimate (according to rules), must be retained. For example, Chrysocoma acaulis is now treated as Vemonia acaulis.
  • When two or more taxa of the same rank are united, the oldest valid name or epithet is selected. For example, if the genera Sloanea, Echinocarpus and Phoenicosperma are united. Sloanea is the oldest name and would be correct. The other two names become Synonyms.
  1. Priority of Names:

Priority is concerned with the precedence of the data of Valid publication and determines the acceptance of one of two or more names. A name is said to Legitimate, if it is in accordance with rules and if it is contrary to the rules.

To avoid disadvantageous changes caused by strict applications of priority, some specific generic and family names are conserved by the action of the International Botanical Congresses. These are called Nomina Conservanda. This means that some names, even though they are not the oldest legitimate names, are used in preference to the older names.

  1. Ranks of Taxa:

Each species belongs to a series of taxa of consecutively higher rank. A species belongs to a genus, a genus to a family, a family to an order, an order to a sub class, a sub class to a class, a class to a sub division and a sub division to a division.

The name of the division should end in phyta, except in fungi. The sub division should end in phytinae, except in fungi. The class will end in opsida, except in algae and fungi. The sub class in nideae, the order in ales, the family in aceae, the sub family in oideae, the tribe in eae and the sub tribe in inae.

The names of the orders are taken from one of the principal genus of the families with the ending “ales”, for example, Rosales is based on principal genus Rosa. Names of families, sub family tribes, and sub tribes are taken from the names of an existing or former genus of the taxon and end in aceae, eae and inae. But the names of the following eight families are excepted, but each have an accepted alternative name which may be conserved for use by anyone who elects the alternative name ending in aceae.

Old Names New Names Type
Graminae Poaceae Poa
Cruciferae Brassicsceae Brassica
Leguminosae Fabaceae Faba
Guttiferae Clusiaceae Clustia
Umbelliferae Apiaceae Ammia
Labiatae Lamiaceae Lamium
Compositae Astraceae Aster
Palmae Arecaceae Areca

 

  1. Citation of Author’s Name:

For the indication of name to be accurate and complete, it is necessary to cite the name of the author who first validly published the name. Author’s name is put after the name of the plant and is abbreviated, for example, Solanum nigrum L. for Linnaeus and Veronica arkansana DC, for A. P. de Candolle.

When names are published by two authors, the authors are linked by either & or et (Latin-and), for instance, Opuntia pollardii Britt.et Rose, for N.L Britton and J. N. Rose,

  1. Type Concept:

The method requires that the author of a species must designate a certain specimen as the type of that species. This is known as type Specimen and is a single specimen or plants on a single herbarium sheet. The genus Aster is the type genus for the family Asteraceae.

Since catastrophes such as fire or other accident may damage or destroy preserved botanical specimens, botanists have devised a system for acceptable substitutes. The system designated several kinds of Types:

Holotype: The specimen designated by the author as type specimen.

Isotype: It is a duplicate specimen of a holotype collected at the same place and time.

Lectotype: It is a specimen chosen by a later worker from original material studied by the author of the species, when no holotype was designated or when the holotype has been lost or destroyed.

Syntype: It is one of the two or more specimens cited by an author of the species when no holotype was designated.

Paratype: If an author cited two or more specimens as types, the remaining cited specimens are paratypes.

Neotype: When all the original specimen and their duplicates have been lost, or destroyed. A neotype may be selected.

 

Cultivated Plants:

The plant brought from the wild habitat and cultivated, retain the names applied to the same taxa in their native habitat. The horticultural plants produced in cultivation through hybridization, selection, or other processes and that are worthy of being named receive Cultivar Names. The term cultivar denotes as assemblage of cultivated plants that is clearly distinguished by any characters (morphological, physiological, cytological, chemical or other) and that following reproduction (sexual or asexual), retains its distinguishing characters. The cultivar names are written with a capital initial letter. They are either preceded by the abbreviation cv (meaning cultivar) or placed in single inverted commas, for example Hosta ‘Decorata’. Cultivar names may be used after generic, specific or common names. The examples of the cultivars are Cornelia japonica cv.

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