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Nomenclature: the rules governing names

 

 

 

 

 

Principles

Nomenclatural rules are highly complex, but the basic underlying principles are simple. They are based upon validity, typification, and priority.

 

 

  • To be valid, names have to be published in a printed publication and diagnosed or described in Latin.
  • The application of a name is fixed to a stated ‘type’, nearly always a pressed specimen stored in a herbarium.
  • The first name validly published at any particular rank has priority (unless officially rejected).

 

The detailed rules, specified in the International Code of Botanical Nomenclature, are revised every few years. They are rather complicated, often somewhat convoluted and quite difficult to digest. The examples given for many of the rules often help to clarify their application considerably. They have evolved slowly, often on a piecemeal basis. Any amendments have to be voted in or out by members of a large international organisation, some with block votes, so nothing changes fast, and standardisation or simplification is very difficult to implement. Together the rules work and make sense, but there is usually much more interlinking, history and hidden agenda to them than meets the eye, and like all complex rules they can be very hard to improve without accidentally making something else worse.

 

 

Synonymy: why plants can have more than one valid name

Although each species is meant to have only one name under our system of nomenclatural rules, there are often several names that are applied under different circumstances. This is because some of them are to be applied following different classification systems, for example when different genera are recognized. Others are only applied when a narrow concept of the species is applied, falling into synonymy if the smaller species are lumped together into larger species, for which fewer names are required.

These names that can all apply to the same plant or group of plants are called synonyms, and there are different kinds of synonym, the basionym and nomenclatural (homotypic) or taxonomic (heterotypic) synonyms.

 

Nomenclatural or homotypic synonyms & the basionym

Each species recognized can only have one correct name within a particular genus. It may have several synonyms if different classification systems have been applied, e.g. if a species has been transferred between different genera. Such synonyms, however, are tied to the same type, and they are known as nomenclatural or homotypic synonyms.

  • Example 1: 

    The name Cephalostachyum latifolium Munro was published by Munro in 1868.

    The name Schizostachyum latifolium (Munro) R. B. Majumdar was published when Majumdar applied a somewhat different classification system in which he did not recognize Cephalostachyum, moving all the species to Schizostachyum.

    The names Cephalostachyum latifolium Munro and Schizostachyum latifolium (Munro) R. B. Majumdar are nomenclatural synonyms. The inclusion of the author leaves a paper trail to show that they have the same type. The earliest nomenclatural synonym is called the basionym. Cephalostachyum latifolium Munro is the basionym of Schizostachyum latifolium (Munro) R. B. Majumdar.

     

  • Example 2:

    The name Cephalostachyum fuchsianum Gamble was published by Gamble in 1896.

    The name Schizostachyum fuchsianum (Gamble) R. B. Majumdar was published later by Majumdar.

    These names are also nomenclatural synonyms of each other.

       

Taxonomic or heterotypic synonyms

As there may be differences of opinion as to whether species (meaning here species names with different types) are really distinct, there is second kind of synonym, the taxonomic or heterotypic synonym.

  • Example: 

    Stapleton (1994) considered that Cephalostachyum latifolium Munro and C. fuchsianum Gamble were not really different species taxonomically speaking, as they both have the same morphological characteristics. They share prominent oral setae on the leaf sheaths, but Gamble’s species was based on young material in which they were still attached, while Munro’s species was based on older material, from which they had already fallen off. As C. latifolium Munro was the first species name published, C. fuchsianum Gamble and Schizostachyum fuchsianum (Gamble) R. B. Majumdar become additional, taxonomic synonyms.

The species is then listed as:

    Cephalostachyum latifolium Munro, Trans. Linn. Soc. London 26: 140. 1868.

      Schizostachyum latifolium (Munro) R. B. Majumdar. Type: Griffith 2682.

      Cephalostachyum fuchsianum Gamble; Schizostachyum fuchsianum (Gamble) R. B. Majumdar. Type: Gammie, Songchonglu, 1892.

All four names would be valid and could be used by different people who had different ideas about the appropriate size and scope of the species and genera concerned.

 

Illegitimate names, the homonym & the nom. nov.

However, there is still a problem, in that when Majumdar moved C. latifolium into Schizostachyum as S. latifolium (Munro) R. B. Majumdar, he had not realised that the name Schizostachyum latifolium had already been published, by Gamble in 1896. Therefore his name, although validly published, fell into a category known as illegitimate, as it is a later homonym. A different name altogether had to be published later to provide a legitimate, correct, name in Schizostachyum for the species—Schizostachyum sharmae S. Kumar & Paramjit Singh. This new name, or nom. nov., still has the same type and the same basionym. The full synonymy when Cephalostachyum is recognized then becomes:

 

    Cephalostachyum latifolium Munro, Trans. Linn. Soc. London 26: 140. 1868.

      Schizostachyum latifolium (Munro) R. B. Majumdar (illeg. hom.); Schizostachyum sharmae S. Kumar & Paramjit Singh nom. nov . Type: Griffith 2682.

      Cephalostachyum fuchsianum Gamble; Schizostachyum fuchsianum (Gamble) R. B. Majumdar. Type: Gammie, Songchonglu, 1892.

 

If Cephalostachyum is not recognized, then the species would be listed as:

 

    Schizostachyum sharmae S. Kumar & Par. Singh, J. Ind. Bot. Soc., 70(1–4): 423. 1991. nom. nov .

      Cephalostachyum latifolium Munro, Trans. Linn. Soc. London 26: 140. 1868; Schizostachyum latifolium (Munro) R. B. Majumdar (illeg. hom.). Type: Griffith 2682.

      Cephalostachyum fuchsianum Gamble; Schizostachyum fuchsianum (Gamble) R. B. Majumdar. Type: Gammie, Songchonglu, 1892.

 

 

 

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