Bulletin 29 - July 1986: Linnaean or Binomial Nomenclature



Linnaean or Binomial Nomenclature

by Ken Campbell FIMLS

(The following article complements that by C.G. Roche, "What's In A Name", Bulletin No. 15, November 1981, pp.9-11 -Ed.)

By the early eighteenth century the increase in interest in natural history and the sudden access to relatively easy travel abroad had led to an exponential increase in the number of species of animals known to science (although at this time the concept of a species had not yet been introduced). The great problem was that an identical organism might be known by one name in one location and by an entirely different name elsewhere. It was impossible to decide which were new animals or plants hitherto unknown to science and which were already known elsewhere. Some more systematic way of naming new organisms was essential and it was at this point that Carl von Linne made his contribution.

von Linne is better known by the Latinised form of his name Linnaeus, and it was he who first proposed the new (now universally employed) nomenclature. In 1758 the book "Historia Naturae" was published, in which Linnaeus first used the system of binomial nomenclature, whereby any organism is given a unique name consisting of two parts; a genus name (shared by several similar species), and a specific name (which may only be applied to one species within a given genus). The genus name may not be used more than once, while the specific name can be but not within the same genus. The full binomial name will thus refer uniquely to one species. Although many of the names invented by Linnaeus have since been changed in the light of new findings, his system has never been seriously challenged. When the scientific name of a species is given in full, the name of the first author to describe and name the species is given in brackets (sometimes with the date of the paper). There are still many entries to be found abbreviated 'Linn.' or 'L.', indicating that Carl von Linne hirnself holds that honour. Examples of native UAE plants in this category include the common caper Capparis spinosa L., the small crucifer Anastatica hierochuntica L. and many grasses such as Poa annua L., Cenchrus ciliaris L. and Aristida adscensionis L.

Prior to the inception of the Linnaean system the scientific name of a new species often consisted of a long-barrelled description in a classical language -- excellent examples can be found within Gilbert White's "Natural History of Selborne". The best solution found to the multiplicity of names on offer was to 'systematise' the earliest version offered, and this system of priority in case of conflict in naming continues to apply.

The assignation of new names now lies with an international commission on naming. The privilege of selecting a new name traditionally rests with the discoverer of a new species; however, only the commission can agree to the claim that the organism is truly new to science and merits a new name. Frequently the name will derive from a classical root or roots and when translated will to some extent describe the species. Take for example the Little Gull, Larus minutus. 'Larus' is Latin for Gull, and 'minutus' is self-explanatory. This does not always apply, so beware; one genus of kingfisher is named Alcedo (for reasons logical but longwinded) and a scientist stuck for a name for a new genus came up with the nonsense anagram Dacelo.

The same system is operated throughout the biological sciences. The crucial aspects are the genus and species names -- from these is derived the unique name of a given species. However, there are other categories above these and a typical breakdown of classification to a species would be:

Kingdom - Animal
Phyllum - Chordata
Class - Aves
Order - Charadriiformes
Family - Laridae
Genus - Larus
Species - minutus

It will be noted that the genus name begins with a capital letter and the species name normally with a lower case letter. Occasionally triple-barrelled names are encountered, and these are used to distinguish between sub-species or races of a given species. The minimal requirement for differentiation between species is that, in the wild, members of one species do not normally inter-breed. Very occasionally clearly separate species, such as chiff-chaff and willow warbler will in fact cross-breed in the wild if they are sufficiently genetically similar. Since most hybrids are sterile it is sometimes suggested that the criterion for differentiation between species and subspecies should be that subspecies can cross-breed to produce fertile offspring, while species cannot. It remains irrefutable that many species produce morphologically distinguishable forms which nonetheless readily interbreed given opportunity. Usually such forms are found at geographical extremes of a contiguous range. An extreme example is where certain members of a species are isolated or an island. The UK mainland species of wren is Troglodytes troglodytes troglodytes. On the island of Hirta, in the Scottish Hebrides Islands, is found a visibly different forrn, Troglodytes troglodytes hirtensis. This can nonetheless interbreed with the mainland form given the chance. It can therefore be seen that there is a logical system, however impenetrable the maze may seem at first glance.

 


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