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A guide to writing zoological names for non-taxonomist authors

by Geoffrey B. Read, Ph.D.

Last updated 12 July 1999.

Species names of animals are not always presented correctly by those who write scientific papers. There is a comprehensive International Code of Zoological Nomenclature which anyone who does taxonomy should study, but most other biologists will get by with a knowledge of a few simple rules derived from the Code. Here are the basics for intelligent usage of names, followed by some of the traps for the unwary.

The basics

Nereis diversicolor. My examples use Nereis diversicolor, a species of marine segmented worm (Phylum Annelida: Class Polychaeta). The scientific name of a species is always the two names together (a binomen), hence the term 'binominal nomenclature' (also written as 'binomial'). The first name, Nereis, is the generic name, the second, diversicolor, is the specific name, or epithet. Only the genus has an initial capital letter. Some situations might require further precision with a subspecies name, thus forming a trinomen.

Nereis diversicolorNereis diversicolor, a member of the polychaete family Nereididae, is a well known animal in ecological studies and in laboratory experiments. Every year there are publications about it. It makes a good example because people can legitimately use varying formulations of the scientific (Latin) name. Some taxonomists think this nereidid belongs in a subgenus called Hediste, some think Hediste ranks as a genus in its own right, and some that Hediste is irrelevant and should not be used at all. Non- taxonomists have either never heard of Hediste or are uncertain as to how to use Hediste with Nereis. This discussion is not concerned with which name is best for our example, only that each variant is written in the correct manner.

Including the subgenus - Nereis (Hediste) diversicolor. The subgenus name may be present or absent between the generic and specific name. If present it must be in parentheses () and with the first letter capitalised, such as Nereis (Hediste) diversicolor.
Explanation: A genus can have many species. Sometimes it contains so many species that taxonomists have created a subgenus to help keep track of the affinities within the genus. However, the subgenus may be totally omitted. It is an interpolation, not part of the species binomen. No one will mind if it is left out, especially in non-taxonomic articles. I would omit it unless there is a special need to include it, as that middle bit just makes the name more difficult to read. Note that a three-part trinomen indicating a subspecies is distinctly different because the second word lacks both an initial capital and the parentheses - Nereis diversicolor monocolor (an invented name), or, including the subgenus - Nereis (Hediste) diversicolor monocolor. Subspecies can also have defined affinity groups with names in parentheses, but these are rarely used. The International Code of Zoological Nomenclature explains them further.

Including the author and date - Nereis diversicolor Müller, 1776. The person who named the species can be indicated after the binomen. The name is enclosed in parentheses only if the genus now is not the one the original author used. The date may be omitted.
Explanation: You might do this once in an article just to give an idea of who described it - the 'author' or authority, and where to find the description should other people wish to check what the species looks like. The date of description is optional, but if given should be separated from the author by a comma - Nereis diversicolor Müller, 1776. If the species was originally described in another genus this is indicated by placing author and date in parenthesis - Hediste diversicolor (Müller, 1776).

Abbreviating - N. diversicolor and Nereis spp.. It is permissible to indicate the genus, and the subgenus, by just the initial capital letter after it has been introduced to the reader. Also, biologists often use the abbreviation sp. (plural spp.) instead of the word species.
Explanation: Constant repetition of the full name may get tedious, especially if it is a long word, or a complex tongue-twister such as Labiosthenolepis. The full generic name should be re-used from time to time, and also if a sentence begins with the species name, and if one or more other species of different genera are discussed. This is a greater problem when the generic names begin with the same letter. In some fields it is commonplace to use two letters to avoid confusion - An. for Anopheles and Ae. for Aedes mosquito genera. It is a matter of judgment. There is no absolute rule here. The aim is to avoid long-winded repetition whilst making sure the reader is not confused by a maze of abbreviations. Finally, the abbreviation sp. for species has no deeper taxonomic significance. Nereis sp. would be used if the full species name was unknown, and Nereis spp. probably when indicating several species, the names of which don't much matter.

Those are the basics. Now to examine the traps into which careless writers fall.

The traps

Trap one - Genus as species: It is never permissible to refer to a species by its generic name alone. Thus "Nereis is a green species" is an incorrect statement because we cannot tell which of the many species of Nereis it might be, although you might legitimately say "this [particular] Nereis species is green [as opposed to all the blue Nereis species]". If you are presenting information derived from known species but think you will leave out the species names and only use genus names because it looks cleaner that way, you are certainly omitting important information for others that would add value to your paper.
If, however, the species is unknown or just not identified then it is fine to say so - "Our amphipods living in Zostera species [or sp.] leaves were eaten by a Nereis species" [or " ... by an unidentified nereidid."]. A generic name by itself denotes the group of animals of that sort, not the species; thus we can say "larval Nereis are mostly planktonic."

There are occasions when the temptation to use just the generic name of an animal is irresistible. In less formal science writing if there is only one species in the genus, or if only one member of the genus is the animal that is very well known, then we can expect 'genus as species' to occur. We assume that the writer either doesn't know the full name, or thinks it is unimportant in the context - thus we never learn the species name of the Brontosaurus in S. J. Gould's entertaining essay 'Bully for Brontosaurus' (concerning the Code rule on priority). Ultimately some generic names of animal groups (and plants) are so often used in everyday talk that they become the ordinary English words for the type of animal, such as amoeba (protozoans), and drosophila (flies). Used thus they are not given an initial capital letter or italics. However, your scientific papers are required to be more accurate than everyday talk or popularised science, so such casual usages are likely to be inappropriate; always use binominals if possible.

Trap two - Alternate name as subgenus: Sometimes a species is better known by an older scientific name and you may wish to point this out. However, it is never permissible to include an alternate generic name as part of the binomen. The only genus-group name that may be between the generic name and specific name is the subgenus. Thus Nereis (Hediste) diversicolor is correct because Hediste can be a subgenus of Nereis. The other way around, as Hediste (Nereis) diversicolor, is wrong however, because in this case Nereis is not, and never will be, a subgenus of Hediste. If you wish to indicate that some people in the past or at present know your Hediste species by another name - Nereis diversicolor - then you should write "Hediste diversicolor (formerly in Nereis)." That is the recommendation of the International Code of Zoological Nomenclature for this problem of presentation. People also write formulations such as Hediste ( = Nereis) diversicolor (also with square brackets used), but this is wrong, since the interpolated name is really a comment and not part of the current name. Others may confuse it with the subgenus name. They may also be confused as to which name - Nereis or Hediste - is the current one.

Trap three - Misleading author: Any author name placed immediately after a species name is assumed to be the person who described it - Nereis diversicolor Müller, 1776. Do not put other references there. Do not combine your citation of other references with the taxonomic authority. Nereis diversicolor (Read 1999) would be misleading, and Nereis diversicolor (Müller, 1776, Read 1999) would be bizarre. If there is no elegant way to avoid the adjacency then add 'see' before the other reference - "Nereis diversicolor (Müller, 1776), (see Read 1999)".

Trap four - Excessive abbreviation: Sometimes you will find a paper where the sentences are bristling with abbreviated names of numerous species - for some reason the author seems determined not to spell out genera, and readers need to strain their brains just to follow which species is being discussed. This problem arises because in earlier days it was expensive to 'set type' laboriously by hand. Abbreviating the genus name to just one letter was one way of saving a bit of time and money. That reason no longer applies, yet the practice is deeply entrenched. Many people still abbreviate with excessive zeal, and lay people in popular articles (gardening columns in newspapers come to mind) may even never tell us the genus full name at all. They think it is somehow more 'scientific' that way. It is not. Clarity and ease of reading should be the main considerations.

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First published 2 May 1999. This is an evolving original document by Geoff Read

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