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.
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 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)
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
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.
Those are the basics. Now to examine the traps into which careless writers fall.
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.
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 ReadYour suggestions are welcome. Look in again soon.