Nomenclature Codes

The Nomenclature Codes (or the "Codes of nomenclature") are the rulebooks that govern biological nomenclature.

After the successful introduction of two-part names for species by Linnaeus it became ever more apparent that a detailed body of rules was necessary to govern scientific names. From the mid-nineteenth century onwards there were several initiatives to arrive at worldwide-accepted sets of rules. In the course of time these became the present Nomenclature Codes governing the naming of:
  • animals (International Commission on Zoological Nomenclature abbrev. ICZN)
  • plants (incl. Fungi, cyanobacteria) (ICN for Plant, Fungi & Algae, ICBN, ICNCP & with supplementary Codes)
  • bacteria (International Code of Nomenclature of Bacteria abbrev. ICNB)
  • viruses

Differences between Codes
Starting point

The starting point, that is the time from which these Codes are in effect (usually retroactively), varies from group to group, and sometimes from rank to rank. In botany the starting point will often be 1753, in zoology 1758. On the other hand bacteriology started anew, making a clean sweep in 1980, although maintaining the original authors and dates of publication.


There are also differences in the way Codes work. For example, the ICBN (the plant Code) forbids tautonyms, while the ICZN, (the animal Code) allows them.


These Codes differ in terminology, and there is a long-term project to "harmonize" this. For instance, the ICBN uses "valid" in "valid publication of a name" (= the act of publishing a formal name), with "establishing a name" as the ICZN equivalent. The ICZN uses "valid" in "valid name" (="correct name"), with "correct name" as the ICBN equivalent. Harmonization is making very limited progress.


The codes differ in terms of what kinds of types are permissible. The bacteriological code generally requires living type cultures. The botanical code requires dried specimens (typically in an herbarium), or sometimes drawings. There has been ongoing debate regarding which kind of type is more useful in a case like cyanobacteria. The zoological code generally requires a dead preserved animal, but sometimes allows a living type.

Other codes

A more radical approach is to replace all existing Codes by a BioCode, basically a synthesis of the existing Codes. The BioCode draft has received little attention since 1997; its originally planned implementation date of January 1, 2000, has passed unnoticed. However, a 2004 paper concerning the cyanobacteria does advocate a future adoption of a BioCode and interim steps consisting of reducing the differences between the codes.

Another code in development is the PhyloCode, which regulates phylogenetic nomenclature rather than Linnaean nomenclature (that is, it requires phylogenetic definitions for every name, and does not contain mandatory ranks). Implementation is tentatively scheduled for sometime before 2010.

The formal names of cultivated plants are governed by the ICNCP. This code operates within the limits set by the ICBN, but uses different basic principles.

Something about Phytosociological nomenclature codes with Biological nomencalture codes

Anyone studying the phytosociological literature observes a considerable volume of syntaxonomic names, including countless numbers of synonyms and homo- nyms, and is often faced with inconsistencies in the application of these names to particular plant communi- ties. Nomenclatural stability is urgently required, to avoid further confusion and allow easy and correct usage of syntaxonomic names by applied vegetation ecologists such as foresters, agriculturalists, and nature conservationists. Such stability can only be achieved by the uniform application of generally accepted nomenclatural rules.

Similar problems were encountered in botanical and zoological idiotaxonomy and were rationalized through the establishment of nomenclatural rules specified in the International Codes for Botanical and Zoological Nomenclature. The Phytosociological Nomenclature Commission was, from the very beginning, unanimously in favour of the priority principle (Principle IV), not because it is the basis of the nomenclature of plants and animals, but because it is the sole objective principle and hence the only one to be adopted by all phytosociologists.

Names are only labels and, as such, they can never be wholly adequate. This is all the more true for the names of syntaxa, since these often have many character and differential species, few of which can be used in their names. It is far more important to know exactly what is meant by a name than to find one that seems in every respect to be characteristic.

While the association was chosen as the basic rank in the system of syntaxa (Principle VI), this did not imply that it was considered to be the fundamental unit. While in earlier times associations were considered to be the smallest units characterized by more or less faithful species, many associations were defined subsequently by differential species so that the fundamental differ- ence between association and subassociation could hardly be sustained.

In this sense, Principle VI has a practical purpose. Subassociations cannot be established without refer- ence to the association to which they belong, whereas the reverse is quite possible. Associations, however, can be defined without establishing or mentioning an alli- ance to which they might belong. This is in marked contrast with idiotaxonomy where, owing to the binary nomenclature, species cannot be described without at- tributing them to existing genera.

Some criticize the rules for syntaxonomic names, suggesting that these follow the rules for idiotaxonomic names too closely, arguing that associations cannot be directly compared with species, and vegetation releves cannot be compared with plant specimens. The Nomenclature Commission has always been fully aware that vegetation classification is not directly comparable with the taxonomy of species. Nomenclature is not a science, however, it is a practical device and as such has much in common with the nomenclature of taxa. Many of the rules deal merely with the matter of names themselves without paying particular attention to the contents of such names. Questions concerning effective and valid publication of names, superfluous names, homonyms, priority of names and other subjects are exactly the same as those affecting idiotaxonomic names. Since idio- taxonomic nomenclature codes have a much longer history, it seems only sensible to profit from the experi- ence gained in taxonomy, insofar as such experience can help in the solution of analogous problems in syntaxonomic nomenclature.

Abstract plant communities are essentially statisti- cal units, based on tables, and not on single releves. Yet it was agreed that single releves would meet the require- ments for a sufficient original diagnosis of associations and subassociations (Art. 7). Formally and practically, there is no other solution. If more than one releve were required, the number of releves would be quite arbitrary. Besides, the required minimum number would largely depend on the variability of the syntaxon in question, being much fewer where the syntaxon was homotoneous (in the sense of Nordhagen) than where it was hetero- toneous. Where synoptic tables are employed, the number of releves may not be apparent. The description of associations based on one or a few releves must, of course, be strongly discouraged and such associations are doubtful units. Whether they prove to be 'good' associations, is a matter that must be determined by further research. A code of nomenclature cannot present rules for the standard of scientific work.

In modern taxonomy, species are not based on an individual, but on populations. Nevertheless, one sin- gle plant or animal suffices for a valid description of a new species or infraspecific taxon. The method of nomenclatural type specimens is the common basis for the nomenclature of botanical and zoological taxa. A nomenclatural type ('name-bearing type'), usually con- sists of a permanently preserved specimen of one sin- gle plant or animal (or a representative part of it, e.g. a tree branch with its leaves and/or flowers). If there were more specimens, it would remain arbitrary, as to which of these provides, in sensu strictissimo, the objective standard of reference by which the applica- tion of the name it bears is permanently settled.

The method of nomenclatural types was adopted for syntaxonomic names (Principle V and Article 15). Since, however, a discrete sample of a plant commu- nity cannot be permanently preserved, a releve must serve as a name-bearing type. The releve cannot be directly compared with an individual plant that be- longs to a single taxon or hybrid. A releve may repre- sent a mixture of different associations, so the rules in this case allow for the rejection of names of syntaxa based on such releves (Art. 37). On the other hand, there are many more cases in which releves are more or less homogeneous, whilst the table is not. In these instances, the type method enables an objective deci- sion on which parti of an association must retain the original name, where a part of the releve set is assigned to another syntaxon by division. Therefore, the name- bearing type-releve is no more than a useful device and must not always be a so-called 'typical' releve. In future, however, the method will probably contribute to a more precise definition of syntaxa.

Authors, when choosing type-releves, will generally tend to select the most typical and complete releve provided in their original diagnosis. The new Art. 16 moves in that direction and requires that (a) the type- releve of an association must contain its name-giving taxon (taxa), and (b) the type releve of a subassociation must contain the name-giving taxon of the subassociation. For associations and subassociations published before 1.1.1979, a synoptic table is allowed as a sufficient origi- nal diagnosis, although the homotoneity of such syntaxa cannot be effectively assessed. This course of action was adopted to avoid a situation where too many old names would become invalid - the Nomenclature Commission was opposed to the widespread alteration of names.

Where names of syntaxa are to be changed for nomenclatural reasons, there is no justification for adding one's name to communities described by others, since this might lead to a deluge of unnecessary alterations. For this and other reasons, Art. 48 dictates that the second authors name may only be inserted in specific cases.

The use of geographical epithets for syntaxonomic names (if they do not belong to a name-giving taxon) is explicitly forbidden, since these contain no floristic information. Such names are better reserved for geo- graphical races/vicariants, if one wants to use that con- cept. The formation of names for geographical races/ vicariants, variants and subvariants and for the highest units, the division and class group, is completely free, since the Code does not deal with syntaxa of these ranks. Experience with the rules may determine whether or not such units should one day be included in the Code.

This edition of the Code contains some major altera- tions and additions to the nomenclatural rules. Perhaps the most important one involves the possibility of re- taining names in current use as nomina conservanda (conserved names). The rigid application of the rules, particularly of the principle of priority, might lead to the rejection of well-known and long-accepted names in favour of previously unused names regarded as the senior synonym. In such cases, the priority principle, originally intended to promote stability, would just serve to load the nomenclature with unknown names pro- duced through constant dredging of the literature. An analogous problem is seen in the unfortunate instability of taxonomic names that has arisen through a similar process. As a result, nomina conservanda (not only for taxa of higher rank, but also for species) have been commonly adopted for a considerable period of time in Zoological nomenclature and have become more ac- cepted in the International Code of Botanical Nomen- clature. At the International Botanical Congress in Japan, held 1993 in Yokohama, the final plenary session adopted the following resolution relating to nomencla- ture: "The XV International Botanical Congress urges plant taxonomists, while such work continues, to avoid displacing well-established names for purely nomen- clatural reasons, whether by change in their application or by resurrection of long forgotten names." The vast majority of phytosociologists have repeatedly and ur- gently requested, at congresses and other meetings, that nomina conservanda be adopted in syntaxonomy. Fu- ture syntaxonomists should seriously consider the value of preserving nomenclatural stability through the use of nomina conservanda.

Another change involves Definition I, which now indi- cates that only phytocoenoses can be considered as syntaxa. Symphytocoenological units, 'sigma-associations', etc., and all synusial units cannot be so designated.

Thus, the 'association names' of the Uppsala School, published before 1.1.1936, with the exception of names of moss and lichen communities, are no longer subject of this Code. They correspond in reality to the 'sociations' of that School and are therefore not identical with the associations of the hierarchical system of syntaxa gov- erned by this Code (Principle II). Some of these 'asso- ciation names', however, which were applied for a long period of time in accordance with the nomenclatural type, may be proposed as nomina conservanda and, after positive decision, will become valid (Principle II, Art. 52).

This Code is moving in the direction of requiring registration of names, so those new syntaxonomic names may be generally known. An article requiring the registration of names as part of their valid publication, was favoured by the Nomenclature Commission, but was withdrawn for pragmatic reasons, and for the time being replaced by a recommendation (Reccom. 1C).

The International Code of Phytosociological No- menclature (ICPN) is one of several Codes that deal with the rules for names used in Biology. The other Codes include the International Code of Botanical No- menclature (ICBN), International Code of Nomenclature for Cultivated Plants (ICNCP), International Code of Zoological Nomenclature (ICZN), International Code of the Nomenclature of Bacteria (IBC) and International Code of Virus Classification and Nomenclature (ICV). The ICBN, ICZN and IBC will possibly be governed in future by a general 'BioCode', ruled by IUBS, the International Union of Biological Sciences, which is the premier organization in Biological Sciences, represent- ing the Academies of Sciences from many countries all over the world.

Faced with such unsolved questions, the Nomenclature Commission decided to retain in this edition the terms of the previous ones. Since the next edition of this Code will not appear before 2010, it may be useful to give a brief survey of the terms of the present Code (ICPN) and the terms of the 'BioCode', which may come into use some day.

References in Nomenclature codes

- Ahoren Oren (2004). "A proposal for further integration of the cyanobacteria under the Bacteriological Code". Int. J. Syst. Evol. Microbiol. 54: 1895–1902.
- International Code of Zoological Nomenclature, Fourth Edition (1999), article 72.5
- John McNeill (1996-11-04). "The BioCode: Integrated biological nomenclature for the 21st century?". Proceedings of a Mini-Symposium on Biological Nomenclature in the 21st Century.