Nomenclature codes orcodes of nomenclature are the various rulebooks that govern the naming of living organisms. Standardizing the scientific names of biological organisms allows researchers to discuss findings (including the discovery of new species).
As the study of biology became increasingly specialized, specific codes were adopted for different types of organism.
To an end-user who only deals with names of species, with some awareness that species are assignable togenera,families, and other taxa of higher ranks, it may not be noticeable that there is more than one code, but beyond this basic level these are rather different in the way they work.
Intaxonomy,binomial nomenclature ("two-term naming system"), also calledbinary nomenclature, is a formal system of namingspecies of living things by giving each a name composed of two parts, both of which useLatin grammatical forms, although they can be based on words from other languages. Such a name is called abinomial name (which may be shortened to just "binomial"), abinomen,binominal name, or ascientific name; more informally it is also historically called aLatin name. In the ICZN, the system is also calledbinominal nomenclature,[1] "binomi'N'al" with an "N" before the "al", which isnot a typographic error, meaning "two-name naming system".[2]
The first part of the name – thegeneric name – identifies thegenus to which the species belongs, whereas the second part – thespecific name orspecific epithet – distinguishes the species within the genus. For example, modern humans belong to the genusHomo and within this genus to the speciesHomo sapiens.Tyrannosaurus rex is likely the most widely known non-human binomial.[3]
Theformal introduction of this system of naming species is credited toCarl Linnaeus, effectively beginning with his workSpecies Plantarum in 1753.[4] But as early as 1622,Gaspard Bauhin introduced in his bookPinax theatri botanici (English,Illustrated exposition of plants) containing many names of genera that were later adopted by Linnaeus.[5]The introduction of two-part names (binominal nomenclature) for species byLinnaeus was a welcome simplification because as our knowledge of biodiversity expanded, so did the length of the names, many of which had become unwieldy.[6]
With all naturalists worldwide adopting binominal nomenclature, there arose several schools of thought about the details. It became ever more apparent that a detailed body of rules was necessary to governscientific names. From the mid-19th century onwards, there were several initiatives to arrive at worldwide-accepted sets of rules. Presently nomenclature codes govern the naming of:
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.[7] Inbotany andmycology, the starting point is often 1 May 1753 (Linnaeus,Species plantarum). Inzoology, it is 1 January 1758 (Linnaeus,Systema Naturae, 10th Edition). On the other hand,bacteriology started anew, making a clean sweep in 1980 (Skerman et al., "Approved Lists of Bacterial Names"), although maintaining the original authors and dates of publication.[8]
Exceptions in botany:[9][10][11]
Exceptions in zoology:[13]
There are also differences in the way codes work. For example, theICN (the code for algae, fungi and plants) forbidstautonyms, while theICZN, (the animal code) allows them.
These codes differ in terminology, and there is a long-term project to "harmonize" this. For instance, theICN uses "valid" in "valid publication of a name" (=the act of publishing a formal name), with "establishing a name" as theICZN equivalent. TheICZN uses "valid" in "valid name" (="correct name"), with "correct name" as theICN equivalent. Harmonization is making very limited progress.
There are differences in respect of what kinds oftypes are used. The bacteriological code prefers living type cultures, but allows other kinds. There has been ongoing debate regarding which kind of type is more useful in a case likecyanobacteria.[14]
A more radical approach was made in 1997 when theIUBS/IUMS International Committee on Bionomenclature (ICB) presented the long debatedDraft BioCode, proposed to replace all existingCodes with a harmonization of them.[15][16] The originally planned implementation date for the BioCode draft was January 1, 2000, but agreement to replace the existingCodes was not reached.
In 2011, a revisedBioCode was proposed that, instead of replacing the existingCodes, would provide a unified context for them, referring to them when necessary.[17][18][19] Changes in the existing codes are slowly being made in the proposed directions.[20][21] However, participants of the last serious discussion of the draft BioCode concluded that it would probably not be implemented in their lifetimes.[22]
Many authors encountered problems in using the Linnean system in phylogenetic classification.[23] In fact, early proponents of rank-based nomenclature, such asAlphonse de Candolle and the authors of the 1886 version of theAmerican Ornithologists' Union code of nomenclature already envisioned that in the future, rank-based nomenclature would have to be abandoned.[24][6] AnotherCode that was developed since 1998 is thePhyloCode, which now regulates names defined underphylogenetic nomenclature instead of the traditionalLinnaean nomenclature. This new approach requires using phylogenetic definitions that refer to "specifiers", analogous to "type" under rank-based nomenclature. Such definitions delimit taxa under a given phylogeny, and this kind of nomenclature does not require use of absolute ranks. TheCode took effect in 2020, with the publication ofPhylonyms, a monograph that includes a list of the first names established under that code.
Someprotists, sometimes calledambiregnal protists, have been considered to be bothprotozoa andalgae, orprotozoa andfungi, and names for these have been published under either or both of theICZN and theICN.[25][26] The resulting double language throughout protist classification schemes resulted in confusion.[27][28][29]
Groups claimed by bothprotozoologists andphycologists includeeuglenids,dinoflagellates,cryptomonads,haptophytes,glaucophytes, manyheterokonts (e.g.,chrysophytes,raphidophytes,silicoflagellates, somexanthophytes,proteromonads), some monadoidgreen algae (volvocaleans andprasinophytes),choanoflagellates,bicosoecids,ebriids andchlorarachniophytes.
Slime molds,plasmodial forms and other "fungus-like" organisms claimed by both protozoologists andmycologists includemycetozoans,plasmodiophorids,acrasids, andlabyrinthulomycetess.Fungi claimed by both protozoologists andmycologists includechytrids,blastoclads, and thegut fungi.
Other problematic groups are theCyanobacteria (ICNP/ICN) andMicrosporidia (ICZN/ICN).
Thezoological code does not regulate names of taxa lower than subspecies or higher than superfamily. There are many attempts to introduce some order on the nomenclature of these taxa,[30][31] including thePhyloCode, the Duplostensional Nomenclatural System,[32][33] andcircumscriptional nomenclature.[34][35]
Thebotanical code is applied primarily to the ranks of superfamily and below. There are some rules for names above the rank of superfamily, but theprinciple of priority does not apply to them, and theprinciple of typification is optional. These names may be either automaticallytypified names or bedescriptive names.[36][37] In some circumstances, a taxon has two possible names (e.g.,Chrysophyceae Pascher, 1914,nom. descrip.; Hibberd, 1976,nom. typificatum). Descriptive names are problematic, once that, if a taxon is split, it is not obvious which new group takes the existing name. Meanwhile, with typified names, the existing name is taken by the new group that still bears the type of this name. However, typified names present special problems for microorganisms.[29]