2. Nomenclature
Nomenclature is a Latin word, derived from “nomen” meaning name and
“clare” to call. Literally it means to call by name.
The purpose of nomenclature is to provide authentic, stable, unique and
universally used labels in the form of scientific names.
The role of nomenclature is to provide labels for taxonomic categories in
order to facilitate communication among biologists.
Thus nomenclature is the language of biology and the rules of
nomenclature is its grammars. Nomenclature can be defined as “The
naming of organisms”.
The names should be scientific, authentic, unique and universal.
3. ICZN
1. All the rules of nomenclature are preserved in an authentic document
called international code of Zoological nomenclature (ICZN). Most of the
nomenclatural work (rules and phenomenon) was done in the first 2/3 of
the 20th century (1964). In 1901, 5th International Congress of Zoology
formulated the rules and named them as “International Rules of
Zoological Nomenclature”. The original code and its revision is the work
of International Congress of Zoology (ICZ). Now a days, the congress is
defunct and their role has been taken by the General Assemblies of
International Union of Biological Sciences (IUBS)
4. ICZN
The code proper includes the preamble followed by 88 consecutively numbered
articles grouped in 18 chapters.
The articles are composed of mandatory rules and provisions, followed by
recommendations like recommendation 9b, 73a. 88c etc. the appendices are like
recommendations. There are three appendices. The 1st and 2nd have status of
recommendations while the 3rd is the constitution of the commission.
The terms used in the text are clearly defined by the glossary. Several editions of
the code have been published but the main are 1961, 1964 and 1985 which are
available at the International trust for zoological nomenclature London or from
the University of California Press.
5. International Commission on Zoological Nomenclature
The commission was founded in 1895 with five members. In 1898 its members raised to 15. In 1948, during
Congress of Zoology held at Paris the number of its members was raised to 28 and this was irrespective of the
specialization of national and regional speciality.
Duties
The commission has the following duties.
1. To consider, at least one year in advance of the congress, any proposal for the change in the court
2. To submit to the congress recommendations for the clarification or modification of the court
3. To render between successive congresses declaration embodying such recommendations.
4. To render opinions and directions on questions of Zoological nomenclature that do not involve changes in the
court
5. To compile the official list of accepted and rejected names and works in zoology.
6. To submit reports to the congress on its work and
7. To discharge other such duties as congress may determine.
6. Origin of Nomenclature
The English vernacular names are generally short and monosyllabic like
bear, finch, snake etc. Common names for species are often modification
of these names with descriptive noun or adjective. For example, a polar
bear, brown bear. These double names are binomial, such names are not
authentic for scientific use because they change from language to
language and area to area. The pre Linnaean taxonomist tried to award
scientific names to taxa but those were not authentic. Some of those
were uninomial and others binomial and even some were polynomial.
They used the names to describe the function of the organism like a
species with relatives can be referred with a qualifying adjective e.g.
Musca carnivora and M canum.
7. Origin of Nomenclature
If they found that an original Musca carnivora has two species they would refer to
call them M carnivora major and M carnivora minor. In other words specific names
evolved to specific phrases. It was the Linnaeus (1758) who proposed Binomial
system of nomenclature in 10th edition of his book “Systema Naturae”. In this
system each organism is give two names, generally Latin or Latinised. The first is
called generic name starting with a capital letter and the second is the specific name
starting with a small letter. The generic name represents the genus of the organism
while the specific name represents species. For example, the common house fly is
called Musca domestica, here Musca is the generic name (the genus in which the
house fly in included) and domestica is the specific name (Species of the house fly).
These names are in italics when printed or under lined when handwritten. For some
polytypic species the names are trinomial like Motacilla alba alba.
Musca Spp
8. Principles of Binomial Nomenclature
Following are the basic principles or rules of binomial nomenclature.
1. The nomenclatures, according to the organism, are of three types; Zoological,
Botanical and Microbial (Bacteriological).
2. Zoological and Botanical nomenclatures are independent of one another, due
to which it is permeasble but not desirable for a taxa (especially) genus to
have the same name in Zoology and Botany like Lymnea in zoology is the
genus of snail and in botany Lymnea is a genus of small floating angiosperms.
3. Within a nomenclature (Botany or Zoology) two taxa cannot have the same
name, each taxa should have a single correct name.
4. Scientific names of taxa are treated as Latin regardless of their derivation.
5. Correct name of a taxon is based on priority of publication.
9. Principles of Binomial Nomenclature
6. For the categories of orders (Botany) superfamily (zoology) and lower
categories (both), the application of name is based on type specimen, type
species or type genus.
7. Generic name is noun and specific name is adjective or genitive.
8. First letter of the generic name is capital and all other letters in the name are
small.
9. Both generic and specific names should be in italics or underlined.
The gender of the species name must be in agreement with the gender of the
genus. if the species name is adjective so its gender must also be in agreement
with genus. The genitive or neuter name is not changed and the masculine
names ends on “us” and feminine ends on “a”.
10. Essential Features of Nomenclature
The three important requisites of nomenclature which should be kept in mind before giving names to
a taxon are:
Uniqueness: The name should be unique and individual. It must be the only name within the
nomenclature and it must represent just a single taxon. The name should be unique because it is the
key to entire literature relating to that species or higher taxon. If several names have been given to the
same taxon, then there must be a clear cut method of determining that which of them has validity.
Universality: The scientific name should be universal and acceptable throughout the word and
throughout biological societies. Vernacular names cannot be used in this nomenclature because it
would be very difficult for taxonomists to learn names of taxa in innumerable languages to
communicate with each other. To avoid these problems zoologists have adopted by an international
agreement a single language and a single set of names for animals to be used on a worldwide basis.
Stability: The biological names should be stable and authentic. It should not be changeable. Any
change of a well-established name is likely to produce confusion and may be retrieved. Since the
name is the key to the information about a particular organism. Therefore, even the principle of
priority can be set aside by the international commission on zoological nomenclature in cases where
stability is threatened.
11. Law of Priority
Law of priority covers the period from 1st January, 1758 to the present. It is covered in the article 25 of
the rules, as amended in Paris (1948). Its essential provisions are that the valid name of a genus or a
species can be only that name under which it was for the first time designated subject to the conditions
that;
1. This name was published (prior to 1st January, 1931) accompanied by an indication or a definition or a
description. In the case of generic or sub generic name, that genus or sub genus was monotypical.
2. The author has applied the principles of binomial nomenclature.
3. No generic or specific name published after 31st December, 1931 have any status of validity and
availability under the rules until and unless it is published either
a. With the statement in words indicating the characters of the genus, species or subspecies concerned.
b. In case of name proposed as a substitute for a name invalid by reason of being a homonym with
reference to name thereby replaced.
4. Even if a name satisfies all the requirements specified above, the name is not valid name if it is rejected
under the law of homonymy.
12. First Reviser Principle
The first reviser principle is very useful in stabilizing nomenclature. When two or
more names are published simultaneously by different scientists and the date is same,
then which will be adapted? Similarly when a new name is spelled in more than one
way in the original publication.
So an authorized person will analyse and will select the one which is better known and
prior than the other. This person is called the first reviser and the process is called first
reviser principle.
13. Synonym and Synonymy
Two or more similar names for the same taxon is called synonyms. The
chronological list of the scientific names applied to a given taxon with the dates
of publication and the authors of the names is called synonymy.
When there are a number of synonyms, the selection of a proper name applicable
to the taxon is done through the law of priority. The oldest available name is the
valid name is called senior synonym while the rest are invalid and called junior
synonyms.
14. The rate of synonymy varies from group to group. In certain cases it may be upto 50%. Solow et al (1995) have
presented a good method of estimating the rate of synonymy through statistics models.
Rate of Synonymy
Significance of Synonymy
Synonymy is of great importance as it provides considerable amount of information
available in the literature under one or more of these names. The presentation of a synonymy
is a key to information contained in the taxon.
15. There are two types of synonymy.
Subjective synonymy: Those synonyms which are based on opinions and are not absolute
are called subjective synonyms, taxonomic synonyms, conditional synonyms or zoological
synonyms.
Objective synonymy: those names which are based on the same type and clearly proposed
for the same object are called objective synonyms, nomenclatural synonyms, obligate
synonyms or absolute synonyms. Such synonyms are always absolute and can never be
separated.
Types of Synonymy
16. Homonyms and Homonymy
One and the same name for two or more different things or identical names for two
different taxa is known as homonym. The list of homonyms or the phenomenon of
homonyms is called homonymy. In case of genera the homonyms are always
unavailable, because all generic names of animals stand on their own. Two genera in
the animal kingdom with the same name would cause confusion. However, the same
name may be used for both the genus of plants and animals. In species level the
identical names are permissible provided that they do not belong to the same genus.
The two names are then homonymous. According to the rules of Zoological code, if
two or more homonyms are found, only the oldest is used and is called senior
homonym, the rest are excluded from the use and called junior homonyms.
17. Types of Homonyms
The homonyms are of two types, Primary and Secondary.
Primary Homonyms: This is the one where both the generic as well as specific names
are the same. For example, X-us albus Smith, 1910, X-us albus Jones, 1915 or Rana
tigrina Linnaeus 1758 and Rana tigrina Fabricius 1795. In each of these cases, the
latter name is junior homonym of the former and must be permanently rejected and
never revived, even if the former one is also replaced later on.
Secondary Homonym: It is the one which results either from the combination of two
genera with the same species or from reclassification or taxonomic transfer. For
example two genera, Vespa and Vespula are combined both containing species
germanica.
18. Taxonomic Grid
In order to determine whether the samples are intrapopulation variants, sub species or
species, the taxonomists rely on three sets of data: reproductive isolation, presence or
absence of morphological differences and geographical relationship. On the basis of
this information a table of eight squares is constructed which is called Discrimination
of Taxonomic Grid
19. Taxonomic Grid
Morphology Not Reproductively Isolated Reproductively Isolated
Similar
Sympatric 1. Same Population 5. Sibling Species
Allopatric 2. Same Subspecies 6. Sibling Species
Different
Sympatric 3. Individual Variants of the same Population 7. Different Species
Allopatric 4. Different Sub Species 8. Different Species
