Subspecies Conventions Zoology Bacteriology Botany

Conventions regarding infra-specific categories vary between biological disciplines as follows:

In zoology, the scientific name of a subspecies is the binomen followed immediately by a subspecific epithet, e.g. Homo sapiens sapiens. The International Code of Zoological Nomenclature (4th edition, 2000) does not attempt to codify any "infrasubspecific entities".

1.2 Bacteriology

In bacteriology, the terms subspecies and variety are usually interchangeable.

1.3 Botany

In botany, different variations within a species are denominated explicitly as subspecies (subsp.), varieties (var.) or forms (f.); a species may be divided into one or more subspecies, with the subspecies further subdivided into one or more varieties, e.g. European black pine (Pinus nigra):

Note that one of the taxa always repeats the same name as for the species as a whole; this is referred to as the type or nominate subspecies and variety, and includes the specimen the species was originally described from.

Variety has often mistakenly been used as a synonym of subspecies, but the two ranks are nomenclaturally discrete under the ICBN. Variety is used for lower degrees of difference than subspecies. A form is usually used to designate a minor variation within a population or region. For instance, white-flowered forms of species that usually have coloured flowers are often designated as "f. alba".

A cultivated variant is identified by quoting the cultivarA cultivar is a cultivated variety of a plant species. Modern cultivars are often, but not necessarily, hybrids between species; they may equally well represent particularly desirable selections from populations of a single species. Cultivars generally ar epithet. For example:

2 Criteria

Subspecies are defined in relation to species. It is not possible to understand the concept of a subspecies without first grasping what a species is. In the context of large living organisms like trees, flowers, birds, fish and humans, a species can be defined as a distinct and recognisable group that satisfies two conditions:

Members of the group are reliably distinguishable from members of other groups. The distinction can be made in any of a wide number of ways, such as: differently shaped leaves, a different number of primary wing feathers, a particular ritual breeding behaviour, relative size of certain bones, different DNADeoxyribonucleic acid DNA is a nucleic acid which carries genetic instructions for the biological development of all cellular forms of life and many viruses. DNA is sometimes referred to as the molecule of heredity as it is inherited and used to propagate sequences, and so on. There is no set minimum 'amount of difference': the only criterion is that the difference be reliably discernable. In practice, however, very small differences tend to be ignored.

The flow of genetic material between the group and other groups is small and can be expected to remain so because even if the two groups were to be placed together they would not interbreed to any great extent.

Note the key qualifier above: to be regarded as different groups rather than as a single varied group, the difference must be distinct, not simply a matter of continuously varying degree. If, for example, the population in question is a type of frogA frog is a fresh-water amphibian which changes from a tadpole and is of the family Ranidae in the Order Anura. They are closely related to toads. The Ranidae are sometimes called the "true frogs" since a few members of other families also have common nam and the distinction between two groups is that individuals living upstream are generally white, while those found in the lowlands are black, then they are classified as different groups if the frogs in the intermediate area tend to be either black or white, but a single, varied group if the intermediate population becomes gradually darker as one moves downstream.

This is not an arbitrary condition. A gradual change, called a cline, is clear evidence of substantial gene flow between two populations. A sharp boundary between black and white, or a relatively small and stable hybrid zone, on the other hand, shows that the two populations do not interbreed to any great extent and are indeed separate species. Their classification as separate species or as subspecies, however, depends on why they do not interbreed.

If the two groups do not interbreed because of something intrinsic to their genetic make-up (perhaps black frogs do not find white frogs sexually attractive, or they breed at different times of year) then they are different species.

If, on the other hand, the two groups would interbreed freely provided only that some external barrier was removed (perhaps there is a waterfall too high for frogs to scale, or the populations are far distant from one another) then they are subspecies.

Note that the distinction between a species and a subspecies depends only on the likelihood that (absent external barriers) the two populations would merge back into a single, genetically unified population. It has nothing to do with 'how different' the two groups appear to be to the human observer.

As knowledge of a particular group increases, its categorisation may need to be re-assessed. The Rock PipitRock Pipit : Animalia : Chordata : Aves : Passeriformes : Motacillidae Anthus petrosus Binomial name ''Anthus petrosus Montagu, 1798) The Rock Pipit Anthus petrosus is a small passerine bird which breeds on rocky coasts of western Europe northwards from B was formerly classed as a subspecies of Water PipitWater Pipit : Animalia : Chordata : Aves : Passeriformes : Motacillidae Anthus spinoletta Binomial name Anthus spinoletta Linnaeus, 1758) The Water Pipit Anthus spinoletta is a small passerine bird which breeds in the mountains of southern Europe and sout, but is now recognised to be a full species. For an example of a subspecies, see Pied Wagtail.

It should be noted that if a subspecies is indicated by the repetition of the specific name, it is known as the nominate subspecies. Thus Motacilla alba alba is the nominate subspecies of White Wagtail, Motacilla alba.

3 See also

Scientific classification

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1 Conventions