Subspecies
Encyclopedia
Subspecies in biological classification
, is either a taxonomic rank
subordinate to species
, or
a taxonomic unit
in that rank (plural
: subspecies). A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one. (However, all but one subspecies may be extinct, as in Homo sapiens sapiens.)
Organisms that belong to different subspecies of the same species are capable of interbreeding and producing fertile offspring, but they often do not interbreed in nature due to geographic isolation or other factors. The differences between subspecies are usually less distinct than the differences between species, but more distinct than the differences between breed
s or races
(races can be assigned to different subspecies if taxonomically
different). The characteristics attributed to subspecies generally have evolved as a result of geographical distribution or isolation.
, the International Code of Zoological Nomenclature
(4th edition, 1999) accepts only one rank below that of species, namely the rank of subspecies http://www.nhm.ac.uk/hosted-sites/iczn/code/index.jsp. Other groupings, "infrasubspecific entities" (e.g. pet
breed
s and Transgenic Animals) do not have names regulated by the ICZN. Such forms have no official status, though they may be useful in describing altitudinal or geographical clines. The scientific name of a subspecies is a binomen
followed by a subspecific name, as Panthera tigris sumatrae (Sumatran Tiger
). A name of this kind is called a trinomen
.
Likewise in bacteriology
, the only rank allowed below species is subspecies. Names published before 1992 in the rank of variety
are taken to be names of subspecies http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=icnb&part=A185 (see International Code of Nomenclature of Bacteria
).
In botany
, subspecies is one of many ranks below that of species, such as variety, subvariety
, form, and subform. The subspecific name is preceded by "ssp." or "subsp.", as Schoenoplectus californicus ssp. tatora (Totora
). Any botanical name including a subspecies, variety, etc., is called an infraspecific name
.
(Motacilla alba).
The repetition of the species name is referred to in botanical nomenclature
as the subspecies "autonym
", and the subspecies as the "autonymous subspecies".
; the notation with parentheses means that some consider it a subspecies of a larger Herring Gull species and therefore call it Larus argentatus smithsonianus, while others consider it a full species and therefore call it Larus smithsonianus (and the user of the notation is not taking a position).
or by different coding sequences of DNA from members of other subspecies of the species. Subspecies are defined in relation to species
.
If the two groups do not interbreed because of something intrinsic to their genetic make-up (perhaps green frogs do not find red 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 were 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. Other factors include differences in mating behavior or time and ecological preferences such as soil content.
Note that the distinction between a species and a subspecies depends only on the likelihood that in the absence of 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 Pipit
was formerly classed as a subspecies of Water Pipit
, but is now recognised to be a full species. For an example of a subspecies, see Pied Wagtail
.
Cryptic species
are morphologically similar, but have differences in DNA or other factors.
species has two or more subspecies, races
or more generally speaking, populations that need a separate description. These are separate groups that are clearly distinct from one another and do not generally interbreed (although there may be a relatively narrow hybridization zone), but which would interbreed freely if given the chance to do so. Note that groups which would not interbreed freely, even if brought together such that they had the opportunity to do so, are not subspecies: they are separate species.
A monotypic species has no distinct population or races, or rather one race
comprising the whole species. Monotypic species can occur in several ways:
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....
, is either a taxonomic rank
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
subordinate to species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, or
a taxonomic unit
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
in that rank (plural
Plural
In linguistics, plurality or [a] plural is a concept of quantity representing a value of more-than-one. Typically applied to nouns, a plural word or marker is used to distinguish a value other than the default quantity of a noun, which is typically one...
: subspecies). A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one. (However, all but one subspecies may be extinct, as in Homo sapiens sapiens.)
Organisms that belong to different subspecies of the same species are capable of interbreeding and producing fertile offspring, but they often do not interbreed in nature due to geographic isolation or other factors. The differences between subspecies are usually less distinct than the differences between species, but more distinct than the differences between breed
Breed
A breed is a group of domestic animals or plants with a homogeneous appearance, behavior, and other characteristics that distinguish it from other animals or plants of the same species. Despite the centrality of the idea of "breeds" to animal husbandry, there is no scientifically accepted...
s or races
Race (biology)
In biology, races are distinct genetically divergent populations within the same species with relatively small morphological and genetic differences. The populations can be described as ecological races if they arise from adaptation to different local habitats or geographic races when they are...
(races can be assigned to different subspecies if taxonomically
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
different). The characteristics attributed to subspecies generally have evolved as a result of geographical distribution or isolation.
Nomenclature
In zoologyZoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...
, the International Code of Zoological Nomenclature
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
(4th edition, 1999) accepts only one rank below that of species, namely the rank of subspecies http://www.nhm.ac.uk/hosted-sites/iczn/code/index.jsp. Other groupings, "infrasubspecific entities" (e.g. pet
Pet
A pet is a household animal kept for companionship and a person's enjoyment, as opposed to wild animals or to livestock, laboratory animals, working animals or sport animals, which are kept for economic or productive reasons. The most popular pets are noted for their loyal or playful...
breed
Breed
A breed is a group of domestic animals or plants with a homogeneous appearance, behavior, and other characteristics that distinguish it from other animals or plants of the same species. Despite the centrality of the idea of "breeds" to animal husbandry, there is no scientifically accepted...
s and Transgenic Animals) do not have names regulated by the ICZN. Such forms have no official status, though they may be useful in describing altitudinal or geographical clines. The scientific name of a subspecies is a binomen
Binomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...
followed by a subspecific name, as Panthera tigris sumatrae (Sumatran Tiger
Sumatran Tiger
The Sumatran tiger is a tiger subspecies that inhabits the Indonesian island of Sumatra and has been classified as critically endangered by IUCN in 2008 as the population is projected at 176 to 271 mature individuals, with no subpopulation having an effective population size larger than 50...
). A name of this kind is called a trinomen
Trinomen
In zoological nomenclature, a trinomen , or trinominal name, refers to the name of a subspecies.A trinomen is a name consisting of three names: generic name, specific name and subspecific name. The first two parts alone form the binomen or species name. All three names are typeset in italics, and...
.
Likewise in bacteriology
Microbiology
Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...
, the only rank allowed below species is subspecies. Names published before 1992 in the rank of variety
Variety (plant)
Plant variety is a legal term, following the International Union for the Protection of New Varieties of Plants Convention. Recognition of a cultivated plant as a "variety" in this particular sense provides its breeder with some legal protection, so-called plant breeders' rights, depending to some...
are taken to be names of subspecies http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=icnb&part=A185 (see International Code of Nomenclature of Bacteria
International Code of Nomenclature of Bacteria
The International Code of Nomenclature of Bacteria or Bacteriological Code governs the scientific names for bacteria, including Archaea. It denotes the rules for naming taxa of bacteria, according to their relative rank...
).
In botany
Botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...
, subspecies is one of many ranks below that of species, such as variety, subvariety
Subvariety
In botanical nomenclature, a subvariety is a taxonomic rank below that of variety but above that of form : it is an infraspecific taxon. Its name consists of three parts: a genus name, a specific epithet and an infraspecific epithet. To indicate the rank, the abbreviation "subvar." should be put...
, form, and subform. The subspecific name is preceded by "ssp." or "subsp.", as Schoenoplectus californicus ssp. tatora (Totora
Totora (plant)
Totora is a subspecies of the giant bulrush sedge. It is found in South America - notably on Lake Titicaca, the middle coast of Perú and on Easter Island in the Pacific Ocean...
). Any botanical name including a subspecies, variety, etc., is called an infraspecific name
Infraspecific name (botany)
In botany, an infraspecific name is the name for any taxon below the rank of species, i.e. an infraspecific taxon. The scientific names of plants are regulated by the International Code of Botanical Nomenclature...
.
Nominate subspecies and subspecies autonyms
In zoological nomenclature when a species is split into subspecies, the originally described population is retained as the "nominate subspecies", which repeats the same name as its species, for example, Motacilla alba alba (often abbreviated Motacilla a. alba) is the nominate subspecies of the White WagtailWhite Wagtail
"Pied Wagtail" redirects here. For the related African bird, see African Pied Wagtail.The White Wagtail is a small passerine bird in the wagtail family Motacillidae, which also includes the pipits and longclaws. This species breeds in much of Europe and Asia and parts of north Africa...
(Motacilla alba).
The repetition of the species name is referred to in botanical nomenclature
Botanical nomenclature
Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical...
as the subspecies "autonym
Autonym (botany)
In botanical nomenclature, autonyms are automatically created names, as regulated by the International Code of Botanical Nomenclature . Autonyms are cited without an author. Relevant provisions are in articles 6.8, 22.1-3 and 26.1-3....
", and the subspecies as the "autonymous subspecies".
Doubtful cases
When biologists disagree over whether a certain population is a subspecies or a full species, the species name may be written in parentheses. Thus Larus (argentatus) smithsonianus means the American Herring GullAmerican Herring Gull
The American Herring Gull or Smithsonian Gull is a large gull which breeds in North America. It is often treated as a subspecies of the European Herring Gull but is now regarded as a separate species by some authorities.Adults are white with gray back and wings, black wingtips with white spots,...
; the notation with parentheses means that some consider it a subspecies of a larger Herring Gull species and therefore call it Larus argentatus smithsonianus, while others consider it a full species and therefore call it Larus smithsonianus (and the user of the notation is not taking a position).
Criteria
Members of one subspecies differ morphologicallyMorphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
or by different coding sequences of DNA from members of other subspecies of the species. Subspecies are defined in relation to species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
.
If the two groups do not interbreed because of something intrinsic to their genetic make-up (perhaps green frogs do not find red 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 were 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. Other factors include differences in mating behavior or time and ecological preferences such as soil content.
Note that the distinction between a species and a subspecies depends only on the likelihood that in the absence of 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 Pipit
Rock Pipit
The Rock Pipit, Anthus petrosus, is a small passerine bird species which breeds on rocky coasts of western Europe northwards from Brittany. It is mainly resident in Ireland, Great Britain and France, in the west of its range, but the Scandinavian and Russian populations migrate south in winter;...
was formerly classed as a subspecies of Water Pipit
Water Pipit
The Water Pipit, Anthus spinoletta, is a small passerine bird which breeds in the mountains of southern Europe and southern temperate Asia across to China. It is a short-distance migrant moving to wet open lowlands such as marshes and flooded fields in winter...
, but is now recognised to be a full species. For an example of a subspecies, see Pied Wagtail
White Wagtail
"Pied Wagtail" redirects here. For the related African bird, see African Pied Wagtail.The White Wagtail is a small passerine bird in the wagtail family Motacillidae, which also includes the pipits and longclaws. This species breeds in much of Europe and Asia and parts of north Africa...
.
Cryptic species
Cryptic species complex
In biology, a cryptic species complex is a group of species which satisfy the biological definition of species—that is, they are reproductively isolated from each other—but whose morphology is very similar ....
are morphologically similar, but have differences in DNA or other factors.
Monotypic and polytypic species
A polytypicPolytypic
In zoology, polytypic refers to a taxonomic unit with more than one subgroup at the next lower level.-See also:*Linnaean taxonomy*monotypic*monotypic habitat...
species has two or more subspecies, races
Race (biology)
In biology, races are distinct genetically divergent populations within the same species with relatively small morphological and genetic differences. The populations can be described as ecological races if they arise from adaptation to different local habitats or geographic races when they are...
or more generally speaking, populations that need a separate description. These are separate groups that are clearly distinct from one another and do not generally interbreed (although there may be a relatively narrow hybridization zone), but which would interbreed freely if given the chance to do so. Note that groups which would not interbreed freely, even if brought together such that they had the opportunity to do so, are not subspecies: they are separate species.
A monotypic species has no distinct population or races, or rather one race
Race (biology)
In biology, races are distinct genetically divergent populations within the same species with relatively small morphological and genetic differences. The populations can be described as ecological races if they arise from adaptation to different local habitats or geographic races when they are...
comprising the whole species. Monotypic species can occur in several ways:
- All members of the species are very similar and cannot be sensibly divided into biologically significant subcategories.
- The individuals vary considerably but the variation is essentially random and largely meaningless so far as genetic transmission of these variations is concerned.
- The variation among individuals is noticeable and follows a pattern, but there are no clear dividing lines among separate groups: they fade imperceptibly into one another. Such clinal variation always indicates substantial gene flowGene flowIn population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
among the apparently separate groups that make up the population(s). Populations that have a steady, substantial gene flow among them are likely to represent a monotypic species even when a fair degree of genetic variation is obvious.
See also
- Color phase
- Variety (botany)
- CultivarCultivarA cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
in botany - StrainStrain (biology)In biology, a strain is a low-level taxonomic rank used in three related ways.-Microbiology and virology:A strain is a genetic variant or subtype of a micro-organism . For example, a "flu strain" is a certain biological form of the influenza or "flu" virus...
in microbiology - LandraceLandraceA landrace is a local variety of a domesticated animal or plant species which has developed largely by natural processes, by adaptation to the natural and cultural environment in which it lives. It differs from a formal breed which has been bred deliberately to conform to a particular standard...