The subspecies or subspecies ( Latin subspecies , abbreviated subsp. Or ssp. ) Is the taxonomic rank directly below the species in biological systematics . In botany , under it are the variety and the form . In zoology and bacteriology , the subspecies is the lowest rank. From a taxonomic point of view, it represents a secondary category, so it is only used when necessary and can be replaced by the technical term population .
Ernst Mayr defined the subspecies as follows in Principles of Systematic Zoology in 1969 :
Like all other hierarchical ranks of biological systematics except for the species, the subspecies as a rank cannot be objectified, but is based on convention .
“In view of the many cases of incorrect use of the term, it must be emphasized that the subspecies is a completely different category from the species. There is no criterion for defining the subspecies category that is not artificial. The subspecies is also not an evolutionary unit - unless it also represents a geographical isolate. "
This does not mean that actually observable or delimitable subspecies are not real biological units. However, it is often controversial between different experts whether the objective differences are sufficient for the definition of a subspecies. Many professionals prefer to use just the term population .
In zoology and botany, groups of similar individuals are referred to as subspecies if, on the one hand, the individuals of one group are obviously capable of pairing with those of the other groups (i.e. do not meet an important criterion for the delimitation of species ), but on the other hand as a group (as Clan ) are clearly distinguishable from other groups (clans) and also inhabit a certain geographical sub-region of the range of the species. The systematists thus introduce subspecies especially in species with a particularly large number of forms, whereby a really sharp delimitation of these infraspecific taxa is not always successful. Recent subspecies are always spread out differently in space or time ( vicarious ), but often not completely isolated. When crossing, they usually form fertile hybrids (abbreviated: nothosubsp . Or nssp ., Greek nóthos = fake, illegitimate).
In the overlapping area of their distribution areas (hybridization zone ), subspecies are usually connected to one another by so-called transition populations. The reason for such smooth transitions is that there are no barriers to reproduction between subspecies with hybridization zones. But if a population is separated from its original population, a new species can develop from it in a continuously ongoing process of speciation , which has then acquired isolation mechanisms from the other populations. With such smooth transitions, there can be many different shapes. Today, to delimit subspecies, as a rule, characteristics that vary continuously across the entire population (clinical variation) are not used and this population is thus subdivided completely arbitrarily, but rather distinct characteristic differences are used that have developed in the course of temporary geographical isolation.
In biological nomenclature , the subspecies is identified with a three-part name, the trinomal . For example, the trinomen Panthera leo massaicus stands for a subspecies of the lion (mostly no longer recognized today) . In botany the abbreviation subsp. insert (e.g. Lilium pardalinum subsp. pitkinense ), the use of the frequently found abbreviation “ssp.” is now advised against by the ICBN .
Subspecies in botany
Carl von Linné did not use the taxonomic term of the subspecies, below the species there was only the variety . It encompassed every deviation from the ideal type of species, and in his work he marked it with a leading Greek letter. In his work Philosophia Botanica of 1751, he defined the variety as an environmental, reversible and non-hereditary change in the phenotype: “The variety is a plant that has changed from an accidental cause: climate, soil, heat, winds, etc. hits back on changed ground. ”But Linnaeus herself did not apply this definition without contradictions.
Similar to the varieties, subspecies can already be found in him, although he has not yet used the term. As with the variety , he added subentries to the species entry with a leading Greek letter, but added their own names to these entries, for example in Primula veris : α officinalis L., β elatior L. and γ acaulis L. In In this special case he clarified the special position of the groups with a note, which records the stability of the characteristics and the importance of geographical distribution: "Although these varieties are constant, I do not distinguish an African from a European species." This is how Linnaeus distinguished Both in terms of content and form, it is between varieties and subspecies in today's sense, but they are all subsumed under the term varietas .
It was only his student Jakob Friedrich Ehrhart who separated Linnaeus' approach linguistically. In 1780, in his attempt to create a register of the plants growing wild around Hanover , he wrote in advance that he had cited the “false species, semi-species or subspecies” with the name introduced by Linnaeus and that others would be re-described. At the same time, he explicitly differentiates this from the variety by stating that he would just as much like to deal with the “varieties or varieties”, but would refrain from doing so here. In 1784 he then provides the first definition of the subspecies:
“Half species, sham species, subspecies. [...] They are, in a word, Varietates constantes, or a mean between species and varieties. They differ from species in that they deviate from one another in small and less considerable circumstances, and they differ from varieties in that they constantly reproduce through the seed and repeatedly produce their own kind. "
Crucial for the breakthrough of the term in botany, however, was its use by Christian Hendrik Persoon in 1805. Conceptually, he continued the subspecies term that Linnaeus had already represented, but for the first time separated both conceptually and nomenclaturally between subspecies and variety. Unlike Ehrhart, he did not use an alternative term such as "Halbart", so that Persoon's term was clear. In Germany and the countries shaped by German botany, the term subspecies initially caught on, but not in French-speaking countries, where the term “form” was preferred. Further terms were created (“race”, “permanent variant”), but none prevailed and the term and rank fell out of use at times.
This was reinforced by the general softening of taxonomic ranks in the wake of the publication of Charles Darwin's " The Origin of Species " wrote Darwin in 1859. "No one can draw a clear distinction between individual differences and slight varieties; or between more distinct varieties and subspecies and species. ”The success of this book led to a relative step backwards from a taxonomic point of view, as its flowing and artificial concept of species meant that previously established delimitations between the ranks were lost again.
Subspecies in zoology
The German entomologist and botanist Eugen Johann Christoph Esper was the first zoologist to introduce the concept of subspecies as a necessary separate rank between subspecies and variety in his dissertation De varietatibus specierum in naturæ productis , published in 1781 . He distinguished between "random varieties", which he called varietates , and "essential varieties", which he called subspecies .
The Danish ornithologist Frederik Faber formulated a geographical and morphological concept of the species in 1825. As with the variety, he distinguished equally different, but constant clans. However, he failed to introduce a term for it. Faber saw the spatial center of a species as its "type location", but recognized morphologically different clans removed from it by migration as inherently constant in their characteristics, whereby the Linnaeus varietas no longer took hold, but the species did not yet take effect, since all representatives continued to belong to a reproductive community.
It was not until the ornithologist Hermann Schlegel in 1844 that the conspecies created a rank corresponding to the subspecies, defined it and introduced a ternary nomenclature, i.e. a further part of the name in addition to the binomials that clearly identify the species .
Subspecies in anthropology
From a genetic point of view ( genotype ), all people are 99.9% identical. Although in some populations, e.g. B. With the Aborigines in Australia, the Negritos in Asia or the San in Africa, spatial isolation has existed for so long that criteria for subspecies from a zoological point of view would be conceivable, if scientifically justified no further subdivision of the species Homo sapiens is made.
Spatial isolation as a precondition for the formation of subspecies prevailed for the human groups of prehistoric times for very long periods of time, since humanity then consisted of only a few hundred thousand individuals. During this time, some new physical characteristics arose due to the evolutionary adaptations to the respective environmental conditions (e.g. epicanthic fold , different skin colors , lactose tolerance , peppercorn hair ). However, over the course of history, the number of people grew exponentially, so that the different populations met and remixed in a variety of ways. This is the reason why the genetic differences between individual people in a population are often significantly greater today than between different populations. The human geneticist Cavalli-Sforza in particular has extensively investigated and proven this fact in humans.
Over time, the abundance of living beings collected and described increased enormously, which led to more and more intra-species differences becoming apparent. The variations themselves, their range and the question of the causes aroused the researchers' interest. From then on one no longer only collected individual, carefully selected specimens, which perhaps seemed particularly splendid, vivid or typical, but entire series at various locations and compared them with one another. It turned out that the collected pieces were particularly similar when they came from the same place or region, whereas the difference was particularly pronounced when series of widely spaced locations were compared with one another. On their extensive travels in the 18th and 19th centuries, the researchers found more and more populations that differed in every possible detail from what was previously thought to be the type of the respective species. When it was recognized that geographical variations are something completely different from what was previously referred to as races or varieties, an attempt was made to express this terminologically. Populations with different characteristics, phenotypic groups or morphs that could be assigned to certain geographical localities, which were restricted to certain sub-areas of the total area of the species , became, in contrast to the taxa previously referred to as varieties or races, as "geographical races", "geographical varieties" and later referred to as "subspecies".
Until around the end of the 19th century, the subspecies was considered a taxonomic unit similar to the morpho species , but of lower taxonomic rank, it was still treated completely typologically. Many authors used the terms subspecies and subspecies in a similarly uncritical and unspecific manner as before race or variety, and used them to designate any distinguishable units that were less different than species. In doing so, they neglected the essential component of the new term already worked out by Pallas and Esper, the at least partial geographical isolation. Subspecies are allopatric and allochronic .
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Ernst Mayr : Basics of the zoological system. Parey, Berlin 1975, ISBN 3-490-03918-1 .
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- Ernst Mayr: The development of the biological world of thought. P. 232.
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- See Ernst Mayr: This is evolution. Munich 2011, p. 217.
- Quoted from Ernst Mayr: The development of the biological world of thought , p. 231
- "Varietates licet constantes, β et γ non specie distinguo uti nec Maurum ab Europaeo." Quoted from: Hans Peter Fuchs: Historical remarks on the concept of subspecies. In: Taxon. 7 (2), 1958, p. 46.
- Hans Peter Fuchs: Historical remarks on the concept of subspecies. In: Taxon. 7 (2), 1958, pp. 44-52.
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- Friedrich Ehrhart: Botanical Remarks In: Hannover. Mag. (11): 168-176, 1784, online
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- German Zoological Society: Jena Declaration. In: Friedrich Schiller University Jena. Friedrich Schiller University Jena, German Zoological Society, September 2019, accessed on March 26, 2020 .
- Luigi Luca Cavalli-Sforza: Genes, Peoples and Languages. The biological foundations of our civilization. Hanser, Munich / Vienna 1999.
- Harald Haarmann: Small Lexicon of Nations. From Aborigines to Zapotecs. Becksche series, Munich 2004.