A type (Latinized from Greek τύπος typos , type, imprint, pattern, archetype, example ') is a selected individual or taxon in biological nomenclatures that forms the basis for defining and naming a higher-level taxon. At the species level and below, these are generally the bodies of individual living beings; for higher taxa, depending on the nomenclature code, subordinate taxa can also be used (i.e. a specific species for a genus or a specific genus for a family). Depending on the discipline and material situation, other forms can also serve as types, for example illustrations in botany or live cultures of bacteria and archaea .
When an individual is originally assigned to a taxon, one speaks of a holotype . In addition, there are various names for types of other types in zoology and botany. The exact basis for typing a taxon can be found in the corresponding nomenclature codes of the relevant disciplines, such as the International Code of Nomenclature for algae, fungi and plants or the International Rules for Zoological Nomenclature . These regulations differ from one another in some places, due to the history and the requirements of their subject, but they follow similar principles.
Meaning of the types
Type specimens play a crucial role in the management of taxa and their names and are their main reference point. Biologists therefore attach great importance to them and strive to preserve them and keep them safe. Inaccuracies in the identification of a type or its loss can lead to large faults that cast doubt on entire taxa. Conversely, one type can also clearly decide controversies about how to deal with certain taxa.
Types are not primarily used to stabilize certain taxa, but rather their names: They are intended to prevent many different names from being used for very similar organisms. But they do not stipulate how similar two living beings have to be to have the same name.
The practice of assigning a specific type to each taxon was not yet provided for in the original Carl von Linnés nomenclature . It did not develop until the late 19th century, after taxidermy and other conservation methods made it possible to preserve organic materials for several decades. At the same time, the increasing number of new names and initial descriptions from many different parts of the world and the death of many pioneers in taxonomy made it necessary to standardize scientific names. Subsequently, the appointment of a type was not only made a condition for a valid publication by the community of taxonomists , types were also subsequently specified for all those common taxa that did not yet have a type.
18th century: beginning of taxonomy and early methodology
In the 18th century, the prevailing view among naturalists and other scientists was that any typology should be based on the broadest possible fund of empirical evidence . The exact definition of a species is only possible after a thorough examination of all available material and consideration of all possible variations . The definition of a single, highly individual type specimen was not compatible with such a view. The early natural sciences emphasized the need for extensive experience in dealing with the phenomena, which could only lead to an exact knowledge of their hidden causes and ideas . According to the opinion of the time, this was the only way to avoid errors in the observation and conclusion, for example a description of individual variations as different species. Carl von Linné , who with his nomenclature aimed at a precise recording of all existing species, accorded little importance to individual specimens. For Linné, the ideal image of a species was not a specific individual, but rather a botanical drawing that, in an abstract way, represented the normal construction plan of the species. Linnaeus and his contemporaries therefore deliberately did not define dead individuals or other objects as types. Only individual taxa could implicitly be considered typical of higher-level taxa if they represented their ideal embodiment, such as the genus Passer for the Passeriformes . However, until the second half of the 19th century there was no uniform conception of a type among naturalists. Successful illustrations as well as particularly exemplary herbarium specimens , but also the blueprint on which a family group is based, could be considered a type. A type uncharacteristic of his group was not part of the prevailing concepts.
19th century: crisis of nomenclature
By the mid-19th century, there was increasing controversy and uncertainty within the scientific community about the names of different taxa. Sometimes two apparently different groups had the same name, sometimes there were several competing names for the same species. The reasons for this development were, among other things, the rapid development of the subject. While Linnaeus listed around 10,000 species in the mid-18th century, the science historian William Whewell estimated the number of known plant species to be around 60,000 in 1845. The fact that scientists in different countries independently named new species, genera or orders led to additional confusion. The pioneers of taxonomy were now dead, so that they could no longer be used as an authority to solve the problem. In Great Britain , leading biologists therefore sought a way out of the uncontrolled increase in ambiguous names. The ornithologist Hugh Edwin Strickland founded a commission to develop new rules for the zoological nomenclature. The Strickland Code presented by her aimed, among other things, at the use of the extensive botanical and zoological collections that had emerged in Europe and North America over the past decades. The specimens and books preserved in them should now be used as reference material in cases of doubt, if a naturalist wanted to compare one of his individuals with those of already existing species. This created the type as an authority on taxonomic questions. However, it continued to encompass the diverse concepts of the previous decades, only that these should now be revealed in the broad stocks of specimens. For the establishment of a new species, consultation of as many individuals as possible was still considered desirable, one type had to be exemplary. This new regulation put at a particular disadvantage the naturalists who were active far away from the European capitals and who could not afford to travel to the important museums in terms of time or money.
Under the leadership of Alphonse Pyrame de Candolle , botany also tried to standardize its nomenclature in the 1860s. At the International Botanical Congress in Paris , the priority rule was adopted, which gave the oldest published name priority over all others and was now applied retrospectively. The community of zoologists soon followed suit. With it, a basic problem of taxonomy, that of competing synonyms, was solved, but at the same time it intensified the problem of access to the collections: For the correct description of a species, knowledge of the literature available up to now was necessary. In the event of an unclear synonymy, however, it offered no other solution than that of Strickland. This was particularly a problem for North American naturalists who were cut off from European collections. The spread of natural research all over the western world ruled out a centralized solution to the problem - such as the leading London museums as taxonomic authorities. Although the democratization of natural history was lamented by many leading naturalists, it was taken for granted that there could be no going back to the early days of the subject. Starting from North America, the proposal finally developed to define precisely named types for each species in order to save the respective scientists from studying all existing stocks. It was promoted above all by orator Fuller Cook and written down in 1893 and 1904 at congresses in Rochester and Philadelphia as an addition to the nomenclature codes. The type method thus appeared alongside the priority rule as the central principle of the nomenclature.
20th century: The atypical type as a model
In addition to the solution to the problem of synonymity, the type as a nomenclature authority was also a result of these agreements. In many cases, however, this posed new problems for taxonomists: In addition to the date of the first description, type specimens of previous first descriptions had to be determined from among thousands of preparations. Since very few naturalists had bothered to define types before the 20th century, the history of individual specimens had to be laboriously traced using diaries, manuscripts, notes on herbarium sheets, correspondence or receipts. However, many collections had been smashed or sold in the past few decades, had fallen victim to fires or suffered from the theft by numerous visitors. Often the types could no longer be identified. For the existing collections, on the other hand, the question arose of how to deal with the types in your own holdings that were suddenly so valuable and irreplaceable. With the narrowing of the material to be studied to a few specimens, one soon got away from understanding the type as particularly characteristic. What a type was was now determined by the biography of a taxonomic author and his collection, no longer by the prevailing doctrine. Where there was only a single specimen in a collection, it became the type of his taxon. A controversy arose in the scientific community as to whether the type should encompass a series of individuals or just a single individual. Since the majority of researchers feared that type series could give rise to renewed confusion of names, they voted for a single type, the holotype, as the basis for a valid initial description.
Since many scientists considered it contradictory to define an atypical specimen as a type, the nomenclature committees explicitly laid down this regulation in their codes. Many zoologists and botanists were annoyed by this and tried to re-establish the old type concept. Since the term “type” was now occupied by the new atypical types, they suggested the designation “norm” for it. In this dispute, the advocates of the holotype method avoided commenting on taxa above the species level. They represented a strict nomenclature definition of a species as a group of individuals, of which the first, appropriately designated, is considered their type. The representatives of this position left open whether and what existence a species has beyond the nomenclature. In some cases, however, they also presented themselves as a countermovement to a metaphysical biology that placed the abstract idea of a species above empiricism. European botanists in particular were reluctant to strictly apply the holotype method until the middle of the 20th century, while it was universally accepted in North America. The International Botanical Congress , held in Brussels in 1910, accepted the holotype method, but it was not made compulsory until 1958. Since the second half of the 20th century, the holotype method has been common and accepted practice in all fields of taxonomy.
In zoological nomenclature, a name-bearing type denotes a specimen highlighted in the first description of a nominal taxon or a further taxon that represents the objective reference basis for the new name. For taxa of the species group this is a specimen, for taxa of the genus and family group a nominal taxon from the rank of the next lower group ( type species / type species or type genus) that corresponds to the respective group name .
The type species is a species that determines (typifies) the genus (“generotype”). It must be expressly stated by the author when creating (initial description) of the genre . Since January 1, 1931, this has been the only possibility, i.e. H. without such an indication, the published name is not valid and therefore a noun nudum . For older genres, the type type can be selected subsequently in various ways (type designatus): from the type epithet of the binomial such as 'typicus', 'typus' etc. (typonomy); if only one species was assigned to the genus when it was listed, i.e. it is monotypical or if the epithet exactly matches the genus name when published.
The listed characteristics of the first description are derived from this specimen, its paratypes or the highlighted taxon. When comparing characteristics, the name of the examined taxon always primarily refers to the type that bears the name, even if the description deviates from this. The definition of the name-bearing type is necessary in order to dispel doubts that arise from an incomplete or incorrect initial description. Such incompleteness is almost inevitable, as the relevance of some of the features is not yet known at the time of the first description.
Types of species group
- The holotype is a single specimen that was already specified as a name-bearing type when a species or subspecies was listed.
- Paratypes are specimens listed in addition to the holotype, which often document the stability or variation of characteristics of a type series.
- Syntypes are the names of the individual specimens of the type series, which in its entirety represents the name-bearing type.
- Lectotype (seldom also known as hololectotype in the German-speaking world ) denotes a specimen that was subsequently identified as a named type from a type series; this is possible with a nominal taxon established before the year 2000. The remaining specimens in the series are known as paralectotypes .
- A new name-bearing type is referred to as a neotype , which can be determined by an editing taxonomist if no type was defined in the past or it is lost. To do this, however, a number of regulations and requirements according to the nomenclature rules must be observed.
In addition, there are other names for types that are not recognized by the nomenclature rules: Some authors refer to a selected paratype as an allotype , which is supposed to represent a gender deviating from the holotype. A specimen of the opposite sex described in a later publication is called a neoallotype , provided that only representatives of one sex were present in the original description. A Topotypus Finally, a copy of the type locality, which was not listed in the type series in the original description. It may also have been collected at a later date.
Named types of the species group are kept in the scientific collections with appropriate notes and marked accordingly. Usually they should be deposited in a public collection (e.g. neotypes require this). The type number that is specific to the collection and the place where it is stored (usually the systematic collection of a university institute or a museum) gives subsequent editors access to the type copy. As an example, the holotype of the extinct Protostegidae species Santanachelys gaffneyi is archived in the Japanese Teikyō-Heisei University in Ichihara , Chiba Prefecture under the number THUg1386. This type was determined by the first descriptor Ren Hirayama through the first description published in Nature in 1998. Typically, types are specially marked with red labels.
The type is regulated in botany (including mycology , algae and paleobotany ) by Articles 7 to 9 of the ICBN (here still the Saint-Louis Code). As a type for species, in addition to images, only preserved plants, algae or fungi are accepted, non-living cultures.
A holotype (holotype) is defined when the first descriptor of a taxon defines a single specimen or illustration as such (Art 9.1). It is not necessary that a holotype be typical. The place where a holotype was first found is called the locus classicus . If the author used several specimens to describe a taxon, it may be necessary to identify a single specimen as the type, which is then called the lectotype (Art 9.2). An isotype is a duplicate of the holotype, but it must always be a copy. A syntype is every instance that is mentioned in the first description if no holotype is defined. A paratype is a specimen that is mentioned in the first description, but is neither the holotype, nor an isotype or a syntype. A neotype is a subsequently selected specimen or an illustration when the original type from the original material (holo-, iso-, syn-, para- or lectotype) is lost. An epitype is selected when the holotype, lectotype or neotype of a correctly published name is demonstrably ambiguous. When choosing the epityps, the holotype etc. to which it relates must be explicitly mentioned. A typotype is a herbarium that serves as the basis for an illustration, which in turn is the type for the description. This case applies to some of the species described by Linnaeus .
The type of a genus (or a taxon below the genus) is the type of the assigned species name (Art. 10). It is sufficient to mention the validly published species name; no direct reference to its type has to be made. It can also be just one type of type that was assigned to the genus when it was first described.
The type of a family (or a taxon below family rank) relates in an analogous way to a genus.
The type principle does not automatically apply to taxa above family rank, unless the name is derived from a typified taxon (such as Magnoliales from Magnolia ); then the type of the eponymous genus is automatically the type of the higher taxon.
In bacteriology, too, a nomenclature type is indispensable and permanently linked to each taxon. These are regulated in the International Code of Nomenclature of Bacteria (ICNB) in Section 4, "Nomenclatural Types and Their Designation". A pure description, a preserved specimen or even just an illustration are admissible and legitimate forms of types, but they should only be used if a live culture is not possible (e.g. in the case of extremophiles ).
In the case of live cultures, the nomenclatory type is always a specific bacterial strain. If this connection of a stem is made explicitly by the author as part of the initial description, then this stem is the holotype . If the strain is lost, a neotype can be suggested by publication in the International Journal of Systematic Bacteriology by clearly naming the original description and thus the new strain is unique. This proposed neotype ( Proposed neotype ) is two years after publication of the proposal for established neotype ( established neotype ), provided its publication remained consistent in the first year.
For genera, one of the types of the first description is the nomenclature type; it is either declared a type when the genus is listed or is subsequently selected from one of the types of the first description. Above the genus up to the order, the type is the eponymous genus, the genus Rhodospirillum is therefore also a type of the family Rhodospirillaceae , the suborder Rhodospirillineae and the order Rhodospirillales . Above orders, the type is one of the orders contained, it is determined by the author of the descriptions. If this provision is missing, it can only be supplemented retrospectively by an opinion from the Judicial Commission of the International Committee on Systematics of Prokaryotes (ICSP) .
Geographical origin of the type material
The area from which the type of a species originates is called Terra typica or terr. typ. ( Latin "typical country") called. In the case of a fossil species, on the other hand, the type locality, Locus typicus (Latin "typical place") is spoken of, which is closely linked to the found layer * , the Stratum typicum (Latin "typical layer"). In botany, the expression Locus classicus (Latin for "classic place") is also used. A specimen copy subsequently collected there is referred to as a topotype . However, this term is not defined in the rules of botanical nomenclature .
- International rules for zoological nomenclature. Fourth edition. Adopted by the International Union of Biological Sciences. Official German text: prepared by O. Kraus. - Natural Science Association in Hamburg, treatises, NF, 34: 232 p .; Hamburg 2000. - [IRZN 2000] online version, English: 
- Lorraine Daston: Type Specimens and Scientific Memory . In: Critical Inquiry . tape 31 , no. 1 , 2004, p. 153-182 , doi : 10.1086 / 427306 .
- Greuter, W. et al. (2000): International Code of Botanical Nomenclature (Saint Louis Code) . Regnum Vegetabile, 138. Koeltz Scientific Books, Königstein. ISBN 3-904144-22-7 . Online version
- McNeill, J. et al. (2006): International Code of Botanical Nomenclature (Vienna Code) . Regnum Vegetabile, 146. Koeltz Scientific Books, Königstein. ISBN 3-906166-48-1 online version
- SP Lapage, PH Sneath, VBD Skerman, EF Lessel, HPR Seeliger, WA Clark: International Code of Nomenclature of Bacteria, 1990 Revision (Bacteriological Code) , ASM Press, Washington, DC, 1992, ISBN 1-55581-039-X , Online version
- type . In: Lexicon of Biology . Spectrum Academic Publishing House. Heidelberg. 1999. Retrieved October 2, 2016.
- Daston 2004, pp. 166-170.
- Alan JD Tennyson, JA Sandy Bartle: Catalog of type specimens of birds in the Museum of New Zealand Te Papa Tongarewa (PDF; 409 kB) In: Tuhinga: Records of the Museum of New Zealand Te Papa Tongarewa , Volume 19, Article 6 , 2008, p. 185.
- Daston 2004, pp. 171-172.
- Daston 2004, pp. 172-174.
- Daston 2004, pp. 174-176.
- Daston 2004, pp. 176-177.
- IRZN 2000: 169
- Ulrich Lehmann : Paleontological Dictionary . 4th edition. Ferdinand Enke Verlag, Stuttgart 1996, p. 250 .
- Ren Hirayama: Oldest known sea turtle. In: Nature. London 392.1998, pp. 705-708.
- Art. 9 ICBN
- Gerhard Wagenitz : Dictionary of Botany. The terms in their historical context. 2nd, expanded edition. Spektrum Akademischer Verlag, Heidelberg / Berlin 2003, ISBN 3-8274-1398-2 , p. 337.
- International Code of Nomenclature of Bacteria (1990 Revision), 3. Rules of Nomenclature with Recommendations, Section 4 “Nomenclatural Types and Their Designation”, online
- Erwin J. Hentschel, Günther H. Wagner: Zoological dictionary , 6th edition. Gustav Fischer Verlag , Jena 1996, page 576.
- Michael Hickey, Clive King: The Cambridge Illustrated Glossary of Botanical Terms. Cambridge University Press, Cambridge (UK), ISBN 978-0-511-25251-8