Editing Identification key

{{Short description|Method of Biological categorization}}
In [[biology]], an '''identification key''', '''taxonomic key''', or frequently just '''key''', is a printed or computer-aided device that aids in the [[identification (biology)|identification]] of biological organisms.

Historically, the most common type of identification key is the '''dichotomous key''', a type of [[single-access key]] which offers a fixed sequence of identification steps, each with two alternatives. The earliest examples of identification keys originate in the seventeenth, but their conceptual history can be traced back to antiquity. Modern [[multi-access key|multi-access]] keys allow the user to freely choose the identification steps and any order. They were traditionally performed using punched cards but now almost exclusively take the form of computer programs.

== History ==
[[File:Lamarck's_key.png|thumb|Identification key published in Lamarck's ''Flore française'', Volume 1.]]
The conceptual origins of the modern identification key can be traced back to antiquity. [[Theophrastus]] categorized organisms into "subdivisions" based on dichotomous characteristics. The seventeenth-century Chinese herbalist, Pao Shan, in his treatise ''Yeh-ts'ai Po-Iu'', included a systematic categorization of plants based on their apparent characteristics specifically for the purposes of identification.<ref name=":2" />{{Rp|page=2}}

Seventeenth-century naturalists, including [[John Ray]], [[Augustus Quirinus Rivinus|Rivinius]], and [[Nehemiah Grew]], published examples of bracketed tables. However, these examples were not strictly keys in the modern sense of an analytical device used to identify a single specimen, since they often did not lead to a single end point, and instead functioned more as synopses of classification schemes.<ref name=":2" />{{Rp|pages=3–8}}

The first analytical identification key is credited to [[Jean-Baptiste Lamarck|Lamarck]] who included several in his 1778 book, ''Flore Françoise.'' Lamarck's key follows more or less the same design as the modern dichotomous, bracketed key.<ref name=":2" />{{Rp|page=10}}

[[Alphonso Wood]] was the first American to use identification keys in 1845. Other early instances of keys are found in the works of [[Asa Gray]] and [[William Harry Evans|W. H. Evans]].<ref name=":2" />{{Rp|page=|pages=12–14}}

=== Terminology ===
Identification keys are known historically and contemporarily by many names, including analytical key, entomological key, artificial key,<ref name=":2" /> diagnostic key,<ref name=":3" /> determinator,<ref name=":0" /> and taxonomic key<ref>{{Cite web |last=Bohemier |first=Kayleigh |title=Yale University Library Research Guides: Taxonomic Keys: Home |url=https://guides.library.yale.edu/keys |access-date=2024-10-20 |website=guides.library.yale.edu |language=en}}</ref>

Within the biological literature, identification keys are referred to simply as ''keys''.<ref>{{Cite book |title=A dictionary of biology |date=2008 |publisher=Oxford University Press |isbn=978-0-19-920462-5 |edition=6th |series=Oxford paperback reference |location=Oxford |pages=356 |chapter=key (identification key)}}</ref> They are also commonly referred to in general as dichotomous keys,<ref name=":5">{{Cite book |last=Lawrence |first=George H. M. |title=Taxonomy of Vascular Plants |date=1951 |publisher=The Macmillan Company |edition=1st |location=New York |pages=225–8}}</ref> though this term strictly refers to a specific type of identification key (see [[#Types of keys|Types of keys]]).

== Use ==
Identification keys are used in [[systematic biology]] and [[taxonomy]] to [[identification (biology)|identify]] the genus or species of a specimen organism from a set of known [[Taxon|taxa]]. They are commonly used in the fields of microbiology, plant taxonomy, and entomology, as groups of related taxa in these fields tend to be very large.<ref name=":0">{{Cite book |last=Winston |first=Judith E. |title=Describing species: practical taxonomic procedure for biologists |date=1999 |publisher=Columbia University Press |isbn=978-0-231-06824-6 |location=New York |pages=367–381 |chapter=Keys}}</ref> However, they have also been used to classify non-organisms, such as birds nests, and in non-biological sciences such as geology.<ref name=":2">{{Cite journal |last=Voss |first=Edward G. |date=December 1952 |title=The history of keys and phylogenetic trees in systematic biology |journal=Journal of the Scientific Laboratories of Dennison University |volume=43 |pages=1–25}}</ref>{{rp|pp=14–15}} Similar methods have also been used in computer science<ref>{{Cite encyclopedia |title=Identification Keys |encyclopedia=Encyclopedia of Statistical Sciences |publisher=John Wiley & Sons |last=Payne |first=R. W. |date=1983 |editor-last=Kotz |editor-first=Samuel |volume=4 |pages=6–10 |isbn=0471055514}}</ref>

A user of a key selects from a series of choices, representing mutually exclusive features of the specimen, with the aim to arrive at the sole remaining identity from the group of taxa.<ref name=":1">{{Cite book |last1=Thain |first1=M. |title=The Penguin dictionary of biology |last2=Hickman |first2=M. |date=2004 |publisher=Penguin Books |isbn=978-0-14-101396-1 |edition=11th |location=London; New York, N.Y |pages=363 |chapter=identification keys}}</ref> Each step in the key employs a ''character'': a distinguishing feature of an organism that is conveniently observable.<ref name=":0" />

== Types of keys ==
Identification keys are sometimes also referred to as ''artificial keys'' to differential them from other diagrams that visualize a classification schemes, often in the form of a key or tree structure. These diagrams are called ''natural keys'' or ''synopses'' and are not used for identifying specimens. In contrast, an artificial identification key is a tool that utilizes characters that are the easiest to observe and most practical for arriving at an identity.<ref name=":3" />{{Rp|page=7}}<ref name=":5" />{{Rp|page=225}} Identification keys can be divided into two main types.

=== Single-access key ===
{{Main|Single-access key}}
[[File:Screenshot from 2024-10-20 20-19-32.png|thumb|300x300px|User interaction steps in a single-access key. The sequence of steps follow the data structure.]]
A single-access key (also called a sequential key or an analytical key), has a fixed structure and sequence. The user must begin at the first step of the key and proceed until the end. A single-access key has steps that consist of two mutually exclusive statements (''leads'') is called a ''dichotomous key''. Most single-access keys are dichotomous.<ref name=":0" /> A single-access key with more than two leads per step is referred to as ''polytomous.''<ref name=":4">{{Cite book |last1=Hagedorn |first1=Gregor |url=https://www.openstarts.units.it/server/api/core/bitstreams/e5c6bdd8-c0ec-4442-bda8-61f66dd43b05/content |title=Tools for Identifying Biodiversity: Progress and Problems |last2=Rambold |first2=Gerhard |last3=Martellos |first3=Stefano |date=2010 |publisher=Edizioni Università di Trieste |isbn=978-88-8303-295-0 |editor-last=Nimis |editor-first=P. L. |pages=59–64 |chapter=Types of identification keys |editor-last2=Vignes Lebbe |editor-first2=R |chapter-url=https://www.openstarts.units.it/server/api/core/bitstreams/d6c3dc5f-17a1-478b-beab-31464b220ce1/content |chapter-format=PDF |via=openstarts.units.it}}</ref>

==== Presentational variants ====
Dichotomous keys can be presented in two main styles: linked and nested. In the linked style (also referred to as ''open,'' ''parallel, linked, and juxtaposition''<ref name=":4" />{{Rp|page=63}}), each pair of leads (called a ''couplet'') are printed together. In the nested style (also referred to as ''closed,'' ''yoked, and indented<ref name=":4" />{{Rp|page=63}}''), the subsequent steps after choosing a lead are printed directly underneath it, in succession. To follow the second lead of the couplet, the user must skip over the nested material that follows logically from the first lead of the couplet.<ref name=":3">{{Cite book |last=Pankhurst |first=R. J. |title=Biological identification: the principles and practice of identification methods in biology |date=1978 |publisher=University Park Press |isbn=978-0-8391-1344-7 |location=Baltimore |pages=11–28 |chapter=Conventional Identification Methods}}</ref> Nested keys are more commonly known as ''indented'', but unfortunately this refers to an accidental (albeit frequent) rather than essential quality. Nested keys may be printed without indentation to preserve space (relying solely on corresponding lead symbols) and linked keys may be indented to enhance the visibility of the couplet structure.<ref name=":4" />{{Rp|page=63}}

=== Multi-access keys ===
{{Main|Multi-access key}}
[[File:Multi-access_key.png|alt=Diagram of possible progressions through a multi-access key.|thumb|300x300px|User interaction steps in a multi-access key. The sequence of steps is determined by the user.]]
A multi-access key (free-access key,<ref name=":4" /> or polyclave<ref name=":1" />) allows a user to specify characters in any order. Therefore, a multi-access key can be thought of as "the set of all possible single-access keys that arise by permutating the order of characters."<ref name=":4" />{{Rp|page=60}} While there are print versions of multi-access keys, they were historically created using punched card systems.<ref name=":1" /> Today, multi-access keys are computer-aided tools.<ref name=":4" />{{Rp|page=61}}

==Key construction==

An early attempt to standardize the construction of keys was offered by E. B. Williamson in the June 1922 volume of Science.<ref>{{Cite journal |last=Williamson |first=E. B. |date=1922 |title=Keys in Systematic Work |url=https://www.jstor.org/stable/1645312 |journal=Science |volume=55 |issue=1435 |pages=703–704 |doi=10.1126/science.55.1435.703.a |jstor=1645312 |pmid=17751446 |issn=0036-8075|url-access=subscription }}</ref> More recently, [[Richard Pankhurst (botanist)|Richard Pankhurst]] published a guidelines and practical tips for key construction in a section of his 1978 book, ''Biological Identification.''<ref name=":3" />{{Rp|pages=15–22}}

Identification errors may have serious consequences in both pure and applied disciplines, including [[ecology]], medical diagnosis, [[pest (animal)|pest]] control, [[forensic]]s, etc.<ref>{{Cite journal |last=Marshall |first=Steve |date=Fall 2000 |title=Comments on error rates in insect identifications |url=https://drive.google.com/file/d/1myv6UguCmEUT4NzFBx92SMa2bV05H4nA/view |format=PDF |journal=Newsletter of the Biological Survey of Canada (Terrestrial Arthropods) |publisher=Biological Survey of Canada |volume=19 |issue=2 |pages=45–47}}</ref>

=== Computer-aided key construction ===
The first computer programs for constructing identification keys were created in the early 1970s.<ref>{{Cite journal |last=Payne |first=R. W. |date=1984 |title=Computer Construction and Typesetting of Identification Keys |url=https://www.jstor.org/stable/2432648 |journal=The New Phytologist |volume=96 |issue=4 |pages=631–634 |doi=10.1111/j.1469-8137.1984.tb03597.x |jstor=2432648 |bibcode=1984NewPh..96..631P |issn=0028-646X}}</ref><ref>{{Cite journal |last=Pankhurst |first=R. J. |date=1970-02-01 |title=A computer program for generating diagnostic keys |url=https://academic.oup.com/comjnl/article-lookup/doi/10.1093/comjnl/13.2.145 |journal=The Computer Journal |language=en |volume=13 |issue=2 |pages=145–151 |doi=10.1093/comjnl/13.2.145 |issn=0010-4620}}</ref> Since then, several popular programs have been developed, including DELTA, XPER, and LucID.<ref name=":0" />{{Rp|pages=379–80}}

Single-access keys, until recently, have been developed only rarely as computer-aided, interactive tools. Noteworthy developments in this area are the commercial LucID Phoenix application, the FRIDA/Dryades software, the ''KeyToNature'' Open Key Editor, and the open source WikiKeys and jKey application on biowikifarm.<ref name=":4" />{{Rp|page=62}}

== See also ==
* [[Species complex]]
* [[Systematics]]
* [[List of research methods in biology]]

==References==
{{Reflist}}
{{Free-content attribution
| title = Types of identification keys
| author = Gregor Hagedorn, Gerhard Rambold, Stefano Martellos
| publisher = Edizioni Università di Trieste
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| license statement URL = https://www.openstarts.units.it/server/api/core/bitstreams/e5c6bdd8-c0ec-4442-bda8-61f66dd43b05/content
| license = CC BY-SA
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}}

== Further reading ==
{{Cite book |last=Pankhurst |first=Richard John |title=Practical taxonomic computing |date=1991 |publisher=Cambridge university press |isbn=978-0-521-41760-0 |location=Cambridge}} Chapters 4-6.

== External links ==
{{Wikibooks|Dichotomous Key}}
{{Wikiversity|Optimal classification}}
* [http://www.herbarium2.lsu.edu/grass2/ Visual, touch, and translatable generic identification to grasses of Louisiana 2013 V3 with HTML 5]
* [https://web.archive.org/web/20120629151733/http://www.eti.uva.nl/products/linnaeus.php Linnaeus II - Interactive identification and descriptive data management software]
* [http://www.xper3.fr Xper3 - Online interactive identification and Collaborative edition tool]
* [https://web.archive.org/web/20110721001541/http://lis-upmc.snv.jussieu.fr/lis/?q=en%2Fresources%2Fsoftware%2Fxper2 Xper2 - Interactive identification and descriptive data management software]
* [http://www.identificationkey.fr Identification key webservice]
* [http://delta-intkey.com/www/interactivekeys.htm Principles of interactive keys] {{Webarchive|url=https://web.archive.org/web/20130503203412/http://delta-intkey.com/www/interactivekeys.htm |date=2013-05-03 }}
* [http://delta-intkey.com/www/idprogs.htm Programs for interactive identification and information retrieval] {{Webarchive|url=https://web.archive.org/web/20130414233318/http://delta-intkey.com/www/idprogs.htm |date=2013-04-14 }}
* [http://www.lucidcentral.org/ Lucid - Interactive Identification and Diagnostics key software]
* [https://web.archive.org/web/20140224105505/http://palachi.com/ BioBASE for Windows 7.0 - Computer-aided identification of Bacteria]
* [http://www.discoverlife.org/ Discover Life - Interactive Guides and free online guide development space]
* [https://web.archive.org/web/20070407001105/http://www.bioimages.org.uk/html/B147338.HTM Bioimages] Comments on [[Royal Entomological Society]] of London Keys
* [http://dmitriev.speciesfile.org/index.asp Dmitriev Interactive keys]
* [http://drawwing.org/dkey DKey - editor of dichotomous taxonomic keys]
* [https://divnavikey.snsb.info/ DiversityNaviKey (DNK)]

[[Category:Wild animals identification]]
[[Category:Plant taxonomy]]
[[Category:Taxonomy (biology)]]