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 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 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.

## Contents

* 1 History
* 1.1 Terminology
* 2 Use
* 3 Types of keys
* 3.1 Single-access key
* 3.1.1 Presentational variants
* 3.2 Multi-access keys
* 4 Key construction
* 4.1 Computer-aided key construction
* 5 See also
* 6 References
* 7 Further reading
* 8 External links

## History

File:Lamarck's key.pngIdentification 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.[1]: 2

Seventeenth-century naturalists, including John Ray, 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.[1]: 3–8

The first analytical identification key is credited to 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.[1]: 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 W. H. Evans.[1]: 12–14

### Terminology

Identification keys are known historically and contemporarily by many names, including analytical key, entomological key, artificial key,[1] diagnostic key,[2] determinator,[3] and taxonomic key.[4]

Within the biological literature, identification keys are referred to simply as keys.[5] They are also commonly referred to in general as dichotomous keys,[6] though this term strictly refers to a specific type of identification key (see Types of keys).

## Use

Identification keys are used in systematic biology and taxonomy to identify the genus or species of a specimen organism from a set of known 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.[3] However, they have also been used to classify non-organisms, such as birds nests, and in non-biological sciences such as geology.[1]: 14–15 Similar methods have also been used in computer science.[7]

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.[8] Each step in the key employs a character: a distinguishing feature of an organism that is conveniently observable.[3]

## 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.[2]: 7 [6]: 225 Identification keys can be divided into two main types.

### Single-access key

Main article: Biology:Single-access key

File:Screenshot from 2024-10-20 20-19-32.pngUser 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.[3] A single-access key with more than two leads per step is referred to as polytomous.[9]

#### 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[9]: 63 ), each pair of leads (called a couplet) are printed together. In the nested style (also referred to as closed, yoked, and indented[9]: 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.[2] 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.[9]: 63

### Multi-access keys

Main article: Biology:Multi-access key

Diagram of possible progressions through a multi-access key.User interaction steps in a multi-access key. The sequence of steps is determined by the user.

A multi-access key (free-access key,[9] or polyclave[8]) 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."[9]: 60 While there are print versions of multi-access keys, they were historically created using punched card systems.[8] Today, multi-access keys are computer-aided tools.[9]: 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.[10] More recently, Richard Pankhurst published a guidelines and practical tips for key construction in a section of his 1978 book, Biological Identification.[2]: 15–22

Identification errors may have serious consequences in both pure and applied disciplines, including ecology, medical diagnosis, pest control, forensics, etc.[11]

### Computer-aided key construction

The first computer programs for constructing identification keys were created in the early 1970s.[12][13] Since then, several popular programs have been developed, including DELTA, XPER, and LucID.[3]: 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.[9]: 62

## See also

* Species complex
* Systematics
* List of research methods in biology

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Voss, Edward G. (December 1952). "The history of keys and phylogenetic trees in systematic biology". Journal of the Scientific Laboratories of Dennison University 43: 1–25.
2. ↑ 2.0 2.1 2.2 2.3 Pankhurst, R. J. (1978). "Conventional Identification Methods". Biological identification: the principles and practice of identification methods in biology. Baltimore: University Park Press. pp. 11–28. ISBN 978-0-8391-1344-7.
3. ↑ 3.0 3.1 3.2 3.3 3.4 Winston, Judith E. (1999). "Keys". Describing species: practical taxonomic procedure for biologists. New York: Columbia University Press. pp. 367–381. ISBN 978-0-231-06824-6.
4. ↑ Bohemier, Kayleigh. "Yale University Library Research Guides: Taxonomic Keys: Home" (in en). https://guides.library.yale.edu/keys.
5. ↑ "key (identification key)". A dictionary of biology. Oxford paperback reference (6th ed.). Oxford: Oxford University Press. 2008. pp. 356. ISBN 978-0-19-920462-5.
6. ↑ 6.0 6.1 Lawrence, George H. M. (1951). Taxonomy of Vascular Plants (1st ed.). New York: The Macmillan Company. pp. 225–8.
7. ↑ Payne, R. W. (1983). "Identification Keys". in Kotz, Samuel. Encyclopedia of Statistical Sciences. 4. John Wiley & Sons. pp. 6–10. ISBN 0471055514.
8. ↑ 8.0 8.1 8.2 Thain, M.; Hickman, M. (2004). "identification keys". The Penguin dictionary of biology (11th ed.). London; New York, N.Y: Penguin Books. pp. 363. ISBN 978-0-14-101396-1.
9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 Hagedorn, Gregor; Rambold, Gerhard; Martellos, Stefano (2010). "Types of identification keys". in Nimis, P. L.. Tools for Identifying Biodiversity: Progress and Problems. Edizioni Università di Trieste. pp. 59–64. ISBN 978-88-8303-295-0. https://www.openstarts.units.it/server/api/core/bitstreams/d6c3dc5f-17a1-478b-beab-31464b220ce1/content.
10. ↑ Williamson, E. B. (1922). "Keys in Systematic Work". Science 55 (1435): 703–704. doi:10.1126/science.55.1435.703.a. ISSN 0036-8075. PMID 17751446. https://www.jstor.org/stable/1645312.
11. ↑ Marshall, Steve (Fall 2000). "Comments on error rates in insect identifications" (PDF). Newsletter of the Biological Survey of Canada (Terrestrial Arthropods) (Biological Survey of Canada) 19 (2): 45–47. https://drive.google.com/file/d/1myv6UguCmEUT4NzFBx92SMa2bV05H4nA/view.
12. ↑ Payne, R. W. (1984). "Computer Construction and Typesetting of Identification Keys". The New Phytologist 96 (4): 631–634. doi:10.1111/j.1469-8137.1984.tb03597.x. ISSN 0028-646X. Bibcode: 1984NewPh..96..631P. https://www.jstor.org/stable/2432648.
13. ↑ Pankhurst, R. J. (1970-02-01). "A computer program for generating diagnostic keys" (in en). The Computer Journal 13 (2): 145–151. doi:10.1093/comjnl/13.2.145. ISSN 0010-4620. https://academic.oup.com/comjnl/article-lookup/doi/10.1093/comjnl/13.2.145.

This article incorporates text from a free content work. Licensed under CC BY-SA License statement: Types of identification keys, Gregor Hagedorn, Gerhard Rambold, Stefano Martellos, Edizioni Università di Trieste. To learn how to add open license text to HandWiki articles, please see this how-to page. For information on reusing text from HandWiki, please see the terms of use.

## Further reading

Pankhurst, Richard John (1991). Practical taxonomic computing. Cambridge: Cambridge university press. ISBN 978-0-521-41760-0. Chapters 4-6.

## External links

| Wikibooks has a book on the topic of: Dichotomous Key

|

* Visual, touch, and translatable generic identification to grasses of Louisiana 2013 V3 with HTML 5
* Linnaeus II - Interactive identification and descriptive data management software
* Xper3 - Online interactive identification and Collaborative edition tool
* Xper2 - Interactive identification and descriptive data management software
* Identification key webservice
* Principles of interactive keys
* Programs for interactive identification and information retrieval
* Lucid - Interactive Identification and Diagnostics key software
* BioBASE for Windows 7.0 - Computer-aided identification of Bacteria
* Discover Life - Interactive Guides and free online guide development space
* Bioimages Comments on Royal Entomological Society of London Keys
* Dmitriev Interactive keys
* DKey - editor of dichotomous taxonomic keys
* DiversityNaviKey (DNK)

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