Species Concepts


A species concept is roughly equivalent to a species definition. Considered in the abstract, the species is a class, or kind, of which particular species are concrete instances. So a species definition is a definition of species in general and not of a particular species. The biological species concept treats species as sexual populations, which are reproductively isolated from one another. The recognition species concept is a variant of the biological species concept that emphasises mate recognition of conspecifics. The evolutionary species concept stresses the point that species are historical lineages as well as populations. The various cladistic species concepts treat parts of biological species as species. Phenetic and morphological species concepts treat species not as populations or lineages but as classes or kinds of organisms that are similar to one another. Preference for one or the other concept often reflects differences among scientists as to what they consider important.

Key Concepts:

  • Species are fundamental units in evolution, classification and biodiversity.

  • Species are the products of the process of speciation.

  • Species concepts and definitions tell us what is meant by the term ‘species’ in the abstract.

  • The species, in the abstract, forms a level in the Linnaean hierarchy used in formal classification (taxonomy). Like the genus and the family, it is a taxonomic category.

  • The groups that are called species are instances of the species category. They are taxa.

  • Populations and lineages are wholes composed of organisms, not kinds of organisms.

  • Species concepts may be difficult to apply to particular cases, in part because species speciate and get transformed.

Keywords: species; speciation; essentialism; typology; category; taxon; philosophy of systematics; philosophy of taxonomy


Cronquist A (1978) Once again, what is a species? In: Romberger JA (ed.) Biosystematics in Agriculture, pp. 3–20. New York: Wiley.

Mayr E (1942) Systematics and the Origin of Species. New York: Columbia University Press.

Further Reading

Claridge MF, Dawah HZ and Wilson MR (1977) Species: The Units of Biodiversity. London: Chapman & Hall.

Ereshefsky M (ed.) (1992) The Units of Evolution: Essays on the Nature of Species. Cambridge, MA: MIT Press.

Ghiselin MT (1997) Metaphysics and the Origin of Species. Albany, NY: State University of New York Press.

Ghiselin MT (2010) Metaphysics and classification: update and overview. Biological Theory 4: 241–247.

Hull DL (1988) Science as a Process. Chicago: University of Chicago Press.

Mayr E (1963) Animal Species and Evolution. Cambridge, MA: Harvard University Press.

Minelli A (1993) Biological Systematics: The State of the Art. London: Chapman & Hall.

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Ghiselin, Michael T(Sep 2010) Species Concepts. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0001744.pub2]