Trends in Ecology & Evolution
OpinionOn the failure of modern species concepts
Section snippets
Ernst Mayr and the origins of the species-concept debate
Concepts are ideas that are typically neither very broad nor overly specific. In the rough hierarchy of referential scope, concepts tend to fall somewhere below theories and somewhere above definitions. Thus, we have an all-embracing theory of evolution, within which occur more modest concepts, such as the concept of fitness. A general concept can, in turn, be defined more specifically, and in different ways at different times, depending on the context. This is particularly true of concepts
The history of ‘concept’ in regard to species
Debates over the meaning of the word ‘species’ were already common before Darwin, although they became even more so afterward. For example, Darwin wrote about the difficulties associated with species definitions [3]: ‘Nor shall I here discuss the various definitions which have been given of the term species. No one definition has as yet satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of a species.’
The discovery that species evolve and give rise to new
The diversity of modern species concepts
Mayr's purpose for delineating multiple species concepts was to emphasize the different kinds of methods and criteria used for species identification. Mayr's equating of species concepts with criteria for identification is clear in 1942, and especially in his writings after 1969 15, 16. Interestingly, for several years in between, Mayr identified two levels of concepts: a primary theoretical level and a secondary level of definitions (that included the biological species concept) 17, 18 (Box 1).
Species pluralism: real or apparent?
An effect of the vigorous debate on species is the often-repeated claim that there can be no single species concept, and that some kind of pluralistic view of species should be adopted. Some proposals for pluralism are philosophical in nature and attempt to accommodate different metaphysical aspects of species 25, 26. More typically, proposals for pluralism are motivated by the fact that particular criteria for identifying species are not applicable in all situations and the observation that
Returning to a common concept of species
One piece of evidence suggesting that we do share a common concept of species is that biologists discuss species regularly without explicit reference to species concepts, and that disagreement over ‘species’ does not necessarily arise unless a discussant explicitly brings up the subject of species concepts. In this literal linguistic sense, we appear to share a species concept 34, 35. Perhaps more to the point: are there any participants in species debates who actually think that species do not
Lessons on the method of multiple concepts
Perhaps the long-running debate over the best species concept is dying. If so, it comes without the oft-hoped for widespread recognition of a common protocol for species identifications. In this light, it is useful to appreciate that some of our most persistent questions on how best to identify species were present long before Mayr's book, and that the fundamental form of those questions has not changed greatly. There were different species definitions in discussion and use before the
Acknowledgements
I thank J. Wilkins, M. P. Winsor, R. Harrison, J. Mallet and K. de Queiroz, as well as A. Templeton and two anonymous reviewers for helpful comments and critique.
References (57)
Opinion: The species problem, can we achieve a universal concept?
Syst. Appl. Microbiol.
(2003)The mind of the species problem
Trends Ecol. Evol.
(2001)The structure of species, outcomes of speciation and the ‘species problem’: ideas for paleobiology
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2001)- et al.
Delimiting species: a Renaissance issue in systematic biology
Trends Ecol. Evol.
(2003) Understanding and confronting species uncertainty in biology and conservation
Trends Ecol. Evol.
(2003)Ernst Mayr through time on the biological species concept – a conceptual analysis
Theory Biosci.
(2002)Systematics and the Origin of Species
(1942)A hierarchy of species concepts: the denouement in the saga of the species problem
On the Origin of Species by Means of Natural Selection
(1859)The philosophy of species-making
Bot. Gaz.
(1896)