|Title||The Evolutionary Species Concept Reconsidered |
|Publication Type||Journal Article |
|Year of Publication||1978 |
|Authors||Wiley, III EO |
|Journal||Systematic Zoology |
|Keywords||Ecology: environmental biology - Animal 16, Ecology: environmental biology - General and methods 07508, Evolution 03506, General biology - Taxonomy, Genetics - Animal 03509, Genetics - Population genetics 07502, nomenclature and terminology 01500, Organisms  Environmental Sciences Ecology Evolution and Adaptation Organisms 00504 |
|Abstract||The concept of species (as taxa) adopted by an investigator will influence his perception of the processes by which species originate. The concept adopted should have an universal applicability as current knowledge permits. Simpson's definition of a species is modified to state: a species is a lineage of ancestral descendant populations which maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate. This definition is defended as that which has widest applicability given current knowledge of evolutionary processes. Four corollaries are deduced and discussed relative to other species concepts: all organisms, past and present, belong to some evolutionary species; reproductive isolation must be effective enough to permit maintenance of identity from other contemporary lineages; morphological distinctiveness is not necessary; and no presumed (hypothesized) single lineage may be subdivided into a series of ancestral-descendant species. The application of the evolutionary species concept to allopatric demes and to asexual species is discussed; the lack of evolutionary divergence forms the basis for grouping such populations into single species. Some ecological species definitions lead to under-estimations of the rate of extinction due to interspecific competition because their logical framework excludes unsuccessful species from being species. Finally, the implications of accepting an evolutionary species concept to the field of phylogeny reconstruction are discussed.