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Contribution to Book
Reference Module in Life Sciences (2017)
  • Frederick M Cohan
The diversity of life is organized into clusters of related organisms that are similar in structure and function, and these clusters form the basis of taxonomy at all levels from kingdoms to species. The clusters recognized as taxa above the species level are universally considered to be categories of convenience. However, many biologists have considered the species rank to hold taxa that have real  biological qualities, which transcend human thought and experience. Some concepts of species, such as the phenetic and phylogenetic concepts, aim to allow objective demarcation of species, although without committing to what might be real about species or indicating how much diversity should be included within a species. Dynamically based concepts consider different species to have the real property that they are irreversibly separate lineages, while organisms within the same species are not irreversibly separate. The various dynamically based concepts recognize some or all of the following characteristics of species: different species are phenetically and ecologically distinct and are genetically incompatible, while members of the same species can potentially interbreed and are genetically cohesive. What constitutes speciation differs across the various concepts, but eventually any two lineages that are irreversibly separate are expected to hold all these features of species, provided they live long enough. Errors in population genetics and evolutionary biology can occur when an investigator is not aware that a species recognized by taxonomy does not necessarily correspond to a particular concept of species.
  • cohesion,
  • divergence,
  • ecotype,
  • hybridization,
  • incompatibility,
  • niche-transcending cohesion,
  • periodic selection,
  • phenetic cluster,
  • reproductive isolation,
  • speciation,
  • speciation-quashing cohesion,
  • taxonomy
Publication Date
B. Osmanaj and L. Escalante Santos
Citation Information
Frederick M Cohan. "Species" Reference Module in Life Sciences (2017)
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