Monophyly

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Phylogenetic tree, the blue (left) and red (right) groups represent monophyletic groups, the green group (centre) being paraphyletic.
Cladogram of the primates, showing a monophyletic group (the simians, in yellow), a paraphyletic group (the prosimians, in blue, including the red patch), and a polyphyletic group (the night-active primates, the lorises and the tarsiers, in red)

In common cladistic usage, a monophyletic group is a taxon (group of organisms) which forms a clade, meaning that it consists of an ancestral species and all its descendants. The term is synonymous with the uncommon term holophyly. Monophyletic groups are typically characterized by shared derived characteristics (synapomorphies).

Monophyly is contrasted with the terms paraphyly and polyphyly, which are most easily understood from the second diagram in this article. In current usage, a paraphyletic group consists of all of the descendants of a common ancestor minus one or more monophyletic groups. A paraphyletic group is thus 'nearly' monophyletic (consistent with the meaning of the prefix 'para', namely 'near' or 'alongside'.) A polyphyletic group is characterized by convergent features or habits (e. g., night-active primates, trees, aquatic insects); the features by which the group is differentiated from others are not inherited from a common ancestor.

These definitions have taken some time to be accepted. When the cladistic school of thought became mainstream in the 1960s, several alternative definitions were in use. Indeed, taxonomists sometimes used terms without defining them, leading to confusion in the early literature,[1] a confusion which persists.

See also: Crown group

Definitions[edit]

On the broadest scale, definitions fall into two groups.

See also[edit]

References[edit]

  1. ^ a b Hennig, Willi; Davis, D. (Translator); Zangerl, R. (Translator) (1999) [1966]. Phylogenetic Systematics (Illinois Reissue ed.). Board of Trustees of the University of Illinois. pp. 72–77. ISBN 0-252-06814-9. 
  2. ^ Colless, Donald H. (March 1972). "Monophyly". Systematic Zoology (Society of Systematic Biologists) 21 (1): 126–128. doi:10.2307/2412266. JSTOR 2412266. 
  3. ^ Envall, Mats (2008). "On the difference between mono-, holo-, and paraphyletic groups: a consistent distinction of process and pattern". Biological Journal of the Linnean Society 94: 217. doi:10.1111/j.1095-8312.2008.00984.x. 
  4. ^ Ashlock, Peter D. (March 1971). "Monophyly and Associated Terms". Systematic Zoology (Society of Systematic Biologists) 20 (1): 63–69. doi:10.2307/2412223. JSTOR 2412223. 
  5. ^ a b Simpson, George (1961). Principles of Animal Taxonomy. New York: Columbia University Press. ISBN 0-231-02427-4. 
  6. ^ Stamos, D.N. (2003). The species problem : biological species, ontology, and the metaphysics of biology. Lanham, Md. [u.a.]: Lexington Books. pp. 261–268. ISBN 0739105035. 

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