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(also polyphylesis), the conjectured origin of a systematic group of organisms (taxon) from two or more ancestral groups as a result of convergence. Some botanists believe, for example, that dicotyledonous and monocotyledonous plants originated from different ancestors and represent two parallel lines of flowering plants, the resemblance between them being the result of convergence.
It has been conjectured that different groups of animals have a polygenetic origin. It is likely, for example, that large groups of mammals originated from different groups of reptiles, the Therapsida. Such cases, sometimes said to be paragenetic, are not polygenetic, since there was only one basic original group. Therefore, if a group of organisms once considered monogenetic has elements of different origins, it should be divided into as many taxonomic entities as necessary to represent the separate and differently related groups constituting it. “There is no place in the phylogenetic system for polygenetic groups. Polygenesis is merely an expression of the imperfection of our classification” (I. I. Shmal’gauzen, Problemy darvinizma, Leningrad, 1969, p. 400).
Particularly unacceptable are artificial taxa for modern evolutionary systematics, one of the main principles of which is the classification of organisms according to the informational content of their genetic program. The taxa of evolutionary systematics can only be monogenetic.
REFERENCEMayr, E. Printsipy zoologicheskoi sistematiki. Moscow, 1971. (Translated from English.)
A. L. TAKHTADZHIAN