Polythetic

Polythetic is a term used in the field of taxonomy and systematics to describe a classification system that groups organisms based on multiple, often unrelated, characteristics. Unlike monophyletic systems, which group organisms based on shared ancestry, polythetic systems do not necessarily reflect evolutionary relationships. Instead, they use a mix of traits such as morphology, physiology, behavior, and ecology to create categories.

The term "polythetic" was first used by the German biologist Ernst Mayr in the 1940s. Mayr argued that many traditional classification systems, particularly those used in botany and zoology, were polythetic rather than monophyletic. He proposed that a more accurate system would be based on evolutionary relationships, leading to the development of phylogenetic systematics.

Polythetic systems have been criticized for their lack of evolutionary significance and for leading to artificial groupings. However, they remain in use in some fields, particularly in botany, where they have been adapted to incorporate phylogenetic information. The debate between polythetic and monophyletic systems continues in the field of systematics, with proponents of each arguing for the merits of their respective approaches.