parafyletická

Parafyletické, or paraphyletic, describes a grouping that includes the most recent common ancestor of the members and some, but not all, of its descendants. The term contrasts with monofyletické groups, which include the common ancestor and all of its descendants, and polyfyletické groups, which do not share a single common ancestor within the group. A parafyletická skupina is therefore incomplete with respect to the full evolutionary subtree rooted at its ancestor, typically because one or more descendant lineages have been excluded.

Parafyletické groupings commonly arise in traditional classifications based on shared morphological traits rather than on comprehensive phylogenetic knowledge. They may reflect real evolutionary relationships but are considered less informative for reconstructing ancestry because they omit certain descendants. In modern systematics, parafyletické groups are generally discouraged as formal names, though they can appear in historical, descriptive, or pedagogical contexts.

Examples cited in the literature often include traditional groups such as Reptilia, which is frequently treated as paraphyletic when birds are excluded, given that birds descended from reptilian ancestors. In other cases, long-standing classifications in plants or invertebrates have been shown by molecular phylogenies to be paraphyletic or to contain nested lineages. Etymology reflects its meaning: from Greek para (beside) and phyletikos (tribe, descendant), indicating a group that sits beside the full clade rather than encompassing it completely.