polifilético

Polifilético, in biology and taxonomy, describes a group of organisms that is defined by shared characteristics but does not include their most recent common ancestor. In a polyphyletic grouping, the members originate from multiple independent lineages, so the group does not form a natural evolutionary unit or clade. The term contrasts with monofilético (monophyletic), which includes all descendants of a single common ancestor, and with parafilético (paraphyletic), which includes some but not all descendants of a common ancestor.

Polyphyly often arises when similarities among organisms are the result of convergent evolution, evolutionary reversals, or when classification relies on traits that are not inherited from a single ancestral source. Modern phylogenetic analyses, especially those based on molecular data, are used to identify polyphyletic groups and revise classifications to reflect evolutionary relationships, typically by redefining groups as monophyletic.

Examples commonly cited in teaching include the designation of “endothermic animals” (warm-blooded) as a single group comprising mammals and birds, despite their last common ancestor not possessing endothermy. Another frequently discussed instance is the idea of “flying vertebrates,” which includes birds and bats (and extinct pterosaurs), a grouping that does not trace to a single ancestral flight-capable lineage. Similarly, informal groupings such as “marine mammals” highlight how convergent lifestyles can produce polyphyletic impressions.

Impact: Recognizing polyphyly has driven taxonomic revisions toward monophyletic groups and underpins the cladistic approach to classifying organisms. Etymology: from Greek poly- “many” and phyletikos “of a tribe, race.” See also monophyly, paraphyly, cladistics, taxonomy, phylogeny.

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