A polyphyletic group or assemblage is a set of organisms, or other evolving elements, that have been grouped together based on characteristics that do not imply that they share a common ancestor that is not also the common ancestor of many other taxa (of course, if "life" is monophyletic, then any set of organisms shares a common ancestor at some point back in the root of the tree). The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of convergent evolution. The arrangement of the members of a polyphyletic group is called a polyphyly/ˈpɒlɪˌfaɪli/[citation needed].
Alternatively, polyphyletic is simply used to describe a group whose members come from multiple ancestral sources, regardless of similarity of characteristics. For example, the biological characteristic of warm-bloodedness evolved separately in the ancestors of mammals and the ancestors of birds.[1]Other polyphyletic groups are for example algae, C4 photosynthetic plants,[2] and edentates.[3]
Many biologists aim to avoid homoplasies in grouping taxa together and therefore it is frequently a goal to eliminate groups that are found to be polyphyletic. This is often the stimulus for major revisions of the classification schemes.
Researchers concerned more with ecology than with systematics may take polyphyletic groups as legitimate subject matter; the similarities in activity within the fungus group Alternaria, for example, can lead researchers to regard the group as a valid genus while acknowledging its polyphyly.[4] In recent research, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse group of species.[5]
https://en.wikipedia.org/wiki/Polyphyly
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