What does a monophyletic group consist of?

A monophyletic group, also referred to as a clade, is defined as a group that includes a common ancestor and all of its descendants. This classification emphasizes the importance of evolutionary relationships, capturing the complete lineage from its origin to all taxa that have evolved from it. In a monophyletic group, every member shares a unique set of traits inherited from the common ancestor, making this grouping fundamental to understanding the phylogenetic tree of life.

In contrast, groups defined by shared traits alone do not necessarily imply a common ancestor and could represent unrelated lineages (as seen in paraphyletic and polyphyletic groups). Similarly, classifications based on analogous traits do not reflect true evolutionary relationships, as these traits may arise from convergent evolution rather than descent from a common ancestor. Thus, the integrity of a monophyletic group rests on its ability to trace all its lineage back to a single ancestor, encompassing all descendants in a universally recognized taxonomic structure.