Clade

Cladogram (family tree) of a biological group. The last common ancestor is the vertical line stem at the bottom. The blue and red subgroups are clades; each shows its common ancestor stem at the bottom of the subgroup branch. The green subgroup is not a clade; it is a paraphyletic group, because it excludes the blue branch, even though it has also descended from a common ancestor. The green subgroup together with the blue one forms a clade again.

A clade (/kld/;[1][2] from Ancient Greek: κλάδος, klados, "branch"), also known as a monophyletic group or natural group,[3] is a group of organisms that are monophyletic—that is, composed of a common ancestor and all its lineal descendants - on a phylogenetic tree.[4] Rather than the English term, the equivalent Latin term cladus (plural cladi) is often used in taxonomical literature.

The common ancestor may be an individual, a population, a species (extinct or extant), and so on right up to a kingdom and further. Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups.

Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms.[5] Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic. Some of the relationships between organisms that the molecular biology arm of cladistics has revealed are that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria, and multicellular organisms may have evolved from archaea.[6]

The term "clade" is also used with a similar meaning in other fields besides biology, such as historical linguistics; see Cladistics § In disciplines other than biology.

  1. ^ Wells, John C. (2008). Longman Pronunciation Dictionary (3rd ed.). Longman. ISBN 978-1-4058-8118-0.
  2. ^ "clade". Merriam-Webster Dictionary. Retrieved 19 April 2020.
  3. ^ Martin, Elizabeth; Hin, Robert (2008). A Dictionary of Biology. Oxford University Press.
  4. ^ Cracraft, Joel; Donoghue, Michael J., eds. (2004). "Introduction". Assembling the Tree of Life. Oxford University Press. p. 1. ISBN 978-0-19-972960-9.
  5. ^ Palmer, Douglas (2009). Evolution: The Story of Life. Berkeley: University of California Press. p. 13.
  6. ^ Pace, Norman R. (18 May 2006). "Time for a change". Nature. 441 (7091): 289. Bibcode:2006Natur.441..289P. doi:10.1038/441289a. ISSN 1476-4687. PMID 16710401. S2CID 4431143.