Editing Cladistics (section)

== Terminology for taxa ==
Mono-, para- and polyphyletic taxa can be understood based on the shape of the tree (as done above), as well as based on their character states.<ref name="Patterson 1988" /><ref name="de Pinna 1991" /><ref>{{Harvnb|Patterson|1982}}</ref> These are compared in the table below.

{| class="wikitable"
|+
! Term
! Node-based definition
! Character-based definition
|- valign="top"
| Holophyly,  [[Monophyly]]
| A [[clade]], a monophyletic taxon, is a taxon that consists of the last common ancestor and all its descendants.<ref>{{Cite journal |last=Podani |first=János |date=2010-08-01 |title=Monophyly and paraphyly: A discourse without end? |journal=Taxon |language=en |volume=59 |issue=4 |pages=1011–1015 |doi=10.1002/tax.594002|doi-access=free }}</ref>
| A clade is characterized by one or more '''apomorphies''': derived character states present in the first member of the taxon, inherited by its descendants (unless secondarily lost), and not inherited by any other taxa.
|- valign="top"
| [[Paraphyly]]
| A paraphyletic assemblage is one that is constructed by taking a clade and removing one or more smaller clades.<ref>Many sources give a verbal definition of 'paraphyletic' that does not require the missing groups to be monophyletic. However, when diagrams are presented representing paraphyletic groups, these invariably show the missing groups as monophyletic. See e.g.{{Harvnb|Wiley|Siegel-Causey|Brooks|Funk|1991|p=4}}</ref> (Removing one clade produces a singly paraphyletic assemblage, removing two produces a doubly paraphyletic assemblage, and so on.)<ref>{{Harvnb|Taylor|2003}}</ref>
| A paraphyletic assemblage is characterized by one or more '''plesiomorphies''': character states inherited from ancestors but not present in all of their descendants. As a consequence, a paraphyletic assemblage is truncated, in that it excludes one or more clades from an otherwise monophyletic taxon. An alternative name is ''[[evolutionary grade]]'', referring to an ancestral character state within the group. While paraphyletic assemblages are popular among paleontologists and evolutionary taxonomists, cladists do not recognize paraphyletic assemblages as having any formal information content – they are merely parts of clades.
|- valign="top"
| [[Polyphyly]]
| A polyphyletic assemblage is one which is neither monophyletic nor paraphyletic.
| A polyphyletic assemblage is characterized by one or more '''[[Homoplasy|homoplasies]]''': character states which have converged or reverted so as to be the same but which have not been inherited from a common ancestor. No systematist recognizes polyphyletic assemblages as taxonomically meaningful entities, although ecologists sometimes consider them meaningful labels for functional participants in ecological communities (e. g., primary producers, detritivores, etc.).
|}