Movatterモバイル変換


[0]ホーム

URL:


What do terms like monophyletic, paraphyletic and polyphyletic mean?

17th July 2003

[<<][Contents][Search][>>]

Question

What do terms like monophyletic, paraphyletic and polyphyletic mean?

Answer

These terms are used to describe groupings of organisms, and indicatethe extent to which they can be considered as ``natural groups''.They are best explained using examples, so consider the followingfamily-tree diagram:
                       Aves                        /                       /          Crocodilia  /Mammalia    \    Dinosauria     \       \      /      \       \    /       \       \  /   Synapsida  Reptilia         \      /          \    /           \  /         Amniota

Here are examples of all three types of group:

So far, so straightforward. The only wrinkle in this scheme is thatsome workers use the word ``monophyletic'' in a sense that includeswhat we have described here as paraphyletic groups. These people thenuse ``holophyletic'' to describe what are usually called monophyleticgroups. It's tempting in the face of this ambiguity just to abandonthe word ``monophyletic'' and use a holophyletic/paraphyleticdichotomy, but this terminological abuse is probably not widespreadenough to merit such extreme measures. It's just something to be onthe watch for.

Because clades are so important, there is common notation forspecifying them (taken from the Phylocode: see note 9.4.1 inhttp://www.ohiou.edu/phylocode/art9.html).

These notations are not standard in formal technical literature, butappear frequently on the Dinosaur Mailing List.

It's unfortunate that this notation is so clumsy. The following,more concise, alternative notation is sometimes used (notably in MikeKeesey's admirableDinosauricon):

As examples of this last, we might describe the informal grouping``non-avian dinosaurs'' as {Dinosauria-Aves}, and the ``traditionalreptiles'' as {Reptilia-Aves}.

[<<][Contents][Search][>>]

Any comments? Good! Please email them todinofaq@indexdata.com
(SeeHow can I help? for more details.)
[About the author]

[8]ページ先頭

©2009-2025 Movatter.jp