follow up on paraphyly / polyphyly

SKÁLA Zdeněk skala at INCOMA.CZ
Thu Nov 11 09:24:53 CST 2004

Going back to the original question, the paraphyly / polyphyly distinction is quite straightforward:

1 - any "-phyly" is a result of splitting up a cladogram (i.e. an oriented graph, technically) and can be well described as a formal process

2 - the pieces of the cladogram can be either internally contected (= paraphyletic or mono/holophyletic) or discrete (= polyphyletic)
[hence the difference between the paraphyletic and polyphyletic taxa is a substantial one, perhaps greater than between the paraphyletic / monophyletic]

3 - given the graph orientation, the subgraph (a taxon) can either include all descendant nodes (in the graph-theory sense) of the basal node or only some of them - here is the difference between the mono/holo- and paraphyly

4 - any rating of different types of taxa as "natural" or "complete" is always a matter of taste and criteria; there were several (long) threads even here in Taxacom about the utility/naturalness of paraphyletic taxa - I would suggest to teach this field as a formal issue leaving the evaluation of different types of taxa as a separate lesson.

Best regards!
Zdenek Skala

-----Original Message-----
From: Derek Sikes [mailto:dsikes at UCALGARY.CA]
Sent: Wednesday, November 10, 2004 9:12 PM
Subject: follow up on paraphyly / polyphyly

Dear Taxacomers,

Thanks to those who have replied already. I thought I might add one
additional bit on this issue:

I have also explained these terms informally (although I expect the
students to understand them formally as well) as follows:

Monophyly: a natural group

Paraphyly: a natural but incomplete group

Polyphyly: an unnatural group

I don't know where exactly I learned these informal definitions but
they're not mine. The problem with these is students memorize them but
often don't understand them!

Derek S. Sikes, Assistant Professor
Division of Zoology
Department of Biological Sciences
University of Calgary
2500 University Drive NW
Calgary, Alberta, Canada, T2N 1N4

dsikes at

phone: 403-210-9819
FAX:  403-289-9311

"Remember that Truth alone is the matter you are in Search after; and
if you have been mistaken, let no Vanity reduce you to persist in your
mistake." Henry Baker, London, 1785

Entomological Society of Alberta:

More information about the Taxacom mailing list