[Previous by date - Re: interesting style of definition]
[Next by date - Re: interesting style of definition]
[Previous by subject - Re: interesting style of definition]
[Next by subject - Re: interesting style of definition]
Date: Fri, 15 Feb 2002 12:11:10 +0100
From: Mieczyslaw Wolsan <wolsan@twarda.pan.pl>
To: PhyloCode@ouvaxa.cats.ohiou.edu, phyloadvisors@ouvaxa.cats.ohiou.edu
Subject: Re: interesting style of definition
Sorry, there was a problem with my previous posting. Now it's ok (I hope). 1) "extant" This problem has already been addressed comprehensively in the literature (see, e.g., Bryant 1996, Syst. Biol. 45: 174-189). 2) "stemming" If clade A stems from B, is it necessary for clade A to contain B? I feel it is not. And this is my point. Of course, a clade consists of an ancestor and all its descendants. The problem I find with the discussed definition is that it is not clear (for me) whether the specified "last common ancestor" is contained in the clade. If I correctly recognize the meaning of the word "stemming" , the phrasing "clade A stemming from B" referes to two different clades: one containing B, and the other without B. 3) "ancestor" There has been much discussion related to the problem, also on the list (recently by Kevin de Queiroz, as far as I remember). The draft PhyloCode defines the term "clade" as "a group of species comprising a common ancestor and all of its descendants". (I would say "a group of lineages" and would replace the word "comprising" by "composed of" because I feel the word "comprise" meant to contain or include, but not to constitute or to compose.) I think that the majority of systematists agree with the draft PhyloCode's definition. However, I do not think that according to this definition it is necessary for the ancestor to be a species. I think many systematists agree that it is not necessary for a clade to begin with a complete species. If one wishes to have a species as an ancestor, this should be explicitly stated in the definition. Mieczyslaw Mieczyslaw Wolsan Professor and Chair Department of Vertebrate Paleontology Institute of Paleobiology Polish Academy of Sciences Twarda 51/55 00-818 Warszawa, Poland Phone: +48-22-697-8793 Fax: +48-22-620-6225 E-mail: wolsan@twarda.pan.pl http://www.paleo.pan.pl