[Previous by date - Re: a comment on ancestors]
[Next by date - Re: a comment on ancestors]
[Previous by subject - Re: a comment on ancestors]
[Next by subject - Re: a comment on ancestors]
Date: Wed, 04 Feb 2004 12:34:29 +0100
From: David Marjanovic <david.marjanovic@gmx.at>
To: PML <phylocode@ouvaxa.cats.ohiou.edu>
Subject: Re: a comment on ancestors
> If you define a taxon by a character or by a type you mean that it
> is possible to allocate any newly discovered item to that taxon
> by observing respective character or type.
This would not guarantee that the taxon would stay monophyletic -- the
character in question could have evolved by convergence.
> The present PhyloCode definition of taxon membership
> presumes that in order to allocate a new item to one or
> another monophyletic group in existing classification, one
> has to run complete cladistic analysis in which all members
> of those groups + new item are to be included.
Correct. Well, not necessarily all members, but some that are universally
agreed to be members of that group (such as the specifiers).
> But what to do if those groups were recognized, say, by
> DNA analysis and no DNA data are vailable for the new item?
:-) Make a morphological analysis for them.
This wouldn't change under an apomorphy-based definition. If
Afrotheria were defined by their unique 9 bp deletion in the gene BRCA1, and
if I wanted to find out if some Paleocene fossil was an afrothere, I'd
likewise have to make a morphological analysis of Placentalia.
> It seems to me that theoretical and empirical definitions of taxon
> membership are mixed in the PhyloCode.
I disagree. The theoretical definition is called "definition" in it, while
the empirical definition is called "diagnosis".