Message 2000-09-0007: RE: Nathan Wilson's question

Thu, 28 Sep 2000 13:53:08 -0400

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Date: Thu, 28 Sep 2000 13:53:08 -0400
From: "Moore, Gerry" <>
To: 'Nathan Wilson' <>
Cc:, "''" <>
Subject: RE: Nathan Wilson's question

NW: Gerry Moore also brings up an interesting point about using members of
non-nested clades as specifiers, but I think the example he gave doesn't
quite make the point.  As Philip Cantino points out there is no problem
under the current definitions if one of the two species belongs to two
non-nested clades. 
Where did Phil say that? Under phylogenetic nomenclature a clade's
circumscription must include all positions where the specifiers show up.  To
me whether or not it is one or two (or three etc.) of the specifiers that
happens to occupy nonnested clades is irrelevant. Are you saying that in my
example, Clade Z's circumscription would not have to be expanded to include
Clade B because only one of the specifiers (species 3) was shown to occur in
more than one nonnested clade?  If so, I don't follow (more below).    

NW: However, there is a problem if both species belong to the same two
non-nested clades.  If that's the case then a node-based clade defined using
those two species has no clear definition since there are now multiple most
recent ancestors and no clear way to choose between them.  

I see this very differently.  To me, the circumscription of the taxon
(clade) defined using these specifiers that are now known to occupy multiple
nonnested clades has to be expanded so as to encompass all the nonnested
clades that the specifiers are now known to occupy.  Again, I fail to see
why there is a problem only if two of the specifiers (as opposed to one)
belong to nonnested clades (see above discussion).  To me the name of the
clade still has a very clear definition; the original circumscription simply
needs to be modified (expanded) to include this new information (i.e., a
specifier occupying nonnested clades).  

I stand by my original conclusions I made regarding the hypothetical example
I presented previously. 

Gerry Moore
28 Sep. 2000   


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