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Date: Sat, 23 Feb 2002 19:16:54 -0500 (EST)
From: "T. Mike Keesey" <tmk@dinosauricon.com>
To: -PhyloCode Mailing List- <PhyloCode@ouvaxa.cats.ohiou.edu>
Subject: RE: interesting style of definition
On Fri, 15 Feb 2002, Bryant, Harold MAH wrote:
> Issues concerning the potential ambiguity of the meaning of the terms
> "stemming" and "ancestor" can be avoided by the following wording:
>
> "The least inclusive clade that includes A and all extant organisms that are
> more closely related to A than to B."
Problem here is that there are different concepts of "relatedness". Say we
have this situation:
-+-A
`-+-B
`------------------------------------------------C
Where A and B are relatively unmodified from the common ancestor, and C is
extremely derived. Is B more closely related to C or to A? It is
morphologically and genetically more similar to A, although it shares more
recent ancestry with C.
Personally, I like the wording "the first ancestor of A which is not also
an ancestor of B, plus all of that ancestor's descendants". Of course, you
then have to specify the nature of the ancestor, although IIRC PhyloCode
indicates it should be considered a species?
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