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Date: Mon, 25 Feb 2002 09:09:10 -0600
From: "Bryant, Harold MAH" <HBryant@mah.gov.sk.ca>
To: "T. Mike Keesey" <tmk@dinosauricon.com>, -PhyloCode Mailing List- <PhyloCode@ouvaxa.cats.ohiou.edu>
Subject: RE: interesting style of definition
I confess that potential ambiguity regarding the meaning of "related" =
had
not occurred to me. However, given that the entire enterprise deals =
with
phylogeny, I think that most people would apply a phylogenetic meaning =
to
the word. But if one wants to avoid that potential misunderstanding, =
the
word "phylogenetically" could be added to modify "related."=20
Or what about the simplier wording: "the most inclusive crown clade =
that
includes A but not B." A definition for "crown clade" can certainly be
added to the PhyloCode glossary.
I don't think that the draft PhyloCode includes a definition of =
"ancestor."
Harold =20
---------------------------------------------------
Harold Bryant
Royal Saskatchewan Museum
2340 Albert Street
Regina, Saskatchewan=A0 S4P 3V7
Canada
306-787-2826
FAX 306-787-2645
-----Original Message-----
From: T. Mike Keesey [mailto:tmk@dinosauricon.com]
Sent: Saturday, February 23, 2002 6:17 PM
To: -PhyloCode Mailing List-
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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