Message 2001-09-0018: Re: Apomorphy-based definitions

Wed, 29 Aug 2001 13:39:41 -0700 (PDT)

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Date: Wed, 29 Aug 2001 13:39:41 -0700 (PDT)
From: Nathan Wilson <>
To: PhyloCode mailing list <>
Subject: Re: Apomorphy-based definitions

On Wed, 29 Aug 2001, T. Mike Keesey wrote:

> Right -- although, you *could* use temporality as a "tiebreaker". That
> doesn't really mesh with the idea of classification by phylogeny, though.

I considered that, but I don't think it's a good idea.  You can get into
really weird situations that way if you start considering species like
redwood trees or some species of fungi which live 1000's of years, but
potentially mate every year.

> > A 'Most Recent Common Ancestor' of a set of individuals is any
> > ancestor of those individuals is an ancestor of all of them and
> > which has no decendent with that property.

> Very nice. I think I like that a lot better than using "species" (with all
> its hundred definitions) as the smallest unit of taxonomy. The only
> improvement I could think of would be something to account for situations
> where one or more internal specifiers are ancestral to one or more other
> internal specifiers.

I don't think there's any problem with internal specifiers being ancestral
to each other.  Is there a case your thinking of?  I guess there's an
issue if you don't consider an individual an ancestor of itself.  I don't
know of a better word to express that concept.

> Of course, in practice, issues like this are not likely to cause much of a
> difference, if any. But it does seem like a more solid theoretical ground
> to rest upon.

Actually I believe this issue could make a significant difference.  For
one thing it eliminates the 'what about species?' issue.  It also allows
for the defintion of sub-species groupings.



Feedback to <> is welcome!