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Re: Clade II



[After this I will use private e-mail for this discussion].

From: "Jonathan R. Wagner" <znc14@ttacs1.ttu.edu>
 >         As I just wrote, this leads to confusion over which taxa are
 > actually monophyletic.  you yourself have pointed out that cladists use
 > paraphyletic groups of convenience.  Why can't you leave it at that?

My point is, if even cladists find it necessary to *use* such groups,
isn't that really an indication that they are, at some level, natural
groupings?  Doesn't this indicate that there is some functionality that
is simply not being addressed by traditional cladistic taxonomy? I mean,
isnt't it really alot easier to say "thecodonts" than to say "basal
archosaurs", or "pseudosuchians" instead of "basal cruritarsians"?

[This is really what I was getting at with my "because children can
tell the difference" remark - it is really the experts who *still*
use these groups that  make my point].

 >  Why do your paraphyletic groups HAVE to be taxa?

Because they capture information that is ignored by a classification
that does not use them.

>From a purely information-theoretic point of view, a hybrid
classification cpatures more data than any pure cladistic one.

My primary reference to support this point is:

Carpenter, Kent, E., 1993. "Optimal Cladistic and Quantitative
Evolutionary Classifications as Illustrated by Fusilier Fishes
(Teleostei: Caesionidae)." Systematic Biology 42(2): 142-154

This article compares the information content of classifications
produced from the *same* *cladogram* using both traditional cladistic
methods and Peter Ashlock's quantitative methods.

 >       But can he tell that an Aardvark, a gliptodont, a staganolepidid
 > (aetosaur), and a nodosaur are not related?  Yes, if you tell him.

Perhaps evedn if you merely tell him how to tell.
 >  As I have repeatedly tried to point out on
 > this list, drawing artificial parapyletic taxa confuses issues.

Only if you expect a classification to answer this one particular
question.  It clarifies *other* issues.  The key is a balance of
treatment.

If your sole interest is in phylogenetic relationships, then present,
use, and discuss a cladogram, which presents that information clearly
and succintly, without any clutter from other matters.  As long as one
expects to use a cladogram for this purpose, and a classification for
other purposes, there *is* no confusion.  It is trying to insist that
a classification serve only this one purpose that then introduces the
confusion.

 > >The issue is whether or not groups are easy to recognize       
 >         Why?  Taxonomy is not a field classification.

It is the *basis* of field classification.

swf@elsegundoca.ncr.com         sarima@ix.netcom.com

The peace of God be with you.