Paraphyly=mistakes? (There's the rub)

Dr. James Adams jadams at EM.DALTONSTATE.EDU
Wed Jan 9 14:20:27 CST 2002


You wrote:

>The issue we are addressing though is the scientific classification - the
>system to be taught to, and used by scientists in their work.

I was skimming messages and obviously did not pick this up as the main
thrust, only one of the thrusts.

My message was not one of disagreement with what you said.  My message was
that you need to gear your discussion appropriately for the audience.  If
you are teaching scientists to do appropriate phylogenetic work, then
clearly they must understand the concepts being discussed (monophyly,
paraphyly, etc.).  I didn't say "accept paraphyletic groups and move
on".  I would never use the word reptiles with a group of phylogenetic
workers, at least not without *explicitly* indicating what I meant when I
used the word.

Julian Humphries wrote:

 > I think the vagueness of the word "reptile" is *exactly*
 > the problem. Turtles? Dinosaurs? Crocs? Were do you start and stop? I
 >can think of no useful way to use the word "reptile" unless you include
 >all the dinos (including birds). Once you start using other definitions,
 >communication suffers as you really don't know what that word means.

I didn't say anywhere "purposely don't define what you mean by reptile in
order to keep the audience in confusion"!  Again, I was trying to make the
point that you gear what you say to your audience.  Of course you define
your terms explicitly to a scientific audience if there is a chance of
confusion.  I would venture to say that besides those feathery reptiles
(the birds) we shouldn't forget the hairy reptiles either!

>I think it is
>essential that the scientific classification be rigorously aligned with our
>best inference as to the true historical branching pattern.

I don't disagree here either.  I didn't say "you can't name monophyletic
groups" or that "paraphyletic groups should be allowed to stand with no
scrutiny."  But again, if you *understand explictly* the branching
patterns, using a word like "reptile" or "moth" from time to time,
*APPROPRIATE TO YOUR AUDIENCE*, is *not* going to assign you to hell!

Thomas also wrote:

>Since we have
>all (I should hope) accepted the evolutionary paradigm, we should recognize
>that artificial groupings are not only meaningless, but downright deceptive
>if used (as they have been) to make biological process arguments.

I understand where you are coming from, but still disagree to an
extent.  If you understand the context, they are not *completely*
meaningless, and are deceptive *only* if you don't pass along the
information that the group you are talking about is paraphyletic.  Again,
if you are talking to an audience who needs the information, then you would
be negligent *not* to tell them that a group is paraphyletic, and explain
the context in which you are using a given name.  I never said "don't do
this" in my original message.

>  If you
>wish to analyze the dynamics of evolutionary change, of what possible use
>would it be to consider Reptilia in its paraphyletic sense?

Okay.  I agree, Reptilia is an assemblage of separate branching events, of
which birds (and mammals) represent other(s).  From this standpoint,
Reptilia is of minimal use.

 > It seems clear to me
>that the only useful approach is to have a classification that recognizes
>real historical units, and to then map divergences on that tree.

Again, I don't disagree with you here either.  In the end, you want a
classification system that mirrors the evolutionary (divergence) events
that have taken place.  I suppose my message was talking on a different
level about the common usage of terms like "reptile" and "moth".

 >. . .rather than having only extremely
>crude statements such as that birds have somehow evolved enough to be
>considered on an equal level with the rest of the reptiles. That is an
>utterly useless scientific statement, and yet it is the best that can come
>of the Darwinian strategy.

I totally *agree* here.  I've *always* had a problem with arbitrary
assignment of a group to a classification level.  With the current
classification scheme, the (uninformed) reader is somehow led to believe
genera of butterflies, birds, ferns, etc. are somehow equivalent.

However, to have a clear picture of what the real
>historical lineages are is profoundly important to advancing scientific
>understanding of all taxa.

I agree here as well.

>I really can't believe that we are still having this conversation in the
>twentyfirst century.

As you can see, I didn't really disagree with most of what you say.  I was
trying to be brief, but I guess I was too brief.

>Tom DiBenedetto

James K. Adams
Phone: (706)272-4427
FAX:  (706)272-2235
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