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Re: Cladists versus non-cladists



At 05:12 PM 5/7/97 -0400, Office wrote:
>Would you (or someone) be kind enough to give just one example of the
>identical nomenclature?
>
>ie. word1 doesn't really equal word1

Well, to start with, both approaches use the word 'taxon' for their groups.
Yet a cladistic taxon and a non-cladistic taxon are truly entirely
different things.  And, until recently, cladists assigned their taxa to
linnaean hierarchical categories (family, order, class, and so on).  Thus
when one spoke of Sublass Archosauria it was not immediately clear if one
is speaking of the cladistic or the non-cladistic version (since they
differ in the inclusion of Aves).  Thus, the effective meaning  of words
like "family" was different in the two systems.

In short, the terminology does not, or did not, clearly differentiate in
use between a clade and a non-cladistic taxon.

There is also the related confusion due to using the same taxonomic names
for cladistic and non-cladistic taxa.  The most obvious case that comes to
mind is Reptilia, which is a very different beast in the two systems.
Similar examples include: Amphibia, Archosauria, and,
if the name is retained in either system, Carnosauria. This would not be so
much of a problem if there were a clear terminological way to indicate if
one were using a name in a cladistic sense or a non-cladistic sense.

The abandonment of linnaean ranks by cladists may go the first step in this
direction.  If this is clearly understood, and widely accepted, then
categorizing a name by its rank will clearly mark its use as non-cladistic.
 In this approach Subclass Archosauria and Archosauria (or Clade
Archosauria) would be different things.  As my parenthetical remark
suggests, I think labeling clades as such, at least in the first use in any
given document, would be a good practice, so that usage is clearly marked
in both directions.

>> Evolutionary taxonomy, on the other hand, provides a way to 
>>summarize and index general information about organisms.  It seeks 
>>to optimize both overall information content and convenience of 
>>access (this last is partly accomplished by keeping the number of 
>>names and categories to be remembered limited).

I am not quite sure what you are confused about here.

Perhaps if you looked at my longer discussion on my Web site,
it would become clearer.

Or, much of my discussion on my web site comes from _Principles of
Systematic Zoology_ by Ernst Mayr and Peter Ashlock (2nd ed.).  The
discussion in there is fairly clear (except for my recent realization that
the two systems actually have different purposes: but it does explain the
purposes of evolutionary taxonomy quite well).

[Or is it that you associate the term "evolutionary taxonomy" with the
cladistic approach, which is often called "phylogenetic taxonomy"?]

--------------
May the peace of God be with you.         sarima@ix.netcom.com
                                          sfriesen@netlock.com