Cladospeak: Bonnan errata and corrections

["Matthew Bonnan" <mbonnan@hotmail.com>]

I too quickly responded to George O.'s post, and it is now apparent on 
reflection that I was incorrect.  Yes, groups are diagnosed on the basis of 
their separation from other taxa, not directly from character data.

I have been using definitions from what I feel is a fine book on 
systematics, "Biological Systematics: Principles and Applications" by 
Randall T. Schuh, 2000.  According to this book,

Diagnosis = in systematics, a summary statement of attributes that allows 
recognition of a taxon and separation of that taxon from one or more taxa.

Definition = an enumeration of the apomorphies for a taxon

Description = in systematics, a detailed written statement of the attributes 
possessed by a given taxon

Synapomorphy = shared, derived, group-defining (not diagnosing) trait

My confusion arose from George's statement that there were no trait-based 
groups.  I thought he was implying that groups are proposed based on a 
preformulated idea about their evolution, which I could not phathom -- 
again, how would someone "know" the evolution of group without using 
characters?  I believe George was saying, instead, that groups are not 
defined by characters but are diagnosed by how those characters separate 
them from other taxa.  Right? =)

In any case, the original point I was attempting to make, which may have 
been lost in all this, was that it is not syanpomorphies that are weak or 
strong, but rather characters.  Because a synapomorphy is a shared, derived, 
group-defining (not diagnosing) trait, if it is "weak" or "insignifcant," it 
cannot be a synapomorphy.  On the other hand, characters and choice of 
characters can be "weak" or "strong," and these choices have many 
interesting ramifications for both functional morphology and systematics.

Matt Bonnan
Assistant Professor
Dept. Biological Sciences
Western Illinois University
Macomb, IL 61455

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