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synapomorphies



This inquiry is based on the "Genetics and Morphology Collide" thread, 
but the subject seems to have changed (the fault of GO and me), so I have 
retitled it.  Unless someone beats me to it, I'll have something else to 
post on the original topic tomorrow that I will use the original label 
for.

I am still trying to separate observation from interpretation.  I think 
it's just a semantic problem.  Earlier, I asked:

>Let me get this straight:  apomorphies are observations--the physical 
>characteristics we think we see.  They are used to construct cladograms. 
 
>The cladogram branches at certain points, and the characters possessed 
in 
>common by the members of a branch are called synapomorphies--still an 
>observation.  

>But wouldn't it be an _interpretation_ that the observed synapomorphies 
>have phylogenetic significance?

To which GO responded: 

>Naturally. Other observers, with different cladograms, would arrive at
>different lists of synapomorphies. Making an apomorphy a synapomorphy 
places
>a phyletic interpretation on the character that is based on one's 
analysis.
>When lots of observers come up with more or less the same lists of
>synapomorphies via different analyses, then, maybe, we can speak with 
some
>assurance about the _real_ synapomorphies in the phylogeny.

My thinking may be wrong, but the following is what I have concluded from 
this discussion.  If the shared characters are _observations_, they can't 
also be interpretations.  In my question above, I assumed that the 
synapomorphies can be objectively recognized; if so, the cladogram can be 
regarded as just a schematic way of showing the groups that share the 
synapomorphies (if that's the right word for this concept, but maybe it's 
not)--it's a "road map" of synapomorphies(?) in the form of a nested 
hierarchy.  If desired, one can assert that this road map shows 
phylogenetic relationships, but other interpretations might be possible.  
Now, GO says that calling these synapomorphies imparts a phylogenetic 
interpretation.  If so, then the inference of phylogeny is an integral 
part of the definition of synapomorphy, and it is not just an 
observation.  Would there be a way to label shared derived characters 
without incorporating such an interpretation to them?

Relative to the last question, is it possible to speak of characters that 
occur in only a few taxa, without calling them _derived_ characters?  Are 
all derived characters necessarily synapomorphies?  In other words, is 
the term "derived character" meaningless without an assumption of 
phylogenetic significance?  If it is, what term could be used in its 
place that wouldn't incorporate such an assumption?  (I think this is 
almost the same question as the first.)

If synapomorphies are based on cladograms, then aren't they all "real," 
in the context of the cladogram that gave rise to them?  Or, do 
synapomorphies exist "out there," and we're just trying to identify them? 
 Are synapomorphies part of the real world, or are they only parts of 
cladograms?  In the latter case, synapomorphies could be incorrect, but 
in the former, they could not.  However, they could be incorrectly 
_identified_, in which case, my original comment/question (the first one 
relative to Chip Pretzman's posting) was not incorrectly stated.

Honest, I'm just trying to figure this out.  Maybe this is a case of old 
dogs having a hard time learning new tricks.


*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu