use of morphological characters

Biology at Biology at
Tue May 2 08:39:11 CDT 2000


I was trying to find literature on alternative applications of morphological
characters for cladistic analyses, in particular, papers discussing binary vs.
multistate characters, independence of characters, splitting of
characters, etc. All I could find was Pimentel & Riggins 'The nature of
cladistic data' (1987), which didn't really answer the problem I had in mind.

To illustrate my quest: Instead of coding certain features of appendage A (of an
arthropod) as a multistate character, it is also possible to split the character
states into separate characters. For example, my first character
would be: appendage A = absent/present. 2nd character = whole appendage
long/whole appendage short. 3rd character = reduced number of segments/number of
segments not reduced. 4th character = proximal segments narrow/proximal segments
dilated.

In my opinion, this method is highly questionable. First to note, all taxa with
state 'absent' for the 1st character would have to be scored as '?' or '-' for
the following characters (2-4). As far as I know, PAUP fills in the
missing states with the most parsimonious solution, which would be contradictory
in this case (an absent appendage cannot be short).

Secondly, I would suspect the above characters, or at least some of them, to be
dependent, e.g. the length of the appendage could be ontogenetically connected
with a reduction of segments, etc.

Any opinions?

Also, literature tips on this matter are much appreciated!

Stefan

Stefan Koenemann
Dept. of Biological Sciences
Old Dominion University
Norfolk, VA 23529-0266
USA
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Email: biolgrad at odu.edu
http://www.odu.edu/~jrh100f/sk/




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