[Taxacom] cladistic analysis of characters with variable presence

[John Grehan]

This question is directed to any on this list who work with cladistics
and feel they may be able to comment. 

 

A recent paper on primate anatomy and phylogeny did a cladistic analysis
for characters where the derived character states were variable in the
population of each species. Thus, character A might have a derived state
that occurred only in the in-group, but in 20% of individuals for taxon
1, 50% of individuals of taxon 2, and 90% of taxon 3. These taxa were
coded such that species with a higher proportion of individuals with the
derived state were coded as being more derived.

 

My question is whether the varying proportions of a character state in
different species can be considered to represent a phylogenetic signal -
i.e. that they are a constant of the taxa involved and invariable over
time so those proportions represent a shared derived state. Intuitively
I think this would not be cladistically valid, but rather an artifact of
population dynamics at any one time. Someone must (?) have commented on
this in the literature - in which case I would be very interested to
know those views.

 

John Grehan 

 

Dr. John R. Grehan
Director of Science and Research
Buffalo Museum of Science
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