[Taxacom] cladistic analysis of characters with variable presence

John Grehan jgrehan at sciencebuff.org
Thu Jul 14 13:28:45 CDT 2011


I would agree that it's a polymorphic situation, but it's not just that there is polymorphy, but whether there is a cladistic basis to treating population differences in frequency of occurrence of one of the morphs as primitive or derived. 

I would not have a problem if something was absent from the outgroup, and then in various percentages of individuals for ingroup taxa and that the presence, regardless of percentage occurrence in the population, was nevertheless treated as a derived condition. It is the varying percentages themselves that is the problem - whether a population percentage can be assumed a priori to represent a stable condition throughout the existence of each ingroup taxon.

But I will check out those papers to see if they address this question. Thanks

John Grehan

-----Original Message-----
From: Sergio Vargas [mailto:sevragorgia at gmail.com] 
Sent: Thursday, July 14, 2011 2:21 PM
To: taxacom at mailman.nhm.ku.edu; John Grehan
Subject: RE: cladistic analysis of characters with variable presence



Hi,

Isn't this a simple case in which one character is polymorphic in one or more species?

if so, there are plenty of ways to code polymorphic characters. Check the following articles:

Wiens, J., 1995. Polymorphic characters in phylogenetic systematics. Syst Biol 44, 482-500.

Wiens, J., 1999. Polymorphism in systematics and comparative biology. Annu Rev Ecol Syst 30, 327-362.

sergio


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.



-- 
Sergio Vargas R., M.Sc.
Molecular Geo- and Palaeobiology Lab.
Dept. of Geo-&  Environmental Sciences, Palaeontology and Geobiology
LMU M√ľnchen
Richard-Wagner Str. 10
80333 Munich, Germany
tel. +49 89 2180 17929
s.vargas at lrz.uni-muenchen.de
sergio.vargasr at ecci.ucr.ac.cr

check my webpage:
https://sites.google.com/site/marinemolecularevolution/

check my research ID:
http://www.researcherid.com/rid/A-5678-2011





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