[Taxacom] Derived characters (was: Evolution of human...)

[John Grehan]

As any cladistic text book has the answer and has done so for years and years I don't see the point in asking me unless you have a problem with something. We also go to some great length to explain our procedure in the Lehtonen et al reply.

If a character is present in the ingroup and the outgroup it is uninformative for relationships within the ingroup since it could represent a primitive retention. That is why we restricted character states to those only found (or almost so) in two or more members of the ingroup. These could be hypothesized as having evolved in the ancestor of one or members of the ingroup.

John Grehan

-----Original Message-----
From: Sergio Vargas [mailto:sevragorgia at gmail.com] 
Sent: Tuesday, August 09, 2011 3:02 PM
To: taxacom at mailman.nhm.ku.edu; John Grehan
Subject: Derived characters (was: Evolution of human...)

Hi,

I would also like to know the answer, Don knows it already (apparently) 
but I don't think the rest of us do.

So, How do you "demonstrate" that a character is "derived"?

I would also like to know how does restricting the data matrix to 
characters exclusive to the ingroup affect the outcome of the analysis, 
and whether this introduces a bias or not. If I am not wrong the only 
problem with characters shared between the ingroup and the outgroups is 
that the polarity of this particular character would be equivocal, but 
the character it self could be used for phylogenetic inference.

txn

sergio

-- 
Sergio Vargas R., M.Sc.
Molecular Geo- and Palaeobiology Lab.
Dept. of Geo-&  Environmental Sciences, Palaeontology and Geobiology
LMU München
Richard-Wagner Str. 10
80333 Munich, Germany
tel. +49 89 2180 17929
s.vargas at lrz.uni-muenchen.de
sevra at marinemolecularevolution.org

check my webpage:
http://www.marinemolecularevolution.org

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