[Taxacom] Underlying synapomorphies

[Bob Mesibov]

I am now thoroughly confused.  Can I ask you to think about two
examples?

(1) I have 50 species in a genus that I want to 'cladify'. I also have
one outgroup. For a character of interest, the state is 0 for 48 species
and the outgroup and 1 for two species.

So 1 is a synapomorphy for the two species. It could be evidence of
close common ancestry, or parallel evolution. I'll have a better idea
after I look at a lot more characters.

The other 48 species might have the *potential* to exhibit state 1.
Should I call 1 an underlying synapomorphy for the whole genus?

(2) Same 50 species and same outgroup. This time 48 species are state 1,
two species and the outgroup are state '0'.

Looks like '1' is a good synapomorphy for the genus. The two '0' species
might have had character reversals, or maybe they don't belong in this
genus. I'll have a better idea after I look at a lot more characters.

The two '0' species might have the *potential* to exhibit state 1.
Should I call 1 an underlying synapomorphy for the whole genus as
currently circumscribed?

My problem here is that I don't understand how the idea of 'underlying
synapomorphies' can help me in a cladistic analysis. It might help me
interpret the results of an analysis after it's done, but even then
there would be other possibilities. How exactly is the idea useful?
-- 
Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery
and School of Zoology, University of Tasmania
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
Ph (03) 64371195; 61 3 64371195
Webpage: http://www.qvmag.tas.gov.au/mesibov.html