[Taxacom] Underlying synapomorphies

[Torbjørn Ekrem]

I am not sure I understand your specific question here, but the idea is 
that if a proportion of unrelated members of a larger group show the 
plesiomorphic character alternative for a complex character (indicating 
multiple secondary reductions), the most parsimonious solution will be 
if the apomorphic character alternative is regarded as a underlying 
synapomorphy for the group as a whole. Thus - the potential of having 
the complex character is what counts. As far as I know it was intended 
to be used on closely related groups to ensure homologous structures. 
Underlying synapomorphies certainly are problematic to use as arguments 
in phylogenetic analyses a priori, although there are examples where 
using them as explanations a posteriori perhaps is not too bad (for 
instance the multiple development and loss of wings in stick insects, 
see Whiting et al. 2003, 
http://www.nature.com/nature/journal/v421/n6920/full/nature01313.html).

Also, some authors have argued that the plesiomorphic character 
alternative should be used when coding polymorphic characters for 
phylogenetic analysis (e.g. Kornet & Turner. 1999. Syst. biol. 48: 
365-379). Is this really different from accepting underlying synapomorphies?

For those intersted, here is the abstract of Sæther's 1979 work: 
http://www3.interscience.wiley.com/journal/119604765/abstract?CRETRY=1&SRETRY=0

Torbjørn

-- 
Dr. Torbjørn Ekrem
Vitenskapsmuseet, NTNU		
Seksjon for naturhistorie	
7491 Trondheim			

Museum of Natural History and Archaeology
Norwegian University of Science and Technology
NO-7491 Trondheim, Norway

Tel: +47 73 59 78 12
Email: Torbjorn.Ekrem at vm.ntnu.no
Web: www.ntnu.no/~torbjoe



Bob Mesibov skrev:
> Can you tell us more? For example, could a cephalopod-and-vertebrate
> style of eye be regarded as an underlying synapomorphy in Gastropoda -
> unexpressed, but possible within the lineage including both cephalopods
> and vertebrates?
>