Striking a balance, weighting and Cladistics

[Pierre Deleporte]

A 10:36 16/02/01 -0500, Thomas DiBenedetto wrote :

>The parsimony criterion deals with the process of sorting
>through the evidence layer, it essentially dictates that one must accept the
>patterns in the evidence that are strongest, i.e. the weight of the
>evidence.

Agreed on general grounds, but the biological debate is : under what
biological criteria do we apply the "parsimony criterion"? What is
considered as providing "evidence" for phylogeny reconstruction? 
OK we will optimize this with parsimony, but what will we optimize and why?

Character state contiguity? Under this or that weighting scheme? Three
taxon statements fitting the cladogram? Grouping by overall similarity?
Optimizing equiprobability of character changes along the branches? 
And why? What do we know of the evolutionary process in order to choose
this or that criterion?

Under what biological criterion do we apply parsimony (or any form of
optimality criterion), and why?
"Parsimony criterion" in itself is not evolutionary biology, as far as I
can understand it... Okkam's razor may be used to cut off an illimited
variety of things (with your permission) under different logics...

Pierre





Pierre Deleporte
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