paraphyly

SKÁLA Zdeněk skala at INCOMA.CZ
Mon Aug 5 09:44:12 CDT 2002


-----Original Message-----
From: pierre deleporte [mailto:pierre.deleporte at UNIV-RENNES1.FR]
>I think that answering the following question could help solving our
>discussion :
>what exactly will a cladist classifier do with a hierarchy of gaps ? With a
>"5 point gaps", he names a monophyletic group above the gap (the
>eclecticist will add: putting a stop to a paraphyletic group below,...
>I see both the cladist and the eclecticist selectin "significant gaps" for
>naming taxa.
>But inside this selection, the eclecticist decides which gaps (the larger
>maybe) are worth naming a special kind of groups (paraphyletic groups),
>when the cladist does not.
>Isn't this a difference ?

I don't think so. In fact, better description of what eclectic classifier does (instead of putting "stops" and "starts" of a taxon) is: (1) split the cladogram at the "significance level 5" and then name all the pieces (both paraphyletic and holophyletic); (2) split these pieces at the "level 3" and again name all the pieces. Simple, isn't it?
Your original point, if I remember well, was that the eclectic (=classical) definition of monophyly generates less parsimonious taxa-delimitation process since there is some additional criterion required that is not needed in the cladistic procedure. As a result of our discussion, we can see that the criteria are the same: cladogram topology and the significance of gaps. Indeed, the algorithms for taxa delimitation differ between cladist/eclectic procedures; otherwise the output would be the same. 
Best!
Zdenek Skala




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