[Taxacom] Molecular data and synapomorphies

John Grehan jgrehan at sciencebuff.org
Mon Dec 1 09:53:16 CST 2008

> From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-
> bounces at mailman.nhm.ku.edu] On Behalf Of Richard Zander

> Comment: What happens in that if you have a terminal group of six
> exemplars, the ones with shared traits of any sort will pop out first
> the cladogram and the ones without any additional shared apomorphies
> tacked on terminally, even if they share nothing more than traits that
> put them in the groups. I've done what John did and found exemplars of
> different genera paired as sister groups on the basis of no shared
> beyond being crowded together.

Which makes my point - that parsimony analysis of molecular data can
produce nonsensical results - results that have no empirical cladistic
support - which is why parsimony does not equal cladistics (as quite a
few molecular systematists have asserted).

> Alan DAvid Forrest:
> In this case molecular data are just another form of data.
> between data types requires analysis of what causes the incongruence,
> not rejection of one data in favour of another based on a priori
> preferences.
Molecular data are based on a few exemplars and, if
> reliable, 

I note the caveat. 

> Combining analyses of evolutionary taxonomy (recognizing paraphyly and
> giving apposite rank to evolutionary novelties) and molecular analyses
> (genetic continuity) gives a good result that maximizes evolutionary
> information in a classification.
But in the case of human origins they appear to give a morphologically
nonsensical result

John Grehan

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