[Taxacom] Molecular data and synapomorphies

[Richard Zander]

I wrote:
> 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.

John Grehan said:
But in the case of human origins they appear to give a morphologically
nonsensical result

Comment: Not so. IF indeed humans and oranges are morphologically more
similar to each other than to chimps and gorillas, we can accept the
molecular lineages and simply assert that the evidence indicates that
the shared ancestral line between oranges and humans was similar to
orangs and humans morphologically, and through punctuated equilibrium,
the short branch leading to chimps and gorillas is unresolved. Thus,
both morphology and molecular studies can be combined. Evolution is, of
course, long on theory and short on facts.

*****************************
Richard H. Zander 
Voice: 314-577-0276
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166-0299 USA
richard.zander at mobot.org
Web sites: http://www.mobot.org/plantscience/resbot/
and http://www.mobot.org/plantscience/bfna/bfnamenu.htm
*****************************


-----Original Message-----
From: John Grehan [mailto:jgrehan at sciencebuff.org] 
Sent: Monday, December 01, 2008 9:53 AM
To: Richard Zander; taxacom at mailman.nhm.ku.edu
Subject: RE: [Taxacom] Molecular data and synapomorphies

> 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
in
> the cladogram and the ones without any additional shared apomorphies
are
> 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
data
> 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.
Incongruence
> 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