Molecular taxonomy: on way out?

John Grehan jgrehan at SCIENCEBUFF.ORG
Wed Jul 20 08:56:01 CDT 2005

> Behalf Of Les Watson
> While it has been apparent for about forty years that comparative DNA
> studies would ultimately provide conclusive evidence for understanding
> phylogeny, 

Apparent? I would say claimed.

classifications derived via DNA sequencing will not be
> definitive
> unless the taxonomic coverage is adequate, 

I take the view that even with adequate taxonomic coverage the current
systematic approaches to DNA sequences will not preclude DNA trees from
being phenetic as the cladistic approaches are only mimics. 

and the DNA sampled can be
> confidently assumed represent complete genomes. Many DNA-based
> classifications of plants have failed to meet even the first
> and
> few if any come near to satisfying the second; indeed, those derived
> entirely from chloroplast DNA do not directly represent nuclear
genomes at
> all. Alternative methodologies for phylogenetically interpreting
> comparisons will be easier to evaluate when the basic data are good
> enough.

If this outlook were taken then it would at least substantiate my view
that the current phylogenies are no better than morphology where these
limitations apply.

> Moreover, purported phylogenies are impossible to evaluate as such in
> absence of adequate evidence from character correlations; and even if
> classification truly reflects evolutionary relationships, it is
useless if
> it does not bestow the ability to generalize about the contents of
> in terms of their structure, physiology, ecology, cytology, etc. 

Cheers, cheers. I would add that unless non-DNA sequence characters are
seen to be independent (and therefore non-subordinate) evidence then
there is no opportunity to test out one set against another.

For too
> long,
> people have been peddling revised classifications in the absence,
> operational, new or properly revised group descriptions. 

This reflects the other comments about Science and nature articles which
are truly dreadful in this respect when it comes to hominid taxonomy (I
classify most of these hominid articles as pseudoscience).

John Grehan

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