Molecular taxonomy: on way out?

John Grehan jgrehan at SCIENCEBUFF.ORG
Mon Jul 18 09:49:21 CDT 2005

> Behalf Of Richard Pyle
> I believe the problems with molecular
> taxonomy are not so much with the molecules themselves, but with the
> limited
> number of them we read, and the ways in which we interpret them for
> inferring phylogenetic histories.  

I would agree with both of these only my view on the way we interpret
them may differ with most. I accept that DNA sequence data can track
phylogeny, the 'evidence' at least being that it can (but not always)
match well substantiated morphological phylogenies, and that it can
track experimental lineages (e.g. bacteria cultures) which may be
extrapolated to long-term lineages. The question is why such mismatches
occur. One possibility is that DNA sequences are measures of overall
similarity (even though the cladistic mimicry method) just as
non-cladistic phenetic methods were overall measures of similarity for
the totality of characters. I would assert that the most reliable
sequences are those that are involved in the evolution of derived
morphological features. This would mean that the matching of sequences
might be broken up all over the genone as a particular uniquely shared
character (such as the ability to make a closed mouth smile) might
involve a complex of genetic elements being brought together in the
developmental process.

> The question to ask as a champion of morphological taxonomy is: "Is
> any information useful for inferring evolutionary relationships that
> be
> interpreted from morphology that is not, somewhere, somehow, also
> represented in the genome?"  Whether or not at this point in history
> have
> the technology and wisdom at our disposal to accurately extract the
> genomic
> information and interpret it correctly, is an entirely separate

I agree and my comments above reflect that.

> Bear in mind that I make this point as a classically-trained,
> morphology-based alpha-level taxonomist, who has yet to base a
> assertion on molecular data.

I have some of the same 'deficiency' although I not even
classically-trained as I completely or mostly lack formal (classroom)
training in the subjects I go on about most (systematics, evolution, and
biogeography - although in the latter I did get exposure to a graduate
plant geography class that bored me to death being nothing more than a
complication of dispersal story after dispersal story). 

John Grehan

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