DNA and all that

Don.Colless at CSIRO.AU Don.Colless at CSIRO.AU
Thu Feb 6 13:05:05 CST 2003

This thread must be thinning fast, but h'with my 2 cents' worth. The group
of Diptera on which I currently work has about 35 species in 2 (arbitrary!)
genera, and I have on average about 30-40 specimens per species. It would be
great to have DNA profiles of the several species. It would, especially,
help associate males and females, which I can't at present do for some
species. It could also provide a competing estimate of phylogeny, for
comparison with a morphological one, with possible improvements in both (I
join Richard Zander in his distrust of trees!). But, as several folk have
pointed out, in reality the work involved would be impossibly demanding of
time and money.

 Occasionally we see the magic word "sampling" injected into the discussion,
as a way to reduce the load - but samples of what? Of sequences from
genomes, perhaps; but the possible traps are obvious. Or of specimens from
taxa - which could obviously help enormously IFF we already had the taxa
delineated and suitable specimens in the freezer. The fallacy here is
obvious enough: the "DNA taxonomy" is supposed to provide the delineated
taxa!. in fact, what has been suggested (in the TREE article at least) seems
to be something along the lines of current bacterial "shotgun" taxonomy - of
genomes, not species.

A well-trained "taxonomic eye" is a tool beyond price, in that it can run
over a couple of hundred specimens and sort them quite rapidly and pretty
accurately into groups, which can then be attacked individually and quite
efficiently. To "sample' the mass of specimens would no doubt pick up the
common species, but very likely miss the less common.

I join many of my colleagues in the fear that the DNA bandwagon will roll
(financially) over traditional taxonomy; but we can just hope that good
sense will eventually prevail - especially when folk who need the services
of a REAL taxonomist can't find one! A propos, there was a wonderful article
in Taxon many years ago - entitled, I think "The Disappearance" (my copy was
lent or stolen). It's worth hunting for.

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