DNA and all that

Dirk Albach albach at GMX.NET
Thu Feb 6 09:00:57 CST 2003


Don,

don't worry about the DNA bandwagon rolling over traditional taxonomy. One
can't live without the other. Traditional taxonomy needs DNA characters for
hypothesis testing. And molecular systematics needs traditional taxonomy for
identifying what they are sequencing. Just look at how many misidentified
species in molecular analyses are reported (Taxon 51(4): p.696 for a recent
example) and based on my own experience this is just the tip of an iceberg, to
which I unfortunately contributed myself at the beginning of my Ph.D. thesis.
This shows the importance of vouchers for DNA sequence - and those able to check
them!

Dirk

> 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.
>

--
Dr. Dirk Albach
Botanisches Institut der Universit├Ąt Wien
Rennweg 14
1030 Wien
Austria

http://www.speedwell.de




More information about the Taxacom mailing list