[obol] DNA bar coding

[John Deshler]

Traditional taxonomists roll their eyes and speak
using nasty expletives when they read all the hype
about DNA bar-coding and all the new species to be
found.  Paul Hebert of Canada is bar-coding's main
proponent and it appears he would like to redraw the
entire taxonomic tree of life using this
quick-and-dirty method.  Perhaps then all the species
could be renamed;  Hebert's Nutcracker, Hebert's
Woodpecker, Hebert's Beetle 328694.

Serious taxonomists continue to use a combined
approach, morphological and molecular.  

Attempting to define species, especially cryptic ones,
using a single 650 base pair sequence of mitochondrial
DNA is indeed controversial and I have heard one
serious taxonomist say it is utterly flawed
(expletives omitted), and read others who appear to
have proved it so.  Nevertheless, Hebert is a serious
scientist not to be easily dismissed.  A 650 base pair
sequence is a very short stretch of DNA.   Yet, the
cytochrome gene of which it is a part has indeed been
used in all types of DNA analysis.  But using it to
discriminate between closely related individuals has
been shown to be its downfall.

Part of the problem with the DNA approach is that
virtually anyone can willy-nilly enter a sequence into
the master database of DNA sequences and label it as a
given species.  Yes, anyone.  So the master database
is a bit wonky.

Another problem is that bar-coding somewhat ignores
the working definition of a species from Ernst Mayer: 
"groups of actually or potentially interbreeding
natural populations which are reproductively isolated
from other such groups".  Everyone understands the
many problems with this definition, but it is still
the most accepted general purpose one.

By the way, the Wikipedia definition falls a bit
short:
"A species consists of individual organisms which are
very similar in appearance, anatomy, physiology and
genetics due to having relatively recent common ancestors."


 
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