David's comments on use of DNA in taxonomy

Subject: David's comments on use of DNA in taxonomy
From: John Penhallurick <>
Date: Thu, 13 Aug 1998 14:43:22 +1000
Thanks to David for his contribution to the discussion on taxonymy, and
particularly the role of DNA studies in it.

I disagree,however, with his doubts about the use of DNA, particularly DNA
sequencing.  Most studies using DNA sequencing analyse the cytochrome b gene
in mitochondrial DNA, which appears to give us a reliable and consistent
measure of genetic distance.

Most studies also cite other data. For example, Brooke and Rowe's paper
1996,Ibis,pp.420-432 which recommended the splitting of Pterodroma atrata,
Henderson's Petrel, which breeds on Henderson Island in the Pitcairns, from
Pterodroma heraldica, based the evidence on vocalisations and breeding
season as well as the sequence of 307 base pairs in the mtDNA cyt b gene.
Indeed one of the useful functions of DNA based analysis is that it causes
anatomists to look again at their data.  I think that Sibley & Ahlquist's
DNA-DNA hybridisation work was the first to suggest that the former
Formicariidae should be split into Formicariidae and Thamnophilidae.  Then
when the anatomists looked again at skeletons, they found that one of the
proposed families had a distinctive notch in the sternum which none of the
other family had.

Another comforting thing about DNA sequencing is that it confirms
well-established findings about species limits.  If it was as unreliable as
David claims, it ought to produce false indications of closeness for taxa
that are well removed.  Yet I am not aware of a single such report in all
the ornithoglical literature.

It seems to me eminently plausible that with groups of sea-birds showing
fidelity to particular islands for breeding (and this is exactly what we get
in the case of the proposed splits among Diomedea and  Thalassarche, they
should reveal genetic divergence.

That's my two-penn'orth anyway.

Good birding

John Penhallurick
Associate Professor John M. Penhallurick<>
Canberra, Australia
Phone BH( 61 2) 6201 2346   AH (61 2) 62585428
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