[Taxacom] Molluscan phylogeny (overview)

Bob Mesibov mesibov at southcom.com.au
Fri Mar 13 16:38:44 CDT 2009

David Campbell wrote:

"Molecular data don't actually significantly support polyphyly of
bivalves; rather, monophyly versus polyphyly or paraphyly is not
resolved.  I believe the best way to get a good feel for this sort of
thing is to play around a lot with the data yourself.  Don't just run
one analysis on your data.  Rather, keep running various analyses, look
at and adjust the alignments, add in additional taxa, etc.  Groups that
are consistently supported across multiple data sets and analyses are
probably real; the novel result in your latest analysis might not be."

Good advice not only for molecular data, of course. Explains why
systematics is a work in progress.

Nevertheless, it's very rare to see the sentiments in Campbell's last
sentence expressed in molecular phylogeny papers. The usual structure
has long been: we took these data, we did this analysis, and here's the
tree with its branch support values. The bit '...and we suspect from
this that clade A is possibly a true evolutionary lineage, but let's
wait to see what other data suggest' is too often missing.

Reminds me a little of Otto Loewy's remark (can't find the exact quote)
that a drug is a substance which when injected into an animal results in
a paper.
Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery
and School of Zoology, University of Tasmania
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
Ph (03) 64371195; 61 3 64371195
Webpage: http://www.qvmag.tas.gov.au/mesibov.html

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