Barcoding (animal) life

Richard Zander Richard.Zander at MOBOT.ORG
Tue Feb 4 07:10:58 CST 2003


Great statement by A. Mitchell . . . we needed a clear political exposition
on the subject.

Note the figure mentioned of 1 billion dollars. This is not for sequencing
all the genes of all taxa, but for sampling. Samples don't include all the
genetic info we need and don't include important associated phenological,
ecological, biogeographical info.

What (selected) small samples do (and this is indeed marvelous!) is
approximately match our general intuitive ideas of evolutionary
relationships. But that's all. Demonstrable reliability is lacking for DNA
results in most cases for resolving actual problems, such as (1) certain
questions of relationship not soluble with morphology and (2) selection of
one solution when relationships implied by morphology and DNA, or by
different genes, conflict.

This is in addition to the usual horrors of sample error (wrong sequences),
dubious alignment, model choice when there are reasonable alternatives, and
differential gene histories, all of which can reduce the chance of being
correct.

Our main problem is that molecular analysis remains a crap shoot. Take any
four taxa. There are three arrangements. There is usually some support (in
numbers of steps) for all three arrangements. How much MORE support is
needed for one arrangement over the other two for it to be a reliable
inference of the gene tree? For parsimony results, this is usually hidden in
present publications or mystically presented in terms of bootstrap
proportions or Bremer support, neither clearly understandable in terms of
relative support over immediate alternative arrangements.

Consider ((AB)C), ((AC)B) and ((BC)A) as three sides of a die. The die is
rolled and ((AB)C) came up. There's 1 billion dollars being bet. Who won?


______________________
Richard H. Zander
Bryology Group
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166-0299
richard.zander at mobot.org <mailto:richard.zander at mobot.org>
Voice: 314-577-5180



-----Original Message-----
From: Andrew Mitchell [mailto:mitchella at NU.AC.ZA]
Sent: Tuesday, February 04, 2003 2:09 AM
To: TAXACOM at USOBI.ORG
Subject: [TAXACOM] Barcoding (animal) life
Hebert et al. estimate that
it would take $1 billion to do the job they propose, although costs for
these large projects have a way of blossoming as they progress. What did
you think, that this money was going to be deducted from your budget for
2004?
Tel:  +27 (0)33 260 5815
Fax: +27 (0)33 260 5462

http://www.nu.ac.za/biogen/mitchell.htm




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