[Taxacom] very nice opinion article in today's Zootaxa

Richard Zander Richard.Zander at mobot.org
Fri Sep 16 17:11:24 CDT 2011


Exactly. The question is whether a one specimen sample will suffice for a species description. YES, that the specimen is connected to a systematic morphological study of many specimens is importanat, but it is not support or refutation of the morphological conclusions. Only if the molecular analysis can stand on its own can it either support or refute another concept.
 
_______________________
Richard H. Zander
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166 U.S.A.
richard.zander at mobot.org
 

________________________________

From: taxacom-bounces at mailman.nhm.ku.edu on behalf of Doug Yanega
Sent: Thu 9/15/2011 5:05 PM
To: TAXACOM at MAILMAN.NHM.KU.EDU
Subject: Re: [Taxacom] very nice opinion article in today's Zootaxa



Among the references that John Shuey listed, I noted the following
one, which I had not seen before:

>Burns, J. M., D. H. Janzen, M. Hajibabaei, W. Hallwachs and P. D. N.
>Hebert 2007. DNA barcodes of closely related (but morphologically
>and ecologically distinct) species of skipper butterflies
>(Hesperiidae) can differ by only one to three nucleotides. Journal
>of the Lepidopterists' Society, 61:138-153.

If that title is taken at face value, would this not invalidate the
premise that patterns of sequence divergences on a tree can be used
to recognize species boundaries? The implication of the parenthetical
phrase above is that morphology and ecology MUST be given primary
credence, which runs contrary to what many seem to be preaching
and/or practicing; that is, if it is admitted that barcodes alone are
insufficient for the task of species delimitation, then what is the
justification for studying and promoting barcodes alone? If good
species can differ by one base pair, then (a) how could one *ever*
know whether a single base pair difference is or is not indicative of
a species-level difference without morphology to back it up, and (b)
can we not therefore assume that there must be many cases where
species have ZERO base pair differences (i.e., that barcodes are not
unique, as claimed)? And, given that subspecies are typically
morphologically distinct, then, by extension, barcodes could never
help distinguish species from subspecies - only ecology (i.e.,
breeding experiments, etc.) would be definitive - in which case
barcoding is of rather more limited utility than its proponents
generally claim; it would seem to come into play only if one has two
otherwise very similar sets of organisms whose barcodes are
*dramatically different*. That's certainly potentially useful in some
contexts, but far from a solution to the "taxonomic impediment" as
was initially claimed by Hebert, and only serves to enhance my
already skeptical view of the barcoding enterprise.

Or am I missing something here?
--

Doug Yanega        Dept. of Entomology         Entomology Research Museum
Univ. of California, Riverside, CA 92521-0314        skype: dyanega
phone: (951) 827-4315 (standard disclaimer: opinions are mine, not UCR's)
              http://cache.ucr.edu/~heraty/yanega.html
   "There are some enterprises in which a careful disorderliness
         is the true method" - Herman Melville, Moby Dick, Chap. 82

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