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

Doug Yanega dyanega at ucr.edu
Thu Sep 15 17:05:18 CDT 2011


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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