[Taxacom] inapplicability of mtDNA barcoding to insects

Thomas G. Lammers lammers at uwosh.edu
Thu Sep 27 12:47:49 CDT 2007


As far as I'm concerned, any study utilizing organelle DNA is a house built 
on sand.  Those genomes had very little to do with the species' evolution; 
at most they were along for the ride and might by chance reflect the true 
phylogeny.  I wouldn't bet the farm on it.

At 12:07 PM 9/27/2007, Doug Yanega wrote:
>This may be old news to many, but I just came across this paper today:
>
>T.L. Whitworth, R.D. Dawson, H. Magalon, E. Baudry (2007) DNA
>barcoding cannot reliably identify species of the blowfly genus
>Protocalliphora (Diptera: Calliphoridae). Proceedings of the Royal
>Society B: 274: 1731-1739
>[http://www.journals.royalsoc.ac.uk/content/tu21831k825kv655]
>
>This excerpt from the abstract is pretty remarkable:
>
>Here, we investigated the performance of barcoding in a sample
>comprising 12 species of the blow fly genus Protocalliphora, known to
>be infected with the endosymbiotic bacteria Wolbachia. We found that
>the barcoding approach showed very limited success: assignment of
>unknown individuals to species is impossible for 60% of the species,
>while using the technique to identify new species would underestimate
>the species number in the genus by 75%. This very low success of the
>barcoding approach is due to the non-monophyly of many of the species
>at the mitochondrial level. We even observed individuals from four
>different species with identical barcodes, which is, to our
>knowledge, the most extensive case of mtDNA haplotype sharing yet
>described. The pattern of Wolbachia infection strongly suggests that
>the lack of within-species monophyly results from introgressive
>hybridization associated with Wolbachia infection. Given that
>Wolbachia is known to infect between 15 and 75% of insect species, we
>conclude that identification at the species level based on
>mitochondrial sequence might not be possible for many insects.
>
>I'm curious to know how many other studies have come to similar
>conclusions, and how the barcoding community is responding to this
>EXTREMELY serious issue - it could potentially invalidate almost
>every barcoding study ever performed with insects (a brief glance at
>a few such studies indicates that screening for Wolbachia is not part
>of barcoding protocol).
>
>Sincerely,
>--
>
>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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Thomas G. Lammers, Ph.D.

Associate Professor and Curator of the Herbarium (OSH)
Department of Biology and Microbiology
University of Wisconsin Oshkosh
Oshkosh, Wisconsin 54901-8640 USA

e-mail:       lammers at uwosh.edu
phone:      920-424-1002
fax:           920-424-1101

Plant systematics; classification, nomenclature, evolution, and 
biogeography of the Campanulaceae s. lat.

Webpages:
http://www.uwosh.edu/departments/biology/Lammers.htm
http://www.uwosh.edu/departments/biology/herbarium/herbarium.html
http://www.geocities.com/TheTropics/Resort/7156/lammers.html
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