Posts Tagged ‘dna barcoding’

You might recall how much I dislike DNA barcoding.

So you can imagine my frustration when, in spite of my best efforts to mount an empirical demonstration of what a waste of time it is, the technique turns out to be extraordinarily useful.  I’ve been processing sequence data all day from the barcoding gene (COI) for a set of 7 Pheidole species distributed from Costa Rica to Argentina.  The results are in hand, and here are the pairwise genetic distances:


See that blank spot in the middle?  That shouldn’t be there.  If barcoding didn’t work, that is.

For this sample of ants, then, any two individuals will either be genetically similar (the bars at left), or different (at right), without ambiguous intermediates.  So it is relatively easy to predict from the COI sequence whether any two ants belong to the same species.  The gap also demarcates the same divisions I’ve found using traditional morphological characters.  It’s remarkably clean.

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It seems my barcoding rant from last week has caught the eye of Alex Smith of the University of Guelph.  Alex is the force behind numerous DNA barcoding projects, including the pioneering study on Malagasy trap-jaw ants, and I have elevated his reply from the comments:

Hi Alex – happened by myrmecos this morning, saw your essay and the comments that have piled up over the past several days and couldn’t help add my two cents.


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One of the most vociferous debates in taxonomy is over a catchy-sounding concept called DNA barcoding.  Since nearly all organisms carry a version of the COI gene in the mitochondrion, the idea is that the DNA sequence of the gene can serve as a standard identification marker.  A barcode, of sorts.  Of course, the practice only works if species have unique COI sequences.  Which they do, much of the time, and the barcoders consequently have been successful in garnering research money and churning out publications.

So what’s the problem? (more…)

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Wired on DNA barcoding

Count me among the skeptics who find that “DNA barcoding” is oversold for what it actually delivers.  Nonetheless, here’s a well-written piece about the approach in Wired.

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