Butterflies poke holes in DNA barcodes
Mixing subspecies make problems for genetic fingerprinting scheme.
A study of butterflies has highlighted a hotly debated glitch in DNA barcoding - a scheme by which some researchers hope to quickly catalogue vast numbers of species. Biologists sampling Karner blue butterflies have found that genetic scans failed to identify the endangered animals.
Read the story here.
Comments
Ms. Hickey interviewed me for this news article, and she neglected to include the two points that I stressed most during our phone conversation:
First, DNA barcoding is aimed at identifying specimens at the species level, not sub-species. None of the practitioners or supporters of DNA barcoding think of it as a tool for distinguishing among subspecies.
Second, any analytical technique will seem to "fail" when it tries to detect patterns of too fine a scale. Limits of resolution are universal in science. It is not surprising, or particularly noteworthy, to discover that a technique cannot resolve patterns at levels of resolution below which it was intended. This inability is not an inherent weakness of the technique – it is a misapplication of the technique.
I also pointed out to Ms. Hickey that the authors of the original article did not criticize or even use the label “DNA barcoding” in describing their technique. They only pointed out that single gene regions could be misleading at the subspecies level, a fact that is understood by virtually all biologists and undisputed by all advocates of DNA barcoding. It was therefore disappointing to see Nature creating strawmen that can be easily knocked down, for the purpose of creating a scientific controversy where none exists.
The Consortium for the Barcode of Life welcomes open discussion of barcoding, its value and its limitations. We hope that Nature is similarly interested in open and well-informed scientific discourse.
Posted by: David Schindel, Executive Secretary, Consortium for the Barcode of Life | February 27, 2006 07:05 PM
Single gene tag as a marker to classify eukaryotes is not going to be very successful, the rate of extinction of butterflies has nothing to do with mutations, it is rather related to environmental change.
Posted by: M M Fawade | February 28, 2006 08:57 AM
Hello - the editor here. It's always a pleasure to hear from scientists that we've talked to for news@nature stories on the blog, and I would like to briefly reply to Dr. Schindel.
While it is true that the paper in question does not use the term 'DNA barcoding' (using instead the more general term 'molecular markers'), the authors of the work presented their study explicitly as a precautionary tale against barcoding in both interviews with Hannah and when presenting results at the Evolution meeting in June. The fact that the work was presented as "DNA Barcoding: Boon or Boondoggle?" suggests that there is indeed a controversy here.
As it says in the story many people have been aware of the difficulty in determining sub-species using a single gene marker - this is simply one more note of caution.
I'm happy with Hannah's reporting on this story, and also very happy that Dr. Schindel has decided to use this forum to clarify his views. We plan to continue covering all aspects of this fascinating topic in future.
Nicola Jones.
Posted by: nicola jones | March 1, 2006 03:52 PM
Regarding the utility of DNA barcoding, the findings with Melissa blues are unremarkable, as there are cases in all animal groups studied so far in which barcoding narrows identification to a few closely-related species, but no further. It may be helpful to point out that DNA barcoding is an instrument, not a theory. Cases of partial resolution do not "disprove" barcoding or invalidate its use. In fact, one application of DNA barcoding will be to quickly highlight such cases which may be biologically interesting as they likely represent recent speciation, ongoing hybridization, or synonymy.
More detailed commentary on this item is posted on The Rockefeller University Barcode Blog http://phe.rockefeller.edu/barcode/blog/
Posted by: Mark Stoeckle | March 28, 2006 03:39 PM