The researchers took a large sample of Pheidole- a common, diverse ant genus found in warmer regions worldwide- from a Brazilian forest reserve, sequenced the mitochondrial COI gene, compared morphogical identifications with identifications suggested by the genetics, and then compared the genetics against known, identified Pheidole DNA. Not a single unknown sample came within 4% of matching an identified reference. That’s actually kind of amazing. Ants are tremendously diverse, and a great many species remain to be discovered.
While the notion we can infer species identity from a snippet of DNA seems simple enough, in practice DNA barcoding remains impractical. This is especially true in large understudied groups. Without a well-curated reference database, most mystery samples will fall between the cracks.
I am not making an argument against barcoding. The technique shows great promise when wedded to a strong taxonomic foundation. But that’s just it. The taxonomic foundation- knowing what species look like, where they are found, and which Latin names apply to them- is a prerequisite for all the rest, and it’s still woefully inadequate.
source: Ng’endo RN, Osiemo ZB, Brandl R. 2013. DNA barcodes for species identification in the hyperdiverse ant genus Pheidole (Formicidae: Myrmicinae). Journal of Insect Science 13:27.