DNA and identifying species has been a lot in the news lately. I found an interesting bit of science here on Deep Sea News about using DNA to identify cryptic species. Cryptic species are not related (not directly, anyway) to "cryptids" or cryptozoology. Cryptic species are those which are very, sometimes impossibly, difficult to distinguish from related species. Birders may grouse (get it?) about all the "little brown jobs," but the situation gets a lot worse when you get to the invertebrates.
As Dr. Holly Bik explains, "A species is a hypothesis." She then writes, "But that doesn’t mean DNA is a magic bullet. DNA provides a new type of evidence for making decisions about species, but that evidence still has to be robustly analyzed and interpreted in the context of historical knowledge (taxonomic classifications and anatomical features of specimens)." Her example here is a genus of sea slugs everyone had thought were pretty well described. Scientists applied "four independent methods of molecular based species delineation" and found that they no longer had two species in the genus: they had 12. There's a good overview here of the process used.
Dr. Bik concludes that the whole species thing is still devilishly hard to sort out (and remember, the species is the most well defined of traditional taxonomic units). It's no wonder people like Dr. Darren Naish advocate giving up on the Linnaen classification system altogether.
Bik closes: "Next time you hear a “global species estimate”, don’t say you believe it, please don’t say you believe it!"