Reptile taxonomy has been upended in recent decades by studies that use mitochondrial DNA—and only mtDNA—to reorganize and subdivide existing species into new groups. In a point-of-view piece for Herpetological Review exploring the usefulness and validity of subspecies as a concept, David Hillis argues against this practice, pointing to a mismatch between mtDNA and intergradation zones, and new studies looking at nuclear gene flow that disagree with mtDNA findings, thanks to which taxonomic changes based on mtDNA are beginning to be reversed. [Andrew DuBois]