The 5 ‘D’s of Taxonomy: A User’s Guide

Much of what has recently been written about taxonomy has focused on negatives in the face of a heterogeneously defined taxonomic impediment. The current review takes a step back from the rhetoric to explicate the modern science of taxonomy with a new practical model, “the five ‘D’s”: taxon discovery, delimitation, diagnosis, description, and specimen determination. Although individual taxonomists may focus more on some of these practices and less on others, taxonomy as a discipline requires all five. Each practice depends on the one prior and necessarily leads to and often overlaps with the one following. In fact, the first ‘D’—taxon discovery—has its origin in the last, specimen determination, thereby closing a recursive loop of taxonomic progress. Hopefully users of taxonomy—almost all biologists—will appreciate a fresh perspective on a foundational science. Several recommendations are offered to biological researchers to account for the iterative improvement, and hence necessary change, in the taxonomy and nomenclature of their study organisms.