Two Simple Ways to Make Taxonomic Diagnoses More Useful

I suggest two ways to make taxonomic diagnoses more useful: they should state overtly (1) what taxa the new one is diagnosed against, I term this the reference group; and (2) how to identify the reference group from others in the higher-level group to which it belongs, I call this more inclusive taxon the recognition group. Making the reference group identifiable within an as-large-as-possible recognition group increases the usefulness of a taxonomic paper. For diagnoses of 313 newly described insect genera, I assess the taxonomic level and number of genera in both reference and recognition groups. The two were identical in almost half of the cases and were at the same taxonomic level, but the reference group was geographically, ecologically or morphologically more restricted in less than 9%, and the recognition group was at a higher taxonomic level in the remainder. When authors explained how to identify the reference group from a larger recognition group, the number of genera from which the new one could be differentiated increased by a factor of more than four. I make a series of recommendations on how diagnoses can be improved based upon analyses of reference and recognition groups.