A plea for preregistration in taxonomy

There are notoriously many different definitions of species and methods of species delimitation, forcing taxonomists to make a long range of methodological decisions in species delimitation. Because of this, there are sometimes multiple viable competing methodological paths, which could lead to different ranking (or even grouping) decisions. As a result, it is often unclear what it means for a group to be recognized as a species, the groups recognized as species are not always comparable, and some have even called ranking decisions ‘subjective’. To mitigate the problems this causes for users of taxonomy and taxonomists, we propose that taxonomists across the tree of life should start preregistering their research design and criteria for species delimitation in advance of their research. We argue that even if it were to require additional effort, preregistering taxonomic research would strongly benefit taxonomy in the long term, by increasing the transparency and usability of taxonomic outcomes and by reducing the need for ad hoc methodological decisions.