Open Nomenclature in the biodiversity era

1. The uncertainty or the provisional status of a taxonomic identification can be expressed by a set of terms and abbreviations known as Open Nomenclature (ON) qualifiers. This approach is widely applied across biological disciplines, and a high amount of biodiversity data left in ON can be found in literature and data bases. However, there is no consensus about ON qualifiers and their meaning. 2. The use of ON qualifiers has been reviewed in order to provide a summary and guide to current practice in zoology. Some recommendation is given to avoid inconsistencies or vagueness. A flow chart is proposed to clarify the sources of uncertainties during identification and to facilitate the application of ON qualifiers. 3. This review provides a guide for taxonomists and ecologists currently involved in biomonitoring and biodiversity programmes, as well as for researchers dealing with biodiversity data infrastructures and tools, offering a starting point for a methodological harmonization.