Synonymy in Taxonomy: Where Is the Evidence?

The International Code of Zoological Nomenclature provides, under its principle of priority, that a name that has been declared a synonym of an earlier proposed species remains contestable and open to future research. However, as the Code is concerned with nomenclature and not with taxonomic concepts, it places no restrictions on declarations of synonymy, enabling them to be published without supporting evidence. This freedom, which is at the core of the synonymy ‘problem’, contributes to taxonomic inflation and constrains estimates of diversity. From a theoretical perspective, evidence in an unsupported declaration devolves to that of one specimen, the holotype. Furthermore, in the absence of other evidence, the declaration further devolves to one of opinion, with readers left to judge its value based on their knowledge of the declarator. This approach, based on typification, is contrasted with one in which a species exists independently of our perception and is viewable as samples of its local populations. Rather than an arbiter of usage, the holotype then acts only as a referent to its local source population, whose properties define much of the species concept. A worked example of these concepts using data from the planktonic Foraminifera supports the view that evidence of synonymy lies in the source populations of the holotypes.