Are phenotypic traits useful for differentiating among a priori Coregonus taxa?

A key for three putative species apparently found in three geographic areas, i.e. Coregonus clupeoides (in Scotland), Coregonus stigmaticus (in England), and Coregonus pennantii (in Wales) given in a recent review was tested quantitatively using 544 individuals from nine populations. The classification success of the key was very low (27%). It was concluded that there is currently no robust evidence for the recognition of the three putative species. Furthermore, the use of phenotypic characters alone to distinguish putative species in postglacial fish species such as those of the genus Coregonus that show homoplasy in many of these traits is questioned. In the absence of further evidence, it was concluded that a single highly variable species best describes the pattern of phenotypic variation in these U.K. populations. On this basis it is argued that taxonomic subdivision of U.K. European coregonids is inappropriate and that Coregonus lavaretus should prevail as the species name applicable to all populations.