A taxonomic revision of ten whitefish species from the lakes Lucerne, Sarnen, Sempach and Zug, Switzerland, with descriptions of seven new species (Teleostei, Coregonidae).

The taxonomy of the endemic whitefish of the lakes of the Reuss River system (Lucerne, Sarnen, Zug) and Lake Sempach, Switzerland, is reviewed and revised. Lake Lucerne harbours five species. and , are described. Haack, 1882, Fatio, 1885, and Nüsslin, 1882, are redescribed. Genetic studies have shown that and are composed of several distinct species endemic to different lakes. The names and are restricted to the species of lakes Sempach and Zug, respectively. The whitefish populations previously referred to as and from Lake Lucerne are described as and , respectively. Furthermore, the whitefish from Lake Zug that were previously referred to as are described as . A holotype is designated for that was previously one of two syntypes of . The other syntype is retained for . is described from Lake Zug, and and from Lake Zug are extinct. Finally, we describe from lakes Sarnen and Alpnach. from Lake Sempach shows strong signals of introgression from deliberately translocated non-native whitefish species, which questions if the extant population still carries a genetic legacy from the original species and thus may need to be considered extinct. is genetically partially of allochthonous origin, closely related to the radiation of Lake Constance. It is therefore compared to all known and described species of Lake Constance: Bloch, 1784, Nüsslin, 1882, Kottelat,1997, and Gmelin, 1818.