Phylogeny and biogeographic history of the cyprinid fish genus Carassius (Teleostei: Cyprinidae) with focus on natural and anthropogenic arrivals in Europe

Freshwater fishes of the genus Carassius, widespread throughout Europe and Asia, are important aquaculture fishes and include the world's most important pet fish, the goldfish. The high morphologic similarity between the species, however, has up to now prevented reliable conclusions on their taxonomy, biogeography and introduction history. A phylogeny of the fish genus Carassius based on the cytochrome b sequence of 404 specimens collected from aquaculture and open water localities across Eurasia identifies most of the presently recognised species as monophyletic lineages, but also that at least one lineage exists that does not correspond to any described species. Within Europe, feral populations of Carassius auratus occur mainly in the Mediterranean area and Great Britain, while Carassius gibelio is found in most of non-Mediterranean Europe and some localities in Italy. Carassius langsdorfii has very scattered points of occurrence in at least six European countries. C. auratus and C. langsdorfii are not native to Europe. The populations of C. gibelio in eastern Central Europe and parts of Eastern Europe are considered as resulting from a natural postglacial range expansion, while the rest of Europe was colonised due to anthropogenic impact. The presence of diploid (2n=100) as well as triploid (3n=150) specimens in the three most widespread species indicates that ploidy level is not a character to identify the species of Carassius. A remarkably low genetic divergence in C. gibelio can be the result of clone selection in the gynogenetic populations. In general, our data present the first comprehensive overview about the genus Carassius in Europe based on genetic data. ► We made phylogeny and biogeography of the genus Carassius in Europe. ► We analysed mtDNA of 404 individuals. ► Altogether 6 mitochondrial lineages were identified. ► Ploidy level is not related to particular lineage. ► Results suggest the existence of one undescribed lineage within the genus.