Genetic constitution and phylogenetic relationships of Japanese crucian carps (Carassius)

The genetic constitution and phylogenetic relationships among the proposed species and subspecies of the crucian carp complex in Japan (Carassius cuvieri, C. auratus subspp. 1 and 2, C. a. grandoculis, C. a. buergeri, and C. a. langsdorfii) were investigated based on analyses of the partial nucleotide sequences of the mitochondrial DNA control region and amplified fragment length polymorphisms of nuclear DNA. Our results demonstrate that C. cuvieri and C. auratus are different entities. However, although several distinct lineages were observed for C. auratus, none corresponded to the proposed subspecies. Moreover, the five subspecies of C. auratus were not necessarily separated genetically from each other. Triploid fish, which are currently classified as a single subspecies (C. a. langsdorfii) but are sometimes treated as an independent species, fell into various clades along with diploid individuals of other subspecies that have the same or similar mitochondrial haplotypes. This suggests that gynogenetic triploid crucian carps distributed throughout the Japanese Archipelago have polyphyletic maternal origins. Our results indicate that Japanese crucian carps are a much more complex assemblage than previously believed.