Mitochondrial genetic variations in fishes of the genus Carassius from South Korea: Proximity to northern China rather than Japanese Islands?

Carassius carp is one of the most popular freshwater fish as a source of food and aesthetic enjoyment from historical times. However, the species status of this group is controversial owing to extreme morphological variation and various ploidy levels, and therefore, many regional groups still remain to be reconsidered. The taxonomy of the Carassius fish in the Korean Peninsula, previously identified as C. auratus langsdorfi, has long been in doubt because several river basins were isolated from each other by the sea to such an extent that the strong geographic structure of the population may have influenced this fish group distributed over whole peninsula. Here, we suggest some clues to resolve the taxonomic entity of Carassius fish in South Korea using mitochondrial genetic variation in a comparison with those from nearby regions with a view to establishing the phylogeography and genetic structure of population. We found three monophyletic phylogroups (pgA, pgB, and pgC), which interestingly do not relate to C. auratus langsdorfi. Geographically, pgA and pgB were observed only in the westward rivers (WWRs) and southward rivers (SWRs), respectively, except for some marginal locations between the two river groups. pgA, including the haplotypes from Weihai, northern China, shared a common ancestry with C. gibelio. pgC may be a lineage that has been introduced, as shown by the result that it belongs to same clade as goldfish. It is likely that pgB has undergone a distinct evolutionary process after separation from pgA and the population of northern mainland China. Our results suggest the need of further taxonomic studies to elucidate the status of these groups and to assign an adequate taxonomic category to each. And, therefore, pgA and pgB, regardless of taxonomic level, deserve conservation as endemic groups in this region.