Scientists from Japan have discovered that the native strain of the wild carp (Cyprinus carpio) in Japan is in danger of extirpation via large-scale introductions of domesticated strains from Eurasia.
In a study published in a recent issue of the journal Molecular Ecology, Kohji Mabuchi, Hiroshi Senou and Mutsumi Nishida conducted a survey of mitochondrial DNA sequences (complete D-loop region) from wild carp collected from 11 localities in Japan.
The authors identified 14 different haplotypes of domesticated carp from Japan, of which 13 haplotypes were deeply nested within a clade consisting of other Eurasian haplotypes.
The significance of this study is that there appears to be large-scale hybridization between Eurasian and Japanese strains of carp within Japan (as a result of 10 million domesticated common carp being introduced into Japanese ecosystems every year until the spread of KHV in 2004).
This dilution of the genotype of the native strain of carp in Japan is worrying, the authors surmise, as ...the Japanese native common carp is the most basal strain of the species identified to date... and ...it is important to conserve this strain in order to maintain the genetic diversity of the species.
For more information see the paper: Mabuchi K, H Senou and M Nishida (2008) Mitochondrial DNA analysis reveals cryptic large-scale invasion of non-native genotypes of common carp (Cyprinus carpio) in Japan. Molecular Ecology 17, pp. 796"809.