Spatio-temporal genetic composition of rosy bitterling Rhodeus ocellatus subspecies in the Himi region, central Japan

The spatio-temporal variation in the hybridization status of non-native distributed rosy bitterlings Rhodeus ocellatus subspecies, Rhodeus ocellatus kurumeus and Rhodeus ocellatus ocellatus, in the rivers of the Himi region, Toyama Prefecture, central Japan was examined. Genetic analyses based on mitochondrial and nuclear DNA showed that individuals with genetic characteristics of both subspecies inhabit these rivers. The molecular phylogenetic tree suggests that such hybrids might have been unintentionally introduced to the Himi region from the Osaka region. Hybridization between the two subspecies was thought to be repeated in the Himi region, and the frequency of occurrence of hybrid individuals showed spatio-temporal variation possibly due to random fluctuations. The detection of the R. o. kurumeus haplotype, which has not been reported in natural habitats, in the Himi region suggests that a genetic legacy remains among individuals artificially introduced to various regions via hybrid individuals.