Distinct genetic isolation between “Kunimasu” (Oncorhynchus kawamurae) and “Himemasu” (O. nerka) in Lake Saiko, Yamanashi Prefecture, Japan, inferred from microsatellite analysis

The possibility of interspecific hybridization between Kunimasu (Oncorhynchus kawamurae) and Himemasu (Oncorhynchus nerka) was investigated in a large number of specimens, in a search for basic data relevant to conservation needs. A Bayesian-based clustering method using five microsatellite DNA loci separated 144 specimens from Lake Saiko, Yamanashi Prefecture, into two genetically distinct groups, corresponding to Kunimasu and Himemasu. Application of a threshold of individual proportion of membership of 0.90, so as to separate hybrids from purebreds, resulted in all specimens except two having high probability of purebred. These results implied that Kunimasu and Himemasu have been maintained as independent genetic entities in Lake Saiko.