Genetic relationships between chars distributed around the watershed borders in the eastern Chugoku Mountains , Japan , on the basis of RAPD analysis

Genetic relationships were examined among specimens of a subspecies of a Japanese char, Salvelinus leucomaenis pluvius (‘Nikkoiwana’), distributed around the watershed boundaries in the eastern Chugoku Mountains on the basis of Random Amplified Polymorphic DNA (RAPD) analysis. Thirty seven individuals were collected from 10 branches of 3 river basins. A total of 12 DNA fragments was amplified, among which no fragments were specific to a river basin. All the individuals were categorized into 18 haplotypes on the basis of fragmental combination. Some haplotypes were observed in the two facing branches of different basins across the pass. An extremely high average BSI (Band Similarity Index) was observed between the two adjacent branches around which stream captures had occurred, whereas relatively low BSIs were observed even between the branches within the same basin. In the cluster analysis on the basis of BSI, an intimate cluster was constructed by the adjacent branches of different basins, where the passes were loose on the Japan Sea side. These results suggest that the Nikkoiwana had expanded their distribution ranges from the Japan Sea side to the Seto Inland Sea side taking advantage of highland marshes or geological events such as a stream capture.