PHYLOGENETIC RELATIONSHIP OF THE GENUS ONCORHYNCHUS SPECIES INFERRED FROM NUCLEAR AND MITOCHONDRIAL MARKERS

The phylogenetic relationship among the salmonid fishes of the genus O ncorhynchus has been analyzed using various kinds of markers for a lon g time. However, there are three major disagreements among those studi es; (1) the authenticity of the Pacific salmon group as a monophyletic cluster, (2) the phylogenetic relationship among three Pacific salmon s (pink salmon, sockeye salmon, and chum salmon), and (3) the phylogen etic position of masu salmon. We used allozyme electrophoresis to clar ify the phylogenetic relationship between the Pacific salmon group and the Pacific trout group. Furthermore, we reanalysed published mitocho ndrial DNA D-loop sequences (Shedlock et al., 1992). Allozymic data an d mtDNA data indicated the following consistent results; (1) all Pacif ic salmons formed a monophyletic cluster, (2) chum salmon and pink sal mon were clustered within those Pacific salmons, (3) masu salmon forme d a cluster with other Pacific salmons and diverged first in this grou p.