Speciation and dispersal of Tribolodon species (Pisces, Cyprinidae) around the Sea of Japan.

Gene products of 22 protein coding loci from 29 populations of a uniquely sea-going cyprinid genus Tribolodon, T. hakonensis (anadromous and/or river-resident), T. brandtii (anadromous), T. ezoe (freshwater) and T. nakamurai (freshwater), were analyzed in order to infer the genetic divergence and dispersal of Tribolodon species around the Sea of Japan. According to the genetic distance, T. brandtii is located near the center between T. hakonensis and T. ezoe-T. nakamurai cluster. The outgroup root (Pseudaspius leptocephalus, Rhynchocypris lagowskii and Leuciscus waleckii) is attached between T. hakonensis-T. brandtii and the T. ezoe-T. nakamurai clusters. The origin of the genus Tribolodon and its salinity tolerance may date back to the Miocene Sea-of-Japan Lake and the Pliocene Paleo-Sea-of-Japan, respectively, as judged from the divergence time between Tribolodon and the outgroups. The genetic relationships and distribution pattern of Tribolodon species suggest they speciated on the Sakhalin-Japan side, and the continental populations of T. hakonensis and T. brandtii originated from anadromous colonizers. A new faunal element of Japanese freshwater fishes, the Sakhalin-Japan sub-element, is proposed for Tribolodon and some other fishes.