Genetic divergence and relationship among fifteen species of genera Trachurus, Decapterus, Selar and Selaroides

Genetic distance and the relationships among 15 species of genera Trachurus, Decapterus, Selar, and Selaroides were estimated from 18 electrophoretically detectable isozyme genes. Estimates of genetic distance (D) between every pair of species within the genus Trachurus ranged from 0.005 to 0.560 with a mean of 0.322, and from 0.484 to 1.868 with a mean of 1.022 within the genus Decapterus. Between species of different genera, estimates of D ranged from 0.786 to 2.863 with a mean of 1.784. From these results, Decapterus species could be considered as having evolved over a long period while Trachurus is a newly arisen genus. A relationship among species suggests that the Decapterus species are expanded to offshore and deep area after being divided into some groups, and that the Trachurus species are divided presumably into at least two groups, one group of which is coastal and the other of which is offshore. Trachurus japonicus and Trachurus novaezelandiae could be considered subspecies on the basis of allelic distribution and genetic distance.