Use of microsatellite DNA and otolith Sr:Ca ratios to infer genetic relationships and migration history of four morphotypes of Rhinogobius sp. OR

The genetic diversity and relationship among four morphotypes of Rhinogobius sp. OR, Gobiidae ('Toshoku', 'Shinjiko', 'Gi-toshoku', and 'Shimahire') were investigated with seven microsatellite DNA loci, and amphidromy of these morphotypes was verified by strontium (Sr) and calcium (Ca) deposition in the otolith. Samples of 'Toshoku', 'Shinjiko', 'Gi-toshoku', and 'Shimahire' were collected from, respectively, three, three, two, and four locations in Japan. Microsatellite analysis detected high genetic diversity (based on the number of alleles, allelic richness, and average observed heterozygosity) in the 'Toshoku' and 'Shinjiko' morphotypes relative to the 'Shimahire' morphotype; the 'Gi-toshoku' morphotype had an intermediate level of variation. Almost all pairwise Fsub(ST) values were significantly different from zero (p0.001), except between two populations of 'Toshoku'. Clear genetic independence was observed between the 'Shinjiko' and 'Shimahire' morphotypes in the Maruyama River. A principle component analysis based on microsatellite data indicated that the 'Toshoku', 'Shinjiko', and 'Gi-toshoku' morphotypes were genetically similar. Furthermore, the three populations of 'Toshoku' were closely related each other, and two of those collected from the Lake Biwa system were a single population. There was, however, a high degree of genetic differentiation between 'Shimahire' and the other morphotypes; moreover, there was high genetic divergence among four populations of the 'Shimahire' morphotype. Amphidromous migratory histories were indicated by Sr:Ca ratios in two of three populations of the 'Shinjiko' morphotype and in one of two 'Gi-toshoku' morphotypes, whereas all populations of the 'Shimahire' morphotype were freshwater residents. The large genetic divergence and low genetic diversity in 'Shimahire' are likely related to migration history.