Abstract: Genetic diversity of three Gobiocypris rarus populations and one inbreeding stock was studied using random amplified polymorphic DNA (RAPD) method. Materials of natural populations were collected from three counties of Sichuan Province , Hanyuan (HY) , Guanxian ( GX) and Pengxian (PX) , where water system belongs to three tributaries of the Yangtz River , Dadu River , Minjiang River and Tuojiang River system , respectively. The inbreeding stock was the tenth generation descendant of a brother- sister mating ( F10 ) system whose parents were collected in Hanyuan. Percentage of polymorphic sites , genetic similarity and the Shannon’s index of phenotypic diversity were used to analyze genetic diversity. The results showed the genetic diversity of F10 was very low , whereas that of natural populations was relatively abundant . In natural populations , nearly half of the RAPD sites were polymorphic , and the average Shannon’s index was 0. 3235 (HY) , 0. 3075 ( GX) and 0. 2911 (PX) , respectively. Genetic similarity among individuals indicated that genetic diversity of HY and GX was higher than that of PX. Difference in genetic structure between F10 and natural populations was fairly obvious. Although the differences on phenotype frequency were detected on 11 to 19 sites , no molecular marker was found to distinguish natural populations. Analysis on the coefficient of differentiation using Shannon’s index revealed that 91. 33 % of total genetic diversity existed within natural populations and 8. 67 % among them. Treating the presence and absence of bands as two phenotypes , Chi- test (χ2) and the analysis of Shannon’s index was suggested to be effective approach for studying population differences.

Key words: Mt. Gongga, Abies fabri, elevation, diversity, population