Genetic diversity and population differentiation of silver carp (Hypophthalmichthys molitrix) in the upper reaches of the Yangtze River

Impacts of hydropower projects (Three Gorges Dam and Xiangjiaba Dam) on genetic diversity and population differentiation of silver carp (Hypophthalmichthys molitrix) in the upper reaches of the Yangtze River were examined．Mitochondrial cytochrome b (Cyt b) was analyzed in silver carps from Xiangjiaba Reservoir (Shaonvping), the main stream (Banan, Fengdu, Wanzhou, Taipingxi) and tributaries (Jiantanhe, Jialingjiang, Xiaojiang) of the Three Gorges Reservoir．The haplotype diversity was found to range from 0.770 to 0.876, nucleotide diversity range from 0.687% to 1.967%, suggesting high levels of genetic diversity． Mismatch distribution in 8 populations showed unimodal distribution．Tajima’s D and Fu’s F_S test values were either positive or negative, but statistically insignificant, indicating that these sliver carp populations were stable．AMOVA analysis found that 95.87% of genetic variations occurred within populations, 4.13% occurred among populations．Pairwise F_ST values suggested that there was no significant genetic differentiation between each population pair, other than those between Jiantanhe and Xiaojiang, Taipingxi populations. Mantel test suggested no correlation between extent of genetic differentiation among populations and geographic distance. Haplotype network suggested no apparent genealogical geographic pattern．We urge to strengthen the protection of genetic resources, and to protect differentiated populations．