Abstract:Genetic diversity of spring and summer populations of Brachionus calyciflorus collected from Lake Jinghu in Wuhu City was analyzed using RAPD method. 10 primers that produced repeatable and discernible bands were chosen from 44 random primers. Among the total of 76 loci detected, 65 loci (85.5%) were polymorphic. UPGMA and ME dendrograms of B. calyciflorus were constructed by clustering the amplified bands on the basis of the index of genetic distance. The average genetic distance among all samples was 0.5219. The genetic distance within summer population (04304) was shorter than that within spring population (0.4416). The genetic distance (0.6010) between the two seasonal populations was longer than that within either seasonal population. The two trees both showed that the sixteen samples were obviously divided into different clades. In UPGMA trees, the spring and summer populations were divided into two clades. In ME trees, all the summer samples except Su2 were separated as an independent clade. The results indicated that there is an obvious genetic difference between the two seasonal populations and a seasonal alternation in B. calyciflorus population collected from Lake Jinghu, and the sample Su2 may be an interim population.