Abstract: Flea beetle Agasicles hygrophila Selman & Vogt, the most effective natural enemy of alligator weed Alternanthera philoxeroideis, is originated from South America, and has been introduced into China for more than 20 years to control the weed. In this study, the technique of  random amplification of polymorphic DNA (RAPD) was applied to assess the genetic diversity of four A. hygrophila geographic populations in Guangzhou, Chongqing, Kunming, and Fuzhou of China,and, taking the population in Florida of US as the reference, the relationships between the genetic differentiation and geographic differentiation among and within the populations were explored at molecular level. Thirteen primers that produced clear and reproducible products were selected from 111 random primers to amplify the 25 samples of the five A. hygrophila populations. The total polymorphic rate was 42.0%, and the polymorphic rate of Florida population was significantly higher than that of four China populations. The genetic differentiation among the four China populations was 25.5%. The cluster analysis by UPGMA indicated that there was a positive correlation between the genetic distance and geographic distance of different A. hygrophila geographic populations.

Key words: Agasicles hygrophila, introduction, geographic population, genetic diversity, RAPD