Abstract: The genetic diversity of 11 Bactrocera dorsalis (Hendel) populations consisting of 224 individuals collected from 9 provinces of South China, Vietnam and Thailand was investigated using simple sequence repeat (SSR) markers to study the genetic differentiation among populations. Total 48 alleles at nine loci were amplified, with average of 5.33 alleles each locus. A relatively high level of genetic diversity was revealed: P=94.45%, Nei's=0.4371, I=0.7870. A higher level of genetic differentiation was detected among populations with Nei's F-statistics, F_st=0.2370. The differentiation in certain degree may result from geographical isolation and barriers to gene flow. UPGMA cluster analysis indicated that the 9 populations from China clustered in two clades, the Southern China clade and the South-western China clade. Populations from Fujian, Taiwan, Guangdong and Hainan gathered into the Southern China clade, while populations from Sichuan, Yunnan, Gaungxi, Guizhou and Hunan formed the South-western China clade. It was so inferred that the evolutionary processes of the populations of the Oriental fruit fly in China are influenced by two factors, i.e, geographical divergence and gene flow by trade communication.

Key words: Bactrocera dorsalis, geographical population, microsatellite, polymorphism, evolution