Abstract: 【Aim】 Liriomyza chinensis, a serious economic pest of onions and garlics, is widely distributed in China. This study aims to analyze the genetic differentiation among the geographical populations of L. chinensis in China. 【Methods】 A total of 253 individuals from 12 different geographical populations from 8 provinces were used as samples, and their mtDNA COI gene was sequenced. The genetic diversity, gene flow levels and genetic variation of the geographical populations of L. chinensis were analyzed by MEGA7.0, DnaSP 6.1 and Arlequin 3.5 based on the obtained mtCOI gene sequences. 【Results】 From the 253 individuals 13 haplotypes of the mtCOI gene fragment of 759 bp in length were defined, and the K2P genetic distance between haplotypes was less than 0.02. Haplotype Hap1 was shared by the 12 geographical populations, and the total occurrence frequency was up to 81.82%. The haplotype diversity (H_d)  of all geographical populations was low (0.327), the nucleotide diversity (Pi) was 0.00159, and the average number of nucleotide difference (K) was 1.21011. The total population had generated moderate genetic differentiation (F_ST=0.06971), and the gene flow was relatively sufficient (Nm=3.33629). The results of molecular variance analysis (AMOVA) showed that the source of genetic variation was within population, and the Tajima’s D test value was significantly negative. Mantel test results showed that the genetic distance was not related to the geographical distance. 【Conclusion】 The geographical populations of L. chinensis in China show low genetic diversity, relatively sufficient gene flow and moderate genetic differentiation, and the geographical distance does not affect the degree of genetic differentiation between geographical populations. The total population of L. chinensis has not experienced significant population expansion and population growth in the recent historical period.

Key words: Liriomyza chinensis, mtDNA COI gene, geographical population, genetic diversity, phylogenetic analysis