Abstract: Gynaikothrips ficorum (Marchal) is a major insect pest damaging Ficus microcarpa and has expanded to all the continents. At present, it damages F. microcarpa seriously in tropical and subtropical areas in Yunnan province. In order to reveal the genetic differentiation among geographic populations of G. ficorum, a 646 bp segment of the mitochondrial cytochrome c oxidase subunit Ⅰ (COⅠ) gene was sequenced from 145 individuals among 10 geographic populations in Yunnan province, and the sequence variability of the COⅠ gene and genetic differentiation among them were analyzed. The results showed that 38 variable sites were detected and six haplotypes were defined based on the COⅠ sequences among 10 geographic populations of G. ficorum, including one haplotype shared by eight populations. The genetic distances ranged from 0 (among populations of Ruili, Mangshi, Yuxi and Chenggong) to 0.043 (between Yiliang population and populations of Longchuan and Mojiang) among the 10 geographic populations, indicating that the genetic distances among G. ficorum populations were not associated with their geographic distances. Analysis of molecular variance showed that 10 geographic populations were clustered into three groups (group I: Longchuan, Ruili, Mangshi, Yuxi, Chenggong, Mojiang, Lincang, and Mengla; group Ⅱ: Mengzi; group Ⅲ: Yiliang). The Fst value was 0.9828 (P<0.05), and the Nm value was 0.01, indicating apparent genetic differentiation among the three groups, but there was only 0.0172 genetic variation from intragroup. A molecular phylogenic tree constructed using neighbor-joining (NJ) method showed that the six haplotypes were clustered into three clades associated with geographic regions. No shared haplotypes were found among the three groups. Molecular analysis showed that these three major groups/clades did not coincidence with the geographic distribution. Based on the information of host plants, we preliminarily presumed that the genetic differentiation between the two populations (Mengzi and Yiliang) resulted from different host variety and growth conditions. Haplotypes among all populations were distributed in different clades on the median joining network, revealing no obvious geographic distribution patterns.

Key words: Gynaikothrips ficorum, geographic populations, genetic distance, genetic differentiation, COⅠ gene