Objective Monochamus alternatus is the primary vector of pine wilt disease. Clarifying the population genetic diversity and genetic structure characteristics of this species is crucial for understanding its demographic history and predicting its dispersal routes in regional scale.

Method Using 10 polymorphic microsatellite loci of M. alternatus, 320 individuals collected from 12 geographical populations in Guangxi Zhuang Autonomous Region were genotyped to analyze population genetic diversity and genetic structure.

Result (1) The overall genetic diversity of M. alternatus populations in Guangxi was at a moderate level (Na = 5.00, He = 0.522). However, significant genetic differentiation existed among populations (Fst = 0.095, P < 0.05), and several populations exhibited obvious inbreeding characteristics, such as the Liuzhou (LZ) population (F = 0.39). (2) The genetic diversity of the population has a significant negative correlation with the annual average temperature, the average temperature of the coldest month, and the average duration of sunshine. It also has a significant positive correlation with the average temperature difference at the sampling sites. (3) Analysis of molecular variance revealed that 90.47% of the genetic variation in M. alternatus from Guangxi occurred within populations, while only 9.53% was distributed among populations. (4) The coancestry coefficient analysis was overall consistent with the genetic clustering analysis at the optimal clustering value of K = 3. Genetic clustering analysis further divided the 12 tested populations into three geographical groups corresponding to northern, southern and eastern Guangxi.

Conclusion The genetic pattern of M. alternatus in Guangxi may be jointly driven by geographical isolation, ecological heterogeneity and human-mediated dispersal. These findings provide key insights into understanding the regional dispersal mechanism of M. alternatus.