[Genetic structure and diversity of Harmonia axyridis populations in Shaanxi Province, China.]

value was 0.024, implying low genetic diffe-rentiation among all populations. Results from neutrality tests suggested that H. axyridis populations followed the neutral evolution model and the population size remained stable. Molecular variance analysis (AMOVA) showed high proportion of total genetic variance attributed to variations within populations. Phylogenetic tree based on Nei's genetic distance of different geographic populations showed clear divergence between northern, central, and southern Shaanxi groups. Results from Mantel test suggested that the genetic distance was weakly correlated with geographical distance between populations. Geographical pattern of genetic structure and diversity in populations from different regions indicated weak gene flow between northern, central, and southern Shaanxi due to Qinling Mountains barrier and climate difference.