Fig. 3

Population structure and geographic expansion of the Harmonia axyridis populations within China. a A biplot of the first two components obtained from the principal component analysis of geographic sample populations clustered into two major groups (super-populations) represented by colors of purple for the west China (WCN) and red for the east China (ECN). b A phylogenetic tree of H. axyridis populations reconstructed with Agrilus planipennis as the outgroup and with the WCN group as the closest to it. c Population structure of sample populations (K = 2, 3, and 4) matching the phylogenetic tree with colored (same as above) triangles representing respective components in each population from the two major groups. d Splits and migrations among sample populations with shades of color representing the weight of migration. e A schematic diagram showing putative origin and dispersal (with arrows representing the direction) of the H. axyridis populations represented by triangles with colors of purple for the west China (WCN) and red for the east China (ECN) super-populations