Fig. 2

Histogram of allele frequency at codons 1532 (a) and 1534 (b) of the VGSC gene in Aedes albopictus populations. SH represents the pool of three populations (SHBS, SHYP and SHGQ). For detailed information, see Additional file 1: Tables S1 and S2. The populations on the left of the dotted line are from collection sites in central and northern China, and the populations on the right side are from sites in southern China. The horizontal axis indicates the populations (see Fig. 1 for details), while the vertical axis denotes the allele frequency. Populations marked with an asterisk indicate the co-occurrence of both mutations (codons 1532 and 1534)