Figure 3

Boxplot of cluster sizes (1, 2) and boxplot of SNP contents (3, 4). Boxplot 1 shows the cluster sizes of the 22 least polymorphic OR genes (≤ 2 SNP). This boxplot should be compared with boxplot 2, showing the cluster sizes of the 27 OR genes with the largest number of SNP (≥ 10 SNP). Boxplot 3 corresponds to the SNP contents of 20 OR genes located in clusters with up to five OR genes. It should be compared with boxplot 4, corresponding to the 18 OR genes located in the largest cluster (243 OR genes). Arrows indicate the median values in the four boxplots.