Boxplot comparing the log10-transformed interval sizes without (black) and with (red) fixed derived amino acids. These derived amino acids are nonsynonymous substitutions that distinguish Arabidopsis IGMTs from those in Arabidopsis lyrata. Each interval is flanked by neighboring shared polymorphisms, defined as the same nucleotides segregating at the same position in two or more gene copies. Shown are mean (crosses), median (black horizontal line), and range of the data including outliers (open circles). Statistical significance is indicated by asterisks (*: P < 0.05; **: P < 0.01; ***: P < 0.001).