Comparison of the widths of the rate distributions for fungi and mammals. The yellow line at σ = 1 shows the expected standard deviation for a Normal distribution. The mammals have an average σ of 2.056, indicating their bias toward both high and low rates – consistent with regional mutation rates. There are three fungal pairwise comparisons (C. dubliniensis/C. albicans, C. tropicalis/C. dubliniensis, and N. crassa/C. globosum) which also have wide rate distributions, with an average σ of 1.825 (see Figure 1c). The species pairs from the remaining 22 fungi have a noticeably lower value of σ (average σ = 1.32, range = [1.02 – 1.40]), consistent with their having uniformly mutating genomes. Plotted values indicate the average σ in each group and horizontal lines mark the range.