(A) The null distribution of RF in sets of 1000 randomly sampled, unrooted trees with either 8 (gray diamonds, corresponding to the number of tips in tree distance networks), 9 (gray squares, the number of tips in each H1N1 tree), or 12 (black circles, the number of tips in each H3N2 tree) leaf tips was determined. A dashed line demarcates the threshold for the 95% confidence interval. (
B–D) The null distributions shown in (
A) were log-transformed (
B, C) or Yeo-Johnson-transformed (
Yeo and Johnson, 2000) (
D) and fit to a linear regression model to establish the cutoff for the first five percentiles (shaded region), which was set as the 95% confidence interval cutoff. The distance at which 95% confidence is exceeded is indicated.