Genealogical diversity at the end of 40 years across 100 simulations for varying mutational parameters. Genealogical diversity varies with (A) mutation rate and with (B) standard deviation of mutation effect. Points represent individual simulation outcomes, and gray bars represent medians and interquartile ranges across replicate simulations. Outcomes with diversity greater than 9 years are shown in blue, and outcomes with diversity less than 9 years are shown in black. Counts of these two classes are shown in blue and black, respectively. Genealogical diversity is measured in years, mutation rate is measured in mutations per infection per day, and standard deviation of mutation effect is measured in antigenic units. Diversity less than 9 years is chosen as a cutoff based on observed patterns of branching in the H3N2 influenza genealogy.