Estimation results for different values of mutation rates m.

Panel a, maximum likelihood objective values for mutation rates m of 1.2×10−5/cycle, 1.2×10−4/cycle, 1.2×10−3/cycle, and 1.2×10−2/cycle. The objective functions are the lowest with m = 1.2×10−4/cycle, suggesting models fit data best with this m value. Panel b, estimated fitness of selected variants at different m values. Similar ranking of fitness estimates were obtained with these different values of mutation rates. Similar fitness estimates suggests robustness to the assumed mutation rate m. Fitness estimates for m = 1.2×10−2/cycle were not reported because of poor model fits.