Fitness in the permissive environment. Malthusian (log) fitness of experimental yeast populations propagated in the permissive environment, ascertained by head-to-head competitions with the ancestor. Each point shows the mean (± SE) of triplicates for each sexual status by mutation rate treatment. The only time points where a two-way ANOVA revealed a significant effect of either sexual status or mutation rate on fitness are at generation 100 and 150 (indicated by ***) where only sexual status had a significant impact on fitness (P < 0.0006). There is no effect of sexual status or mutation rate on fitness at any other time point (P > 0.2). Models describing individual linear fits for each treatment did not fit the data any better than one linear fit given all the data (P = 0.37).