Fitness in the stressful environment. Malthusian (log) fitness of experimental yeast populations propagated in the stressful 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 P values revealed by a two-way ANOVA of fitness for each time point are shown at the top of the plot, values below P = 0.031 are highlighted in red. Note that this analysis was conducted on each time point independently. Sexual populations have greater fitness from generation 225 onward and mutation rate does not significantly affect fitness at any time point. The best-fit linear model for each treatment is also shown. Comparisons of linear models show there is a significant effect of sexual status on fitness trajectories (P = 0.0013), but not mutation rate (P = 0.3308); there is no difference between sexual WT and sexual mutator fitness (P = 0.652), but a reduced probability that the observed difference in fitness trajectories between the asexual-WT and asexual-mutators was by chance (P = 0.0591).
Gray and Goddard BMC Evolutionary Biology 2012 12:43 doi:10.1186/1471-2148-12-43