a, Cell density of the new type. b, Proportion of the new cell type divided by the total number of cells. Each circle represents the mean of 42–45 lines (that is, three replicates for each of the 15 ancestral and 14 derived lines). Lines that failed to produce the required type were excluded. Black, derived; grey, ancestral. Error bars are s.e.m., based on n ≤ 15. *P < 0.05, using analysis of variance (ANOVA) and post hoc contrasts.