a, Proportion of lines producing SM. b, Total cell density. c, Cell density of the new type. d, Proportion of SM cell types divided by the total number of cells. Each square represents the mean of 45 lines (that is, 3 replicates for each of the 15 lines); however, for c and d lines that failed to produce SM were excluded. Black, derived; grey, ancestral. Error bars are s.e.m., based on n ≤ 15. *P < 0.05, using a generalized linear model (error structure: binomial; link function: logit) and post hoc contrasts for a; and using analysis of variance (ANOVA) and post hoc contrasts for b–d.