Figure 1

Relationship between log ₁₀ mean and log ₁₀ variance of bacterial density. Shown for all 40 data points (a) and for the experimental treatments (b-e). Each panel shows the regression line fitted for the respective treatment. The dotted line describes a relationship with a slope of 2. (a) The overall slope 1.89 ± 0.03 (± standard error) is only slightly, though statistically significantly, less than 2. (b) Ancestors (+ in square, dotted regression line) and controls (+ in circle, solid regression line). (c) Phage treatment (solid triangle). (d) Rif treatment (solid circles). (e) Rif plus phage treatment (solid diamonds). The low slope (1.51) of the rif plus phage treatment was not driven by the leftmost filled diamond in (e) because the slope was 1.49 instead of 1.51 when that point was omitted.