Figure 3

Intensity of disruptive selection as function of the intensity of competition. The relationship between quadratic selection and two measures of intraspecific competition. The intensity of disruptive selection on trophic morphology was greater in ponds with (A) lower per capita resource density and (B) higher conspecific density. Standardized quadratic selection differentials above the dotted line are positive and indicate disruptive selection, while those below the line are negative and indicate stabilizing selection. Significant selection differentials (black), non-significant selection differentials (grey) and significant selection differentials with no fitness minimum or maximum in the range of the data (open) are all shown. Solid and dashed lines show respectively, the median and 95% confidence intervals of the regression coefficient obtained from bootstrapping. Each point in the analysis was weighted by the populations’ sample size.