Figure 2.

Variance in allometric slopes across 182 subfamilies of birds versus (a) degree of polygamy (subfamilies with higher values have proportionally more polygynous species), (b) range in sexual size dimorphism, (c) mean standardized sexual size dimorphism and (d) degree of sexual dichromatism (subfamilies with higher values have more species where males are more colourful than females). Allometric slopes were calculated with RMA models of log male wing length regressed onto log female wing length: higher slopes correspond with stronger positive allometry for sexual size dimorphism, i.e. Rensch's rule. See table 1a for the statistics of the regression lines.