Figure 7

The evolutionary relationship between claw force and signaling morphology. A) Symbols are claw frontal area divided by claw mass, plotted against the estimate of major claw closing force at the tubercle. B) Symbols are claw length divided by claw mass, plotted against the estimate of major claw closing force at the tubercle. All values are phylogenetically independent contrasts of weight-normalized species averages. Linear fits of standardized contrasts are constrained to pass through the origin and there is a significant negative relationship between these variables (claw area: r=-0.67, F=15.3, d.f.=19, p<0.05; claw length: r=-0.69, F=17.69, d.f.=19, p<0.05). As species can produce relatively larger closing forces, the major claw’s efficiency as a signal decreases, implying that there is an evolutionary trade-off between morphology that should maximize the major claw’s functionality as a weapon and morphology that should maximize the major claw’s functionality as a signal.