Evolutionary-rate ratio increases linearly with RSA. The solid line shows ω = dN/dS versus RSA as estimated by the best model (linear ω, linear t, per-bin κ). The dots show the same for the best model with per-bin ω (which has linear t and per-bin κ). Both models are consistent with each other and strongly support a linear relationship between ω and RSA.
Scherrer et al. BMC Evolutionary Biology 2012 12:179 doi:10.1186/1471-2148-12-179