Determining the genetic load of the population

Genetic load is defined as the relative deviation in a populations fitness from the fitness optimum, L=(wmax-w¯)/(wmax). We set the phenotypic optimum to be zero; P_opt = 0. When determining fitness for the site based models, we subtract one from all phenotypes. This implies that wmax=e-Popt22σs2=1 and that load is a simple function of the phenotypes of the population, L=1-e-P22σs2. We also used the mean number of mutations per individual, and the mean frequency and effect sizes of segregating risk variants as proxies for the genetic load [21, 90]. Lastly, we calculated Burden Ratios (B_r) [91] as the ratio of load between an equilibrium and non-equilibrium population. We calculated B_r using both the true load and the number of mutations per individual.