Figure 3.

In Father’s Curse (Models 6 and 7) and Nuclear Mother’s Curse (Models 8 and 9), the uniparentally inherited sex chromosome (Y or W) can drive the fixation of an allele that is deleterious in the homogametic sex. Analytical work examines invasion of the sex-specific alleles(Y and W) and the sexually antagonistic alleles (X, Z, or autosomal) from the lower left corner, but higher frequency starting points better illustrate the dynamical behavior. These figures clearly demonstrate that both variants will fix as long the selective cost in the ‘cursed’ sex is smaller than the selective advantage in the benefitting sex. For Models 6–9, both alleles start with an initial frequency of either 0.25 (a-d) or 0.5 (e-h), and the change in allele frequency at every generation is tracked for a total of either 5000 (a,e,c,g) or 10,000 (b,f,d,h) generations. Simulations were run for 100 randomly selected combinations of s_f and s_m for each model. Trajectories where the absolute value of the selection coefficient in females (s_f) is less than that in males (s_m) are shown in red, and the opposite in black.