Problems with classical models of sex-ratio evolution
The classical theory of the sex-ratio evolution, known as the sex-ratio game, is based on the maximization of the number of grandchildren, treated as a fitness measure of a female producing offspring of the sex ratio that is coded in her genes. The theory predicts that it is more profitable to produce offspring with less numerous sex. We can find in the literature mutually exclusive conclusions based on this prediction: some textbooks say that populations with the equal number of sons and daughters are evolutionarily stable, others identify this ratio as a stable state of a population with different individual strategies being allowed. It is also not clear whether a primary or secondary sex ratio is a target of evolution. Moreover, the classical theory ignores the role of males, who host non-expressed sex-ratio genes. Our new approach, based on multipopulation dynamic evolutionary games, shows that in populations of players with individual strategies, the secondary sex ratio is attracted by the current value of the primary sex ratio, which slowly converges to the unique stable value of 0.5. Male hosts of the sex-ratio gene are important because perturbations of a stable state of males subpopulation can destabilize the whole system.