Size-dependent sex change can be the ESS when mortality is size-dependent, without any size advantage of reproduction.

Sex change in fishes and terrestrial plants has been discussed mostly based on the size advantage model, which assumes that reproductive rate increases with body size for at least one sex and differently between the sexes. However, size-dependent sex changing terrestrial plants often show size-independent reproductive success, presumably due to limited pollen delivery by pollinators. To answer this question, we analyze a game model of size-dependent sex expression for terrestrial plants. We assume: (1) reproductive success is independent of size for both sexes; (2) mortality decreases with size in the same way for both sexes; (3) growth rates decrease at maturity, more for females than for males.