HOW SERIOUS IS THE ASSUMPTION OF NO PHENOTYPIC VARIATION IN OPTIMALITY MODELS - A SEX-RATIO EXAMPLE

With the use of a sex ratio model, I illustrate when the assumption of no phenotypic variation may lead to inaccurate predictions. Local mat e competition sex ratio models is one case where an asymmetric fitness function around the optimum may cause optimality predictions to be in accurate. Despite this asymmetry, I illustrate that variation in sex r atios must be substantial in order to lead to inaccuracies, and binomi al variation around the optimum will not lead to any observable deviat ions. The model allows an easy understanding of how selection on varia tion in sex ratio decreases as the optimality point is approached.