Effects of Selection on the Evolution of the Sex Ratio

Abstract

Hypotheses as to the biological bases of observed sex ratios must explain the departures found in natural populations from the ratio which might be expected from the mechanism of sex determination in the species. Models based on the concept of parental investment (Fisher 1930) have been used to explain such departures but do not predict equilibrium sex ratios when viability selection discriminates between the sexes in the period between the end of parental investment and the maturity of the offspring.