Fixation time of overdominant alleles influenced by random fluctuation of selection intensity

Abstract

SUMMARYIt was demonstrated that the number of generations until fixation or loss of an overdominant alleles is influenced by random fluctuation of selection coefficients. When 2<Vs, whereis the mean selection coefficient against either homozygote andVsis the between -generation variance of the selection coefficient, overdominance generally accelerates rather than retards fixation of segregating alleles. This finding should have important bearing on our consideration of the behaviour of polymorphic variants which are nearly neutral but have very slight overdominance. When the population size (Ne) is extremely large, not onlyNebut also/Vshave to be considered in discussing the effectiveness of overdominance.