Rate of evolution of a character without epistasis
Abstract
It is shown that the rate of change of the mean of a character under selection is [Formula: see text] where C, ¯W, Δ̄Z, and B denote the genic (additive genetic) covariance of the character and fitness (i.e., the covariance of the average effect on the character and the average excess for fitness of every allele that affects the character), the mean fitness, the average of the changes in the genotypic values of the character over the next generation, and a correction term, respectively. Generations are discrete and nonoverlapping; the monoecious population mates at random. The character is determined by arbitrarily many multiallelic loci without epistasis; the linkage map is also arbitrary. If there is no dominance, then B = 0; if, in addition, the genotypic values of the character are constant, then Δ¯Z = C/¯W. Even if dominance is present, for weak selection and slowly varying genotypic values, Δ¯Z ≈ C/¯W. If the character is fitness itself, then C is the genic variance in fitness.
