trans gene regulation in adaptive evolution: A genetic algorithm model

This is a continuation of earlier studies on the evolution of finite populations of haploid genotypes within a genetic algorithm framework. We had previously explored the evolutionary consequences of the existence of indeterminate-''plastic''-loci, where a plastic locus had a finite probability in each generation of functioning (being switched ''on'') or not functioning (being switched ''off''). The relative probabilities of the two outcomes were assigned on a stochastic basis. The present paper examines what happens when the transition probabilities are biased by the presence of regulatory genes. We find that under certain conditions regulatory genes can improve the adaptation of the population and speed up the rate of evolution (on occasion at the cost of lowering the degree of adaptation). Also, the existence of regulatory loci potentiates selection in favour of plasticity. There is a synergestic effect of regulatory genes on plastic alleles: the frequency of such alleles increases when regulatory loci are present. Thus, phenotypic selection alone can be a potentiating factor in favour of better adaptation. (C) 1997 Academic Press Limited.