Inter-locus interactions: A review of experimental evidence

In quantitative genetics, experiments designed to elucidate the nature of gene action and hence the importance of epistasis, have included analysis of genetic differences among individuals in random mating populations (partitioning of genetic variation, analysis of selection responses), of differences among inbred lines or selected populations (variance components in crosses among lines, chromosome analysis using genetic markers and crossover suppression), of the effects of inbreeding, and of population structure. Evidence in population genetic studies has come from studies of linkage disequilibrium and co-adaptation in natural populations, and of multilocus fitness estimation and linkage disequilibrium and associative overdominance in experimental populations. While it is clear that epistasis does contribute to the genetic variation in some quantitative characters, and in particular reproductive fitness, much of the evidence is equivocal and unsatisfying.