Maintenance of quantitative genetic variation in regions of restricted recombination via associative overdominance

Mutation-selection balance is considered the primary mechanism for preserving additive genetic variance in quantitative traits among natural populations. It is widely recognized that genetic variants influencing traits (QTLs) are scattered throughout species genomes. Nevertheless, deleterious mutations that have a significant impact on fitness are typically recessive.

Genomes often contain regions with limited recombination, which can result in close linkage between numerous recessive deleterious alleles. This situation can generate elevated heterozygosity through associative overdominance.

The study reveals that weakly selected QTLs connected to genomic areas displaying AOD can augment VA beyond the expected levels without the presence of unconditionally deleterious mutations. However, when traits are subject to selection under these conditions, recessive deleterious alleles may be exposed as homozygotes, leading to a decline in fitness.

Consequently, although AOD can aid in preserving VA, the genetic variation maintained through this mechanism might not be readily accessible through either natural or artificial selection.