Recombination load in a chromosomal inversion polymorphism of Drosophila subobscura.

Chromosomal inversions suppress recombination in heterokaryotypes and may help to maintain positive epistatic interactions among groups of alleles at loci contained in the inversion. Here I evaluate the protective effect of inversions on recombination when different chromosomal segments, or even the whole chromosome O of Drosophila subobscura, can be effectively prevented from undergoing recombination in several naturally occurring heterokaryotypes. The fitness of flies made homozygous for recombinant chromosomes was generally lower when compared to their nonrecombinant counterparts, thus suggesting that segregating gene arrangements in this species hold together favorable combinations of alleles that interact epistatically.