Heteroclinic Cycles and Segregation Distortion

Segregation Distorters are genetic elements that disturb the meiotic segregation of heterozygous genotypes. The corresponding genes are “ultra-selfish” in that they force their own spreading in the population without contributing positively to the fitness of the organisms carrying them. We consider here autosomal two-locus drive systems consisting of a “killer locus” and a “target locus”. The diploid population dynamics is approximated by a game dynamical model leading to replicator equations. We investigate in detail the dynamics of the SD-system ofDrosophila melanogasterand the competition of two killer alleles at the same gene locus. We show that heteroclinic cycles are a common type of attractor in models of segregation distortion systems, while they rarely occur in models with Mendelian segregation.