Social heterosis and the maintenance of genetic diversity at the genome level

Social heterosis is when individuals in groups or neighbourhoods receive a mutualistic benefit from across-individual genetic diversity. Although it can be a viable evolutionary mechanism to maintain allelic diversity at a given locus, its efficacy at maintaining genome-wide diversity is in question when multiple loci are being simultaneously selected. Therefore, we modelled social heterosis in a population of haploid genomes of two- or three-linked loci. With such linkages, social heterosis decreases gametic diversity, but maintains allelic diversity. Genomes tend to survive as complimentary pairs, with alternate alleles at each locus (e.g. the pair AbC and aBc). The outcomes of selection appear similar to fitness epistasis but are novel in the sense that phenotypic interactions occur across rather than within individuals. The model's results strongly suggest that strong linkage across gene loci actually increases the probability that social heterosis maintains significant genetic diversity at the level of the genome.