Figure 5. Inheritance and expression of harmful mutations in zygotic offspring.

The Punnett square shows the reconfiguration of the haplotypes in the offspring of random mating individuals in the polymorphism. SAs, and haplotypes, are labelled according to the legend in the lower left corner of the figure. Silenced SAs, more likely than expressed SAs to accumulate harmful mutations, are indicated by black ovals encircling the allele. By recombination, the altered SAs are expressed in the offspring (indicated by a white oval) reducing its fitness. Homozygotes mating strictly assortatively are the only parents avoiding expression of harmful mutations in their offspring, thus there is selection for assortative mating. For clarity the figure illustrates only the inheritance of accumulated harmful mutations, without chromosomal cross-over that occurs rarely in the model. The proportional output of genotypes from mating is indicated as a ratio (e.g. 1∶2∶1). Solid lines represent the reproductive barrier induced by assortative mating where the four upper-left squares makes up the Punnett square from matings in niche 1, and the lower-right square shows the result from matings in niche 2.