Relative fitness for the two-locus fitness-valley component.

The rows and columns denote the haplotypes (set of alleles inherited from each parent) of a diploid genotype. The toxin st is expressed in individuals carrying either a C or D allele but not both. The payload sp is expressed if the individual carries at least one engineered allele (dominant payload). The resulting fitness landscape has two stable equilibria (cd or CD fixed), separated by a fitness valley caused by the toxin load.