Fig. 4

Epistasis between markers associated with fgfr1b and fgf20a. In all graphs, Labeotropheus fuelleborni possess the A allele, and T. red cheek possess the B allele. Thus, F₂ animals denoted AA have inherited two L. fuelleborni alleles. a At the fgfr1b locus there is a strong association between genotype and scale phenotype. b At the fgf20a locus there is no such association. c When grouped by genotype at fgf20a, the genotype-by-phenotype association at fgfr1b is especially robust. The association is most pronounced in animals that are homozygous for the B allele at fgf20a. Bars indicate standard errors of mean phenotypic values for each genotype