Figure 4. Testing predictions of frequency-dependent selection: inconsistent allele effects across sites. A. The percentage of deviation residuals explained by the MHC term and the MHC × sample site interaction term in the regression models, which regressed the infection load of certain parasite against a particular MHC allele, sample site, and the MHC × sample site interaction. Each dot represents a MHC-parasite combination. The dotted line is a line of equal effect size (slope of 1, intercept of 0). The models with either term significant are plotted with black dots, and all the non-significant models are in grey. Two significant examples were highlighted in A, and plotted in B and C. B. The effect of MHC allele prot_1215 on the infection load of parasite Bunoderina in Mud lake and Little Mud lake. C. The effect of MHC allele prot_110 on the infection load of parasite Nematode spp4 in McCreight lake and McCreight stream. Note that the y axes of B and C are on log scale.