Fig. 6

Likelihood surface describing inferred selection parameters for the resistance allele. Within our model, the fitness of a genotype is determined by the alleles at a single resistant allele, with homozygous susceptible worms having fitness 1, homozygous resistant worms having fitness 1 + s, and heterozygous worms having fitness 1 + hs in the presence of the drug. In each plot, calculated for both the parental (a) MHco10(CAVR) and (b) MHco4(WRS) populations, we identify the location of the maximum likelihood values for selection (s) and dominance coefficients (h) (black dot), and the likelihood landscape surrounding this maximum value (log likelihood heatmap scale: yellow = high likelihood; blue = low likelihood) for the position in the genome of the resistant allele. Changes of the order of 100 likelihood units indicate substantial differences in the extent to which the model fits to the data