3.4.2 Pattern of non-synonymous versus synonymous substitutions
As presented above, the mean dN/dS ratios observed across TLR loci was higher than 1, indicating that overall, amino acid substitutions were favoured, as they should increase the individual’s fitness. The Figure 2 highlights that dN/dS higher than 1 are mostly encountered at the extra-cellular domain, suggesting that positive selection is predominant over this region of the protein. On the contrary, with 4 exceptions, dN/dS ratios are either equal or lower than 1 at the intra-cellular domain, suggesting that synonymous substitutions are favoured (i.e., neutral or purifying selection). Therefore, contrasted pattern of selection are likely to occur at both extra- and intra-cellular domains.