Substitutions. Visualization of the number of pairwise substitutions observed in a comparison of 65 orthologous membrane proteins  between two groups. The size and colour of each marker indicates the magnitude of the substitution (see colour-bar). A tilde (~) indicates deletion/insertion. Favoured substitutions with p-values < 0.05 in the Replaced (mesophile)→Replacement (psychrophile) direction are marked with upward-pointing triangles, and the non-favoured substitutions with p-values < 0.05 are marked with downward-pointing triangles.