FIG. 3.

(a) Compatibility matrix of polymorphic positions. The matrix was constructed based on 68 polymorphic positions at four MNR loci of 41 E. coli strains with the Reticulate software. Each square describes pairwise compatibility relationships between the 68 sites. Black squares, incompatibility; white squares, compatibility between two polymorphic sites at two different loci (between loci); colored squares, compatibility between two polymorphic sites at the same locus (within locus). (b) Compatibility at four MNR loci. Levels of between-loci compatibility are plotted against with-in locus compatibility.