Pervasive, genome-wide positive selection leading to functional divergence in the bacterial genus Campylobacter

Positive selection (PS) distribution pattern in Campylobacter (A,C) and Streptococcus (B,D). (A,B) Lineage pairwise similarity indexes between the random model of selection, a random model with a set of genes devoid of positive selection, and the observed indexes. (C,D) Global pattern of selection distribution, with the observed pattern (black and thick lines), as well as simulated patterns with different settings (dashed lines). The random distributions with two categories of genes were set with 150 genes, five times and seven times less likely to be under positive selection for Campylobacter and Streptococcus, respectively.