Unrooted phylogenetic tree of the five strains used in the genome-wide analyses. This tree represents the consensus tree of 2267 gene cluster alignments used for analyses. Branches tested for positive selection are indicated as TLM1A (Test L . m onocytogenes lineage I Ancestral), TLM2A (Test L . m onocytogenes lineage II Ancestral), and TLI/LM (Test L . i nnocua/L . m onocytogenes).