Recombination and positive selection contributed to the evolution of Listeria monocytogenes lineages III and IV, two distinct and well supported uncommon L. monocytogenes lineages

► Listeriamonocytogenes lineages III and IV form two distinct monophyletic groups. ► Virulence genes evolved by positive selection in lineages III and IV. ► Recombination contributed mainly to the evolution of lineage III isolates.