Experimental design of ingroup and outgroup crosses.

<p><b>A</b>) Schematic illustration of the crosses between a low or highly virulent α parent and a high or low virulence <b>a</b> parent respectively. <b>B</b>) Summary of the strains used for mating, their ability to proliferate intracellularly within macrophages (IPR), and the number of progeny isolated from each cross. ^†Subsequent whole genome sequence analysis revealed that the progeny and restored ‘haploid’ strains are aneuploid strains. Progeny showed regions of triploidy and restored strains regions of diploidy (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003771#pgen.1003771.s001" target="_blank">Figure S1</a>).