Total segregating sites for each lineage include all segregating sites where genotype calls were made in at least half of the isolates. Average pairwise-segregating sites are the average numbers of sites with different genotypes between all pairs of isolates within a lineage. Total homozygous segregating sites include all sites within a lineage where there is at least one homozygous difference between isolates. Average pairwise-homozygous segregating sites are the average numbers of sites with different homozygous genotypes between all pairs of isolates within a lineage. Nucleotide diversity (π) is the mean of the per-site nucleotide diversity. Tajima’s D is reported as the mean over 1-kbp bins.