Polymorphic Tf insertions found in wild strains clustered next to sporulation frequency genes. (A) Enrichment for the term “decreased sporulation frequency” for genes adjacent to polymorphic LTRs in wild strains. The number of sporulation genes among the total number of genes adjacent to polymorphic LTRs is given in parentheses. Significant enrichments (FDR-adjusted P-values) are indicated in red. (B) Cluster dendrogram of wild strains calculated from the presence–absence of polymorphic Tf1 insertions. Approximately unbiased (AU) P-values are indicated for each node. Significant AUs are indicated in red.