The ancestral state reconstruction of Ple.18S1 introns, showing their host alternation within Pleosporales, based on an unrooted ML tree (Suppl. material 2: RAxML_bipartitions.125_onlyintron_ML). The ancestral states are categorised into different families of intron carriers. Colours at each terminal node indicate the family of the intron host. Pie charts at each node indicate the relative likelihoods of ancestral states. Stacked colour chart approximately demonstrate the ecological traits of the habitats from which the fungi were recovered, according to the sequence information deposited in GenBank.