Phylogenetic relationships of mitochondrial subgroup IIB1 introns based on aligned ribozyme sequences (see Materials and Methods and Supplemental Data Set). Introns are designated as in Table 1; the cox1 introns from P. brasiliensis and C. parapsilosis, the sequences of which are markedly divergent from the rest, were used as outgroups. Numbers next to nodes are bootstrap proportions (200 replicates) ≥75% (corresponding branches are thickened). The roots of well-supported, major clades of ribosomal introns are indicated. The length of the 5′ terminal insertion, when present, is provided to the right of an intron name (boxed numbers preceded by + sign). RT, LAGLIDADG, GIY . . YIG, and “Unknown” designate proteins potentially encoded by the introns (see Table 1; note that only some versions of the G. intraradices LSU1787 intron include an ORF).
