Fig. 1.

Phylogenetic distribution of intron A in Xdh. The time when intron A was gained in animals is indicated by an arrow. The vertical line in the amino acid and nucleotide alignments indicates the site of intron insertion. The two boxes on the nucleotide alignment enclose the protosplice-site motifs. The5 willistoni sibling species are Drosophila equinoxialis, Drosophila paulistorum, Drosophila willistoni, Drosophila tropicalis, and Drosophila insularis; the 5 saltans group species are D. saltans, Drosophila prosaltans, Drosophila neocordata, Drosophila emarginata, and Drosophila sturtevanti; the 5 melanogaster group species are D. melanogaster, Drosophila simulans, Drosophila teissieri, Drosophila erecta, and Drosophila ananassae; the 8 obscura group species are Drosophila pseudoobscura, Drosophila miranda, Drosophila persimilis, Drosophila bifasciata, Drosophila affinis, Drosophila athabasca, Drosophila azteca, and Drosophila subobscura; the 20 repleta group species are Drosophila borborema, Drosophila serido, Drosophila koepferae, Drosophila buzzatii, Drosophila starmeri, Drosophila venezolana, Drosophila uniseta, Drosophila martensis, Drosophila stalkeri, Drosophila richardsoni, Drosophila aldrichi, Drosophila arizonae, Drosophila mojavensis, Drosophila mulleri, Drosophila spenceri, Drosophila leonis, Drosophila eremophila, Drosophila mercatorum, Drosophila eohydei, and D hydei; the 5 virilis group species are Drosophila ezoana, Drosophila lacicola, Drosophila americana, Drosophila lummei, and Drosophila virilis; and the two Hawaiian species are Drosophila gymnobasis and Drosophila mimica.