The phylogeny of North AmericanUrospora(Ulotrichales, Chlorophyta) based on sequence analysis of nuclear ribosomal genes, introns and spacers

Amplification of the ribosomal cistron of Urospora isolates from within the 18S ribosomal RNA (rRNA) gene through the internal transcribed spacer (ITS) and 5.8S regions into the 28S rRNA gene produced fragments of varying lengths. The lengths depended on the absence or presence of up to three group I introns, located at positions 943, 989 and 1512 of the 18S rRNA gene (positions based on the Escherichia coli sequence). The 943 and 1512 introns belong to subgroup IC1 and the 989 intron to subgroup IE. Introns occurred in all species except U. penicilliformis. Intron sequence data and phylogenetic analyses based on the intron sequences supported recognition of the same species groups as the ITS data and helped resolve relationships between the species. Urospora penicilliformis, U. wormskioldii and two undescribed taxa (‘Aberdeen’ and ‘Viking’) occurred in one clade, and U. neglecta in a separate clade. Pacific U. neglecta differed from Atlantic U. neglecta in both intron sequence and occurrence. Th...