XVI International Botanical Congess

The limitation of the nuclear-encoded small subunit ribosomal RNA gene (small subunit nrDNA) to resolve the early evolution of filamentous ascomycetes is well documented. This molecule provides very few unambiguous synapomorphies at the base of this clade resulting in very short internodes with virtually no bootstrap support. Without solving this problem it is not possible to reconstruct with confidence the origin of lichen-forming ascomycetes and determine their relationships to non-lichenized ascomycetes. The inclusion of more taxa in phylogenetic analyses using this molecule did not help to resolve these deep phylogenetic relationships. To alleviate this problem we have sequenced the large subunit nrDNA and a nuclear protein coding gene for the same species for which the small subunit was sequenced. The selection of taxa includes representatives from 12 of the 15 orders of ascomycetes that comprise lichen-forming species and from more than 14 orders of ascomycetes that comprise non-lichenized species. The potential impact of the resulting multi-gene phylogeny on future classifications of ascomycetes will be explored.