Consequences of Mutualism (Lichenization) on the Phylogeny and Diversification of Ascomycetes

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9615542 Lutzoni Symbiotic associations between distantly related life forms that have complementary functions provided key innovations that led to the origin and diversification of major groups of organisms. Lichen symbioses, resulting from mutualistic interactions between fungi and photosynthetic algae (usually green algae or cyanobacteria), enabled the evolution of at least 20% of all named species of fungi. Most lichens include fungi that are ascomycetous in nature (the others are basidiomycetes); 50% of all known species of ascomycetes are involved in lichen symbioses. Despite the indisputable significance of mutualism as a major evolutionary force, very little is known about the origins and pathways of diversification among mutualistic groups. It is clear that the phylogeny of filamentous ascomycetes and the impact of mutualism (lichenization) on the evolution of this phylum can be understood only with taxonomic sampling of lichen-forming ascomycetes that is at least comparable to the sampling currently underway for non lichen-forming ascomycetes. Dr. Lutzoni at the Field Museum in Chicago is commencing molecular phylogenetic analyses of lichen-forming ascomycetes as part of this enterprise. One goal of the project is to discover the ancestry and relationships of lichen-forming fungi relative to their non-lichenized counterparts. To attain this goal, three molecular data sets, from three nuclear genes expected to show informative variation, will be gathered from representatives of a wide array of lichenized and non-lichenized ascomycetes. Special emphasis will be directed toward the Gyalectales and Lichinales, two taxonomic orders of lichen-forming fungi believed to comprise the early radiation of filamentous ascomycetes. Theoretical issues relating to constructing phylogenetic trees from DNA sequence data from multiple genes will also be explored.