The Agaricales: Molecular Systematics and Evolution of Mushrooms

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9708035 Vilgalys Mushrooms are among the most conspicuous groups of fungi found in nature, and are of ecological and economic importance. This project by Dr. Rytas Vilgalys of Duke University and his colleagues in Canada and the U.S. supports the development of a DNA sequence data base for taxonomic studies of mushroom fungi and their allies (usually placed in the order Agaricales, of the basidiomycetes). Although there has been much speculation about the relationships of diverse mushroom groups (gilled or poroid forms, underground "truffle" forms, etc.), little is known about their phylogenetic origins or the characters that reliably define each of the lineages. The taxonomy of mushrooms has traditionally relied on morphological features that are known or suspected to be subject to parallel or convergent evolution, or are phenotypically plastic within species or genera; as a result, many families are considered artificial assemblages, keyed to easily recognizable characters that nonetheless do not correlate with other features of their biology. An independent data set of DNA sequences from the nuclear ribosomal genes, from more than 500 representative species sampled from tropical, temperate, and boreal regions, provides for measurement of mutational differences that can then be used to construct phylogenetic trees for mushroom groups. When compared and integrated with traditional morphological and life-history characters of the fungi, the molecular sequence data will aid researchers in the identification of new or poorly known species, and provide a comparative basis for studies on mushroom ecology and biology. The evolutionary origins and diversity of "fruit body" formation in mushrooms, of their enzymatic capabilities for digesting wood and carbohydrates, and of their general nutritional modes (saprophytic, parasitic, mutualistic) can be studied in a rigorous comparative manner in the context of a well-supported phylogenetic framework that establishes the genealogical connections among species. Dr. Vilgalys is one of the leaders in this new comparative biology of fungi.