Evolution of Functional Groups in Basidiomycetes (Fungi)

Abstract

Being dependent on organic substrates, fungi play essential roles in parasitic, symbiontic, and saprobic interrelationships. Diverse groups of fungi have evolved convergently as specialized substrate users. Fungal parasites inhabit all kinds of organisms, including fungi themselves. Coevolutionary processes tended towards more and more specifity, thus creating increased species diversity. Most serious parasites of useful plants such as crop rusts and smuts are represented in these groups. Animal and human pathogens occur in various groups of major taxa. Symbiontic systems originated not only polyphyletically but also evolved convergently to form new taxa with new structures and functions in lichens. These organisms are most important ecologically in diverse and often extreme habitats. Other major symbiontic systems are mycorrhizae, which have key functions in the evolution of land plants and terrestrial ecosystems. Saprobic fungi grow on various kinds of dead organic materials and have an essential functional importance in wood degradation, decomposition of herbaceous substrates of plants, and in litter and humus layers. There are various parallel evolutionary lines from structurally simple to complex organizations highly adapted to successional niches. In most cases, the species diversities are equivalent to functional specializations. Therefore, the ecosystem function is essentially dependent on fungal functional interactions.