Role of fungi in freshwater ecosystems

There are more than 600 species of freshwater fungi with a greater number known from temperate, as compared to tropical, regions. Three main groups can be considered which include Ingoldian fungi, aquatic ascomycetes and non-Ingoldian hyphomycetes, chytrids and, oomycetes. The fungi occurring in lentic habitats mostly differ from those occurring in lotic habitats. Although there is no comprehensive work dealing with the biogeography of all groups of freshwater fungi, their distribution probably follows that of Ingoldian fungi, which are either cosmopolitan, restricted to pantemperate or pantropical regions, or in a few cases, have a restricted distribution. Freshwater fungi are thought to have evolved from terrestrial ancestors. Many species are clearly adapted to life in freshwater as their propagules have specialised aquatic dispersal abilities. Freshwater fungi are involved in the decay of wood and leafy material and also cause diseases of plants and animals. These areas are briefly reviewed. Gaps in our knowledge of freshwater fungi are discussed and areas in need of research are suggested.