Biogeography of aquatic hyphomycetes: Current knowledge and future perspectives

Since Ingold's (1942) initial description, mycologists have been interested in deciphering global distribution patterns of aquatic hyphomycetes, a group of fungi that play a key role in plant-litter decomposition in freshwaters. However, many questions remain largely unanswered. In this review, we used distribution data of morphospecies from studies throughout the world in an attempt to better understand the magnitude of global species richness, patterns of biodiversity and the extent of cosmopolitanism versus endemism. Sampling efforts have varied among geographic regions, and correlate significantly with species richness. Community similarity decreased with geographic or latitudinal distance. Species richness was highest at mid-latitudes (temperate streams), and high community similarities were found between geographically distant locations in similar climatic zones. Studies relying on morphotypes have undoubtedly provided relevant information on the geographic distribution of aquatic hyphomycetes. However, metagenomic approaches combining taxonomic, phylogenetic and functional diversity in coordinated surveys will be the best option to better decipher diversity patterns of these fungi and their functional roles at a global scale.