Frontiers of Biogeography

Global estimates of the number of species of Fungi have ranged from 1.5 to 13.2 million, but have been based more on opinion and simple ratios than quantitative assessment. We analysed trends in the rate of description of fungal species over four centuries, noted the use of molecular methods in species delimitation, and used a statistical model designed for such data to predict future trends. A total of 144,035 fungal species were analysed, along with smaller species groups extracted from the core dataset that approximated biological and ecological traits. The groups explored included fungi of medical significance (728 spp), those associated with the marine environment (972 spp), rust and smut fungi (9,125 spp), arthropod ectoparasites of class Laboulbeniomycetes (2,376 spp), mushroom-forming fungi of class Agaricomycetes (37,717 spp), the budding yeasts of subphylum Saccharomycotina (1,165 spp), the class Dothideomycetes (30,912 spp), and lichenized fungi of classes Lecanoromycetes and Arthoniomycetes (12,154 spp). There was an acceleration in overall fungal description rates within the last two decades accompanied by the increased use of genetic data in new species descriptions. Mushroom-forming, lichenized, and plant-associated fungi were predicted to experience the greatest increase in new species. Increased description rates are supported by an increase in the number of authors describing species. However, the number of species described per author in a year has been declining since 1875. Because less than 10% of currently accepted fungal species have molecular data associated with corresponding type specimens, genetic data should not be used to discriminate new species without associated phenotypic information. An additional 68,750 species (48%) were predicted to be described this century, making Fungi the least well-described Kingdom assessed to date.