This paper summarizes the opinions of 26 mycologists who have worked in more than one hemisphere or continent regarding the locations, correlates, and potential causes of centers of fungal endemism and diversity in non-lichenized fungi. These views were initially obtained via a survey and then summarized by the lead author. Most authors working on basidiomycetes thought that fungal diversity was more strongly correlated with host and habitat diversity than with resource abundance, whereas most of those working on ascomycetes and Hyphomycetes indicated that all three factors were very important. Overall diversity was highest in the tropics, at intermediate to high rainfall, and at middle to low elevations. Certain fungal groups, however, such as the Cortinariaceae (Agaricales), and some members of the Heterobasidiomycetes are more diverse at middle to high latitudes and elevations. There was no apparent variation in Gasteromycete diversity with latitude. The Neotropics were ranked as having a greater diversity of fungi than Africa by three of the four authors with experience in both. Although this pattern might be related to historical factors or to a higher diversity of host plants in the Neotropics, collections of fungi from Africa and the Asian tropics have been too limited to make confident comparisons between continents. Except for the Gasteromycetes and certain plant parasites, Europe was always ranked lowest in fungal diversity when it was included in comparisons, even though collecting has been most intense there.
The types of areas most frequently mentioned as having many species that are unknown elsewhere were humid forests on islands, tropical mountaintops, and large tropical river basins. For example, Australia, New Zealand, New Guinea, Sulawesi, the Andes, and parts of Africa and South America, especially the Congo and Amazon river basins were thought to have many unique species. These areas encompass many wet to moist centers of endemism for plants. The concordance suggests that despite differences in the mechanisms of dispersal and sexual incompatibility, there may be similar forces governing the isolation and speciation of plants and fungi growing in humid areas. Some plant parasitic Heterobasidiomycetes that are host-restricted occur in all regions and habitats, including dry ones. Species with limited ranges also appear to be common in the Agaricales regardless of the region. Unfortunately, there is currently too little knowledge of fungal mating systems and dispersal barriers with regard to their roles in fungal evolution and distribution. The various gaps, hypotheses, and global patterns of fungal diversity identified in this paper are worthy of pursuit through experiments and comparable surveys.