Mycological Research

The magnitude of fungal diversity: the 1·5 million species estimate revisited 1

David  L. HAWKSWORTH  a1
a1 Departamento de Biología Vegetal lI, Facultad de Farmacia, Universidad Complutense, Plaza de Ramón y Cajal, Ciudad Universitaria, E-28040 Madrid, Spain. E-mail:


The number of known species of fungi is estimated as at least 74 K, but could be as much as 120 K with allowances for ‘orphaned’ species. Yet in 1990 the magnitude of fungal diversity was estimated ‘conservatively’ at 1·5 M species. This figure has been widely accepted as a working hypothesis, but subsequent estimates have ranged from 500 K to 9·9 M and the bases of these suggestions are analyzed. Additional data pertinent to the estimation of the number of fungal species on Earth that has become available since 1990 is discussed. Site inventories demonstrate the need for long-term (20 yr plus) intensive studies to determine the number of species in a site. Fresh data sets on fungus[ratio]plant ratios and degrees of host specificity, especially from well-studied hosts in the tropics, are consistent with earlier estimates. The extent of novelty discovered in recent monographic generic revisions and studies of species in particular habitats varies from 0–96%. Allowances for cryptic species, now known to be widespread by incompatibility and molecular studies, could on their own justify an upward revision by a factor of at least five. To enable confidence in any overall estimate to be increased, more detailed studies, especially on particular sites in the tropics, are needed. The consensus of tropical and molecular mycologists in particular is that an increased estimate could be justified. However, it is prudent to retain 1·5 M as the current working hypothesis for the number of fungi on Earth while additional data to test it further accumulates.

(Received July 10 2000)
(Accepted April 14 2001)


1 Paper presented at the Asian Mycological Congress 2000 (AMC 2000), incorporating the 2nd Asia–Pacific Mycological Congress on Biodiversity and Biotechnology, and held at the University of Hong Kong on 9–13 July 2000.