Fungi are unique organisms which are placed in their own Kingdom and are quite distinct from animals and plants. They are a huge and immensely diverse group, of inestimable ecological and economic significance. They are the primary agents of decay and nutrient recycling worldwide, play key roles as mycorrhizal partners essential to the development and health of almost all vascular plants, and have enormous numbers of other essential partnerships and associations with living organisms from all other kingdoms of life. Yet fungi remain vastly under-studied compared to plants. Although most of the world has long since been surveyed for vascular plants and a host of regional floras and monographs have been published, as yet most of the world has not been surveyed for fungi. Very few mycotas or monographs exist and even in better-known areas, including the British Isles, comprehensive, modern checklists are almost non-existent. Identification of collections commonly poses severe difficulties even to the few specialists available, and the discovery of species new to science is commonplace.
Understanding the basic units of fungal diversity is the essential starting point for all other research on the group. Around 100,000 species have so far been described, most of which are still poorly known, yet it is estimated that total numbers are far greater and that over 90% of fungal species still await description.
RBG Kew is one of the key international centres for the study of fungal diversity. It has one of the most comprehensive global reference collections to be found anywhere, together with the facilities, the expertise, and above all a long-standing reputation as a world authority on systematic mycology. Work is focused in the baseline Fungal Diversity Research programmes based on the 800,000 fungal collections in the Kew herbarium the most extensive collections worldwide and the mycological library at Kew, the most complete and up to date of its kind. The research primarily involves morphological analysis, supported by a molecular laboratory, the end products of which are papers describing new species, monographic studies, checklists, and local and regional mycotas (the fungal equivalent of floras). Kew is the only British institute with the resources to support such research on a world basis. The immense diversity of fungi is now well established, and the need for user-friendly keys, checklists and descriptive data remains a major concern worldwide. Documenting this diversity remains the single most important and most requested service that Kew alone can provide.