Evidence that the arbuscular mycorrhizal fungi are not closely related to the zygomycetes, with which they have traditionally been placed, has been growing. Fast tracked in this issue is a paper comparing the SSU rRNA gene sequences in a wide range of these and other fungi and formally establishing a new phylum, Glomeromycota, and further three new orders for these fungi (pp. 1413–1421).

The ecologically and economically important arbuscular mycorrhizal (AM) fungi, crucial in the ecology and physiology of land plants, and the endocytobiotic fungus, Geosiphon pyriformis, are phylogenetically analysed by their small subunit (SSU) rRNA gene sequences. They can, from molecular, morphological and ecological characteristics, unequivocally be separated from all other major fungal groups in a monophyletic clade. Consequently they are removed from the polyphyletic Zygomycota, and placed into a new monophyletic phylum, the Glomeromycota.

The recognition of this monophyletic group, which probably diverged from the same common ancestor as the Ascomycota and Basidiomycota, gives these fungi their proper status, and provides a basis for a new and natural systematics of these fascinating, yet largely hidden organisms, with three new orders (Archaeosporales, Paraglomerales, Diversisporales) described herein. Additionally, several clades resolve at family level; their formal description is in progress.

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.

The taxonomy of lichenized fungi (lichens) is relatively well-known compared to that of other fungi because lichens are long-lived and possess a thallus that requires exposure to light. Therefore they are easily observed on their natural substratum and sampling can be carried out much more thoroughly than in other fungal groups. Comprehensive catalogues of lichen taxa known worldwide are available and currently about 13500 species are accepted.

An analysis of selected, recently revised groups suggests that there has been a mean increase in species number of about 25% since 1931. One third of the species recognized before 1931 were withdrawn, and almost half of the currently recognized species have been described after 1931. Some 3000 names seem to be ‘orphaned’, not included in currently accepted genera and not appearing in recent species counts. New species are being described at an increasing rate, so that large numbers of ‘missing lichens’ seem to be present. However, there is no clear indication how numerous they are, only an estimation that they amount to some 25% of all species.

A geographical analysis of checklists suggests that most missing species will be found in the tropics and the southern hemisphere. A taxonomic analysis of recently published species suggests that there is no particular group yielding more novelties than others. Our own fieldwork impressions suggest that tropical primary forests are the most productive in revealing undescribed species. These are found in particular on leaves and on bark high up on the tree trunks. In well-studied areas like western Europe the new discoveries tend to be cryptic species or species rarely producing ascocarps.

In conclusion, the ‘missing’ lichens are estimated at about 4000, and are to be found everywhere and in all taxonomic groups, but predominantly in primary tropical forests. This would result in a total of about 18000 lichen species.

The distribution of the major components of the bolete mycobiota of South East Asia is considered and suggestions made as to their possible origin, mycogeography and relationships. The final number of species of boletes in South East Asia is likely to be well in excess of the number compiled in Corner’s 1972 monograph. Molecular information is incorporated into the theme where of interest.

Estimates of global fungal numbers rely heavily on the ratios of unique fungi to host plants. Evidence for host-specificity, which is basic to our understanding of host to fungus ratios, is therefore explored in this review. There is considerable evidence that some endophytes, pathogens and mycorrhizal fungi are host-specific. Host-specificity however, may be an unwise term for saprobic fungi, and ‘host-exclusivity’ and ‘host-recurrence’ may be more appropriate terms. Concepts of host-specificity, host-exclusivity and host-recurrence are therefore defined and discussed. Suggestions for future work needed in order to establish host-exclusivity and host-recurrence in saprobic fungi are made.

Fungal communities on decaying fronds of Livistona australis, Oraniopsis appendiculata (Australia), Arenga engleri, Livistona chinensis (Hong Kong), Arenga undulatifolia, Salacca affinis, and Oncosperma horridum (Brunei) were examined for fungi. In all, 288 different taxa were identified. The fungal communities on different frond parts (i.e. leaves, rachis-tips, mid-rachides and rachis-bases), on different hosts, at different sampling sites, at different stages of decay, and in different seasons were compared.

Fungal species compositions were distinct on different hosts and at different sites. Three-dimensional correspondence analysis resulted in: (a) three clusters corresponding to distinct communities on samples in Australia, Brunei and Hong Kong; (b) fungi on palms of the same genera (Arenga undulatifolia and A. engleri; Livistona australis and L. chinensis) at different sites, being more coherent than on palms of different genera at different sites; (c) fungi on palms of different genera at the same site being more coherent than on palms of the same genera at different sites. Fungal taxa on the same palm genus or species in different sampling sites were significantly different. Evidence for host specificity and fungal recurrence on different hosts and frond parts were found. No evidence of seasonal patterns of fungal communities was found on the palm hosts. Only 10% of the fungi were common to all three palm species studied in Brunei and 17% were common to the two palm species at Victoria Peak, Hong Kong.

Significant differences were found in the fungal communities colonising each of the different frond parts (leaves, rachis-tips, mid-rachides and rachis-bases). The greatest differences in most palms were found between the leaves and rachides.

When investigating fungal diversity it is recommended to examine a combination of naturally occurring fronds and frond baits throughout the decomposition process. Since a large number of forests, plant species and even types of plant tissues have yet to be explored by mycologists, we predict that there are an incredibly large number of fungi on these unexplored substrata.

This study has confirmed that fungi on palms are very diverse and suggests some reasons for this. The data has important implications towards future biodiversity studies and estimates of global fungal numbers. Future studies and estimations must reflect and incorporate these results.

The saprobic microfungi associated with endemic plants of Mauritius have been studied. Over 200 taxa were identified of which approximately 90% are new records for Mauritius including one genus and 38 new species. The mycobiota encountered on the monocotyledonous genus Pandanus is more distinct than that on three dicotyledonous hosts Sideroxylon, Cordemoya and Olea. Arguments are presented to support the inclusion of microfungi in in situ conservation management policies.

The South African Cape Floral Kingdom is the world’s smallest and most diverse plant Kingdom, but is greatly under threat from urbanisation and agriculture. It covers only 90000 km2 and has a Mediterranean climate. This area has a long history of botanical studies, but little research has been undertaken on the associated fungi. Therefore, a biodiversity study of the fungi has been initiated. The catalyst for this study has been the diversity of unusual fungi encountered whilst studying the fungal pathogens of Proteaceae. These pathogens include species, or entire genera of fungi that are specific to genera of Proteaceae. The diversity and uniqueness of the Proteaceae pathogens may indicate a similar diversity in saprobic fungi in this unusual habitat. Therefore, microfungi associated with genera of Proteaceae in various habitats are being systematically sampled over a two-year period. The initial results of this study are presented.

Samples of standing senescent culms of Panicum maximum, Pennisetum purpureum, Phragmites australis, Miscanthus floridulus, Saccharum arundinaceum and Thysanolaena maxima (Gramineae), and Schoenoplectus litoralis (Cyperaceae) were collected in Hong Kong between 1997 to 1999. A total of 205 fungal taxa were identified on these samples, including 61 ascomycetes, and 144 mitosporic taxa. Common fungal genera included Diaporthe, Leptosphaeria, Massarina, Ophiobolus and Ophioceras (ascomycetes), and Monodictys, Phaeoisaria, Periconia, Phoma, Phomopsis, Rhinocladiella, Septoria and Sporidesmium (mitosporic taxa). Different grass species were host to different fungal communities and diversities of taxa. Diversity indices for fungi on the hosts varied from 3·3 to 8·7, the highest index being from Pennisetum purpureum, and were overall higher from species offering more durable, strongly sclerenchymatic substrates. No single saprobic fungus collected in this study is thought to be specific to any one grass, however, certain fungi tended to reoccur on single grass species, but not on adjacent grasses. A ‘core fungal group’ was commonly associated with the decaying grasses and this ‘core’ was thought to be important in nutrient cycling in the grasses. A comparison of the fungi occurring on grasses with those on other monocotyledonous hosts is made. The numbers of fungi known to occur on Juncus roemerianus and Phragmites australis are briefly summarised.

Fungi on submerged wood in streams are a diverse group, comprising taxa from various families. Fungal communities on submerged wood collected from Sungai Sitam in Brunei, Tai Po Kau Forest Stream in Hong Kong, and from a stream in Lipur Lentang Nature Reserve in Malaysia are reported. One hundred and forty-seven taxa were recorded. A higher species diversity including temperate and tropical species was recorded in Tai Po Kau Forest Stream in the subtropics. Ascomycetes and their asexual stages were dominant in tropical and subtropical freshwater habitats, while discomycetes were rare in these habitats. Distinct fungal communities are found on submerged wood in tropical, subtropical and temperate regions and these are discussed. Including the fungi identified in this study, over 1000 fungi has been recorded from freshwater habitats.

Fungal endophytes have been found in every plant species examined to date and appear to be important, but largely unquantified, components of fungal biodiversity. Endophytes are especially little known in tropical forest trees, where their abundance and diversity are thought to be greatest. Here, we explore the occurrence of endophytes in a broad diversity of woody, angiospermous taxa in a lowland, moist tropical forest in central Panamá. We use similarity indices to assess host preference and spatial heterogeneity of endophytes associated with two co-occurring, but distantly related, understorey tree species in two sites of that forest, and assess the utility of indices based on frequencies of morphospecies occurrence (Morisita-Horn index) and on presence-absence data (Sørensen’s index). We suggest that our understanding of fungal diversity will be enhanced by exploring ecological patterns underlying endophyte occurrence in host species, and discuss methods for assessing the proportion of fungal biodiversity represented by tropical endophytes.

Endophytic fungi were isolated from 7500 samples of wild Musa acuminata collected from five sites at Doi Suthep Pui National Park, Thailand during December 1998 to July 1999. Overall colonization rates from surface sterilized tissues were 56·5, 48·9, 48, 47·9 and 41·7% for the Medicinal Plant Garden, Ban Suthep, Queen Sirikit Botanic Garden, San Gu, and Montatarn waterfall sites respectively. Sixty-one different fungal taxa were isolated. Fewer isolates were recovered from younger than older samples. Xylariaceous taxa and Guignardia cocoicola were the most frequently isolated endophytes from leaves and were either absent or rare in midrib, petiole and pseudostem. Colletotrichum gloeosporioides, C. musae, Guignardia cocoicola, various sterile mycelia and xylariaceous spp. were common at all sites. The endophyte fungal communities at the five sites were found to differ. Deightoniella torulosa was the most frequent isolate at the Ban Suthep site and was either absent or rare at other sites. Colletotrichum species were most common in the midribs and petioles at all sites, while Pyriculariopsis parasitica and Dactylaria sp. were most common in the pseudostems. The endophyte communities isolated from M. acuminata in this study are compared with those from previous studies on tropical hosts. Several of the endophytes isolated are established pathogens of banana and provide support for the hypothesis that some endophytes are latent pathogens. The diversity of fungi on banana is discussed in relation to global estimates of numbers of fungus species.

There are approximately 70000 species of described fungi, representing about 5% of the estimated 1·5 M species world-wide. Proportionally there are numerous undescribed species and most habitats and hosts should provide a bounty of novel fungi that can be exploited in a wide variety of ways. Where, however, are these missing fungi? Data indicates that they may occur in poorly studied countries, hosts, habitats, niches or tissues, and are mostly microfungi. Host specificity and/or tissue recurrence are important considerations in biodiversity estimates. We are a long way from establishing where we can find the missing 1·43 M fungi, but evidence presented here resulting from data from Hong Kong indicates many places where we could look.

Phylogeographic divergences of four coprinoid species, Coprinus comatus, Coprinellus disseminatus, Coprinellus micaceus and Coprinopsis lagopus were investigated using nuclear ITS sequences. Each taxon showed genetic variation that corresponds with the geographic origins of collections. Groupings produced from ITS1 and ITS2 sequences were similar together. In C. comatus, East Asian strains were well separated from New Zealand and North American strains. In C. disseminatus, Hawaiian strains formed an independent clade with that from Nepal, separating those from East Asia. And there were two distinct East Asian groups for C. disseminatus. East Asian C. micaceus strains constituted a distinct group from Hawaiian strains. In C. lagopus, Hawaiian and European strains were clearly separated from each other. There was a great genetic diversification in C. disseminatus and C. micaceus from East Asia, suggesting divergence process of these taxa in that region. However, Hawaiian strains lacked genetic variation, which indicated their recent origin in Hawaii.

The haplophase of the pine blister rust Cronartium flaccidum was used to grow mycelial clones axenically from single genotypes. Single telia were suspended over the media in order to obtain a direct cast of uninucleate basidiospores, providing nurse cultures from a mass basidiospore inoculum. Nurse culture and medium composition were crucial factors in successful germination and establishment of single-spore colonies. Significant differences in percentage germination between treatments and controls suggested that an extracellular matrix secreted by high density seeded basidiospores could be involved in the germination of single propagules. Proteins present in this matrix could exert a surface contact stimulus triggering germination of newly seeded basidiospores. Pre-production of extracellular enzymes in the medium could also initiate early substrate catabolism and thus create a favourable environment to support subsequent colony establishment. Growth was good on various media, and excellent on HG1Y+BSA medium. Primary mother colonies were divided into several smaller ones, re-grown axenically, then macerated. Aliquots of the resulting mycelial fragments were dispensed with a micropipette into fresh agar media. Clones derived from each pure culture were in general morphologically similar in texture, margin, compactness, and surface topography. These genetically pure lines grew at a faster rate and rapidly produced a considerable amount of mycelium. The significance of culturing rust fungi from single genotypes is discussed in relation to potential applications and new directions of research.

If is with deep regret that we announce the sudden, tragic, and unexpected death of Dr Stephen Moss, President of the British Mycological Society for 2001-2002. Stephen, aged 58 years, died at his home in Portsmouth on Friday 26 October 2001. He was a caring and conscientious person who dedicated his life to mycology, and in particular the Society, throughout his career. Our thoughts are with his wife Jan and all the family at this dificult time. A full obituary will appear in a future issue of Mycological Research.