Preface

In 2007 it is 25 years since the publication of Decomposer Basidiomycetes: Their Biology and Ecology (Frankland et al., 1982). This was a seminal book but, while most of what was written remains true, our breadth and depth of understanding of many areas has extended dramatically—particularly the mycelium, though inevitably some areas have lagged behind, for example enzymology in the natural environment. New vistas have opened up with the advent of powerful computing, modelling and molecular approaches. Undoubtedly, understanding the ecology of basidiomycetes is tantamount to understanding the role of fungi in natural ecosystems since they are major agents of decomposition and nutrient cycling, and yet this important branch of mycology does not seem to have attracted the attention that it deserves. This volume should help to redress the balance.

The book is not a collection of articles that hang loosely together under an umbrella heading, but rather a set of tightly connected chapters selected to cover the area of saprotrophic basidiomycete ecology. It essentially falls into three main sections covering: (1) the basidiomycete life-style; (2) interactions with each other and with other fungi and with other organisms; and (3) structure and function of basidiomycete communities.

The crucial role of the mycelium in the ecology of fungi, only touched on in Frankland et al. (1982) but highlighted in Jennings and Rayner (1984), is now well established. The first four chapters therefore set the scene by discussing the major aspects of basidiomycete mycelial structure and function, and the effect of the abiotic environment on function. Fricker et al. (Chapter 1) demonstrate that mycelial network architecture is of major significance in the acquisition of and distribution of nutrients, in interplay between different regions of the mycelium and in survival when parts of the network are destroyed. They also consider the costs and benefits of different architectures to large mycelial networks, and how network construction may be analysed using modern graph theory approaches. The enzymes produced by saprotrophic basidiomycetes to obtain energy and mineral nutrients for growth are then reviewed (Chapter 2), Petr Baldrian pointing out that the main gaps in our current knowledge are in the ecology of enzyme production under natural conditions. When energy and nutrients have been obtained they must be routed to the site of need, hence translocation mechanisms are reviewed by Watkinson et al. in Chapter 3, with particular emphasis on environmentally essential nitrogen. Mycelial network architecture, enzymology and nutrient uptake and translocation are all influenced by the abiotic environment, and Naresh Magan (Chapter 4) considers the effect of temperature, water availability and their interactions on growth.

Past overemphasis on fruit bodies in fungal ecology does not mean that their role is insignificant, and the importance of sexual reproduction is cogently argued in Chapter 5. Here Moore et al. not only review physiological factors favouring production and development of fruit bodies, but also summarize principles of fungal developmental biology. They also reveal dramatic changes in the seasonal pattern of fruiting in the U.K., correlated with climate change, which must surely reflect changes in mycelial activity. Stenlid then addresses issues in population biology (Chapter 6), notably aspects of fungal individuality, the size and dynamics of individual mycelia and how their integrity is controlled through somatic incompatibility, gene flow and long distance dispersal.

The second section covers interactions of basidiomycete mycelia with other saprotrophs, ectomycorrhizas and root pathogens (Chapter 7), bacteria (Chapter 8) and invertebrates (Chapter 9). Woodward and Boddy emphasise the role of interactions in ecosystem functioning, particularly nutrient cycling and release, effects on decomposition rates and the potential of saprotrophs as biological control agents. They note that interactions can be mediated: (1) at a distance; (2) following contact at the hyphal level; and (3) following contact at the mycelial level, and that antagonism at a distance and at the mycelial level are effected by volatile and diffusible chemicals including enzymes, toxins and other anti-fungal metabolites. de Boer and van der Wal introduced the, until recently, little studied area of bacterial-fungal interactions, showing that bacteria can affect functioning of saprotrophic basidiomycetes both negatively and positively. Then Boddy and Jones review the wide field of interactions with invertebrates. Following the extensive reviews in Anderson et al. (1984) and Wilding et al. (1989), considerable research has been performed in many such areas, not least effects of grazing on both groups of organisms. They point out that attention must now turn to effects on ecosystem processes and consequences of global environmental change.

The third section opens with a consideration of litter layer basidiomycetes (Chapters 10 and 11). Lindahl and Boberg emphasise the use of modern molecular approaches to reveal community structure during different stages of community development, and the role of these fungi in carbon and nitrogen cycling in boreal forests. This is complemented by the chapter by Lodge et al. on the greatly neglected tropical rain forest. Here mat-forming basidiomycetes play a crucial role in litter stability, prevention of erosion as well as decomposition and nutrient cycling.

Basidiomycete community structure development and function has been studied most intensively in wood, as reflected by the five chapters covering this topic in Frankland et al. (1982) and the major treatise by Rayner and Boddy (1988). This is probably not only because of the commercial value and ecological importance of wood, and the 100,000 or more species involved in wood decomposition, but also because the three-dimensional structure of communities can be relatively easily revealed. The plethora of studies on temperate angiosperm wood have revealed much about the ecological strategies adopted by wood-decay Basidiomycota, habitat factors influencing community development, and community development pathways during early to middle stages of decomposition in the standing tree and on the forest floor, but much remains to be discovered about late stages of decay (Boddy and Heilmann-Clausen, Chapter 12). Boreal wood decay communities are, by contrast with temperate forests, less diverse and more similar on a global scale, with about 2,500 species in Fennoscandia (Stenlid et al., Chapter 13). Classic inventory approaches, complemented by pure culture studies of mycelia and recently by molecular detection methods, show parallels with temperate forests in terms of fungal community structure and development. Attention is now being widened to consideration of the distribution of wood-decay fungi at the landscape and global scale (Heilmann-Clausen and Boddy, Chapter 14). It is becoming increasingly clear, from molecular and mating studies, that many species, previously thought to have a wide distribution, actually circumscribe several biological taxa, each with a much more restricted distribution. Thus continental drift, glaciations and other long-term geological and geographical factors have more impact on the current distribution patterns of fungi than hitherto realized.

The role of basidiomycetes in grasslands has been a neglected area of study. Griffith and Roderick point out its significance in Chapter 15, where they review the four functional groupings—litter decomposers, dung fungi, ter-ricolous species and root endophytes—that encompass the several hundred basidiomycete saprotrophs which are preferentially found in grassland. Basidiomycetes in aquatic ecosystems are also often forgotten. Gareth Jones (the only author who also contributed to Frankland et al., 1982) and Rattaket Choeyhklin provide an up-to-date review of marine and freshwater bas-idiomycetes which, although few in number compared to their terrestrial counterparts, colonize a wide range of substrata, particularly those that are woody. Nearly every sampling study has found a genus new to science, with unique adaptations to their habitat.

The final chapter, by Heilmann-Claussen and Vesterholt, focuses on the urgent need for fungal conservation, highlighting different selection approaches, and explaining the difficulties in using criteria designed for red-listing other organisms.

Note on terminology. While editing, we have not aimed at total uniformity between chapters in all terms. Most notably 'Basidiomycota' and 'basidiomycetes', 'saprotrophs' and 'saprobes' have been used interchangeably. The term 'habitat' has been used to define 'the place' where a fungus lives, therefore including aspects of the physico-chemical environment. 'Substratum', albeit only occasionally used, alludes to the medium in which the fungus is growing within a habitat, while 'substrate' has been reserved for a specific chemical molecule utilized by the organism. 'Resource' is a general term meaning 'food source', and so has been used interchangeably with substratum and substrate, depending on context.

Acknowledgement. Finally, we would like to thank Mrs. Julie Harris for unstinting secretarial support and Jacob Heilmann-Clausen for help with taxonomy.

Lynne Boddy, Juliet C. Frankland and Pieter van West

Anderson, J.M., Rayner, A.D.M. and Walton, D.W. (eds.). (1984). Invertebrate-Microbe Interactions. Cambridge University Press, Cambridge. Frankland, J.C., Hedger, J.N. and Swift, M.J. (eds.). (1982). Decomposer Basidiomycetes: Their Biology and Ecology, 355 pp. Cambridge University Press, Cambridge.

Jennings, D.H. and Rayner, A.D.M. (eds.). (1984). Ecology and Physiology of the Fungal Mycelium. Cambridge University Press, Cambridge. Rayner, A.D.M. and Boddy, L. (1988). Fungal Decomposition of Wood: Its Biology and Ecology. Wiley, Chichester.

Wilding, N., Collins, M.M., Hammond, P.M. and Webber, J.F. (eds.). (1989). Insect-Fungus Interactions. Academic Press, London.

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