An enormous volume of research has been done on this topic (for reviews see Moore-Landecker, 1993; Jennings, 1995; Moore, 1998a), though it is important to remember that conditions in the laboratory are far removed from the natural environment. The crucial insights came from Hawker's (1939,1947) experiments: simple sugars tend to favour asexual spore production while oligo- and poly-saccharides are especially good carbon sources for production of fruit bodies. Glucose often represses fruit body production, even in very low concentrations. The rate with which a fungus can hydrolyse a carbohydrate determines the ability of the carbohydrate to promote fruit body formation (Hawker and Chaudhuri, 1946), so what seems to matter most is the rate of supply and ease of use of substrates as determinants of their value in promoting fruit body formation. It comes as no surprise, therefore, that saprotrophic Basidiomycota on dung fruit more readily than those utilising leaf litter, and in turn than wood decomposers, though, of course, these resources also differ in mineral nutrient content. Likewise, fungi that participate early in community development within a resource fruit more readily than most later colonizers (Cooke and Rayner, 1984; Rayner and Boddy, 1988; Chapter 11), whose carbon sources are more recalcitrant.

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