Functional Groups Of Grassland Fungi

There has been a tendency in fungal ecology to assign species of known function to particular groupings and to use the term saprotrophic as a 'dustbin' group for the remainder. With the exception of the rust and smut fungi (which have no contact with dead organic matter), all basidiomycetes have some saprotrophic ability and for many involved in mutualistic associations with plants, their ability to release nutrients from organic matter (Read and Perez-Moreno, 2003) is a crucial part of the mutualism. Furthermore, the situation is confused by the occurrence of species which inhabit recently dead plant tissues having first colonized the living host (latent endophytism). Examples of such establishment strategies in woodland systems include Oudemansiella mucida on beech (Rayner and Boddy, 1988) and some members of the genus Crinipellis (Griffith and Hedger, 1994). For these examples there is circumstantial evidence that biotrophic infection by basidiospores occurs even though the dominant phase of the life cycle is saprotrophic.

The niche occupied by basidiomycetes is usually ascribed to the resources upon which they fruit but fruiting on dead tissues does not exclude some biotrophic/endophytic capability. The degree to which such a life strategy is ne-crotrophic is also difficult to establish. For instance, some fairy ring-forming basidiomycetes (see below) are occasionally termed 'weakly pathogenic'. Many asymptomatic endophytic fungi are known, though basidiomycetes have tended to be overlooked due to their slow growth on agar media. The potential diversity of basidiomycetes associated with grass leaves was highlighted in bamboo by Zhang et al. (1997) and a similar situation was also found in cocoa leaves (Arnold et al., 2003). Thus, many predominantly saprotrophic basidiomycetes may have life cycles that are more complex than previously suspected. Hibbett et al. (2000) have estimated that ca. 50% of saprotrophic homobasidiomycetes (including many agarics) may have evolved from ectomycorrhizal ancestors. As such, several species may belong to more than one of the groups defined below.

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