Tree Species and Composition of Fungal Communities

Many wood-inhabiting fungi appear, based on fruit bodies, to have a preference for certain tree species. In some cases host preferences relate to interspecific differences in chemical composition, e.g. pH, presence of allelopathic compounds, bark and wood morphology (Rayner and Hedges, 1982; Rayner and Boddy, 1988). The heartwood of Quercus robur, for instance, is well known for its high durability and distinctive mycota owing to its low pH and high content of tannins (Wald et al., 2004; Heilmann-Clausen et al., 2005). In other cases intimate interactions between living host tissue and fungi able to infect functional sapwood seem to play a key role (e.g. Hrib and Rypacek, 1981; Chapela et al., 1991; Hendry et al., 1993).

The percentage of apparently specific and selective species in different fungal groups is variable, tending to be higher among polypores and pyre-nomycetes than corticoids and agarics (Figure 1). These differences reflect differences in dominating ecological strategies among these groups. Fungal species interacting with live hosts, i.e. latent decay fungi (see below) and heart rot agents, are well represented among pyrenomycetes and polypores, but less so by agarics and corticoid species. Based on incidence of fruit bodies, heart rot fungi often appear selective for individual or closely related tree species, e.g. F. hepatica and P. quercinus for Quercus spp. Other fungi are apparently strongly selective for a particular tree genus, but sometimes occur albeit infrequently on other trees, e.g. Grifola frondosa and Inonotus dryadeus on Quercus (Ryvarden and Gilbertson, 1992). Further, some appear to be selective for unrelated tree species, e.g. Laetiporus sulphureus on Quercus, Prunus, Salix and Taxus spp., though in North America there is some indication, based on fruit body morphology, cultural characteristics and molecular evidence, that there may be five taxa of Laetiporus (Banik and Burdsall, 2000).

Among latent decay fungi host selectivity is prominent and in some genera strict host specificity seems to occur, at least based on sporocarp observations, e.g. some Peniophora species (Table 2).

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