4.5. Basidiomycetous hyperparasites

Examples of basidiomycetous hyperparasites are surprisingly scarce. Roughly 200 species of mycoparasites have been described in this phylum, with a dozen of them being putative hyperparasites. Examples of hyperparasitism have been documented in four classes: Agaricomycetes, Tremellomycetes (Agaricomycotina), Ustilaginomycetes (Ustilaginomycotina), and Pucciniomycetes (Pucciniomycotina). The best studied group of hyperparasites within Basidiomycota is Helicobasidiales (Pucciniomycetes). This order comprises species of Tuberculina , which are hyperparasites of rusts (4.1.4. Hyperparasites of rusts). Within Agaricomycetes and Tremellomycetes, evident examples of hyperparasitism are extremely rare, but see Table 1 for specific examples.
In Agaricomycetes, only two examples of hyperparasitism are known. Both Collybia cookei and Entoloma abortivum have been reported as hyperparasites on species of Armillaria (Lindner et al., 2001) (Table 1). Armillaria species are devastating, necrotrophic phytoparasites on various tree species, but may shift to saprotrophism once the host tree has died. Most species within Tremellomycetes are mycoparasites and lichen parasites (Diederich et al., 2022; Millanes et al., 2011; Weiss et al., 2014). However, host species identity is often uncertain (only identified to genus or form group) or not known at all. This makes it very hard to estimate which proportion of these mycoparasites are to be considered hyperparasites. Further, for the majority of these hyperparasites, no cultures nor genetic data are available, and their classification remains tentative based on (micro)morphological similarities (Schoutteten et al., 2023; Weiss et al., 2014).