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).