R-L categories correct, but text here does not match final assessment. Updated version will be published in IUCN´s Red List.
Squamanita paradoxa is a biotrophic fungus with extreme host specificity, that parasites the closely related saprotroph Cystoderma amianthinum. Widespread in Europe and North America, it seems globally rare, though seen in Europe with slightly more frequency than in North America. Its host, however, is widespread and common, with no evidence of decline. Therefore, the species is assessed as least concern (LC).
Synonyms: Squamanita basii Harmaja and S. umbilicata Harmaja
An overall rarely seen biotrophic species, with extreme host specificity that parasites Cystoderma amianthinum.
Squamanita paradoxa known distribution spans Europe and North America.
Globally rare, though seen in Europe with slightly more frequency than in North America. Its host is widespread and common, with no evidence of decline. Occasionally, Squamanita paradoxa is locally abundant e.g. in a particular episode following heavy rains in the UK in 2009 (Kibby, 2009ab) that reports 32 occurrences (NBN Atlas). Europe: In Sweden, there are over 50 reports (GBIF). In the UK, it seems widespread, occasionally reported as locally abundant, and improving although this is probably the result of increasing recording efforts in semi-natural grasslands. Elsewhere in Europe, it seems widespread (it is reported from 12 countries), but seemingly rarer (1-10 occurrences; GBIF). In North America, it is rarely reported (MyCoPortal). Seven reports in the USA: two in 1946 (Oregon), three in 1947 (Oregon), one in 1971 (Hawaii; questionable), one in 1972 (Idaho). One report from Canada in 2009 (British Colombia).
Population Trend: Uncertain
Squamanita paradoxa is an obligate mycotrophic species that parasites a closely related taxon, Cystoderma amianthinum (molecular confirmation; Matheny & Griffith 2010). It belongs to the only agaric genus where all species (ca. 10) are parasitic on other Agaricales. Several Squamanita species appear to fruit over a wide area for two or three years and then disappearing from sight for decades and, for a while, S. paradoxa fruiting hasn’t been seeing to persist above two years at e.g. any British site. More recently, one site (ECN Wyddfa, Wales) was specifically surveyed for S. paradoxa over 10 seasons: S. paradoxa was found in four different years, whereas the host C. amianthinum was observed in six of the years. Habitat in Europe - mostly grasslands while in North America (Pacific Northwest) occuring in temperate old-growth forest dominated by Douglas Fir and Western Hemlock, with a thick moss understory.
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Griffith G.W., Gajda K.P., Detheridge A.P., Douglas B., Bingham J., Bowmaker V., Turner A., Debbie A.E., McAdoo W.G., Dentinger B.T.M. 2019. Strangler unmasked: Parasitism of Cystoderma amianthinum by Squamanita paradoxa and S. pearsonii. Fungal Ecology 39: 131-141
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Kibby G. 2009. Editorial. Field Mycology 10(1): 2. (cited in Fungi 4:5 Winter 2011)
Matheny P.B. & Griffith G.W. 2010. Mycoparasitism between Squamanita paradoxa and Cystoderma amianthinum (Cystodermateae, Agaricales). Mycoscience 51: 456–461.
Mushroom Observer website at http://mushroomobserver.org/63086 Accessed 26 January 2018.
MyCoPortal at http://mycoportal.org/portal/collections/list.php Accessed 26 January 2018.
NBN Atlas website at http://species.nbnatlas.org/species/BMSSYS0000017806 Accessed 26 January 2018.
Redhead S.A., Ammirati J.F., Walker G.R., Norvell L.L. & Puccio M.B. 1994. Squamanita contortipes, the Rosetta Stone of a mycoparasitic agaric genus. Canadian Journal of Botany 72: 1812–1824.