• Proposed
  • Under Assessment
  • LCPreliminary Assessed
  • 4Assessed
  • 5Published

Squamanita paradoxa (A.H. Sm. & Singer) Bas

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Scientific name
Squamanita paradoxa
(A.H. Sm. & Singer) Bas
Common names
Powdercap strangler
Korrelig dikpootje
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Preliminary Assessed
Preliminary Category
Proposed by
Davide Puddu
Susana C. Gonçalves
Sean Cooch, Davide Puddu
Comments etc.
Anders Dahlberg, Javier Marcos Martínez, Else Vellinga, Debbie Viess

Assessment Status Notes


Squamanita paradoxa is a biotrophic species, 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). However, its host is widespread and common, with no evidence of decline. Therefore, the species is assessed as least concern (LC).

Taxonomic notes

Why suggested for a Global Red List Assessment?

An overall rarely seen biotrophic species, with extreme host specificity that parasites Cystoderma amianthinum.

Geographic range

Squamanita paradoxa known distribution spans Europe and North America.

Population and Trends

Globally rare, though seen in Europe with slightly more frequency than in North America. Occasionally, locally abundant e.g. in a particular episode following heavy rains in Great Britain in 2009 (Kibby, 2009a and b) that reports 32 occurrences (NBN Atlas). In Sweden there are over 50 reports (GBIF).
Europe- In the UK, it seems widespread, occasionally reported as locally abundant, and improving although this is probably the result of increasing recording efforts in unimproved grasslands. Sweden reports over 50 occurrences. Elsewhere in Europe, it seems widespread (it is reported from 10 countries), but seemingly rarer (1-10 occurrences; GBIF).
North America- Rarely reported (MyCoPortal); seven reports in the USA: two in 1946 (Oregon), three in 1947 (Oregon), one in 1971 (Hawaii), one in 1972 (Idaho); one report from Canada in 2009 (British Colombia).

Population Trend: Uncertain

Habitat and Ecology

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, S. paradoxa fruiting hasn’t been seeing to persist above two years at e.g. any British site.

Europe - Mostly grasslands
North America (Pacific Northwest) - temperate Old growth forest dominated by Douglas Fir and Western Hemlock, with a thick moss understory

Temperate ForestTemperate Grassland


Agro-industry farming

Conservation Actions

Resource & habitat protection

Research needed

Life history & ecology

Use and Trade


Bas, C., 1991. Een tweede Squamanita soort voor Nederland. Coolia 34: 45–47.

Matheny P.B. & Griffith G.W. 2010. Mycoparasitism between Squamanita paradoxa and Cystoderma amianthinum (Cystodermateae, Agaricales). Mycoscience 51: 456–461.

Evans S., Henrici A. & Ing B. (eds). 2006.The Red Data List of Threatened British Fungi. Preliminary Assessment. 2006. British Mycological Society.

NBN Atlas website at http://species.nbnatlas.org/species/BMSSYS0000017806 Accessed 26 January 2018.

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.

Henrici A. 2013. Squamanita in Britain and Europe. Field Mycology 14: 56-63.

Kibby G. 2009. Editorial. Field Mycology 10(2): 38. (cited in Fungi 4:5 Winter 2011)

Kibby G. 2009. Editorial. Field Mycology 10(1): 2.  (cited in Fungi 4:5 Winter 2011)

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.

Known distribution - countries

Regional Population and Trends

Country Trend Redlisted