Tentative global red-list assessment?:
VU to EN (D, D1) Number of mature individuals is less than 1000, probably less than 250. Number of known localities in the last 10 years is around 20 with 1-2 individuals per site. Assessed for 10 years period proposed by Dahlberg & Mueller (2011) for fungi on short-lived discrete substrata, likely to have short generation length.
EN (B2a+bii+biii) AOO is less than 500 km2 and population is severely fragmented with observed and estimated continuing decline of area of occupancy and quality of habitat.
CR (C2ai) Small declining population with number of mature individuals in each subpopulation less than 50.
This species is rare, has an overall small population and is declining. As an parasitic fungicolous species it it a very extraordinary agaric. It has been found exclusively in alluvial forests.
Only very few localities are known and the species fruits only occasionally. Switzerland and Hungary, where the species has been recorded more frequently at past reported strong decline of the species during the last 10 years. Other countries report only isolated occasional records.
Considering overall bad state of the habitat (hardwood alluvial forests) in Europe we can estimate that decline of the species will continue also in future.
Estimated number of mature individuals is less than 1000, probably less than 250. Number of known localities in the last 10 years is around 20 with 1-2 individuals per site.
Though the EOO is more than 20 000km2, AOO is less than 500 km2 and population is severely fragmented with observed and estimated continuing decline.
Population Trend: Decreasing
Occuring in alluvial forests, parasitic on Amanita solitaria and Amanita strobliformis which are mycorrhizal with various deciduous trees mostly hardwood (e.g. Quercus, Fagus, Tillia).
Squamanita schreieri is known as parasite of two Amanita species (A. strobiliformis and A. echinocephala) which are themselves considered rare. Both Amanita species are xerothermophilous, mycorrhizal with various deciduous, mostly hardwood trees (Quercus, Fagus, Tillia a.o.). This is in contrast with the preferred habitat of S. schreieri, which is alluvial forests. Despite the lack of data this leads to the conclusion that S. schreieri probably needs hardwood alluvial forest (Querco-Ulmetum), corresponding with NATURA 2000 habitat 91F0 - Riparian mixed forests of Quercus robur, Ulmus laevis and Ulmus minor, Fraxinus excelsior or Fraxinus angustifolia, along the great rivers (Ulmenion minoris).
In Slovakia A. strobiliformis frequently occurs in alluvial forests (hardwood and softwood) but Squamanita has been observed only in hardwood sites. Since 2007 no recent record of Squamanita, despite intensive search.
The current state of NATURA 2000 habitat 91F0 - Riparian mixed forests of Quercus robur, Ulmus laevis and Ulmus minor, Fraxinus excelsior or Fraxinus angustifolia, along the great rivers (Ulmenion minoris) is assessed as ‘unfavourable-bad’ in most European countries, reflecting the ’bad’ status o f the habitat area and structure and function. The functions of the habitat are closely linked to the flood regime of the river. This habitat is seriously threatened due to management of water levels and the regulation of water courses with very few of Europe’s larger rivers having a natural flood regime. (Eionet Forum, Article 17 - Reporting under Habitats Directive).
Moreover, this habitat is threatened by invasive logging, replanting of the native hardwood trees by rapidly growing cultivars and non-native species, inappropriate forestry techniques, resulting in land degradation and spreading of invasive plant species and water pollution.
Loss of the habitat results in decreasing populations of Amanita host species of S. schreieri and finally in significant decline of S. schreieri itself.
The species is redlisted in 4 countries, in Hungary it is protected by law.
Some of the sites (e.g. in Slovakia) are within protected areas.
Research needed in bionomy and ecology of the species.
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