• Proposed
  • Under Assessment
  • Preliminary Assessed
  • Assessed
  • VUPublished

Tricholoma acerbum (Bull.) Vent.

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Scientific name
Tricholoma acerbum
Author
(Bull.) Vent.
Common names
Sīvā pūkaine
räffelmusseron
IUCN Specialist Group
Mushroom, Bracket and Puffball
Kingdom
Fungi
Phylum
Basidiomycota
Class
Agaricomycetes
Order
Agaricales
Family
Tricholomataceae
Assessment status
Published
IUCN Red List Category
VU A2c+3c+4c
Proposed by
Tor Erik Brandrud
Assessors
Tor Erik Brandrud
Contributors
Inita Daniele, Michael Krikorev, Tatyana Svetasheva
Comments etc.
Claudia Perini

Assessment Status Notes

Taxonomic notes


Why suggested for a Global Red List Assessment?

Tricholoma acerbum is associated with rich/calcareous Quercus(-Carpinus) forests, in Europe with a S European, maybe a SW European core area, but also known from N Europe and E to Japan. The species is regarded as threatened (endangered to critically endangered) in the Nordic countries, as well as in some countries in W/C Europe (Germany, The Netherlands, Switzerland, formerly also Great Britain). The species was included in a preliminary proposal for a European red-list in 1993. The major habitat of the species; temperate, deciduous oak forests, is a strongly decimated/depauperated and fragmented habitat on a European base, where less than 2% of the original, old, thermophilous, deciduous forests are left at present. In the evaluation period (50 y), the richer (mesotrophic-calcareous) oak forests has had a habitat loss estimated to >30% in Europe (including a number of Natura 2000 habitats).
Preliminary global and European Red List assessment;
VU (A2c+3c+4c), with an estimated decline of >30% during evaluation period of 50 years.

Cause:
The estimated decline is due to a long-term and persistent decline in oak forest habitats, both in area (due to altered land-use/urbanization, Phytophtora deseases on oak, etc.) and in habitat quality (lack of old-growth forests due to forestry, and also lack of “old-fashioned” grazed forests/woodland meadows).


Geographic range

The species has a wide distribution in S, W and E Europa, with outpost areas to the north in SW Fennoscandia. The species is furthermore reported from SE Asia (the conspecificity of the Asian populations should be verified genetically).


Population and Trends

The species probably has its core areas in S-SW Europa, where it occurs both in Mediterranenan areas as well in montane districts, eg. reported to be rather frequent in the Appennines in Italy, and less frequent in Catalonia in Spain. The species is widely distributed but rather infrequent in W and C Europe. The species is locally not so rare in Great Britain, Switzerland and Austria (approx. 100 localities known from Great Britain and Switzerland+Austria, resp., per. 21012), rare in Germany (70 locs. known), scattered/not rare in Hungary, and occurs southeast to montane areas of Greech andTurkey. On the northern flank, the species has one, larger outpost area along the southernmost coast of Norway (with 22 known localities). The species is extremely rare in Sweden (2 known locs.) and Denmark (5 locs.). 
The fungus is furthermore reported from North Africa (Morocco; Canary Islands), and from temperate regions of E Asia, both Japan, China and Korea.
In Europe as a whole, the number of known localities is probably around 400-500, with an estimated number of approx. 4000-5000 total localities in this area, maybe a total of 7000-10.000 localities in the entire Eurasian(-North African) distributional area. It is very doubtful that the reports of Tricholoma acerbum s. lat. (including T. manzanitae) from Canada and USA represent the same species (deviating morphology; should be phylogenetically studied), so we do not consider american populations in this evaluation.
The species is regarded as threatened (endangered to critically endangered) in the Nordic countries, as well as in some countries in W/C Europe (Germany, The Netherlands, Switzerland, formerly also Great Britain). The species was included in a preliminary proposal for a European red-list in 1993.
An ongoing decline is due to decrease and depauperation of European oak forests. The habitat loss is estimated to >30% in Europe in the evaluation period (50 y), for these richer (mesotrophic-calcareous) oak forests, including a number of Natura 2000 habitats. Oak forests decreased with approx 20% 1960-98 in Russia, and richer/calcareous, old-growth forests probably more. The situation in E Asia is not known, but it is likely that the species (assuming this is the same taxon) is decreasing also in this region as well, due to e.g. deforestation of oak forests.

Preliminary global and European Red List assessment;
VU (A2c+3c+4c), with an estimated decline of >30% during evaluation period of 50 years.

 

Population Trend: Deteriorating


Habitat and Ecology

The species is mainly associated with Quercus spp. (mycorrhiza), but apparently also with Castanea, Tilia and Corylus, possibly also with Fagus. The species occur in montane forests with deciduous Quercus species (such as Quercus robur, maybe also Q. pubescens) and Castaneus in S Europe, but in mediterranean areas also with the sclerophyllous Quercus ilex. In S Europe, the species is reported mainly from mesotrophic to somewhat base-richer, but not calcareous forests (mainly on loamy-clayey soils). In C-W Europe, the species occurs in richer forests of the Quercus-Carpinus type. In the Norwegian outpost area, the species occurs in richer to calcareous Quercus-Tilia forests, in Russia reported from calcareous oak forests In S Sweden, the species is reported from Fagus forests, possibly with single Quercus trees.

Temperate Forest

Threats

The species is threatened by loss and fragmentation of intact Quercus forest habitat, due to altered land-use, including deforestation, shift in silviculture from oak to conifer species, as well as depauperation of oak forests due to e.g. intensive forestry, but also loss of forest traditional grazing, which kept the forests semi-open, and assured oak recruitment.


Conservation Actions

To prevent decline and fragmentation of oak forests with good habitat quality, it is important to set aside Quercus forests reserves and woodland key biotopes, and in many cases (re-)introduce a moderate disturbance regime with cattle grazing, assuring semi-open conditions and oak recruitment.


Research needed

There is a need for taxonomic studies, with focus on phylogeographic patterns. Probably the North American versus Eurasian populations of T. acerbum ss. lato belong to two distinct species, but this must be verified phylogenetically and morphologically.
Intact, little disturbed, deciduous oak forests is a hot-spot habitat for mycorrhizal species in different regions, and these species such as Tricholoma acerbum requirements for forests age/continuity, disturbance regime, etc. should be further studied.


Use and Trade


Bibliography

Brandrud, T.E. 2013. Rødlistede og sjeldne musseronger (Tricholoma spp.) har internasjonalt viktige populasjoner i Norge/Norden. Agarica 33: 57-72.
Dumolin-Lapègue S, Demesure B, Fineschi S, Le Corre V, Petit RJ, 1997. Phylogeographic Structure of White Oaks Throughout the European Continent. Genetics 146: 1475-1487.
Galli R, 1999. I Tricholomi. Edinatura. Milano.
Ing B, 1993. A provisional European red list of endangered macrofungi. European Council for the Conservation of Fungi. Newsletter 5: 3-7.


Known distribution - countries

Regional Population and Trends

Country Trend Redlisted