R-L categories correct, but text here does not match final assessment. Developed and updated version published at IUCN´s Red List update, July 18th 2019.
Pluteus fenzlii is a very rare fungus known only from several countries in Europe and Asia. It inhabits wood of broadleaved tree species. The most frequent substrate in Europe is Quercus cerris. Basidiomata grow on fallen trunks with different diameters (including their branches) and branches separated from old living trees and lying on soil. P. fenzlii can be consider a species of ancient broadleaved forests.
The species is endangered by intensive forest management when no woody debris (nor branches) is left in a forest. It is not included in any national red list or list of protected species worldwide despite its rareness. Currently the occurrence of the species can be estimated to ca. 1500 localities worldwide. This species qualifies for listing as Endangered.
The species was described as Agaricus fenzlii Schulzer (Schulzer et al. 1866). First detailed revision was published by Singer (1979) under name Chamaeota fenzlii (Schulzer) Singer. Name Pluteus fenzlii (Schulzer) Corriol & P.-A. Moreau was firstly published by Corriol & Moreau (2007).
There is a very similar species in North America, Pluteus mammillatus (Longyear) Minnis, Sundb. & Methven (Minnis et al. 2006), which differs from P. fenzlii only by white to greyish-red lamellar edge (yellow in P. fenzlii).
Pluteus fenzlii is a very rare fungus known only from several countries in Europe and Asia. It inhabits wood of different broadleaved tree species. The most frequent substrate in Europe is Quercus cerris. Basidiomata grow on fallen trunks with different diameters (including their branches) and branches separated from old living trees and lying on soil. The species is endangered by intensive forest management when no woody debris (nor branches) is left in a forest, especially if in general localities in dominant hilly landscape are easily accessible.
Pluteus fenzlii is a Eurasian species with its main known distribution in Central Europe. Currently, Slovakia (9 localities) and Hungary (5 localities) are countries with the highest number of localities of P. fenzlii in Europe. New records or new data are recently presented or indicated from Siberia, Russia (Malysheva et al. 2016, Holec et al. 2018).
Pluteus fenzlii is extremely rare species, ca. 30-35 localities are currently known worldwide and total number of localities can be estimated to be 1500. It occurs in Slovakia (9 localities), Hungary (5 localities), France (4 localities), Poland (1 locality) and Russia (the number of localities not exactly known, but can be estimated to be at least 15 - Zvyagina, Malysheva pers. comm.). In countries like Slovenia, Serbia and Croatia the species was not found for decades (Holec et al. 2018). The total number of localities in Europe can be estimated to be 250. The species has small subpopulations and besides Slovakia are severally fragmented (Fig. 12 in Holec et al. 2018). Number of mature individuals can be estimated to be less than 250.
The species seems to be limiting by lack of wood substrate of broadleaves. Oak (Quercus spp.) wood is usual substrate of the species in central Europe (Holec et al. 2018) and oak forests dominate in hilly country of the territory - prevalent landscape part of occurrence of P. fenzlii. Decline of oaks in Europe (Gentilesca et al. 2017) is present wide-spreading problem and potential threat. The occurrence of P. fenzlii might be also shifted by the global warming. An indication of this is that there are no recent records of the species in Balkan countries (Serbia – country of type locality, Croatia, Slovenia) but the species has been found in regions located more north (Hungary, Slovakia, Poland, continental Russia) (Holec et al. 2018).
Current population trend: Decreasing.
Pluteus fenzlii is a wood-inhabiting fungus growing on wood of broadleaved tree species. Based on data from Poland, Slovakia and Hungary, the most frequent substrate in this part of Europe is Q. cerris (5 localities), followed by F. sylvatica (2) (Holec et al. 2018). Basidiomata grow there on fallen trunks (10-55 cm in diameter) as well as branches (diameter 20 cm) separated from old living trees and lying on soil, either from decorticated wood or cracks in the bark, often at sites covered by mosses. In hemiboreal conditions of the Białowieza forest it was collected probably on Tilia sp. (Holec et al. 2018). In central Russia and western Siberia the species was recorded on wood of deciduous trees, particularly on Tilia, Acer and Betula (Malysheva et al. 2007) and in southern Siberia it was recorded on Betula pendula (Malysheva et al. 2016). It is also documented from Acer campestre, Carpinus betulus and Populus tremula (Holec et al. 2018).
All localities in Europe is the more or less natural broadleaved (or mixed) vegetation, often protected in nature reserves of various rank. In Slovakia the species usually occurs in hilly areas with more or less natural broadleaved habitats, mostly thermophilic ones (Holec et al. 2018). It also occurs in open and light habitats of pine (Pinus sylvestris) forests alternating with broadleaved forests with Tilia cordata, Acer platanoides, Quercus robur, and Ulmus glabra or in moderately continental, secondary deciduous-coniferous forests with mossy or grassy cover and swamp parts in European Russia (Malysheva et al. 2007). In Asian Russia, P. fenzlii was recorded in light coniferous herb forests (sub-taiga), forest-steppe and steppe, in parts with dominating Betula pendula (Malysheva et al. 2016). It is not easy to find common feature for all localities of the species but most of them are forests dominating by broadleaves in continental regions of Eurasia. Wood with P. fenzlii is always originating by trees which are native and natural part of vegetation in the area (Holec et al. 2018), so the species can be consider a species of ancient broadleaved forest.
Pluteus fenzlii in general occurs in hilly regions (altitude 230–425 m in Slovakia and France, with one exception at 740 m in France) mostly adjacent to higher mountain ranges (Pyrenees, the Carpathians, Caucasus). Exceptions are the hilly country of the Zhigulevsky State Nature Reserve in Middle Volga region (no mountain range in the vicinity) and the Białowieza National Park (lowland forest on glacial deposits, about 150 m a.s.l.).
Detailed vegetation data from Poland and Slovakia (Holec et al. 2018) show that some of the localities are more or less influenced by man (clearing, cutting, grazing from unnaturally high populations of wild game). The species can suffer from intensive forest management practices when a little amount or no woody debris is left in a forest (Holec et al. 2018). Most of localities of P. fenzlii occurs in hilly landscape (Holec et al. 2018). Due to for man easily accessible forests P. fenzlii is firstly threaten by cutting and wood cleaning. At a few localities the species survives in intensively managed forests only at woody remnants of broadleaves.
To protect localities with occurrence of the species. In areas with occurrence of the species which are not strictly protected, or if can not be protected and forest management practices will continue, is crucial to avoid a clearing in broadleaved forests, especially after a cutting. The most effective action in managed forests is to leave woody debris of broadleaves, at least branches in forests after management.
Further studies are necessary to evaluate the taxonomic status of the Australian subpopulation following the evaluation of microcharacters variability and its possible relation to the population structure of this species. Research is also needed to determined how much of decaying wood is enough for surviving of the species population at localities which are influenced by extensive forest management.
No use of fruitbodies of the fungus is known.
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