• Proposed
  • Under Assessment
  • Preliminary Assessed
  • VUAssessed
  • 5Published

Arrhenia discorosea (Pilát) E.A. Zvyagina, A.V. Alexandrova, T.M. Bulyonkova

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Scientific name
Arrhenia discorosea
Author
(Pilát) E.A. Zvyagina, A.V. Alexandrova, T.M. Bulyonkova
Common names
Аррения розоводисковая
kalichovka fialovoružová
kalichovka lužní
IUCN Specialist Group
Mushroom, Bracket and Puffball
Kingdom
Fungi
Phylum
Basidiomycota
Class
Agaricomycetes
Order
Agaricales
Family
Tricholomataceae
Assessment status
Assessed
Preliminary Category
VU C2ai
Proposed by
Thomas Læssøe
Assessors
Irmgard Krisai-Greilhuber
Editors
Tor Erik Brandrud
Contributors
Tatiana Bulyonkova, Andreas Gminder, Thomas Læssøe, Elena Zvyagina
Comments etc.
Anders Dahlberg, Daniel Dvořák, Vladimír Kunca, Tatyana Svetasheva

Assessment Notes

R-L categories correct, but text here does not match final assessment. Updated version will be published in IUCN´s Red List June or Nov 2019.

Justification

Arrhena discorosea is a distinct saprotrophic small gilled mushroom with red brown colour, pinkish red lamellae and red spore deposit. It is wood-inhabiting and confined to very big trunks of aspen. More rarely it takes other hard woods as hosts, such as Fraxinus, Ulmus or Tilia. This thermophilic species is depending on moist and rotten hardwood and is mostly known from riparian forests along rivers. It needs natural or near-natural alluvial and flood-plain forests. This type of forests is strongly underrepresented for instance in Central Europe, but it is vital for mushrooms depending on old aspen. Such big trunks of aspen are now a very rare sight. The global area of occupancy of Arrhenia discorosea is estimated as being 640 km2. The species is only present with few subpopulations and altogether estimated 960 mature individuals. The number of mature individuals in each subpopulation is less than 250 and thus it is considered as highly endangered. The assessment is based on quite small population size, fragmentation, loss of habitat and diminishing habitat quality.


Taxonomic notes

Arrhenia discorosea
Synonyms:
Omphalia discorosea
Omphalina discorosea
Rhodocybe xylophila
Omphalina xylophila


Why suggested for a Global Red List Assessment?

It is a rare, distinct omphalinoid species with red spore deposit confined to very big aspen wood, more rarely other hard wood hosts.
We need to have a clear idea on the decline rate of coarse trunks within its distribution area. Such trunks are now a very rare sight in Europe and in Europe the species could already be extinct or nearly so.
Assessed as DD at present but could qualify for NT/VU if a suspected decline of substrate could be qualified.


Geographic range

Its geographic rangee extends from Far Eastern Russia across temperate Asia to western Europe. It is known from one site in Belgium and likewise in Poland. It is not known from Scandinavia, the Netherlands; known occurrences (no. in brackets) are:  Russian Federation (40), Austria (11), Belgium (1), Bulgaria (1), Czech Republic (2), Germany (6), France (12), Georgia (1), Canada (1), Mongolia (1), Poland (1), and Slovakia (1).


Population and Trends

Based on GBIF and databases available (see below) 80 subpopulations are nown worldwide. The number of mature individuals has been estimated to be 960 following these lines: (a) likely number of current localities (estimated to be ca. 160) (b) translation of the estimated total number of localities to an estimate of the total number of mature individuals in 2 steps (i calculate the number of functional individuals (ie. conspecific sporomata inhabiting an individual tree, template = 3, = 480): estimation of total number of localities × estimation of the average number of functional individuals/locality; ii convert the number of functional individuals into mature individuals following Dahlberg & Mueller 2011, template = 2 because few aggregated sporomata on a trunk should be counted as two mature individuals; = 960). The number of known localities is 80 and the number of yet unknown localities was estimated to be twice as high. Mature individuals are very rare.
The AOO was estimated as being 640 km2, following IUCN guidelines, 2 x 2 m = 4 km2 for each locality, because almost all of the basidiospores of a mature fruit body are deposited within this area.
Functional individuals of lignicolous fungi have to be calculated per trunk or log because of the mycelia (ramets) inhabiting the log. For the AOO one has also to consider spore dispersal distance. Most spores of a mature individual are dispersed within 10s of metres, only a minor proportion is dispersed over longer distances.
The average daily deposition rate, e.g. of Phlebia centrifuga (Norros et al. 2012) shows that dispersal from a single fruit body decreases from a few thousands to ca. 150 spores m–2day–1 in the first 60–80 m. Due to competition with other spores and other environmental factors (e.g. wood degradation stage, succession stage), colonization ability leading to a new generation via spore germination and establishment is only possible with a high number of spores deposited. This high number is only reached within the above mentioned 60-80 m, meaning that the AOO of a single ramet and its offspring is no more than 80 m. So calculating with the suggested 2 x 2 km is more than sufficient for AOO. For taxa that have a cryptic life form (such as fungi) occurrences may be estimated by tallying the area of 2 x 2 km (= 4 km2) grid cell in which observation records are located using equation 4.1. (IUCN Guidelines 2017): AOO = no. occupied cells × area of an individual cell. As it is still very difficult to have accurate distribution data, in case of macromycetes the no. of occupied cells is equated with no. of sites known.

Population Trend: Decreasing


Habitat and Ecology

It is found on decaying, sometimes standing aspen (Populus tremula) trunks but also other hardwood species such as Fraxinus, Ulmus and Tilia.
The species is a typical representative of the floodplain forest. If we take Germany as an example (Welle 2018), then naturally 6.7 % (21.4 million ha) of the forest would be riparian and wetland forest. There are now only 0.7 % left (230,200 ha) as a forest. In relation to the current forest area of Germany, which is about 10.3 million ha (about 32% of the country’s surface area) this corresponds to 2.2%. The percentage of alluvial and wetland forests with near-natural tree species composition is 1.3% (131,000 ha) in relation to the current forest area. The ratio of current forest area to potential forest area (Welle 2018) gives a representation of 0.33, so this forest type is strongly underrepresented. Taking into account the near-natural sites it results in a representation of 0.19. This means that the near-natural part of the alluvial and wetland forests is also strongly under-represented and gone. However, this type of forest is vital for mushrooms that depend on old aspen. Concerning riverine forests with aspen the situation is similar in other European countries, e.g. Austria.
Further Kunttu et al. (2018) showed that dead wood restoration in forests alone does not automatically led to high fungal species diversity. Instead special attention has to go to restoration of different dead wood types, that is fine and coarse and of different tree species, not only focussing on a sufficient amount of dead wood. So in the case of Arrhenia discorosea it is extremely important to leave a high amount of living and dead aspen trees in suitable forests.

Temperate Forest

Threats

It is threatened by removal of coarse woody debris, such as aspen trunks and dead wood in general. Due to management changes like drainage of riparian forests, riverbed regulation and dam construction its habitats are diminishing.

Logging & wood harvestingUnintentional effects: subsistence/small scale (species being assessed is not the target) [harvest]Other ecosystem modificationsHabitat shifting & alteration

Conservation Actions

Its sites should be protected and coarse woody debris should be left in the forests.

Resource & habitat protection

Research needed

The extend of habitat damage within the distribution area should be investigated in detail. Many other species from a range of taxonomic groups depend on coarse aspen. Its population size and population trends should be monitored.


Use and Trade

There is no use or trade known.


Bibliography

Dahlberg, A., Mueller, G., 2011: Applying IUCN red-listing criteria for assessing and reporting on the conservation status of fungal species. Fungal Ecology 4: 147-162.

Herink, J. & Kotlába, F. 1975. What is Rhodocybe xylophila Vasil’k. and Omphalina lilaceorosea Svr. et Kub.? Ceská Mykologia 29(3): 157-166.

Kunttu,P., Junninen,K., Kulju,M., Kouki,J., 2018: Major wood-decay fungal groups have disting occurrence patterns on woody substrates. – Baltic Forestry 24(2): 164-180.

Kunttu,P., Junninen,K., Kulju,M., Kouki,J., 2018: Major wood-decay fungal groups have disting occurrence patterns on woody substrates. – Baltic Forestry 24(2): 164-180.

Norros, V. et al. 2012. Dispersal may limit the occurrence of specialist wood decay fungi already at small spatial scales. 
– Oikos 121: 961–974.

Vassilkov, B.P. 1971. A new species of agaric fungi in the Transcaucasus. Mikologiya i Fitopatologia 5: 384-385.

Welle,T., Sturm, K., Bohr, Y.,2018: Alternativer Waldzustandsbericht. Eine Waldökosystemtypen-basierte Analyse des Waldzustandes in Deutschland anhand naturscutzfachlicher Kriterien. Naturwald Akademie.

Zvyagina, E.A, Alexandrova, A.V. & Bulyoncova,T.M. 2015. Omphalina discorosea: taxonomical position of the species. Phytopatologiya 5(4): 384-385.


Known distribution - countries

Regional Population and Trends

Country Trend Redlisted