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Flaviporus citrinellus (Niemelä & Ryvarden) Ginns

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Scientific name
Flaviporus citrinellus
Author
(Niemelä & Ryvarden) Ginns
Common names
Zitronengelbe Krustentramete
Lemon-colored Antrodiella
outkovečka citronová
Sidrunkollane antrodiell
antrodiela žltorúrková
Citrondzeltenā antrodīte
IUCN Specialist Group
Mushroom, Bracket and Puffball
Kingdom
Fungi
Phylum
Basidiomycota
Class
Agaricomycetes
Order
Polyporales
Family
Meruliaceae
Assessment status
Published
Assessment date
2019-03-26
IUCN Red List Category
EN
IUCN Red List Criteria
A2c+4c
Assessors
Krisai-Greilhuber, I.
Reviewers
Mueller, G.M.

Assessment Notes

The content on this page is fetched from The IUCN Red List of Threatened Species: https://www.iucnredlist.org/species/147295216/147880737

Justification

Flaviporus citrinellus is a European endemic. This lemon yellow wood-inhabiting annual polypore is restricted to old growth fir or spruce -fir forests with abundant large coarse woody debris. These forests are highly endangered by logging and management changes in many European countries, e.g. in Austria, only 3% of Austrian forests are virgin forests (including very steep inaccessible ones) and Carbonate- and clay-spruce-fir-beech-forests, habitats of occurrence of Flaviporus, are endangered biotopes types (Essl and Egger 2010). Phenologically it is usually  associated with the very abundant polypore Fomitopsis pinicola, on which it is considered a parasite.

It is included in the Red Lists of 9 countries, mostly listed as EN or CR.

Due to the steep decline in suitable habitat, the species is assessed as EN A2c+4c.

Geographic range

Flaviporus citrinellus is a European endemic.  It is restricted to old growth fir or spruce -fir forests with abundant large coarse woody debris.  Known Localities (number in brackets): Czechia (31), Estonia (29), Lithuania (4), Germany (7), Austria (3), Norway (66), Sweden (25), Switzerland (13), Poland (1), Russian Federation (100), Finland (130), France (1), Slovakia (4), Bosnia & Herzegovina (1), Croatia (1).

Population and Trends

Mature individuals are very rare. Based on GBIF and available databases (see references) 500 localities are known worldwide with a global estimate of 750. The number of mature individuals has been estimated at 3000 following Dahlberg and Mueller (2011).

It is restricted to old growth forests with abundant large coarse woody debris.  This forest type is under considerable decline throughout its region which is causing a decline in population size of F. citrinellus.  It is included in Red Lists of 9 countries, mostly listed as EN or CR.

Population Trend: decreasing


Habitat and Ecology

Flaviporus citrinellus is a rare wood-inhabiting annual polypore causing white rot primarily of Picea abies and Abies alba, much less frequently on broadleaf trees (Fagaceae). It prefers old growth forests with abundant large pieces of coarse woody debris (Dvořák et al. 2017)  Phenologically it is usually  associated with the very abundant polypore Fomitopsis pinicola, on which it is considered a parasite.  Whereas perennial fruitbodies of F. pinicola develop over the year from spring to autumn,  F. citrinellus develops fruit bodies mainly in late autumn (October, November) and again in spring (April to June).

It occurs on slopes of hills and mountains and at bottoms of deep river or stream valleys in waterlogged spruce forests and ravine forests. Most records are from montane and supra-montane spruce forests (ca. 1000-1300 m) and submontane to montane mixed forests dominated by beech, spruce and fir. In Switzerland and Poland it fruits also in lowlands below 600 m. Most records are from fallen trunks 10–100 cm in diameter, rarely stumps. In Czechia the wood decay stage is 2–5 with a peak in stage 3.  The species is a important indicator species for montane old-growth forests  and should be considered by authorities and conservationists when negotiating protected sites. These forests are highly endangered by logging and management changes in many European countries, e.g. in Austria, only 3% of Austrian forests are virgin forests (including very steep inaccessible ones) and Carbonate- and clay-spruce-fir-beech-forests, habitats of occurrence of Flaviporus, are endangered biotope types (Essl and Egger 2010). 
The fruit bodies are quite hidden and difficult to find. The increase in number of recent reports is due to enhanced in awareness and interest by mycologists.

Threats

Flaviporus citrinellus is restricted to old growth forests with abundant large coarse woody debris.  These habitats are declining and the species is under threat throughout its range due to habitat destruction and anthropogenic habitat changes.  Warming climate may also negatively impact its population as its growth optimum is at rather low temperatures (5-10 °C).

Conservation Actions

Protection of natural and near-natural forest sites is needed, no forest management should be done at the protected sites except game management in a certain amount to guarantee tree growth and young tree regeneration. Leaving a high amount of high quality, i.e. coarse, dead wood is recommended.

Fortunately, in Czechia, most of the Flaviporus localities are protected as nature reserves or strictly protected zones of national parks. This is not the case in other countries, e.g. in Austria. In Sweden two of the known three sites are protected.

Research on population size, population trends and distribution monitoring are needed.

Source and Citation

Krisai-Greilhuber, I. 2019. Flaviporus citrinellus. The IUCN Red List of Threatened Species 2019: e.T147295216A147880737. https://dx.doi.org/10.2305/IUCN.UK.2019-2.RLTS.T147295216A147880737.en .Downloaded on 31 January 2021

Country occurrence