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Cortinarius stjernegaardii Brandrud & Frøslev

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Scientific name
Cortinarius stjernegaardii
Brandrud & Frøslev
Common names
knölfotad bananspindling
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Assessment date
IUCN Red List Category
IUCN Red List Criteria
B2ab(ii,iii,v); C2a(i)
Brandrud, T.-E., Krisai-Greilhuber, I. & Saar, I.
Dahlberg, A.

Assessment Notes

The content on this page is fetched from The IUCN Red List of Threatened Species: https://www.iucnredlist.org/species/204092017/204094318


Cortinarius stjernegaardii is a rare ectomycorrhizal European fungus restricted to the boreonemoral zone of southern Scandinavia, Germany, Latvia and Estonia, where it is associated with calcareous Tilia cordata forests and Corylus avellana-Quercus spp. woodland. The species is known from approx. 50 sites and it is estimated to be present in up to 150 sites in total. The forest habitat types of C. stjernegaardii have been sharply reduced in Norway and Sweden due to a loss of area due to urbanization, roads, limestone quarries, forestry and in some places also due to increased growth of shrubs and spruce following ceased historic management e.g. cattle grazing. The species is estimated to have a total population of 3,000 mature individuals and is confined to fragmented small areas. According to the C and B criteria (C2a(i)), and B2ab(ii,iii,v)) the species qualifies to be red-listed as VU, based on a continuous decline, population size <10,000 individuals, small area and very small/isolated subpopulations.

Taxonomic notes

Cortinaius stjernegaardii was described in 2017 (Frøslev et al. 2017). Formerly, the species has been called C. bulbopodius (Chevassut & Rob. Henry) Bidaud & Reumaux (or C. nanceiensis var. bulbopodius) in Scandinavia.

Geographic range

Cortinarius stjernegaardii is almost exclusively restricted to the southern Scandinavian boreonemoral zone. The species occurs in calcareous Tilia forests mainly the Oslofjord area of south-east Norway, and in calcareous Corylus(-Quercus) woodlands mainly in south-east Sweden near Vänern and at Öland and Gotland. Outside southern Scandinavia, the species is so far verified from one locality in Tilia forest along the Rhine valley in south-west Germany. In addition it is recorded in 11 environmental soil samples in Estonia and one soil sample in Latvia. The species was described in 2017, but has been known for a longer time from the Oslofjord-Vänern-Öland area, under the incorrect name C. bulbopodius (Frøslev et al. 2017). The Scandinavian sites are believed to be old, relic ones, being remnants of a formerly larger population of Tilia and Corylus forests from during the Holocene climate optimum 5,000-8,000 years ago.

Population and Trends

Cortinarius stjernegaardii is known from 30 localities/sites in the Oslofjord district. The habitat of calcareous lime forests is very well investigated for fungi in Norway (including a specific monitoring programme), and the total number of localities is estimated to ca. 45, corresponding to 900 mature individuals. In Sweden, the species is recorded from approximately 10 localities from Kinnekulle (Vänern), south-west Gotland and Öland. In Estonia and Latvia it is recorded from approximately 15 localities. The total population is estimated to be approximately from 150 sites, corresponding to about 3,000 mature individuals (cf. Dahlberg and Mueller 2011). The calcareous Tilia forest type is Red Listed as EN in Norway, according to the national nature type Red List (Artsdatabanken 2018), due mainly to a loss of area due to urbanization, road construction, lime quarries, etc. (see also Direktoratet for naturforvaltning 2011, Brandrud et al. 2011). Cortinarius stjernegaardii is also Red Listed as EN in Norway, based on a decline in habitat and a very small population (the species is not yet assessed in Sweden, 2020).

Population Trend: decreasing

Habitat and Ecology

The species forms mycorrhiza with Tilia cordata and Corylus avellana, possibly also Quercus spp, in calcareous Tilia forests and calcareous Corylus-Quercus woodlands, usually on very dry, shallow-soil limestone outcrops/plateaus or small scree areas with limestone/shale gravel. Probably the species formerly had a wider European distribution associated with Tilia-Corylus forests on calcareous ground, during the Holocene climate optimum, when Tilia cordata-Corylus avellana forests were more frequent. Subsequently, the species has probably been outcompeted by Fagus-Quercus-Carpinus species in forests nowadays dominated by these trees and has been restricted to Tilia-Corylus forests of a relic nature, mainly outside the distributional area of Fagus and Carpinus.


Both the habitat in south-east Norway (calcareous Tilia forests) and the major habitat in south-east Sweden (calcareous Corylus(-Quercus) woodlands) are declining, due to a loss of area  due to an increase of urban areas, including increase in roads, and limestone quarries, forestry, expansion of Picea abies and abandonment of non-intensive management with cattle grazing etc., which traditionally kept a semi-open structure of the woodlands (Knutsson 2014, Direktoratet for naturforvaltning 2011, Brandrud et al. 2011). The calcareous Tilia forests in south-east Norway have been declining by >30% the last 50 years, and also suffer from decreasing habitat quality, and are assessed as EN in the latest nature type Red List of Norway (Artsdatabanken 2018).

Conservation Actions

Some of the Tilia or Corylus sites with Cortinarius stjernegaardii are nature reserves, but more sites need to be set aside to prevent declines and further fragmentation as the remaining small calcareous Tilia or Corylus(-Quercus) woodlands with good habitat quality are very vulnerable. It is especially important to set aside reserves on calcareous lime-hazel forest hotspots, housing many rare/Red Listed, habitat-specific species such as C. eucaeruleus, C. odoratus, C. osloensis and C. suaveolens. It is also important to identify sites where less strict conservation regimes can be appropriate, e.g. as woodland key habitats or with with cautious extensive forestry that may enable survival of established mycorrhizal fungal species. Additionally, more mapping, surveying and monitoring of C. stjernegaardii is desired; and more information on occurrences in fragments of appropriate calcareous Tilia cordata-Corylus avellana forests potentially hosting C. stjernegaardii in various parts of northern Europe would be valuable.

Use and Trade

No use or trade is known.

Source and Citation

Brandrud, T.-E., Krisai-Greilhuber, I. & Saar, I. 2021. Cortinarius stjernegaardii. The IUCN Red List of Threatened Species 2021: e.T204092017A204094318. https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T204092017A204094318.en .Accessed on 10 October 2023

Country occurrence