Assessment Notes

Justification

Pseudoxenasma verrucisporum is a resupinate fungus known from Europe, where it grows mainly in humid spruce forests. Total population size is estimated at 111,000 mature individuals, with no evidence of population decline so the species is assessed as Least Concern (LC).

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Taxonomic notes

Pseudoxenasma verrucisporum is the type and only species in the Pseudoxenasma genus, created based on microscopic characteristics (Hjorstam and Larsson 1976). Molecular data has since been used to verify its position as monotypic genus, but the original placement of this species in Russalales was not confirmed and is for now unresolved (Larsson and Larsson 2003).

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Geographic range

This species is only known from northern and western/central Europe. It is found mostly in the southern regions of Sweden and Norway (often along the coast), but also in Finland, Austria, Belgium and Switzerland (Kunttu et al. 2021, GBIF.org 2023). GBIF also includes a soil sample record from Estonia that may indicate a further distribution in this country, but no fruiting bodies have been reported so far.

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Population and Trends

Pseudoxenasma verrucisporum is known from 37 sites in Europe: Sweeden (22), Norway (seven) Austria (five) and Belgium, Finland, and Switzerland. It is an inconspicuous species and likely under-recorded, though Kunttu et al. (2021) describe it as overall rare, but locally common. The total number of sites, including a multiplier for unrecorded sites, is therefore estimated at 18,500. Assuming three functional individuals per site (e.g. branches or logs) and two mature individuals per functional individual, the population size is estimated at around 111,000, following guidelines by Dahlberg and Mueller (2011). There is no evidence of a population decline.

Population Trend: Unknown

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Habitat and Ecology

This is a saprotrophic resupinate fungus. It grows on fallen or, still attached, dead branches and trunks in closed humid coniferous forests, mainly composed of Picea (e.g. Picea abies) and more rarely on pines (Pinus sp.) (SLU Artdatabanken 2020). It is often found with Globulicium hiemale (Kunttu et al. 2021).

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Threats

No significant threats were identified for this species, and its likely main host (Picea abies) has been assessed as Least Concern (stable population) (Farjon 2017).

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Conservation Actions

Pseudoxenasma verrucisporum has been assessed in the National Red Lists of Sweden (SLU Artdatabanken 2020) and Norway (Brandrud et al. 2021) as Least Concern. No specific conservation actions are needed for this species.

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Source and Citation

Cunha, S.P. & Gonçalves, S.C. 2025. Pseudoxenasma verrucisporum. The IUCN Red List of Threatened Species 2025: e.T266015830A266020636. Accessed on 23 November 2025.

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• Country occurrence