Assessment Notes

Justification

Rubroboletus dupainii is an ectomycorrhizal fungus with conspicuous red sporocarps associated with trees in the Fagaceae, typically Quercus. It is rare, but widespread in central-southern Europe and in the Russian Caucasus and Turkey. The species is reported to be in decline in some countries and is included in Red Lists in most countries of occurrence. The conservation status of its most common habitat is reported as “unfavourable-inadequate” by EU Habitat Directive mid term report . Major threats relate to forest management and forest exploitation, especially conversion of broadleaf forests to conifer plantations.

It is assessed as near threatened under criterion C1 because population size is estimated at <20,000 and past and future estimated population decline ca. 10 % in a 50-year period.

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Taxonomic notes

The taxon current names include Suillellus dupainii and Rubroboletus dupainii, with Boletus dupainii as basionym. Reports from North and Central America, Russia far east, and Israel are not considered conspecific in this assessment.

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Geographic range

This species is widespread in central-southern Europe (absent from the UK and Scandinavia). It is also reported from the Russian Caucasus (Krasnodar Kray) and Turkey.

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Population and Trends

This species is overall rare, though more abundant in southern European countries. According to Fraiture and Otto (2015) the number of known sites is around 100, of which more than 50 are from France and Italy. Although R. dupainii´s suitable habitat is extensive, and it is a conspicuous, well-known and easily identifiable fungus, it is not commonly reported. It has a broad distribution and the total number of localities is estimated to be significantly higher than reported, but not to exceed 1000. With an estimated average of 10-20 mature individuals at each locality, the total number of mature individuals will not exceed 20,000. The habitat of R. dupainii is considered to have declined by more than 20% during the last 50 years. This is due in large part to the conversion of broadleaf forests to conifer plantations. It is anticipated that this decline will continuing at the same rate over the next 50 years (cf, European Commission, 2015). This species forms ectomycorrhizas with species of Fagaceae, so the decline in hosts directly negatively impacts the population size of R. dupainii.

Population Trend: decreasing

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Habitat and Ecology

It is ectomycorrhizal with trees in  Fagaceae, typically Quercus (e.g. Q. cerris, petraea, pubescens, suber, ilex, rotundifolia), but also Fagus and Castanea. The species mainly occurs in termophilous deciduous natural or semi-natural forests dominated by Quercus, often old-growth, sometimes preferring more open areas. Due to climate change effects, it is expected to slowly spread northwards occupying potentially suitable habitats in Central Europe. The species occurs in the following Natura 2000 habitats (codes): 9150 (“Medio-European limestone beech forests of the Cephalanthero-Fagion”; the most common habitat), 9160, 9170, 91G0, 91H0, 91M0, 91AA, 9330, 9340.

According to the last report under Article 17 of the EU Habitats Directive (European Environmental Agency, 2007-2012) the conservation status of its most common habitat is “unfavourable-inadequate” and in all regions except Mediterranean, “unfavourable-bad,” and Carpathian “favourable”.

Range and area are “favourable” in all regions and both structure & functions and future prospects are the reason for the “unfavourable” assessments. The "Mid-term review of the EU biodiversity strategy towards to 2020" (European Commission 2015) specifies that the vast majority of assessments of conservation status for woodlands remains “unfavourable” (80 %). The majority of the assessments of conservation status for woodland and forest species from the Habitats Directive are “unfavourable”, with 44% assessed as “unfavourable-inadequate” and 16% assessed as “unfavourable-bad”. As for the trends in conservation status of (target) species occurring in these woodlands, nearly a quarter of the assessments are assessed as “unfavourable-stable” (22%), while only 6% are assessed as “unfavourable-improving”; a significant amount of the remaining assessments (17%) are assessed as “unfavourable-declining” (European Environmental Agency 2015).

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Threats

Threats mainly relate to forest management (e.g., fire, clearcutting; Fraiture and Otto 2015). Habitats may be irreversible destroyed due to the substitution of native oak forests by conifers (e.g. Pinus nigra) and spreading of the invasive alien species Robinia pseudoacacia.

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Conservation Actions

The species is included on Red Lists and / or protected by law in most of the countries where it occurs. For the sites that are within the Natura 2000 network, appropriate forest management plans can play a role in improving the conservation status of the species. For the localities outside protected Natura 2000 network, improving EU-level information on forest status will allow a more precise assessment of the situation and the design of appropriate policy responses. Individual mycelia of ectomycorrhizal fungi persist with their host trees. Therefore, site protection, along with long term management is needed to maintain appropriate habitat with required host trees.

Research needed: Reports from North and Central America, Russian far east, and Israel need confirmation for conspecificity.

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Source and Citation

Perini, C. & Gonçalves, S.C. 2019. Rubroboletus dupainii. The IUCN Red List of Threatened Species 2019: e.T70402507A70402516. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T70402507A70402516.en .Accessed on 2 February 2023

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• Country occurrence