R-L categories correct, but text here does not match final assessment. Developed and updated version published at IUCN´s Red List update, July 18th 2019.
It is a distinctive large fleshy bolete with beautiful pale greyish cap, bloodred pores and a stem with a conspicuous red net. In Europe it is widespread meridional to temperate, but only occasionally found in the far north and generally more common in the south. It occurs in broadleaf deciduous and evergreen forests in climax state and is ectomycorrhizal with beech (Fagus) or oaks (Quercus), somestimes it grows in chestnut coppices, in roadside verges and parks with isolated trees. Its preferred soils are calcareous sandy or sandy-loamy soils, from sea level up to the mountains. This bolete is considered rare and threatened in most of its area and is red-listed in 13 European countries. Being confined mainly to older Fagus and Quercus stands and to isolated old trees in parks and along roads, it is highly endangered by intense forestry, e.g. clear cutting or removing old park trees, which abruptly stops the life of this mycorrhizal fungus. Based on GBIF and databases available (see below) there are 550 subpopulations known worldwide with an estimated total number of mature individuals of 22000. Its area of occupancy is estimated as 2200 km2.It is threatened by loss of habitat, modern forestry and air pollution.
It is assessed as Near threatened: A3c because population size reduction is suspected due to habitat loss and habitat management changes (cultivation of non-native tree species, e.g. Quercus rubra, conversion into young forests with short turnover times due to wood production for biomass plants); B2ab(iii), because the area of occupancy (2200 km2) is only a bit over the borderline to VU, and C2ai, number of mature individuals is only 22000 and number of mature individuals in each subpopulation is less than <250. The assessment is based on population size, habitat loss and a diminishing habitat quality.
Rubroboletus rhodoxanthus (Krombh.) Kuan Zhao & Zhu L. Yang
This is a rare and distinctive large fleshy bolete with beautiful pale greyish cap, bloodred pores and a stem with a conspicuous red net. It is threatened by loss of habitat, air pollution, and modern forestry. It is red-listed in 13 European countries and has small subpopulations.
In Europe it is widespread meridional to temperate, but only occasionally found in the far north and generally more common in south. The species is considered rare and threatened in most countries of its occurrence. Being confined mainly to older Fagus and Quercus stands, and to isolated old trees in parks and along roads, it is highly endangered by intense forestry, e.g. clear cutting or removing old park trees, which abruptly stops the life of this mycorrhizal fungus.
Based on GBIF and databases available (see below) 550 subpopulations are known worldwide. The number of mature individuals has been estimated at 22000 following these lines: (a) likely number of current localities (estimated to be ca. 1100) (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. sporomata separated by 10 m, template = 2, = 2200): estimation of total number of localities x estimation of the average number of functional individuals/locality; ii convert the number of functional individuals into mature individuals following Dahlberg & Mueller 2011, template = 10 because for terrestrial fungi each functional individual is suggested to account for 10 mature individuals; = 22000). The numbers of known localities is 550 and the number of yet unknown localities was estimated to be twice as high. Mature individuals are rare and rarely reach spore production due to collecting activities. The Netherlands subpopulation is increasing due to climate warming.
The AOO was estimated as 2200 km2, 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.
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 established mycelia, 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 km2 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 km2 (= 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
It inhabits broadleaf deciduous and evergreen forests in climax state and is ectomycorrhizal with beech (Fagus) or oaks (Quercus), sometimes also occuring in chestnut coppices, in roadside verges and parks with isolated trees, on calcareous sandy or sandy-loamy soils, from sea level up to the mountains.
It is threatened by loss of habitat, air pollution, modern forestry and clear cutting. In some countries it could be endangered by side effects of harvesting edible mushrooms in enormous quantities (raking of litter and soil, intensive trampling and soil erosion, the deposition of waste etc). These methods may damage the habitats of the edible fungi, perhaps in an irreversible way.
Protection of ancient woodland and especially of known sites, where a management system ensuring the right age profile in the stands of the tree partner should be implemented.
Research on distribution, population trends and the ecological requirements of the species is needed.
It is an edible species and collected in several countries.
Dämon & Krisai-Greilhuber, 2017: Die Pilze Österreichs, Verzeichnis und Roge Liste 2016. – Wien: Österr. Mykolog. Ges.
Krieglsteiner, G.J.,2000: Die Großpilze Baden-Württembergs Band 2. Ulmer.
Noordeloos, M.E., Kuyper, T.W., Somhorst, I., ellinga, E.C., 2018: Flora Agaricina Neerlandica 7 Boletales. – Origgio, Editrice Candusso.
Wright M, 2011. Boletus rhodoxanthus: First authentic British record. Field Mycology 12(3):