Suillus americanus is an edible ectomycorrhizal fungus associated with five-needle pines, across the northern hemisphere. It is common and there is no evidence of significant decline. Therefore, it is assessed as being of Least Concern (LC).
The species was previously known under two names, Suillus sibiricus and S. americanus, and subsumed under S. americanus by Klofac (2013). Molecular data from Nguyen et al. (2016) supported this change due to a lack of discernable phylogenetic structure based on ITS sequences in the S. americanus clade.
Why suggested for a Global Red List Assessment?
Suillus americanus is a widespread species in the Northern Hemisphere. It is found in North America, Central and Eastern Europe, and Asia to Russia, China and Japan, Pakistan and India. It does not occur naturally in the Southern Hemisphere, although it might have been introduced with the establishment of five-needle pine plantations (e.g. Pinus strobus in South Africa). The area of occupancy (AOO) of this species is much larger than 2,000 km², and its extent of occurrence (EOO) is much larger than 20,000 km².
Population and Trends
The population size of Suillus americanus is very large, as it is such a widespread species. Its population may be in decline due to loss of hosts across some of its range, but likely stable in other large areas, especially Russia.
Population Trend: Uncertain
Habitat and Ecology
Suillus americanus is an ectomycorrhizal fungus that associates exclusively with five-needle pines, usually called white pines (e.g. Pinus strobus, P. monticola, P. lambertiana, P. longaeva, P. ayacahuite, P.cembra, P. peuce, P. wallichiana) in natural forests, near-natural forests (extensively used), plantations, and isolated trees.
Boreal ForestTemperate Forest
There appear to be no particular threats worldwide.
In North America, four white pine species, hosts of Suillus americanus, are threatened by the compound effects of white pine blister rust (Cronartium ribicola, a non-native fungus introduced to North America in 1906), mountain pine beetle (Dendroctonus ponderosae), and fire (Dudney et al. 2020). The dramatic declines resulted in the white pine (Pinus albicaulis) being classified as Endangered in the IUCN Red List (Mahalovich and Stritch 2011). In Europe, S. americanus is threatened by habitat loss due to the felling of subalpine forests where its host trees occur (e.g. to build infrastructure for winter sports); one of its two only hosts in Europe, the endemic P. peuce, is classified as Near Threatened (Farjon 2017). Past deforestation and conversion of forests in China has likely resulted in population decline.
Tourism & recreation areasSmall-holder plantationsAgro-industry plantationsNamed species
Reducing habitat loss is the main needed action. In North America, efforts to maintain populations of host trees are ongoing. In Europe, many sites are within nature reserves, so threats to the species are reduced.
Site/area protectionResource & habitat protection
Careful morphological studies coupled with molecular data from genes other than the ITS, including from type specimens, and host association data are needed to ascertain the (subtle) differences between the varieties and formae within Suilus americanus (Nguyen et al. 2016).
Use and Trade
Suillus americanus is edible, but not much used.
Food - human
Suillus sibiricus ssp. helveticus by Matthias Theiss