• Proposed
  • Under Assessment
  • Preliminary Assessed
  • Assessed
  • CRPublished

Bridgeoporus nobilissimus (W.B. Cooke) T.J. Volk, Burds. & Ammirati

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Scientific name
Bridgeoporus nobilissimus
(W.B. Cooke) T.J. Volk, Burds. & Ammirati
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Incertae sedis
Incertae sedis
Assessment status
IUCN Red List Category
CR A2c; C2a(i)
Proposed by
Else Vellinga
Else Vellinga
Anders Dahlberg, Tsutomu Hattori, Else Vellinga

Assessment Status Notes

Taxonomic notes

Why suggested for a Global Red List Assessment?

Bridgeoporus nobilissimus’ perennial fruitbodies only occur on very old and large, majestic veteran trees and stumps of Abies species in old-growth forests in the states of Washington, Oregon and northern California (USA); it is known from less than 30 localities. Logging of old-growth Abies forests, changes in forest composition, forest fires, and the disappearance of big enough trees to support the fruit bodies are the main threats. Fruitbodies are also prone to vandalism.
Critically endangered based on criteria A2(c) + C2(a ii) + D.
The habitat of this species, old-growth Abies forest, has declined more than 90% over the last century. The known sites of the species are protected, but the tree composition has been changed into Pseudotsuga dominated forest.
The number of mature individuals per site is one or two, and the total number of sites does not exceed 50. The species has been extensively surveyed in all its known sites and possible habitats, and cannot have been overlooked as it forms huge conspicuous fruitbodies that are present the whole year through.
The total number of mature individuals is estimated to be less than 50, based on the extensive surveys that have taken place since 1998.

Geographic range

Cascade Mountain Range in Washington and Oregon (USA), Coast Range on the Olympic Peninsula (Washington) and in Oregon, and one locality in north coastal California (USA).

Population and Trends

Less than 25 sites with each one perennial big fruit body are currently known to exist and to sporulate, these are scattered over an area from northern California (USA) to central Washington (USA). Estimated number of sites does not exceed 35.
Confined to old-growth Abies stands, a type of habitat that has been extensively logged. Only 9% of the old-growth forests in the area still exists. The species is not known to occur outside the western USA.
Decline expected to continue, as the existent trunks are being decayed and no new big trees and trunks are available.

Population Trend: Deteriorating

Habitat and Ecology

Forming perennial conks at the base of very old very big living trunks, or dead snags and stumps of Abies procera, and A. amabilis,  A. grandis in old-growth forests predominantly in the mountains, but also known from one coastal site in California. The fruit bodies are long-lived, and more than 100 tube layers per fruit body have been found. Fruit bodies are very rare, but the mycelium of fungus has been detected in living smaller trees of these and other species in the same areas where the fruit bodies are found (Gordon 2009a and b). They only have been found fruiting on Abies.

Temperate Forest


Firstly habitat destruction. Old-growth forest, with the size of trees that will support the very large fruit bodies is rare and vulnerable. Logging for timber has decreased the extent of Abies. Forests are now managed for douglas fir (Pseudotsuga menziesii) as it grows faster than Abies.
The main host, Abies procera, is restricted to mountain tops.
Forest fires are of major concern, as the fuel load of the present day forests is much higher than in the past, which will cause the fires to burn more severely, being crown fires and killing the trees, instead of only killing the undergrowth.
Deliberate destruction of the fruitbodies is also a major threat. For instance the one specimen recently discovered in northern California (Mushroomobserver.org/116383) was broken off the tree. The fruitbodies are perennial.

Unintentional effects: subsistence/small scale (species being assessed is not the target) [harvest]

Conservation Actions

Habitat conservation, ensuring continuing growth of the host tree species (Abies) is most important.

This species is a so-called Strategy 1 species under the Northwest Forest Plan, and has been surveyed and managed within the range of the northern spotted owl (Strix occidentalis caurina). All possibly suitable Abies stands have been surveyed and the presence of the species in only <50 sites have been confirmed.

Site/area protection

Research needed

The clues for fructification are not known - is it the size of the tree ?

Population size, distribution & trendsLife history & ecology

Use and Trade


Burdsall HH, Volk TJ, Ammirati JF, 1996. Bridgeoporus, a new genus to accommodate Oxyporus nobilissimus (Basidiomycotina, Polyporaceae). Mycotaxon 60: 387–395.

Castellano, M.A., Smith, J.E., O’Dell, T., Cazáres, E., and Nugent, S.. 1999. Handbook to strategy 1 fungal species in the Northwest Forest Plan. Gen. Tech. Rep. PNW-GTR-476. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 204 p.

Cooke WB, 1949. Oxyporus nobilissimus and the genus Oxyporus in North America. Mycologia 41: 442–455.

Gordon M. 2009a. Detecting Bridgeoporus nobilissimus in wood cores using a genetic test: a test of a
core processing method and method sensitivity. Final report submitted to USDI Bureau of Land
Management, Oregon State Office.

Gordon M. 2009b. Bridgeoporus nobilissimus genetic presence in Abies trees survey report. Final report submitted to USDI Bureau of Land Management, Oregon State Office.


Redberg GL, Hibbett DS, Ammirati JF, Rodriquez RJ, 2003. Phylogeny and genetic diversity of Bridgeoporus nobilissimus inferred using mitochondrial and nuclear rDNA sequences. Mycologia 95: 836–845.

Trappe JM, 1990. The “most noble” polypore endangered. In Norse EA, Ancient Forests of the Pacific Northwest: 126–127.

Known distribution - countries

Regional Population and Trends

Country Trend Redlisted