• Proposed
  • Under Assessment
  • Preliminary Assessed
  • Assessed
  • ENPublished

Rhizopogon alexsmithii (Trappe) Vizzini & Zotti

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Scientific name
Rhizopogon alexsmithii
(Trappe) Vizzini & Zotti
Common names
IUCN Specialist Group
Cup-fungi, Truffles and Allies
Assessment status
IUCN Red List Category
EN B2ab(ii,iv,v); C1+2a(i)
Proposed by
Michael Castellano
Jean Berube
Michael Castellano

Assessment Notes

Taxonomic notes

Originally proposed as Alpova alexsmithii Trappe (1975).  Transferred to Rhizopogon by Vizzini and Zotti (2010) based on molecular evidence.

Why suggested for a Global Red List Assessment?

Easily recognized mycorrhizal, hypogeous, sequestrate (truffle-like) species endemic to the Pacific Northwest of North America.  Characterized by the knobby to lobed sporocarp and the pink to flesh-colored and white marbled gleba.  Known only from mid to high elevational Tsuga forests in the Cascade Mountains.

11 total known sites, 5 are historic and not redocumented for more than 30 years.  Historic sites include the single localities in both Canada and Washington.  6 extant sites all located within Oregon in the Cascade mountains.

Random Grid survey of 750 plots for two years across this region, including plots in this habitat type, did not reveal any new collections or sites for this species.

EN C2(ai) - extremely small population size, habitat declining due to forest fire and logging.

11 known sites x 5 potential mycelia per site x 10 = 440 potential mature individuals

Geographic range

Known from southwestern British Columbia, Canada and the Cascade Mountains of Washington and Oregon

Population and Trends

Ten known sites in Pacific Northwest USA and one known site in southwestern British Columbia, Canada. 

Six of the ten known sites from Oregon and Washington are from more than 30 years old.  Only one known site from that timeframe has been redocumented; Still Creek campground on the Mount Hood National Forest has 6 additional collections up through 2004.  The Canadian and Washignton sites have been revisited numerous times without redocumentation of species presence.

Random Grid survey of 750 plots for two years across this region, including plots in this habitat type, did not reveal any new collections or sites for this species.

Extremely small population size, habitat declining due to forest fire and logging.

11 known sites x 2 potential mycelia per site x 2 ramets per mycelia = 44 mature individuals x 10 (for potential other mature individuals) = 440 potential mature individuals

Population Trend: Decreasing

Habitat and Ecology

Hypogeous, mycorrhizal sequestrate (truffle-like) species associated with the roots of mature to old-growth Abies procera, A. lasiocarpa, Tsuga mertensiana and Tsuga heterophylla.  Most known sites located at 3,000-6,000 ft. elevation.  Dependent on mycophagy (eaten by small mammals and defecated) for spore dispersal.  Home range of primary spore vector(small mammals) is less than 2 ha. Fruiting August through October.


This is a mycorrhizal fungus species so is dependent on living host trees for viability.  Threats to the high elevation late serial to old growth habitat include, logging, and human activities such as campground development and road building.  Forest fire is of concern due to remote locations of some known sites.  Summer forest fires are common near these known site locations due to dry summer thunderstorms.  Soil compaction in known sites that are campgrounds.  In addition climate change have potential severe impacts on habitat availability.

Conservation Actions

The ongoing action plan as part of the Survey and Manage plan of the Northwest Forest Plan to protect habitat for the Northern Spotted Owl is to protect known sites and buffer known sites from ground and host disturbances. Revisit known sites to confirm persistence and determine extent of populations, particularly for known sites more than 30 years old.  Mitigate impacts during vegetation management (clearcutting or thinning of surrounding forests) in or near known sites.

Research needed

Use molecular tools to examine other potential hosts, i.e., Abies amabilis that occur in similar habitat.

Purposive surveys in potential habitat to discover additional occupied sites. 

Use molecular tools to visit known sites to evaluate population size and structure.

Use and Trade


Trappe, J.M. 1975. A revision of the genus Alpova with notes on Rhizopogon and Melanogastraceae.  Nova Hedwigia 51:279-309.

Castellano, M.A.; Smith, J.E.; O’Dell, T. [et al.]. 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.

Cushman, K., and Huff, R. 2007. Conservation assessment for fungi included in Forest Service Regions 5 and 6 Sensitive and BLM California, Oregon and Washington special status species programs. R6 USFS and OR/WA BLM Interagency Special Status/Sensitive Species Program (ISSSSP). Appendix 1. http://www.fs.fed.us/r6/sfpnw/issssp/planning-documents/assessments.shtml

Vizzini, A., Zotti, M., Ryman, S., and Ghignone, S. 2010. Typification of Octaviania rubescens (Paxillineae, Boletales) and phylogenetic hypotheses for genus Alpova. Mycologia 102:967-975.

Interagency Special Status / Sensitive Species Program (ISSSSP) Conservation Planning Documents - Fungal Species Fact Sheets- available at: http://www.fs.fed.us/r6/sfpnw/issssp/planning-documents/species-guides.shtml  accessed on April 23-2015

Known distribution - countries

Regional Population and Trends

Country Trend Redlisted