• Proposed
  • Under Assessment
  • ENPreliminary Assessed
  • 4Assessed
  • 5Published

Rhizopogon togasawarensis Mujic, K. Hosaka & Spatafora

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Scientific name
Rhizopogon togasawarensis
Author
Mujic, K. Hosaka & Spatafora
Common names
Togasawarasyoro
IUCN Specialist Group
Mushroom, Bracket and Puffball
Kingdom
Fungi
Phylum
Basidiomycota
Class
Agaricomycetes
Order
Boletales
Family
Rhizopogonaceae
Assessment status
Preliminary Assessed
Preliminary Category
EN C2a(i)
Proposed by
Masao Murata
Assessors
Masao Murata
Comments etc.
James Westrip
Reviewers
Anders Dahlberg

Assessment Notes

Justification

Rhizopogon togasawarensis is a hypogeous ectomycorrhizal fungus confined to the endemic Japanese Doulas-fir (Pseudotsuga japonica). Japanese Doulas-fir is a slow growing rare tree with a declining population consisting of small and scattered subpopulations of about 2000 trees and globally red-listed as Endangered. Based on R. togasawarensis being strictly dependent on Japanese Douglas-fir, its estimated population to be in the same range or smaller as P. japonica and its population being subjected to the same decline as its host tree, the fungus is assessed as EN under the C criterion.


Taxonomic notes

Rhizopogon togasawarensis was described in 2014 by Mujic, Hosaka and Spatafora.


Why suggested for a Global Red List Assessment?


Geographic range

Rhizopogon togasawarensis is an endemic fungus only recorded at stands of Japanese Douglas-fir (Pseudotsuga japonica) that grows in east Kochi prefecture and the Kii peninsula in Japan. Estimated area of occupancy (AOO) 2000 km2 and estimated Extent of occurrence (EOO) as for P. japonica.


Population and Trends

Rhizopogon togasawarensis is strictly associated with Pseudotsuga japonica. Hence, the population size of R. togasawarensis relies on the presence of P. japonica. The host tree is endemic to Japan and remains in several small and scattered subpopulations, and its total population is estimated to consist of approximately 2000 mature trees. The total population of the tree is estimated to be continuously declining and is globally redlisted as Endangered (Katsuki, Luscombe and Farjon 2013). The population size of R. togasawarensis is estimated to be in the same range, or more likely, smaller than that of the tree host having the same population trend, i.e., declining.

Population Trend: Decreasing


Habitat and Ecology

Rhizopogon togasawarensis is a hypogeous ectomycorrhizal fungus living in obligate symbiosis with Japanese Douglas-fir. Its truffles have only been found a few times since the first record in 2010 (Mujic et al 2014; Murata et al 2017). However, a study using molecular technique detected R. togasawarensis as a frequent component of the soil spore bank of ectomycorrhizal fungi in Japanese Douglas-fir stands (Murata et al 2017). Some Rhizopogon species are known to develop very long-lived spore banks.

Rhizopogon togasawarensis belongs phylogenetically to a group of Rhizopogon (the section Villosuli) that associates solely with Pseudotsuga (Pinaceae). Otherways, many Rhizopogon species typically associate with pine trees. This specificity was tested in a bioassay where spores of R. togasawarensis were inoculated to seedlings of different conifer species (Murata et al 2017). Colonization took place with Pseudotsuga but not with Pinus, confirming the dependence of R. togasawarensis on Japanese Douglas-fir.

Temperate Forest

Threats

Given the observed specificity of Rhizopogon togasawarensis for Pseudotsuga and its phylogenetic position within the Pseudotsuga-specific Rhizopogon lineage Villosuli, its geographical distribution is likely restricted to the remaining Japanese Douglas-fir forests, indicating a high extinction risk for this fungus as well as its endangered host. The main threat is the same as P. japonica, e.g., habitat change. Regeneration is poor, and older trees are declining. In the past, habitat conversion to plantation forestry and other uses took place. The total population of P. japonica in Japan today is estimated to be ca. 2,000 mature trees and is considered to be continuously declining (Katsuki, Luscombe and Farjon 2013).

Scale Unknown/UnrecordedIntentional use: subsistence/small scale (species being assessed is the target) [harvest]

Conservation Actions

No specific conservation action has been initiated for R. togasawarensis, but it benefits from that a few areas with Japanese Douglas-fir are protected.

Site/area protection

Research needed

Life history & ecologyThreatsActions

Use and Trade

None.

Unknown

Bibliography


Country occurrence

Regional Population and Trends

Country Trend Redlisted