• Proposed
  • Under Assessment
  • 3Preliminary Assessed
  • 4Assessed
  • 5Published

Boninogaster phalloides Kobayasi

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Scientific name
Boninogaster phalloides
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Under Assessment
Proposed by
Tsutomu Hattori
Jean Berube
Anders Dahlberg
Comments etc.
Michael Castellano, Tsutomu Hattori

Assessment Status Notes

New information 2016

It was once taken for an extinct species, but it has been found in several areas within the Bonin Islands, during the recent intensive expeditions. It is frequently found in secondary areas, and the host range seems wide though it was once taken for a specialist on an endemic species. So, there is no clear threat for this fungus.
Tsutomu Hattori and Kentaro Hosaka (May 20th 2016)

Hence the preliminary assessment below is not appropriate and need to be revised (Anders Dahlberg May 20th 2016)

Preliminary assessed as EN B2ab(iii)+C2(ai)

AOO < 500 km2; severely fragmented and number of locations less than 5; continuous decline is estimated in area, extent or quality of habitat: EN B2ab(iii).
Number of mature individuals < 2500; decline estimated; number of individuals in each subpopulations <250: EN C2a(i).

Taxonomic notes

This fungus was described in a monotypic genus Boninogaster by Kobayasi (1937). It had been considered a member of Hysterangiaceae, but Hosaka (2014) recently revealed that it may be accommodated in Sclerogastraceae on the basis of phylogenetical analyses.

Why suggested for a Global Red List Assessment?

Boninogaster phalloides was described based on a specimen collected in Bonin (Ogasawara) Islands. Bonin Islands are ocean islands, about 1000 km south of the Japanese main islands, and never combined with other islands or continents since their establishments. Therefore, many of the naturally distributed plants are endemic in these islands. Since the original report, this fungus had been unreported for a long time, but rediscovered during the intensive expeditions to these islands made in the last 10 years. However, this fungus is still unknown from other areas of Japan including subtropical islands of Okinawa, and considered an endemic species to Bonin Islands. Because of its rare occurrence and fragile habitat, this fungus is considered threatened for their existence.
Population size reduction of this fungus unknown, so Criterion A cannot be applied.
AOO < 500 km2; severely fragmented and number of locations less than 5; continuous decline is estimated in area, extent or quality of habitat: EN B2ab(iii).
Number of mature individuals < 2500; decline estimated; number of individuals in each subpopulations <250: EN C2a(i).

Geographic range

Hitherto recorded from Chichijima, Hahajima, Anijima and Mukojima Islands, all belonging to Bonin Is., Japan.

Population and Trends

It has been recorded from 4 islands, but localities in total are still less than 10. Forested area of the above 4 islands is ca. 38 km2 in total, so the area of possible locality for this fungus should be less than 38 km2. Unknown from other areas.
Detailed recent records are as follows:
Hahajima I., Nishiura (2011, 2012, 2013); Mt.Chibusayama (2014); Minamizaki (2011, 2014)
Chichijima I., Asahiyama (2010. 2012); Higashidaira (2012, 2014); Buta Beach (2013, 2014)
Anijima I., Tamana Beach (2013).
Population trend of this fungus is still unclear, but more than 15% of the forested area of Hahajima have been occupied by an introduced tree species Bischofia javanica, and can be influenced by this. Area of the occupation by introduced trees is now increasing in other islands as well as in Hahajima.

Population Trend: Uncertain

Habitat and Ecology

This is a saprotrophic fungi, and most specimens were made on rotten wood or fruit of Pandanus boninensis, an endemic species in Bonin Islands. Some limited specimens were also made on rotten wood of other trees, suggesting that it does not show a high specificity for Pandanus. It is found in moderately wet hillside forests, and is not restricted to old growth forest areas.  Spore dispersal by wind is not expected or limited.

Subtropical/Tropical Moist Lowland Forest


Most of the forested areas in Bonin Islands are highly reserved now, and further deforestations will be not expected. However, forest ecosystems in these islands are fragile, and ecosystem themselves are threatened in several parts of the islands because of the introduced tree species including Bischofia javanica (Euphorbiaceae) and Casuarina spp. (Casuarinaceae) replacing the original vegetation.

Named species

Conservation Actions

Forested areas in Bonin Islands should be strictly conserved. Control the introduced trees to conserve the original vegetation on these islands.  Now, they are trying to control Bischofia by Roundup and logging.

Site/area protectionInvasive/problematic species control

Research needed

More intensive monitoring is desirable in various areas of the Bonin Islands to reveal more accurate distribution in these islands and preferable forest condition for this fungus. Current and population trend is still incomplete.

Population size, distribution & trendsLife history & ecologyPopulation trendsHabitat trends


Hosaka, K. 2014. Phylogenetic analyses of a truffle-like genus, Boninogaster, from Hahajima Island, the Bonin Islands, Japan. Bull. Natl. Mus. Nat. Sci., Ser. B, 40(2):61–67.
Kobayasi, Y. 1937. Fungi Austro-Japoniae et Micronesiae. I. The Bogtanical Magazine 51:749–758.

Known distribution - countries

Regional Population and Trends

Country Trend Redlisted