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  • Under Assessment
  • Preliminary Assessed
  • VUAssessed
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Marasmius horridulus Singer

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Scientific name
Marasmius horridulus
Common names
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Preliminary Category
VU C1+2a(ii)
Proposed by
Dirce Komura
Comments etc.
Dirce Komura
Gregory Mueller

Assessment Notes


Marasmius horridulus has been recorded from only 7 collections on Amazonian Terra Firme Forest in the Amazonas State, in Brazil. All the collection sites are located in protected areas in the metropolitan area of Manaus and none of the specimens were found in a secondary forest. The basidiomata are more robust and resistant when compared with other marasmioid fungi and the basidiomata production period mostly occurs in the dry season. So, even with its tiny size, this mushroom can be easily observed. While the species may have additional subpopulations within the Amazonian Forest, based on reviews of fungarium data and extensive suverys for leaf inhabiting fungi it is a rare species with an inferred population size of less than 10,000 mature individuals, all in one subpopulation. The main threat is loss of quality of habitat, especially deforestation and the expansion of urban occupation around areas where the fungus was found. The species is assessed as Vulnerable C1+2a(ii).

Taxonomic notes

Marasmius horridulus Singer was collected in Manaus, Amazonas State, Brazil by Rolf Singer in 1978, and this single collection was properly described in 1989. Marasmius horridulus has been misidentified as Crinipellis.

Why suggested for a Global Red List Assessment?

Marasmius horridulus has been recorded from only 7 collections on Amazonian Terra Firme Forest in the Amazonas State, in Brazil. All the collection sites are located in protected areas in the metropolitan area of Manaus and none of the specimens were found in a secondary forest. The basidiomata are more robust and resistant when compared with other marasmioid fungi and the basidiomata production period most occurs in the dry season. So, even its tiny size, this mushroom could be easily observed. So even while the species may have additional subpopulations among the Amazonian Forest, its population in this forest is rare. The estimated size of the population is up to 10,000 mature individuals. The main threat is loss of quality of habitat, especially deforestation and the expansion of urban occupation around those areas where the fungus was found. More research on marasmioid fungi in neotropical forest is needed to confirm the distribution, possible substrate preference, and phenology.
This species should be considered Endangered (EN) under the criterion of C2a(ii).

Geographic range

Marasmius horridulus is endemic to Manaus region of Amazonas State, Brazil. It has been recorded only six times since it was described. All the records are from Amazonian Terra Firme Forest. Recent INPA herbarium revision (in Marasmius and Crinipellis) failed in finding additional specimens of this species. Also, since 2005 several expeditions and surveys have been carried out, some of them focusing on leaf litter fungi in areas of the potential occurrence of the species (Amazonian Terra Firme Forest), and no specimens of this species were found. Thus, it suggests that this species has a restricted occurrence to the metropolitan region of Manaus.

Population and Trends

Marasmius horridulus has been recorded only from 7 collections in Amazonian Terra Firme Forest in the Manaus Metropolitan area, Amazonas State, in Brazil. It has not been found during recent fungarium revisions or surveys of leaf litter fungi in Amazonas or other states in northern Brazil. Recently, the area at Scientific Station of Uatumã in São Sebastião do Uatumã (metropolitan area of Manaus, Amazonas, Brazil) was monitored monthly for two years and just one collection was recorded. This tiny fungus has a unique morphology and it is more robust when compared with other marasmioid fungi. It is also resistant to desiccation, persisting for more time after the basidiomata forms, and so, it can be easier to find in comparison to other species in the group.
Based on the few known records, its observed restricted distribution, and fact that new records were not obtained during extensive surveys of litter fungi in the region, this is likely a rare species and the total population is inferred to be less than 10,000 mature individuals. The estimated decline of the species for the next 10 years is 10%. The population decline was estimated in light of the loss of suitable habitat (Zhang et al. 2015) and the putative influence that habitat degradation has on species occupation in a given environment (Berglund & Jonsson 2001, Haddad et al. 2015).

Population Trend: Decreasing

Habitat and Ecology

Marasmius horridulus is a saprotrophic fungus found growing on Micropholis williamii (Sapotaceae) leaves (including the type specimen of the fungus) and leaf litter of other unidentified hardwood hosts in well-preserved areas of Terra Firme Forest of Amazon.To date, it has only been recorded from forest reserves in the Manaus Metropolitan area. Based on fungarium data, this fungus forms basidiocars between from July to October (the dry period in the Manaus region) with only one record from March (rainy season). So far the species has not been found in secondary forests or altered forests, even in well-sampled localities within the possible area of distribution.

Subtropical/Tropical Moist Lowland Forest


All the specimens were collected in protected areas located in the metropolitan area of Manaus, Amazonas, Brazil. The species has not been recorded from secondary forests or altered forest such as the INPA herbarium campus and “Bosque da Ciência’‘, a forest open for visitation for the general public. The loss of quality habitat, especially those areas currently under initial urban expansion and irregular occupation of land located in protection areas (Ramos et al. 2018; The Guardian 2019) is the major threat to known sites of the species. The Amazonian rain forest is one of the highest biodiversity areas and recently official deforestation rates have been on an upward trend, worsening in recent years. The Amazonian Terra Firme Forest is threatened due to logging. To date, c.18% of the region’s tropical forest has been cleared, with average annual losses in the last decade of 1.8 million hectares per year (INPE 2020). The development of infrastructure is also recognized as a contributing driver of this forest loss. Lack of enforcement of laws and policies for effective management of the Amazon is contributing to the loss and degradation of habitat.

Housing & urban areasTourism & recreation areasAgro-industry grazing, ranching or farmingIntentional use: large scale (species being assessed is the target) [harvest]Other threat

Conservation Actions

All known records were collected in protected areas near Manaus, Amazonas, Brazil. Thus, the main action to prevent a possible decline of the species is the preservation of quality of habitat with the inclusion of the local population and public action to ensure sustainable urban growth. Creation and proper maintenance of additional conservation areas is needed. The promotion of citizen science to include the local population and students in the preservation of these areas would be highly beneficial. Effective enforcement of conservation laws and policies is needed.

Site/area protectionResource & habitat protectionSite/area managementAwareness & communicationsNational levelSub-national level

Research needed

Addtional surveys and long-term studies are needed to assess its potential habitat and endemism as well as to understand its phenology and substrate preference.

Population size, distribution & trendsLife history & ecology

Use and Trade

No use/trade is known.



Berglund H; Jonsson BG 2001. Predictability of plant and fungal species richness
of old-growth boreal forest islands. J Veg Sci 12: 857-866.

Haddad NM; Brudvig LA; Clobert J; Davies KF; Gonzalez A; Holt RD; Lovejoy T; Sexton JO; Burt MA; et al. 2015. Habitat fragmentation and its lasting impact on Earth’s ecosystems. Sci Adv 1(2)

Laurance WF; Cochrane MA; Bergen S; Fearnside PM; Delamônica P; Barber C; D’Angelo S; Fernandes T. 2001. The Future of the Brazilian Amazon. Science 291: 438-439.

Kew Mycology Collection - online database. In: https://herbtrack.science.kew.org/search
Access in: 15-Out-2021.

Komura DL; Oliveira JJS; Moncalvo JM; Margaritescu S; Zartman CE. (2016) Marasmius calvocystidiatus sp. nov. and M. horridulus (Marasmiaceae): characterization of two unusual species from central Amazonia. Phytotaxa (on-line), 280: 222-240.

​​Mycoportal Collection Portal. In: https://mycoportal.org/portal/collections/list.php. Access in: 15-Out-2021.

Oliveira JJS; Moncalvo J-M; Margaritescu S; Capelari M. 2020. Phylogenetic and morphological analyses of species of Marasmius sect. Marasmius from the Atlantic Rainforest, Brazil. Plant Systematics and Evolution, 206 (31).

Portal TerraBrasilis (Instituto Nacional de Pesquisas Espaciais (INPE), 2020); http://terrabrasilis.dpi.inpe.br

Ramos CJP; Graça PMLA; Fearnside PM. 2018. Deforestation Dynamics on an Amazonian Peri-Urban Frontier: Simulating the Influence of the Rio Negro Bridge in Manaus, Brazil. Environmental Management, 62: 1134–1149.

Silva-Junior CHL; Pessôa ACM; Carvalho NS et al. 2021. The Brazilian Amazon deforestation rate in 2020 is the greatest of the decade. Nature Ecology & Evolution 5, 144–145.

Singer, R. 1986. The Agaricales in Modern Taxonomy. 4th ed. Koeltz Scientific Books, Koenigstein, Germany, 981 pp.

Singer, R. 1989. New taxa and new combinations of Agaricales (Diagnoses fungorum novorum Agaricalium IV). Fieldiana Botany 21: 1–133. Available from: https://archive.org/details/newtaxanewcombin21sing (accessed 20 September 2021).

Soares-Filho BS, Nepstad DC, Curran LM et al. (2006) Modelling conservation in the
Amazon basin. Nature, 440, 520–523.

​​SpeciesLink network. In: http://www.specieslink.net/search. Access in: 15-Out-2021.

The guardian. Cities: The jungle metropolis: how sprawling Manaus is eating into the Amazon 23 Jul 2019. In:
https://www.theguardian.com/cities/2019/jul/23/the-jungle-metropolis-how-sprawling-manaus-is-eating-into-the-amazon. Access in 08 Oct 2021.

Zhang K et al. 2015. The fate of Amazonian ecosystems over the coming century arising from changes in climate, atmospheric CO2, and land use. Global Change Biol 21: 2561-2587.

Country occurrence

Regional Population and Trends

Country Trend Redlisted