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).
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.
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).
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.
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
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.
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.
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.
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.
No use/trade is known.
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