Assessment Notes

Justification

Stropharia venusta is a mushroom-forming species restricted to Araucaria moist forests of southern Brazil and likely northern Argentina. It is currently known only from two sites and is likely to be a rare species as there are few records even in well surveyed areas in its potential range. Only seven specimens have been found in the over 10 years since its description. The species' total population is estimated at no more than 10,000 mature individuals distributed in up to 250 sites, but all in one subpopulation. South American Auricaria moist forest is a fragile habitat that is estimated to has already declined approximately 97% and is projected to decline further in the future. This species is assessed as Vulnerable due to its small population size which is threatened by loss of habitat resulting in likely further population declines.

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Geographic range

The species is currently known from São Francisco de Paula National Forest, in Rio Grande do Sul state, and São Joaquim National Park, in Santa Catarina state, both in southern Brazil. The species is restricted to Araucaria moist forests and cloud forests associated with Araucaria. It is expected to be found throughout Araucaria moist forests in southern Brazil and a small part of northern Misiones, Argentina.

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Population and Trends

Stropharia venusta is currently known from two localities. It is likely to be a rare species, as there are few records even in well surveyed areas in its potential range, such as the São Joaquim National Park and the São Francisco de Paula National Forest, and only a total of seven specimens have been found in over a decade of intensive surveying. The species' total population is estimated at no more than 10,000 mature individuals, distributed in up to 250 sites, each with up to 40 mature individuals. Araucaria moist forests, where the species is found, have declined by approximately 97%, with the remaining patches heavily fragmented. Over 80% of the remaining fragments show signs of disturbance, are less than 50 ha in size, and are surrounded by agricultural lands which have been shown to hold a smaller diversity than larger forests (Ribeiro et al. 2009, Souza et al. 2012, Nodari 2016). Between 2001 and 2018, the habitat has had a loss in cover of approximately 3.1% (13% loss and 9.9% gain) (World Resources Institue 2020). Additionally, in chronically disturbed areas, Araucaria moist forests are kept at early successional stages, which may not hold the appropriate conditions to support species from pristine fungal communities. Despite this, though, it is thought that the species could be said to be in one subpopulation.

Population Trend: decreasing

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Habitat and Ecology

Stropharia venusta is a saprotrophic mushroom found on soil, litter and decomposed wood in South American Araucaria moist forests.

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Threats

The species is threatened by habitat loss, mainly due to logging, fire, and conversion of forests into agricultural lands. Araucaria moist forests have lost approximately 97% of their original extent, with 80% of the remaining area being composed of disturbed fragments under 50 ha in size located inside private farms and surrounded by crop fields and grasslands. Only 3.1% of the remaining habitat is in protected areas, which corresponds to 0.09% of the original Araucaria moist forest range. Araucaria moist forests are restricted to higher altitudes with subtropical climates, high year-long precipitation, cold winters and temperate summers. Studies have shown that by 2070, Araucaria angustifolia, the dominant tree of the AMF, will likely be restricted to highland microrefugia as an impact of climate change. This suggests that the structure of the AMF will be drastically different, or that the AMF itself will also be restricted to these microrefugia.

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Conservation Actions

The main actions to preserve the species are the protection of its habitat, restoration of Araucaria moist forests, and creation of new conservation areas to harbour the probable microhabitats to which the AMF may be restricted in the future. Also, measures must be taken to assure that the protected AMF areas reach a mature state. More surveys are needed in other areas to confirm the species range, including its association with mature forest conditions. There are no DNA sequences available for the species, and no phylogenetic studies have been conducted to test its phylogenetic position. Additionally, herbaria revisions from specimens identified as Stropharia rugosoannulata from AMF may represent new records from S. venusta, as the species are reported by the authors to be morphologically similar.

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Use and Trade

No use/trade is known.

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Source and Citation

Kossmann, T., Martins da Cunha, K., Santos, P. & Drechsler-Santos, E. 2021. Stropharia venusta. The IUCN Red List of Threatened Species 2021: e.T196136132A196845821. https://dx.doi.org/10.2305/IUCN.UK.2021-1.RLTS.T196136132A196845821.en .Accessed on 31 March 2024

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• Country occurrence