Assessment Notes

Justification

Cinereomyces dilutabilis is a rare wood-decaying resupinate polypore. It occurs in the Atlantic Forest of Southern Brazil and in Tropical Dry Forest of Costa Rica, both highly threatened and degraded vegetational domains. Total population is estimated at no more than 10,000 to 20,000 mature individuals. It is possible that these numbers are overestimates, as conditions to may not occur in much of its potential range given the poor current state of the forests where it could possibly be found. The species has a past and projected decline in population size of at least 20-25% covering three generations of the species. It is assessed as Near Threatened.

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Geographic range

Cinereomyces dilutabilis is only known from six sites, five in Brazil and one in Costa Rica. The Brazilian specimens were collected in the Atlantic Forest domain of southern and south-eastern Brazil, in the states of São Paulo (two collections), Santa Catarina (five collections) and Rio Grande do Sul (five collections). It is expected that the species occurs throughout the Atlantic Forest fragments of Brazil. There are only two collections from the tropical dry forest domain of Costa Rica, Guanacaste province. It is expected that the species occurs in other tropical dry forests in Central America.

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Population and Trends

Cinereomyces dilutabilis is known from only six sites and 13 collections. Most records are from the Atlantic Forest of Brazil, in São Paulo, Santa Catarina and Rio Grande do Sul states. It is expected that the species occurs throughout the Atlantic Forest of Brazil, which is now mainly composed of fragments and secondary forests, with only 28% of its original area remaining (Tabarelli et al. 2010, Rezende et al. 2018). There are only two collections reported from outside of Brazil. These are both from Costa Rica, Guanacaste province, in the tropical dry forest domain. This forest type extends from Costa Rica to the Chiapas region of Mexico, so, the species is expected to be found in other Central American areas with similar habitat. The Tropical Dry Forest domain has suffered a massive loss of area, with less than 2% of its original area intact (Janzen 1988). Specifically, in Costa Rica, only 24% of the original forest cover is left (Portillo-Quintero and Sánchez-Azofeifa 2010). The collections of Costa Rica and southern Brazil are 5,600 km apart, characterizing two known subpopulations for the species. In areas where fungi has been intensively surveyed, such as parts of the Atlantic Forest domain in Brazil, the species was scarcely found, which indicates that the species is likely to be rare. Taking into account the the amount of potential appropriate habitat for the species, there are up to 2,000 estimated sites, with 5-10 mature individuals each. Therefore, the total population is estimated at 10,000 to 20,000 mature individuals. It is possible that these numbers are overestimated, as the species may not find conditions to occur in much of its potential range, given the poor current state of the forests where it could possibly be found. With the two subpopulations occurring in threatened domains (Myers et al. 2000), the largest subpopulation occurring in the Atlantic Forest domain, that has just 28% of its original area remaining, mostly composed by secondary forests (Tabarelli et al. 2010, Rezende et al. 2018), and an ongoing decline predicted to continue in the near future, the species has a past and projected decline in population size of at least 20-25% covering three generations of the species.

Population Trend: decreasing

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Habitat and Ecology

Cinereomyces dilutabilis is a wood-decaying fungus currently found in the Atlantic Forest domain of Brazil and the tropical dry forest domain in Costa Rica. The species is expected to be rare but widespread throughout these domains.

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Threats

Cinereomyces dilutabilis is found in the Atlantic Forest of Brazil, regarded as a biodiversity hotspot for conservation priorities due to its high diversity, endemism rates and habitat loss (Myers et al. 2000). This phytogeographical domain is estimated to have only 28% of its vegetation remaining, with the remnants being fragmented and composed mostly by secondary forests (Tabarelli et al. 2010, Rezende et al. 2018). According to Pinto et al. (2006), the Atlantic Forest is found in this situation due to predatory exploration of resources and human actions, like territorial occupation. About 60% of the Brazilian population lives in the Atlantic Forest, mainly in coastal areas, where the country’s largest cities are located (Rezende et al. 2018). Other threats to the Atlantic Forest include increase in fire frequency and intensity, introduction of exotic and invasive species and the connection between these factors (Brooks and Balmford 1996, Tabarelli et al. 2006, Pinto et al. 2006). Also, reduction and ‘savannization’ of Atlantic Forest is expected due to climate change in the next decades (Salazar et al. 2007). The tropical dry forest domain in Central America is even more endangered, with only 2% of its original area intact along the Pacific side (Janzen 1988). According to Portillo-Quintero et al. (2010), the tropical dry forest area in North and Central America has undergone a loss of 72% of the original extent (203,884 km² or the original 719,338 km²) with only 624 km² (0.3%) under protection. In Costa Rica, only 24% of original area remains (Portillo-Quintero and Sánchez-Azofeifa 2010). Most of the remaining tropical dry forest domain is severely fragmented, and the threats are multiple and complex due to a combination of economy, policies, land owners, historical losses, and other factors within Central American countries (Janzen 1988).

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Conservation Actions

The main actions to prevent the decline of the species are the protection of its habitat by the implementation of Protected Areas and enforcement of public policies to recover secondary forests. More surveys are needed to better understand the species ecology. Also, further analyses are needed to confirm the conspecificity of the Brazilian and Central American subpopulations. Currently, there are no available DNA sequences of this species, and its phylogenetic and taxonomic status need to be better studied.

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Use and Trade

No use/trade is known.

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Source and Citation

Martins da Cunha, K., Kossmann, T., Drechsler-Santos, E. & Leopoldo, E. 2021. Cinereomyces dilutabilis. The IUCN Red List of Threatened Species 2021: e.T196135662A196845697. https://dx.doi.org/10.2305/IUCN.UK.2021-1.RLTS.T196135662A196845697.en .Accessed on 2 April 2023

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• Country occurrence