Rickiella edulis has been recorded from 4 distinct localities: South Region of Brazil, in Araucaria Forest vegetation; Asunción, in Paraguay, and two large areas in Argentina: one in Salta, belonging to the Gran Chaco vegetation (Romero et al. 2012), and one in Misiones, belonging to Atlantic Forest vegetation (Vignale et al. 2015). There is only the one record from Paraguay, near Asunción, and that site likely is no longer extant. Within Brazil and Argentina it has rarely been collected even though the species is relatively large and distinctive, and there have been a number of mycological surveys within potential habitats. Thus, the species is considered rare throughout its range. Before deforestation, the species was likely broadly distributed but uncommon. Assuming that there were over 10,000 mature individuals in the past, land use changes over the last 100 years have decreased the population to less than 2,000 mature individuals. It is, therefore, listed as Endangered.
Rickiella edulis was originally described by Spegazzini (1891) as Peziza edulis. Now this species belongs to the monotypic genus Rickiella (Pfister 1987). The species Rickiella transiens Sydow, described in 1904 (Sydow in Rick 1904) was considered a synonymy of R. edulis by Pfister (1987).
This is a very rare species, having being recorded for only 4 localities in over 100 years since it has been described. The ascomata are large and unmistakable, making this species very conspicuous when the reproductive structures are present.
Rickiella edulis has been recorded from 4 distinct localities: South Region of Brazil, in Rio Grande do Sul state, São Leopoldo municipality, in the Araucaria Forest vegetation; Asunción, in Paraguay and two large areas in Argentina: one in Salta, in the Gran Chaco vegetation (Romero et al. 2012), and one in Misiones, in the Atlantic Forest vegetation (Vignale et al. 2015). It probably occurs in additional sites that have similar vegetation.
The species was first recorded in 1891 in Paraguay. There are 4 known localities: one in southern Brazil, in Atlantic Forest, one in Paraguay, in Gran Chaco and two in Argentina, one in Gran Chaco (Salta) and another one in Atlantic Forest (Misiones), representing 15 collections.
Deforestation in the Atlantic Forest has largely declined over the last two decades. However, it has been heavily exploited, and only 28% of its natural coverage remains, largely composed by forest fragments and secondary forests (Tabarelli et al. 2010, Rezende et al. 2018). The locality in the Atlantic Forest belongs to Mixed Ombrophilous Forest (Araucaria Forest), which has only 13% of its original cover remaining (Ribeiro et al. 2009), almost all severely disturbed and fragmented (Vibrans et al. 2011). Although Misiones is the most preserved fragment of Atlantic Forest in Argentina, only about 17% of the province is in protected areas (Izquierdo et al. 2008). The other two known localities are in Gran Chaco, an extremely threatened biome, suffering from long-term and expanding human occupation and high rates of deforestation (200,000 ha/year) (Gasparri et al. 2008, Gasparri and Grau, 2009, Aide et al. 2013, Volante et al. 2016, Volante and Seghezzo 2018). The native forest on this region is quickly giving way to agricultural activities (Fehlenberg et al. 2017), especially soybeans (Gasparri and Grau 2009, Delvenne et al. 2013).
There is only one record from Paraguay, near Asunción, and that site is probably no longer extant. In Brazil and Argentina it has rarely been collected, even though the species is relatively large and distinctive, and there have been a number of mycological surveys within potential habitats. Thus, the species is considered rare throughout its range. Before deforestation the species was probably broadly distributed but uncommon. Assuming that the there were over 10,000 mature individuals in the past, land use changes over the last 100 years have decreased the population to fewer than 2,000 mature individuals.
Population Trend: Decreasing
The species is restricted to the now fragmented and scattered Atlantic Forest (Araucaria Forest and Seasonal Semideciduous Forest) and Chaco vegetation. It is a saprotrophic species, growing on dead fallen twigs and logs of unidentified angiosperms, usually that are in an advanced decomposition state. According to fungarium collections, the ascomata are found during the summer (Jan-Feb).
Rickiella edulis occurs in the Atlantic Forest and Gran Chaco, both deforestation hotspots. There are many threats that can lead to habitat loss in unprotected areas, especially the intensification of replacing native forests with exotic tree plantations, intensive agriculture, and clearing for pastures, as well as expansion of cities (Izquierdo et al. 2008), which have been exacerbated by government subsidies (Placci and Di Bitetti 2006).
The main action to prevent the further decline of the species is preservation of the habitat. If in fact the species is edible, as suggested by its specific epithet, it should be investigated as a strong candidate for ex situ conservation initiatives.
More surveys are needed to identify other localities and improve knowledge on population trends and ecology. An interesting research need is about its edibility, given its species epithet (edulis). If edible, the environmental factors for producing the ascomata, secondary metabolites and nutritional values of R. edulis should be investigated as well.
The ascomata are suggested to be edible, but there are no data to substantiate this idea.
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