Assessment Notes

Justification

This species is endemic to Rio Grande do Sul State (southern Brazil) and Uruguay, and is suffering habitat loss for extensive soy plantations, associated with fires. Recent reports of it are rare and the biggest subpopulation known from field observations (at Piratini Municipality, Rio Grande do Sul State) during the years 2011-2019 is becoming heavily threatened from the surrounding soy plantations and use of fire, being restricted to only some rocks that are not at the border with the soy plantations. Due to the small population size (up to 157 mature individuals) with up to 50 mature individuals in the biggest subpopulation (considering the lower end of the population size estimate), the species is precautionarily assessed as Critically Endangered under criterion C2a(i).

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Taxonomic notes

Hue (1899) described Parmelia pachyderma from Montevideo, Uruguay. Hale (1976) combined it in the genus Everniastrum, and Culberson and Culberson (1981) described it in the new endemic genus Concamerella. In 2005, based on genetic evidence from Concamerella fistulata (Tayl.) W Culb. & C. Culb., the Parmotrema pachydermum species was finally placed in the genus Parmotrema (Blanco et al. 2005).

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Geographic range

Parmotrema pachydermum is endemic to southern Brazil (Rio Grande do Sul) and Uruguay. The type collection of P. pachydermum is from Montevideo, Uruguay. Additional localities from Uruguay include Durazno, Lavalleja, Maldonado and Rocha (Culberson and Culberson 1981). In Brazil it is known from Rio Grande do Sul only, but reported in field observations from Bagé, Caçapava do Sul, Guaíba, Porto Alegre and São Francisco de Paula (see the references in Spielmann (2006), as Concamerella pachyderma), and Piratini (field observations). No collections are known from the adjacent Santa Catarina (Brazil), Paraguay or Argentina.
 
Apparently the species is typical for the Pampa Biome, although some rare individuals were found elsewhere in the Rio Grande do Sul Highlands (Campos de Cima da Serra), where the environment is quite similar to the Pampa Biome.

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Population and Trends

Based on the scarcity of known records, the number of locations (8-15) and amount of suitable environment (potentially restricted to small patches within large plantation areas), the population size is estimated to be no more than 157 mature individuals, unevenly distributed across subpopulations. The species is declining as its area of occurrence is historically threatened by large plantations and farming, as well as the associated use of fire in these activities. The decline is ongoing.

Population Trend: Decreasing

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Habitat and Ecology

Parmotrema pachydermum is typical of the Pampa biome. It is exclusively saxicolous and grows at sunny places, usually at rocky outcrops or mountains.

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Threats

The Pampa Biome is suffering a lot of threat in recent years, especially by the extensive soil use for soy plantation and parallel fires, which can reach the rocks where Parmotrema pachydermum grows. The habitat decline is estimated at 44% due to deforestation.

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Conservation Actions

One of the most representative subpopulations of Parmotrema pachydermum stands in Cerro do Ubaldo, Municipality of Piratini, Rio Grande do Sul. Piratini is one of the places where Malme collected many lichens during the First Regnellian Expedition (1892-1894). This place should be elected as a specially protected area.

Determining the real range of distribution of Parmotrema pachydermum requires more field work. No genetic data are known either, although recent collections are under study.

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Use and Trade

No use and trade known for this species.

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Source and Citation

Spielmann, A., Costa-Rezende, D.H., Kossmann, T., Drechsler-Santos, E.R. & Gumboski, E.L. 2022. Parmotrema pachydermum. The IUCN Red List of Threatened Species 2022: e.T209742965A210566580. Accessed on 22 November 2025.

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• Country occurrence