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Hericium rajchenbergii Robledo & Hallenb.

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Scientific name
Hericium rajchenbergii
Author
Robledo & Hallenb.
Common names
 
IUCN Specialist Group
Mushroom, Bracket and Puffball
Kingdom
Fungi
Phylum
Basidiomycota
Class
Agaricomycetes
Order
Russulales
Family
Hericiaceae
Assessment status
Published
Assessment date
2020-05-27
IUCN Red List Category
CR
IUCN Red List Criteria
A2c+4c
Assessors
Robledo, G., Bittencourt, F., Kossmann, T., Martins da Cunha, K. & Drechsler-Santos, E.R.
Reviewers
Mueller, G.M.

Assessment Notes

The content on this page is fetched from The IUCN Red List of Threatened Species: https://www.iucnredlist.org/species/211978019/211978033

Justification

Hericium rajchenbergii is currently known to grow exclusively on dead and/or living standing trunks of Lithraea molleoides (Anacardiaceae) in the subxerophytic Mountain Chaco forests (“Bosque Serrano”) of in the Sierras Chicas of Córdoba province central Argentina, in an altitudinal range from 600 to 1,400 m a.s.l. There are only four specimens recorded, even with extensive surveys in the area. The total population size is estimated at no more than 500 mature individuals. The species is suspected to have had a population decline of 80-90% in the last 50 years (three generations), due to habitat loss. The forests where the species lives are extremely endangered, and more than 90% were lost between 1969 and 1999 (Zak et al. 2004, Atala et al. 2009). This decline is still ongoing, mainly due to loss of its host to logging and fire. As such it is assessed as Critically Endangered.

Taxonomic notes

Hericium rajchenbergii Robledo & Hallenberg was described from Córdoba Mountains, central Argentina (Hallenberg et al. 2012). The species has no synonyms. It represents an independent lineage related to Hericium coralloides (Scop.) Pers. and Hericium novae-zelandiae (Colenso) Chr.A. Sm. & J.A. Cooper.

Geographic range

Hericium rajchenbergii is known from only four specimens growing exclusively on dead and/or living standing trunks of Lithraea molleoides (Anacardiaceae) in the subxerophytic Mountain Chaco forests (“Bosque Serrano”) in the Sierras Chicas of Córdoba province of central Argentina, in an altitudinal range from 600 to 1,400 m a.s.l. Despite its host being widespread throughout central South America, H. rajchenbergii is likely endemic to the Mountain Chaco forests of central Argentina.

Population and Trends

To date the species is known only from the Cordoba region, central Argentina. It has only been found associated with Lithraea molleoides in the Bosque Serrano in the Sierras Chicas and Sierra Grande mountains, at an altitudinal range between 600 and 1,400m. The particular type of forests where the species grows extends from Cordoba mountains in central Argentina to the north, in a thin strip of intermittent patches reaching southern Bolivia. The species is expected to be found throughout this habitat, although it has not been reported outside Cordoba and San Luis provinces even after extensive search. There are an estimated 50 sites, each site with up to 10 mature individuals. Total population size is estimated at no more than 500 mature individuals.

The species is estimated to have had a population decline of 80-90% over the last 50 years (three generations) due to habitat loss. These forest fragments are extremely endangered, and more than 90% of its area was lost between 1969 and 1999 (Zak et al. 2004, Atala et al. 2009). This decline is still ongoing, mainly due to loss of its host to logging and fire.

Population Trend: decreasing


Habitat and Ecology

Hericium rajchenbergii is an obligate parasite of Lithraea molleoides. So far it has only been found in the Mountain Chaco forests of Cordoba mountains (in a range from 600 to 1,400 m a.s.l.), despite its host being widespread throughout central South America. It likely occurs along the distribution of its host in the Mountain Chaco forests from Córdoba to Bolivia. The species has only been collected in late autumn, with cold and humid weather. It has been recorded on or near the same date in different years.

Threats

The species is strongly threatened by deforestation of the Mountain Chaco forests. These forest fragments are extremely endangered, and more than 90% of its area was lost between 1969 and 1999 (Zak et al. 2004, Atala et al. 2009). The host tree was one of the dominant trees of the ecosystem (Cabido and Zak 1999). Traditionally the wood of L. molleoides has been used as firewood, and it has been stated as “in regression” (Atala et al. 2009). Mature trees of the species are now much less common. In 2009, the Mountain Chaco forests covered 2,334,712 ha in Cordoba, of which only 8.25% (193,689 ha) correspond to dense or mature forest, as the rest has been degraded to open forests, shrublands and grasslands (Atala et al. 2009). During the last 10 years, intentional forest fires, as well as the advance of the agricultural frontier and urbanization have continued on an increasing scale. In addition, the exotic invasive tree, Glossy Privet (Ligustrum lucidum), has increased 50 fold (from 50 to 2,500 ha) (Gavier-Pizarro et al. 2012).

Conservation Actions

The main action to prevent the decline of the species is the protection of its habitat. A survey of presence and abundance of the species in the existing Protected Natural Areas that includes “Bosque Serrano” is needed as well as enforcement of public policies aimed at recovering secondary forests and supporting existing “forests restoration programmes” organized by local NGOs. The surveys will allow decisions to be made about the creation of new conservation areas, as well as the reintroduction of the species in protected areas where it is not present or occurs in low abundance. As the species is able to be grown in culture, the production of basidiomata ex-situ is being investigated (Terzzoli et al. unpublished data). This may enable the reintroduction of the species, and the development of production techniques will also have a direct impact on reducing future extraction pressure.

Surveys are needed to determine the distribution of the species, both documenting its precise distribution in areas where its presence is known (Sierras de Córdoba), as well as documenting its presence within its potential distribution throughout its host range. As other Hericium species, H. rajchenbergii is edible (Gerardo Robledo personal experience). The chemical and nutritional compositions of basidiomata are being studied (Rodríguez et al. unpublished data) and will be compared with other Hericium species.

Use and Trade

The species is not currently consumed or commercialized, and until now it has not been included in the National Alimentary Code. However, it has potential as wild edible species, and its nutritional characteristics are being described.

Source and Citation

Robledo, G., Bittencourt, F., Kossmann, T., Martins da Cunha, K. & Drechsler-Santos, E.R. 2022. Hericium rajchenbergii. The IUCN Red List of Threatened Species 2022: e.T211978019A211978033. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T211978019A211978033.en .Accessed on 29 July 2023

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