Agaricus pattersoniae 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Fungi Basidiomycota Agaricomycetes Agaricales Agaricaceae

Scientific Name: Agaricus pattersoniae Peck
Taxonomic Notes: Originally described as Agaricus pattersonae.

Assessment Information [top]

Red List Category & Criteria: Vulnerable C2a(i) ver 3.1
Year Published: 2015
Date Assessed: 2015-04-27
Assessor(s): Vellinga, E.
Reviewer(s): Dahlberg, A.
Agaricus pattersoniae is restricted to mature Cupressus macrocarpa stands with an undisturbed duff layer in central coastal California. Its habitat is threatened by developments, decline of Cupressus due to infection with Seiridium cardinale and increasing drought. Conservation of mature C. macrocarpa stands and younger stands that will provide the habitat in the future will effect a number of species that are restricted to this habitat, such as Lepiota and Leucoagaricus species plus other Agaricus taxa.

Agaricus pattersoniae is assessed as Vulnerable (VU) under criterion C2a(i) as the number of known localities is small (less than 50) and the number of mature individuals numbers about 1,000 with each subpopulation having fewer than 500 mature individuals. It also almost fulfill the criteria for A3c for VU as the number of sites is declining and projected to decline by about around 25% in the next 20 years.

Geographic Range [top]

Range Description:Agaricus pattersoniae is probably endemic to California as it only is known from the central coastal region in California (USA): Sonoma County southwards into San Luis Obispo County. A few reports are from the eastern part of the USA but these have to be confirmed.
Countries occurrence:
United States (California)
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Agaricus pattersoniae is known from less than 50 sites based on collections ( and recent observations (2009-2015; in California (USA). The species and its habitat are currently stable, but is prone to future decline of cypress groves. The fungus grows in the original Cupressus macrocarpa stands, and secondary occurrence in planted stands. C. macrocarpa is native to California where it occurs in two main subpopulations, but is widely planted as windbreaks in coastal areas around the world.
Current Population Trend:Stable
Additional data:
Number of mature individuals:1000Continuing decline of mature individuals:Yes
Continuing decline in subpopulations:Yes

Habitat and Ecology [top]

Habitat and Ecology:Agaricus pattersoniae is saprotrophic in duff of mature (over 40 years old) Cupressus macrocarpa stands and groves with an undisturbed duff layer, fruiting from (November) December through March, after heavy winter storms. The species does not occur under solitary trees or stands with a well-developed herb and grass layer.
Generation Length (years):7

Use and Trade [top]

Use and Trade: This is edible like most Agaricus species

Threats [top]

Major Threat(s): Cupressus macrocarpa is endemic to California, and occurs in two main natural subpopulations; planted groves exist, but are considered non-native and are threatened with replacement by native tree species. C. macrocarpa is prone to infection by Seiridium cardinale which damages and kills older and more exposed trees. Habitat destruction is the main threat; for instance the cypresses at the type locality have been removed. Due to the absence of late winter rains in the winters of 2012-2015 the species has not been fruiting in its usual localities. C. macrocarpa is currently assessed as Vulnerable on the IUCN Red List because of its restricted range and susceptibility to increased risk of fire due to future climate change.

Conservation Actions [top]

Conservation Actions: Most of the main stands of  Cupressus macrocarpa are protected, however, the habitat needs to be properly managed, especially to reduce the risk of fires in the future.

Errata [top]

Errata reason: The name of the Assessor has been corrected to include all of their initials.

Citation: Vellinga, E. 2015. Agaricus pattersoniae (errata version published in 2016). The IUCN Red List of Threatened Species 2015: e.T75093504A97167420. . Downloaded on 22 September 2018.
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