Amanita ocreata was described from southern California, USA (Peck 1909). Amanita bivolvata Peck is a synonym.
Recent unpublished genetic studies have suggested that there may be a cryptic species falling under the umbrella of Amanita ocreata.
Amanita ocreata is a common species with oaks in California, especially in live oak woodlands. There is some decline of this habitat in California, and continued threats, but not sure it’s at a scale to list as anything other than Least Concern (LC).
Widespread in southern California, continuing north in coastal and Coast Range forests, to the northern part on the San Francisco Bay Area, continuing north inland on the eastern portion of the Coast Range, and around the Central Valley into the Sierra Nevada foothills.
Population is widespread, and locally a common species. There has been some decline, due to habitat loss from urban development, Sudden Oak Death, and climate change. Corresponding data to assess population decline overall is lacking.
Population Trend: Decreasing
Ectomycorrhizal with oaks (Quercus spp.), especially Coast Live Oak (Quercus agrifolia). Fruiting in spring.
Habitat loss, due to urban development, and clearing of woodlands for horticulture. Drought and climate change, especially in southern California. Sudden Oak Death (Phytophthora ramorum) has had detrimental affects on Coast Live Oak habitat. Stand replacing fires.
No specific conservation actions is needed with regards to this species.
Research into if it’s a species complex is needed, as preliminary phylogenetic data has suggested it is.
This species is deadly toxic.
Arora, D. 1986. Mushrooms Demystified. Ten Speed Press: Berkeley, CA. 959 p.
Desjardin, D.E., Wood, M.G. and Stevens, F.A. 2015. California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Peck, C.H. 1909. New species of fungi. Bull. Torrey bot. Club 36: 329-339.
Siegel, N. and Schwarz, C. 2016. Mushrooms of the Redwood Coast. Ten Speed Press: Berkeley, CA. 601 p.
Thiers, H.D. 1982. The Agaricales (Gilled Fungi) of California. 1. Amanitaceae. Mad River Press: Eureka, CA. 53 p.
Wood, M.G. and Stevens, F.A. 2021. MykoWeb: The Fungi of California. https://www.mykoweb.com/CAF/species/Amanita_ocreata.html