Omphalotus mexicanus is a rare, large and conspicuous well known mushroom endemic to southwestern Mexico. Its is associated with large old Quercus trees. Even while its EOO is large, its suitable habitat within this area is severely fragmented and declining. Its estimated population size is based on extensive search that resulted in just 25 records in 35 years, which suggest that its rarity is a robust assumption.
Assessed as Near Threatened (NT) under criterion C2a(i) as the number of estimated subpopulations is not more than 500, each with between 3-5 mature individuals, and with ongoing and projected habitat loss and fragmentation due to change in land use and logging of 20%-40% over three generations (50 years).
Omphalotus mexicanus was described in 1984.
Guzmán & V. Mora, Boletín de la Sociedad Mexicana de Micología 18: 117 (1984)
It is a large, distinctive, blackish blue to black mushroom that grows in large clusters. It is easy to see and striking enough that it is reported when found.
Omphalotus mexicanus is an uncommon large and conspicuous mushroom endemic to Mexico where it associates exclusively with mature oak trees. Most localities for the species recorded before 1995 have been transformed into agricultural or grazing fields. These forests are also endangered because Quercus species are used as timber.
Restricted to southwestern Mexican temperate and subtropoical Quercus forests. Recorded from Tapalpa, Mazamitla, Tequila volcano and Sierra de Manantlan in Jalisco state; Oaxaca Sierra; Michoacan state, near Morelia state, and the State of Mexico (GBIF, 2018). Omphalotus mexicanus was also reported by Kirchmair et al. (2002, 2004) from Guatemala.
Omphalotus mexicanus is a rare, large and conspicuous well known mushroom endemic to southwestern Mexico. Its is associated with large, old Quercus trees. There are a total of 15 known subpopulations in Mexico (8 in Jalisco, 4 in Michoacan, 3 in Oaxaca); and one unconfirmed subpopulation in Guatemala. These reports include several historical locations that have been lost due to land transformation.
There are several subpopulations recorded from Jalisco state growing in oak-pine forests, including the type collection in Tapalpa. Other records from Jalisco include one each from Mazamitla, 2.5 km S from La Manzanilla, 7.5 km SW from San Miguel Cuyutlán, three locations near crater of Tequila volcano, 1 km SW from Chilacayote, Cerro las Capillas at Sierra de Manantlán, 7 km SW from El Nogal, and one 5 km E from Los García. There are four subpopulations recorded from the Oaxaca mountains: 4.7 km SW from San Bartolo Soyaltepec, 2.5 km NE from La Estancia, 7.5 km NE from San Juan Bautista Atlahuca, and 2.3 km W from San Francisco Teopam. Four subpopulations are recorded from Michoacan state: near Contepec, 5.5 km SE from Morelia; Senguio, and Cerro Grande at 2 km from Tanque de Peña (GBIF, 2018). It is included in a species list from Guatemala but no location data was provided and this record (Kirchmair et al. 2004) was not considered in this assessment.
Even while its EOO is large, 102,000 km2, its suitable habitat within the area is severely fragmented, restricted to small patches, and declining due to cutting by locals and logging. Extensive search in appropriate habitat has resulted in just 25 records in 35 years, so its rarity is a robust assumption. While impossible to give a precise estimate of population size, we estimate that there are less than 500 subpopulations, each with between 3-5 individuals, for an estimated total of less than 1600 mature individuals.
Population Trend: Deteriorating
Saprotrophic, it is reported only with hardwood trees, mostly with large, old Quercus trees. Growing at the base of the tree or in soil near dead Quercus. The forest composition can vary from pure Quercus, Quercus-Pinus mixed forests, and tropical montane cloud forest where old Quercus are important components of the community.
Many of the sites where the species is recorded are close to human populations. Four records (probably the same subpopulation) from Senguio, Michoacan from 2008, 2010, 2011 and 2012 disappeared because the site was converted into an agricultural field. Another two populations, 5.5 km SW and 5.5 km NW from La Venta del Astillero (1982, 1986), disappeared due to habitat destruction.
Mature Quercus forests are dissapearing rapidly from Mexico due to logging and changes in land cover to agricultural lands or avocado orchards. Consequently this habitat is declining and severely fragmented.
The habitat of this species are old oak forests or old oak dominated forests. These forests are often surround by urban areas and are subjected to high anthropogenic pressure. As some subpopulations have disappeared due to changes in land cover, protection of known subpopulations and potential sites is needed. Additionally, logging of large old oaks should be halted in these forests.
Increase sampling effort to confirm distribution. Most collection records of O. mexicanus state “associated with Quercus sp.” without identifying the oak species, so better data on association would be informative. A better understanding of the ecology and biology is needed in order to propose more specific conservation plans.
Omphalotus mexicanus is considered to be a toxic species so it is not harvested for culinary or other uses.
Leopoldo Galicia and Leticia Gomez-Mendoza (2010). Temperate Forests and Climate Change in Mexico: from Modelling to Adaptation Strategies, Climate Change and Variability, Suzanne Simard (Ed.), ISBN: 978-953-307-144-2,
Mora VM, Guzmán ,1984. Agaricales poco conocidos en el Estado de Morelos [Agaricales little known in the state of Morelos Mexico]. Boletín de la Sociedad Mexicana de Micología 18: 115–39.
Kirchmair M, Poder R, Huber CG, Miller OK., 2002. Chemotaxonomical and morphological observations in the genus Omphalotus (Omphalotaceae). Persoonia 17 (4): 583–600.
Kirchmair M, Morandell S, Stolz D, Poder R, Christian Sturmbauer C, 2004. Phylogeny of the genus Omphalotus based on nuclear ribosomal DNA-sequences. Mycologia, 96(6), 2004, pp. 1253–1260.
Petersen, RH.; Hughes, KW, 1997. Mating systems in Omphalotus (Paxillaceae, Agaricales). Plant Systematics and Evolution 211(3-4): 217–29.
Luna-Vega I, Alcántara Ayala O, Contreras-Medina RL, Ponce-Vargas A, 2006. Biogeography, current knowledge and conservation of threatened vascular plants characteristic of Mexican temperate forests. Biodiversity and Conservation 15:3773–3799 DOI 10.1007/s10531-005-5401-1