Amanita ristichii has only been reported from eleven sites in northeastern North America, despite extensive surveys over numerous years by American forays and Canadian mycological groups since its description 1989. It is unlikely that the species has commonly been overlooked because it is easy to identify in the field due to its characteristic pinkish/cream gills and relatively small size. Most of the sites where the species has been reported are located in fragmented forest patches within suburban areas. These fragmented forest patches are impacted by urban development.
There are 11 sites where the species is known to grow, but there are probably 5-10 times more. The total number of sites is estimated not to exceed 100 and the total number of mature individuals not to exceed 2000. Hence, A. ristichii is assessed to meet the category Vulnerable (VU) under the criteria C2ai.
Amanita ristichii has basidia dominantly 2-spored and was described in 1989 (Tulloss, 1989). There are no known synonyms for A. ristichii.
Since its description by Tulloss (1989) and despite extensive surveys over numerous years by American forays and Canadian mycological groups, Amanita ristichii has only been reported from eleven sites in northeastern North America. It is unlikely that the species has commonly been overlooked because it is easy to identify in the field due to its characteristic pinkish/cream gills and relatively small size. Most of the sites where the species has been reported are located in fragmented forest patches within suburban areas. These fragmented forest patches are impacted by urban development.
Amanita ristichii is endemic to northeastern North America. It has been found in southeastern Canada (Quebec: Laurentides, Monteregie, Outaouais and Capitale-Nationale regions; mycoquebec.org and R. Lebeuf, personal communication) and in northeastern United States (Maine: Androscoggin Co., Cumberland Co., Oxford Co.; New Hampshire: Carroll Co., Hillsborough Co.; Tulloss 1989, amanitaceae.org).
Amanita ristichii has been reported from 11 sites in northeastern North America. Even though the species was described from southern Maine and New Hampshire, it is possibly more common further north in Canada (Tulloss, 1989; amanitaceae.org). Six out of 11 sites where the species was found are located in Quebec province along the St. Lawrence River and we consider them part of the same subpopulation. Since the St. Lawrence River coincides with the highest human population density and growth in the province, urban development is impacting potential/actual habitat for A. ristichii. Despite extensive surveys over numerous years during northeastern American forays, A. ristichii has not been found in New Hampshire or Maine since respectively 1959 and 1988. The species might have been extirpated from these states.
USA: 3 sites in Maine (1984//1984,1988 twice//1985), 2 sites in New Hampshire (1906//1959). See amanitaceae.org (Tulloss). Canada: 6 sites in Quebec province along the St. Lawrence River (Laurentides, Monteregie, Outaouais and Capitale-Nationale regions; 1993//??//2003//2007//2015//2015). See mycoquebec.org. Also Yves Lamoureux and Renée Lebeuf, personal communications.
Given that A. ristichii is fairly easy to identify (its small size and pinkish/cream gills are characteristic in most specimens), grows often in surburban areas and is part of a popular group (Amanita), we believe this species is rarely overlooked and is usually correctly identified when found. However, it has to be noted that A. ristichii is relatively small and could be mistaken with other white Amanitas.
The total number of A. ristichii sites is estimated to be 5-10 times higher than the number of currently known sites, i.e. 50-100. Each site is thought to represent 2 functional individuals, and each functional individual is expected to represent 10 mature individuals (Dahlberg and Mueller, 2011). The total number of A. ristichii mature individuals is estimated not to exceed 2000.
Population Trend: Deteriorating
Amanita ristichii is a mycorrhizal fungus species so it is dependent on living host trees for population viability. This mutually beneficial symbiotic association between fungus and plant host roots conveys numerous critical advantages for plant host survival. Mycorrhizal fungi are essentially the uptake organs for many nutrients i.e., nitrogen, phosphorus, numerous micronutrients, i.e., boron, selenium, copper, and plays a major role in uptake of water. Both the fungus and the plant host does not exist in nature without each other.
Amanita ristichii grows solitary to subgregarious in sandy soil and can be found from mid-July to September. In Quebec province (Canada), this species is reported to be growing under Betula sp. and Populus tremuloides (mycoquebec.org). In Maine, it was found under Tsuga canadensis and Acer rubrum in the floodplain of a river. It was also found under T. canadensis and Pinus strobus as dominant trees in mixed woods (Tulloss 1989). In New Hampshire, A. ristichii has been found under Pinus sp. (Tulloss 1989).
In Quebec province (Canada), where most of A. ristichii sites are located, A. ristichii often grows in forests fragments within residential areas along the St. Lawrence River. Over 6000 km2 of forested land along the St. Lawrence River have been lost between 1970 and 1990-2000 (Gouvernement du Québec 2010), and many forests fragments in that area are still at risk of being negatively impacted by urban development. In Maine and New Hampshire, A. ristichii sites are located within floodplains. In these locations, A. ristichii could be periodically threatened by negative impact of intense flooding on its dependent mycorrhizal host plants.
There is no current conservation actions for Amanita ristichii. The species distribution needs additional studies before a conservation plan can be created. Protection of Quebec suburban and urban forests is recommended as a precaution. Amanita ristichii has some fairly characteristic features, thus amateur mycologists could be of great help in data collection after learning where to find and how to identify A. ristichii.
Amanita ristichii has been found in mixed forests containing Betula sp., Populus tremuloides, Pinus sp. and Tsuga canadensis. Ectomycorrhizal associations require additional study.
Amanita ristichii is an easily identified species due to its pinkish/cream gills and small size. In northeastern North America, where A. ristichii is found, there are numerous groups of amateur mycologists. Members of these groups can be recruited and instructed where to find and how to identify A. ristichii so they can target this species during forays. Data from amateur mycologists can be critical to define A. ristichii population size, distribution and trends, as well as its ectomycorrhizal associations.
Amanita ristichii (2014). Retrieved 15 April 2016 from mycoquebec.org
Gouvernement du Québec (2010). Suivi de l’état du Saint-Laurent. L’occupation du sol le long des Grands Lacs et du Saint-Laurent. Retrieved 27 April 2016 from planstlaurent.qc.ca.
Tulloss, R. E. Amanita ristichii. Retrieved 15 April 2016 from amanitaceae.org
Tulloss, R. E. (1989). Amanita ristichii: a new species from New England with basidia dominantly 2-spored. Mycotaxon 35 (2): 363-369.
Tulloss, R. E. (2008). Notes on Amanita section Caesareae, Torrendia and Amarrendia (Agaricales, Amanitaceae) with provisional division into stirpes and world key to species of the section. Web publication retrieved 15 April 2016 from tullabs.com/amanita/content/uploaded/pdf/hemibkey.pdf