A new paper just came out on the Gymnopilus junonius group in North America, focusing on the northeastern species. It's very good, and goes a long way towards answering several pressing questions that have been open for a long time. It's conclusions are supported by high quality microscopy and ITS+LSU DNA sequences.
One striking finding is that Gymnopilus junonius does not occur in North America, and is not psychoactive. It occurs in Europe, Australia and South America, solving the mystery of why European big laughing gyms consistently fail to cause laughter.
The mushrooms we have been calling Gymnopilus junonius in eastern North America fall into four species - the previously described Gymnopilus subspectabilis and G. luteus, and the newly named Gymnopilus voitkii and Gymnopilus speciosissimus. Only G. speciosissimus is mentioned as staining green in the paper, but some or all of the others definitely also contain psilocybin. The species can be difficult to tell apart macroscopically, but are easy to separate with a microscope or via DNA sequencing.
Gymnopilus luteus was the first North American species in this group to be named, described from New York in 1898. The easiest way to separate it from the others is the presence of a strong anise odor in the gills, large size, light yellow color and its habit of fruiting in small clusters or solitary on hardwood. It stains green and is relatively potent, for a Gymnopilus.
The next North American member of the Gymnopilus junonius complex to be named is Gymnopilus subspectabilis, described from Michigan in 1969. It is much smaller than G. luteus but otherwise macroscopically similar and also fruits on hardwoods. It has a strong mushroom odor, but not of anise.
Gymnopilus voitkii is described from New Brunswick, growing at the base of Abies balsamea. It is named after Dr. Andrus Voitk, who studies mushrooms in Labrador and Newfoundland, where this species is common. This species differs from the others by it's growth on conifer wood and is very large and very orange in color with a well defined annulus.
Gymnopilus speciosissimus is also described here, from a collection from Montreal, Quebec. It's name is Latin for “the most splendid or remarkable”. It is differentiated from other large Gymnopilus species by its robust fruiting bodies growing in cespitose clusters on hardwood, a brownish red cap contrasting with an off-white stipe, occasionally with a bluish-green zone below the ring. It is the largest eastern North American Gymnopilus, with a cap up to 35 cm across, stem up to 35 cm long and can be up to 7 cm wide.
Gymnopilus ventricosus is also mentioned, and is a very large western US species which lacks green staining and psychoactive effects. One of the DNA sequences used in their phylogentic tree was generated at the DNA sequencing workshop I taught in Seattle.
Gymnopilus orientispectabilis is also named here, a large, hallucinogenic species from Japan.
Two big questions this paper does not answer are which of these species are hallucinogenic, and how the other species of Gymnopilus fit in with the G. junonius group. If you have collections of Gymnopilus which have been eaten and either do or fail to produce effects, it would be a good idea to study the microscopy and/or DNA sequences to further the state of knowledge about these taxa. The squamulose, red capped Gymnopilus are also particularly interesting for their beautiful coloration and green staining, and are not mentioned here.