Deadly Galerina

''Galerina marginata'', known colloquially as funeral bell, deadly skullcap, autumn skullcap or deadly galerina, is a species of extremely poisonous mushroom-forming fungus in the family Hymenogastraceae of the order Agaricales. Before 2001, the species ''G. autumnalis'', ''G. oregonensis'', ''G. unicolor'', and ''G. venenata'' were thought to be distinct from ''G. marginata'' due to differences in habitat and the viscidity of their caps, but phylogenetic analysis showed that they are all the same species.

The fruit bodies of the mushroom have brown to yellow-brown caps that fade in color when drying. The gills are brownish and give a rusty spore print. A well-defined membranous ring is typically seen on the stems of young specimens but often disappears with age. In older fruit bodies, the caps are flatter and the gills and stems browner. The species is a classic "little brown mushroom" – a catchall category that includes all small to medium-sized, indistinguishable brownish mushrooms – and thus can easily be misidentified.

''G. marginata'' is a wood-rotting fungus that grows predominantly on decaying conifer wood. It is widespread in the Northern Hemisphere, including Eurasia and North America, and has also been found in Australia. It contains the same deadly amatoxins found in the death cap (''Amanita phalloides''). Ingestion in toxic amounts causes severe liver damage with vomiting, diarrhea, hypothermia, and eventual death if not treated rapidly. About ten poisonings have been attributed to the species during the 20th century.

Taxonomy

What is now recognized as a single morphologically variable taxon named ''Galerina marginata'' was once split into five distinct species. Norwegian mycologist Gro Gulden and colleagues concluded that all five represented the same species after comparing the DNA sequences of the internal transcribed spacer region of ribosomal DNA for various North American and European specimens in ''Galerina'' section ''Naucoriopsis''. The results showed no genetic differences between ''G. marginata'' and ''G. autumnalis'', ''G. oregonensis'', ''G. unicolor'', and ''G. venenata'', thus reducing all these names to synonymy. The oldest of these names are ''Agaricus marginatus'', described by August Batsch in 1789, and ''Agaricus unicolor'', described by Martin Vahl in 1792. ''Agaricus autumnalis'' was described by Charles Horton Peck in 1873, and later moved to ''Galerina'' by A. H. Smith and Rolf Singer in their 1962 worldwide monograph on that genus. In the same publication they also introduced the ''G. autumnalis'' varieties ''robusta'' and ''angusticystis''. Another of the synonymous species, ''G. oregonensis'', was first described in that monograph. ''Galerina venenata'' was first identified as a species by Smith in 1953. Since ''Agaricus marginatus'' is the oldest validly published name, it has priority according to the rules of botanical nomenclature.

Another species analysed in Gulden's 2001 study, Galerina pseudomycenopsis, also could not be distinguished from ''G. marginata'' based on ribosomal DNA sequences and restriction fragment length polymorphism analyses. Because of differences in ecology, fruit body color and spore size combined with inadequate sampling, the authors preferred to maintain ''G. pseudomycenopsis'' as a distinct species. A 2005 study again failed to separate the two species using molecular methods, but reported that the incompatibility demonstrated in mating experiments suggests that the species are distinct.

In the fourth edition (1986) of Singer's comprehensive classification of the Agaricales, ''G. marginata'' is the type species of ''Galerina'' section ''Naucoriopsis'', a subdivision first defined by French mycologist Robert Kühner in 1935. It includes small brown-spored mushrooms characterized by cap edges initially curved inwards, fruit bodies resembling ''Pholiota'' or '' Naucoria'' and thin-walled, obtuse or acute-ended pleurocystidia that are not rounded at the top. Within this section, ''G. autumnalis'' and ''G. oregonensis'' are in stirps ''Autumnalis'', while ''G. unicolor'', ''G. marginata'', and ''G. venenata'' are in stirps ''Marginata''. ''Autumnalis'' species are characterized by having a viscid to lubricous cap surface while ''Marginata'' species lack a gelatinous cap—the surface is moist, "fatty-shining", or matte when wet. However, as Gulden explains, this characteristic is highly variable: "Viscidity is a notoriously difficult character to assess because it varies with the age of the fruitbody