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The Genus Megacollybia
by Michael Kuo
Until recently, mycologists assumed the world had one species of Megacollybia, the "Megacollybia platyphylla" (AKA Tricholomopsis platyphylla) featured in field guides--a medium-sized, deadwood-associated mushroom with a white spore print, a streaked-looking brown to gray-brown cap, and a stem base often attached to white cords. However, a recent study (Hughes and collaborators, 2007) based on DNA results for specimens from across the globe found support for at least eight or nine separate species, with Megacollybia platyphylla limited to Europe. In North America the authors found support for four species. However, specimen sampling included very few from western North America, and almost none from the Midwest; it remains to be seen whether further North American species might turn up with additional study--in fact the authors suggest the possibility of "further cryptic species" within at least one of our North American taxa.
Figuring out what the four (so far) North American species are is not the easiest task if one doesn't have a pocket DNA sequencer (one doesn't). Physical features--both macro- and microscopic--are quite similar among the species, and the researchers were hard put to
Many contemporary researchers face a similar dilemma; DNA-defined species do not always express themselves with observable differences in physical features. But Hughes and collaborators found some tentative morphological separators; I have combined these with ecological and geographic data to construct the key below.
Tentative Key to 5 Megacollybia Taxa in North America
Hughes, K. W., R. H. Petersen, J. L. Mata, N. V. Psurtseva, A. E. Kovalenko, O. V. Morozova, E. B. Lickey, J. C. Blanco, D. P. Lewis, E. Nagasawa, R. E. Halling, S. Takehashi, M. C. Aime, T. Bau & T. Henkel (2007). Megacollybia (Agaricales).Reports of the Tottori Mycological Institute 45: 1–57.
Smith, A. H. (1960). Tricholomopsis (Agaricales) in the Western Hemisphere. Brittonia 12: 41–70.
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Cite this page as:
Kuo, M. (2010, May). The genus Megacollybia. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/megacollybia.html