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The Genus Melanoleuca
by Michael Kuo
I mean no disrespect to anyone whose studies are devoted to Melanoleuca, but I find these mushrooms to be tedious. Most of them are small to medium-sized, brownish to whitish things with few distinctive features (even the harpoon-like, microscopic cystidia get boring after one or two views), and identifying them is nearly as tedious as singing Suzanne Vega's "My Name is Luka" with the words changed to "Melanoleuca" turns out to be after the first couple of times.
Most Melanloleucas can be identified to genus without recourse to microscopic examination, through a combination of features:
Larger species can be confused with Tricholoma, but one peek at the spores will clear up confusion; the spores in Melanoleuca are ornamented with amyloid warts. Leucopaxillus, which also has amyloid, warty spores, can usually be eliminated because species of Melanoleuca do not feature copious mycelium attached to the stem base, or gills that "do the Leucopaxillus thing" (see the linked page).
Literature for Melanoleuca in North America is almost non-existent. Beyond field guide treatments, I am aware of only one paper (Gillman & Miller, 1977), now 30 years old, devoted only to boreal and montane species--and a study (Pfister, 1984) of the 131 species of Melanoleuca described by Peck and Murrill, whose concept of the genus predated the contemporary definition requiring spores with amyloid ornamentation, finding only six of the 131 taxa to be true Melanoleucas. But I admit that my literature search was not thorough, since I quickly tired of attempting to limit results in biology databases when "melanoleuca" produced thousands of returns, including pages and pages of references to papers on the semen of pandas. If you have more patience than I do, you will need to ask your database to eliminate results that include "ailuropoda" (Ailuropoda melanoleuca is a panda), "tringa" (Tringa melanoleuca appears to be a shore bird called "yellowlegs"), "naja" (Naja melanoleuca is a "black forest cobra")--and probably many other terms, since melanoleuca is obviously a popular taxonomic name.
The species names used for North American Melanoleucas, with a few exceptions, are European names approached with a "best fit" attitude, and all North American Melanoleuca identifications should be viewed as tentative, awaiting a thorough study of the genus on our continent (see the comments under "Melanoleuca melaleuca" for more information).
DNA studies have not focused on Melanoleuca (again, to my knowledge), but a rough-sketch study of gilled mushrooms (Moncalvo and collaborators, 2002) placed the genus near Amanita and Pluteus (basal to Pluteus with the Melanoleuca-Pluteus clade sister to Amanita-Limacella) with poor bootstrap support (under 40%).
Key to 11 Species of Melanoleuca in North America
The species name Melanoleuca melaleuca is featured in most North American field guides, but descriptions vary substantially and, to make a long story short, the North American concept of this species is incoherent. The name for your boring, medium-sized, brown Melanoleuca might just as scientifically be "Boring, Medium-Sized, Brown Melanoleuca"--or if that's too much of a mouthful, just "Darren" would work, too. Several species names have been proposed, most based on erudite differences in microscopic features (the precise shape and size of cystidia, spore measurements)--and authors interpret these species differently. Smith, Smith & Weber (1979) follow Kühner's concept (1978), by which Melanoleuca melaleuca lacks prominent cystidia, but most other North American (and European) authors describe a species with harpoon-like cystidia. Phillips (1991) appears to have changed his mind about his North American collections, since his Web site now features the photos that were labeled "Melanoleuca melaleuca" in his field guide under the name Melanoleuca polioleuca.
This is all pretty discouraging if your goal is to name your collection. But if you are an amateur who is interested in helping the science of mycology, please don't throw the mushrooms away in frustration. Intensive critical study of Melanoleuca in North America, based on hundreds of well documented collections and supported not only by morphological data but ecological and molecular (DNA) data as well . . . this is the only road that actually leads to a legitimate scientific horizon. In short, one or a few researchers may need to devote entire careers to the effort, unless amateurs and mycological societies pitch in (see "Mushrooming in the Age of DNA: Now Comes the Fun Part" for details). For those who are bound and determined to name their boring, medium-sized, brown Melanoleuca collections, come hell or high water, the European keys (Breitenbach & Kränzlin, Moser, and Hansen & Knudsen) in the list below will provide several identification options--or, if the mushrooms were collected in montane or boreal ecosystems in North America, the key by Gillman & Miller may be useful.
Boekhout, T. (1999). Melanoleuca. In Bas, C., Th. W. Kuyper, M. E. Noordeloos & E. C. Vellinga, eds. Flora Agaricina Neerlandica: Critical monographs on families of agarics and boleti occurring in the Netherlands. Volume 4. Rotterdam: A. A. Balkema. 153-165.
Breitenbach, J. & Kränzlin, F. (1991). Fungi of Switzerland, Vol. 3. Lucerne: Sticher Printing. 359 pp.
Gillman, L. S. & Miller, O. K. (1977). A study of the boreal, alpine, and arctic species of Melanoleuca. Mycologia 69: 927-951.
Kühner, R. (1978). Agaricales de la zone alpine. Genre Melanoleuca Pat. Bull. Mem. Soc. Linn. de Lyon 47: 12-52.
Moser, M. (1983). Keys to Agarics and Boleti (Polyporales, Boletales, Agaricales, Russulales). Ed. Kibby, G. Transl. Plant, S. London: Roger Phillips. 535 pp.
Pfister, J. (1984) Etudes des types de Peck et de Murrill appartenant ou ayant appartenu au genre Melanoleuca. Mycotaxon 19: 101-132.
Vesterholt, J. (2008). Melanoleuca. In Knudsen, H. & J. Vesterholt, eds.Funga Nordica: Agaricoid, boletoid and cyphelloid genera. Copenhagen: Nordsvamp. 347-352.
Cite this page as:
Kuo, M. (2007, May). The genus Melanoleuca. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/melanoleuca.html