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The Genus Melanoleuca  

[ Basidiomycetes > Agaricales > Tricholomataceae . . . ]

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:

  • Terrestrial habitat;
  • White spore print;
  • Nearly flat cap;
  • Tough, slender stem;
  • Gills close or crowded, attached to the stem (often "notched") but not running down it;
  • Boring colors.

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%).

 

Melanoleuca angelesiana

Melanoleuca graminicola

Melanoleuca graminicola

Melanoleuca evenosa

Melanoleuca brevipes


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Key to 11 Species of Melanoleuca in North America


 Frequently collected look-alikes:
 

  • In wood chips; cap reddish brown, convex until old age.

  • In clusters in grass; gills widely spaced.

  • Under conifers in the West; gills thick and purplish.



  • 1.Mature cap large for the genus, measuring 8-15 cm across.
    2

    1.Mature cap normally smaller than 10 cm across.
    3


    2.Gills white at first but soon yellowish-pinkish to pale tan; odor fairly strong, somewhere between sweet and mealy; widely distributed.

    2.Gills long remaining white; odor pleasant but not distinctive; apparently western in distribution.


    3.Stem with prominent Leccinum-like, brown scabers over a white background.
    Melanoleuca verrucipes
    (Photo only; see also DeShazer collection at Mushroom Observer.)

    3.Stem not as above.
    4


    4.Cap gray, medium-sized (3-7 cm) at maturity; stem conspicuously short in relation to the cap width; cystidia present.

    4.Not completely as above.
    5


    5.Fresh cap whitish to pale yellow.
    6

    5.Fresh cap more highly colored (microscopic analysis required).
    9


    6.Fresh cap sticky, white becoming yellow-stained; found in California.
    Melanoleuca lewisii

    6.Not as above.
    7


    7.Stem off-center; odor spermatic; cystidia absent; found under conifers in the Pacific Northwest; apparently rare.
    Melanoleuca eccentrica

    7.Not as above.
    8


    8.Cap medium sized to large (4-11 cm), often with a pale brownish center; stem whitish; flesh white in cap and stem; cystidia present and prominent.
    Melanoleuca alboflavida
    at Roger's Mushrooms

    8.Not as above (microscopic analysis required).
    9


    9.Cystidia absent--or present only as cheilocystidia (on the gill's edge) and then scarcely projecting, never prominent.
    10

    9.Cystidia easily demonstrated--scattered to abundant on the edges and/or faces of the gills, projecting substantially, often developing harpoon-like, encrusted apices.
    11


    10.Cap small (2-3 cm across); growing in grass (often in urban areas or parks) or disturbed-ground areas.

    10.Cap medium-sized (4-7 cm across); growing under conifers from the Rocky Mountains westward, often (but not always) at high elevation near melting snowbanks.


    11.Growing in summer in boreal tundra.
    Melanoleuca borealis and others
    (See Gillman & Miller, 1977)

    11.Growing elsewhere; cap brown, medium-sized.




    "Melanoleuca melaleuca"

    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.




    References

    Arora, D. (1986). Mushrooms demystified: A comprehensive guide to the fleshy fungi. Berkeley: Ten Speed Press. 959 pp.

    Bessette, A. E., O. K. Miller, A. R. Bessette & H. H. Miller (1995). Mushrooms of North America in color: A field guide companion to seldom-illustrated fungi. China: Syracuse UP. 172 pp. Note: This book treats Melanoleuca angelesiana, and includes comments by Miller referring "Melanoleuca graminicola" of Gillman & Miller (1977) to Melanoleuca angelesiana.

    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. See note above under Bessette et. al (1995).

    Hansen, L. & Knudsen, H., eds. (1992). Nordic macromycetes Vol. 2: Polyporales, Boletales, Agaricales, Russulales. Copenhagen: Nordsvamp. 474 pp.

    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. Available online here, at Libri Fungorum.

    Smith, A. H., Smith, H. V. & Weber, N. S. (1979). How to know the gilled mushrooms. Dubuque, Iowa: Wm. C. Brown. 334 pp.



    Cite this page as:

    Kuo, M. (2007, May). The genus Melanoleuca. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/melanoleuca.html