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Boletus subvelutipes species group
by Michael Kuo
I'm going to make this easy. If your red-pored, blue-staining Boletus was collected under hardwoods east of the Rocky Mountains, has a fairly smooth stem that lacks reticulation but features a finely fuzzy coating over its base (or occasionally over its bottom half), and does not have a distinctive odor or taste, call it Boletus subvelutipes.
That's pretty much as accurate as you can be--even from a scientific standpoint, unless by "scientific" you mean "like the microscope-based mycology of thirty years ago." See the comments below if you feel I need to back up my sweeping claims with reasoned argument, or if you have been using keys and descriptions in an attempt to identify a subvelutipes-like bolete and have found yourself immersed in a dilemma regarding "red hairs" on the stem.
Ecology: Mycorrhizal with hardwoods; growing alone, scattered, or gregariously; summer and fall; widely distributed in eastern North America; perhaps also in New Mexico.
Cap: 5-10 cm; convex, becoming broadly convex; dry; smooth or finely velvety; variable in color (brown, red, reddish brown, orangish, cinnamon, olive, olive-brown, yellowish, yellow-brown) but not pallid or whitish when fresh; sometimes bruising dark blue to blackish.
Pore Surface: Red or orange-red; frequently yellow or pale orange at the margin; bruising instantly dark blue to blackish; pores circular, fairly small (1-3 per mm); tubes yellow, to about 2 cm deep.
Stem: Up to about 10 X 2 cm; more or less equal; dry; solid; not reticulate; with a variously colored (whitish, yellowish, reddish, rusty brown) velvety, fuzzy covering over the base (sometimes obscured by leaves or substrate) that occasionally extends up the stem for half its length or more; bruising dark blue to blackish.
Flesh: Whitish to yellowish or bright yellow; staining quickly blue on exposure.
Odor and Taste: Not distinctive.
Chemical Reactions: KOH on cap orange or dark red; on flesh orange. Ammonia on cap negative, reddish, grayish, or pale orangish (and sometimes eroding darker cap colors); on flesh negative to pale orangish. Iron salts on cap grayish to olive, orangish, or negative; on flesh grayish to olive, orangish, or negative.
Spore Print: Olive brown.
Microscopic Features: (From the Smith & Thiers study of the apparent type collection.) Spores 14-18 (20) X 5-6.5 (8) µ; smooth; subfusiform. Pleurocystidia rare; fusoid-ventricose; 30-42 X 7-12 µ; hyaline or pale yellowish in KOH. Caulocystidia clavate to fusoid-ventricose; 33-50 X 6-14 µ; with yellowish contents in KOH. Pileipellis a cutis of cylindric, non-gelatinized hyphae 2.5-5 µ wide; terminal elements with blunt or tapered tips; yellowish in KOH.
REFERENCES: Peck, 1889. (Saccardo, 1891; Snell & Dick, 1970; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Lincoff, 1992; Both, 1993; Barron, 1999; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Miller & Miller, 2006; Binion et al., 2008.) Herb. Kuo 07209400, 07140308, 07220300, 07230309, 07250305, 09190303, 06190401, 07140400, 08290500, 09070701.
Boletus erythropus, an oak-associated European species that may or may not occur in North America, has a dark brown cap and a distinctive stem surface densely adorned from top to bottom with tiny clumps of red material that does not qualify as a "tomentum" or "strigosity" in Mycologese, or as "fuzz" or "hairs" in plain English (follow the link for illustrations).
Searching for Dark Red Hairs
Charles Peck (1889) named his Saratoga, New York, species subvelutipes ("nearly-fuzzy-stemmed"); think of the fuzz on the stem of Flammulina velutipes . . . then "sub" it. According to Peck, the stem was
equal or slightly tapering upward, firm, even, somewhat pruinose above, velvety with a hairy tomentum toward the base (emphasis in Peck), yellow at the top, reddish-brown below, varied with red and yellow within.
If you read this description carefully, you will see that Peck does not specify the color of the velvety tomentum, though he does say the stem's overall color is reddish brown near its base. If your field guide insists on "dark red hairs" at the base of the stem for Boletus subvelutipes, the author is citing Smith & Thiers (1971)--or citing some other author who is citing Smith & Thiers. In The Boletes of Michigan, Smith & Thiers put the words "base of stipe with dark red hairs" in their key to "Stirps Subvelutipes," and described their Michigan material as having a stem base with "red strigosity" (349, 359).
But the fuzzy coating on the stem base of Boletus subvelutipes is variable in color, ranging from whitish to yellowish, olive, or, indeed, red. Additionally, the fuzzy coating is subject to blue bruising, just like the rest of the stem surface, and is often reddish brown after the blue has faded away, regardless of its initial, pre-bruising color. In some of my collections, the tomentum has been yellow in the field, but reddish by the time I have been studying the mushrooms at home. And as Ernst Both (1993) has pointed out, the tomentum "becomes reddish-rust or rusty only near maturity." The most accurate description of the tomentum comes from Snell and Dick (1970: "the basal strigosity pale to rich buff-yellow or deep red or somewhat olivaceous") but their work, The Boleti of Northeastern North America, is never cited as religiously as the publication of Smith & Thiers--probably because Snell and Dick did not emphasize microscopic features.
Smith & Thiers placed Boletus subvelutipes near Boletus erythropus and Boletus spraguei in a group of species they named "Stirps Subvelutipes," and added four new species to the group (Boletus subluridellus, Boletus pseudo-olivaceus, Boletus roseobadius, and Boletus rufocinnamomeus), basing the species in great part on microscopic characters like spore dimensions, the length of the caulocystidia, and the color of the cuticular hyphae when mounted in Melzer's reagent.
Regular readers of my pages at this Web site, or those who have heard my lectures, will not be surprised to hear me say that I doubt many of these "species" reflect natural, genetically distinct organisms. What continually astounds me is that we are surprised when DNA studies (continually) reveal we have been wrong in our assumptions about how to distinguish mushroom species. We were never using a theory that even remotely corresponded to what we knew about evolution and speciation. Take the Melzer's reaction of the cuticular hyphae as a quick example: the "theory," such as it is, goes something like "these organisms have evolved together so that the cells on the surface of the cap, for some reason we don't even think about, turn reddish when humans examine them with a microscope and mount them in an obscure reagent that does not occur naturally anywhere on earth."
When we have erected a huge taxonomic house of cards based on this kind of theorizing, how can we be surprised when we discover we weren't playing with a full deck? DNA studies of mycorrhizal mushrooms tell us again and again that determining specific mycorrhizal association is a better character than many physical features (microscopic or not)--and that analysis of differences in physical features, while not useless, tends to reflect actual genetic difference only when placed in the context of ecology and DNA and subordinated to limited taxonomic areas.
"These organisms have evolved along with their mycorrhizal hosts as part of an ecosystem" is a legitimate theory, reflective of what we know about the natural world--as is "the genetic code of these organisms reflects differences that are about the same as the differences we use to define other species." Thus, if Boletus rufocinnamomeus turns out to be a genetically distinct species that grows only in association with Quercus rubra in dry, second-growth hardwood forests that have reached maturity, it will be a coincidence that Smith & Thiers stumbled on a "good species," not a vindication of micromorphology--and it will be entirely likely that the characters used by Smith & Thiers to define Boletus rufocinnamomeus do not actually define it, since other mushrooms that they would have named differently might easily also match Boletus rufocinnamomeus. (Incidentally, I mean no disrespect to Smith or Thiers; they are two of my heros, and were superhuman in their rigorous collecting and documentation of morphological variance.)
We will only know for sure, however, once we have collected many (I mean hundreds or even thousands) of North American subvelutipes-like boletes, thoroughly documented their ecology and morphology, and tested their DNA. This is why I stress, in my lectures to mushroom clubs and mycological associations, the need for a fundamental change in the way "forays" and "identification tables" operate. Instead of picking a bunch of mushrooms without paying the slightest attention to the ecosystems in which they have evolved, we should be carefully documenting the potential mycorrhizal plants and trees under which they occur, along with other ecological details. Instead of arranging the mushrooms on tables that are labeled according to morphology-based taxonomic schemes from the seventies, gawking at them, then tossing them all into the garbage, we should be placing them on tables labeled "Spruce-Fir Zone" or "High Oak-Hickory Woods," carefully documenting their morphology with photos and descriptions (including microscopic details), and preserving the specimens so that mycologists and molecular biologists can study them.
I have come a long way from Boletus subvelutipes, but I felt I should justify painting the species with such broad strokes--and I wanted to convince you, regardless of what name you decide to apply to your bolete, to take notes on its ecology, to photograph or scan it, to describe it, and to preserve your specimen.
Further Online Information:
Boletus subvelutipes in Smith & Thiers, 1971
Cite this page as:
Kuo, M. (2007, February). Boletus subvelutipes species group. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_subvelutipes.html