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kuld-puiduheinik

Page history last edited by PBworks 17 years, 4 months ago

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kuld-puiduheinik (Tricholomopsis decora)

Tricholomopsis decora

 

by Michael Kuo

 

Whenever mycologists start talking about "intergrading species," you can bet you're going to have an identification mess on your hands, and it is worth remembering that a "species" is a human idea rather than a natural distinction. So, when Alexander Smith (1960) writes:

 

Collections of (Tricholomopsis sulfureoides), and of T. thompsoniana and T. bella, indicate clearly that we have, in this group, a species-complex in which intergradation between the member species is of frequent occurrence. A study of this complex in culture is badly needed, and should include T. decora as well.

. . . we should recall that what is intergrading is the concepts of the species--not the mushrooms. Smith's reference to "culture" studies is an indication that (in 1960, at least) he thought that a biological species concept might better be applied to this area of Tricholomopsis. A biological species concept is what we use, for example, with large mammals when we define their species status on the basis of whether they can mate and breed.

 

As far as I know, no one ever took Smith up on his suggestion, and a mating study to better define species of Tricholomopsis never happened. (If you're interested in how mating studies apply a biological species concept to mushrooms, see what Ron Petersen and others have done with Flammulina and Pleurotus at this site.) These days, however, a DNA-based species concept is often recognized when it comes to thinking about mushrooms and their evolution. But a DNA study of Tricholomopsis (again, to my knowledge) has not been done, outside of broader-based studies that included a few Tricholomopsis species to see whether the genus itself was genetically valid (it was, once Tricholomopsis Megacollybia platyphylla was removed).

 

So we are left with using the morphological species concept for Tricholomopsis and analyzing the mushrooms' physical features (with and without a microscope). Thus, if your Tricholomopsis has gray to dark gray scales on a yellow background and a stem that has yellow flesh and does not radicate (form a root), it is Tricholomopsis decora.

 

Sounds easy enough, but take a closer look at the scales on your mushroom. Are they really dark gray, or are they brown? Because, if the scales are "yellow to yellow brown or fulvous," you're looking at something else. Now go outside and look at the scales in the sunlight. Now try assessing the color of the scales when the mushroom is a little damp . . . You get the picture. You are welcome to get out your microscope, but I'm telling you now to forget it; the microscopic characters "intergrade" as well.

 

While all of the species Smith mentioned are found decomposing the dead wood of conifers, Tricholomopsis decora and Tricholomopsis sulfureoides (especially the latter) seem to have a preference for the wood of hemlocks (including Eastern Hemlock). Is this important? Is there some sort of "ecological species concept" that might help sort out the species in this cluster?

 

Food for thought. Meanwhile, I will describe Tricholomopsis decora below on the basis of its official, morphological features--and you will notice that the mushrooms illustrated to the right have yellowish, brownish, reddish brown or grayish scales, depending on where you look. For more knee-slapping fun, get out your field guides and compare the descriptions to the photos--then make comparisons between field guides. Be sure to pay special attention to the color of the scales since this character is, um, definitive.

 

The edibility of the species in this cluster is not known; do not experiment.

 

Description:

 

Ecology: Saprobic on the wood of conifers, especially hemlocks (see Eastern Hemlock); growing alone, scattered or gregariously; summer and fall; possibly widely distributed in North America, depending on how one defines the species and how much one trusts other collectors through history to have defined the species the same way (have I mentioned yet that Tricholomopsis decora was originally described in 1821, in Sweden?).

 

Cap: 3-8 cm; convex with an incurved margin, becoming broadly convex, flat, or centrally depressed with the margin somewhat wavy; moist when young; yellow, covered, at least over the center, with small scales that have gray tips.

 

Gills: Attached to the stem; close or crowded; yellow.

 

Stem: 4-8 cm long; .5-1 cm thick; more or less equal; hollow; pale yellow; smooth.

 

Flesh: Yellow to pale yellow.

 

Taste: Mild; odor not distinctive.

 

Spore Print: White.

 

Microscopic Features: Spores 6-7.5 x 4.5-5 µ; smooth; more or less elliptical; inamyloid. Pleurocystidia rare; barely projecting beyond basidia. Cheilocystidia abundant; variously shaped; 36-62 x 9-20 µ. Gill trama slightly interwoven. Clamp connections present. Incidentally, the cystidia "revive poorly, even on carefully dried specimens" (Smith)--so have fun analyzing them.

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