Observation 20518: Austroboletus mutabilis Halling, T. Osmundson, & M.A. Neves

There is a dramatic color shift on the pileus as the basidiomes age: deep red to orange and finally yellow. It may occur as a consequence of time, but may be mediated by exposure to light and/or a fluctuation in humidity. Single basidiomes may exhibit any color in this range. Under the light microscope, the plage appears smooth on spores that are otherwise ornamented with pits and fissures.

Duplicate specimens in BRI & NY (Halling #8768).


Manipulated in situ. Natural light.
Manipulated in situ. Natural light.
SEM ultrastructure showing ornamentation and smooth to eroded plage.
With light microscope (Nomarski DIC). Scale bar = 5 µm.

Proposed Names

91% (2)
Eye3 Eyes3
Recognized by sight: Vicinity of type locality
Based on microscopic features: Spores are ultrastructurally unique so far in the genus: pitted and with meandering fissures BUT with a smooth to eroded plage.

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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By: Roy Halling (royh)
2009-04-30 15:16:24 CDT (-0400)

Austroboletus was used first as a subgenus of Boletus by Corner in 1972. 5 species from Malaysia included. Raised to generic rank by C.B. Wolfe in 1979. A. gracilis & A. subflavidus appear to be the only ones in N. America. That’s right, the taxon called A. betula is really a Heimioporus. There are one or two things in Mexico and montane tropical America that are greenish and allied to A. subvirens.

manipulated in situ…
By: Debbie Viess (amanitarita)
2009-04-23 13:57:26 CDT (-0400)

that sounds so devious, somehow!

Seriously, tho, cool mushroom, and nice to see some of the color range possible. I know that we have this genus in North America, too, altho methinks that it must have been originally described from OZ, eh? What with the Austro part of the name and all…

Nice EM photo, too…perhaps a first for this site?! No fair, tho; I’m still trying to get the hang of my ancient light microscope, and squinting to see those tiny spore details…:(

Created: 2009-04-23 11:55:26 CDT (-0400)
Last modified: 2009-04-23 11:55:26 CDT (-0400)
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