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The Genus Chroogomphus  

[ Basidiomycetes > Boletales > Gomphidiaceae . . . ]

by Michael Kuo

This small genus of gilled mushrooms is actually more closely related to the boletes than to the "true" gilled mushrooms. Like species of Phylloporus and Gomphidius (among others), the mushrooms in Chroogomphus appear to have developed their gills independently, on the bolete branch of the evolutionary tree, according to genetic evidence.

Sometimes referred to as "pine spikes," the mushrooms in Chroogomphus are mycorrhizal partners with conifers, recognized by their blackish spore prints, their gills (which are attached to the stem or, more commonly, begin to run down it), and the orangish to yellowish or reddish color of the flesh in the cap. They can be distinguished from species of Paxillus by the fact that the gills are not separable in a layer (see the page for Paxillus vernalis for an illustration), and from species of Phylloporus by the fact that the gills are not thick, waxy, and yellow. Additionally, the spore print is not blackish in either Paxillus or Phylloporus.

The more difficult distinction is between Chroogomphus and Gomphidius. Absent a microscope, the differences include the sliminess of the cap (more so in Gomphidius) and the orange-yellow-reddish flesh; species of Gomphidius are white-fleshed in the cap when young, though they frequently develop yellow colors on the stem, particularly at the base. The matter is quickly resolved with microscopic analysis, however, since species of Chroogomphus have cells that turn purple in Melzer's Reagent (see the illustration), while species of Gomphidius do not.

 		 

Chroogomphus sp.

Chroogomphus vinicolor


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Identifying Chroogomphus species ranges from fairly easy to fairly difficult, requiring microscopic analysis. The late Orson Miller published treatments of the genus throughout his esteemed career, and in recent years he was able to begin redefining species on the basis of preliminary DNA evidence (2003, 2006). One recent development of particular interest is Miller's discovery that "Chroogomphus rutilus" does not occur in North America; see the explanation on the page for Chroogomphus ochraceus.


Key to 9 Chroogomphus Taxa in North America  


1.Gills poorly formed (densely cross-veined and contorted); cap with grayish olive fibers and scales over an orangish to yellowish surface; stems often fused; under mountain hemlock; known from Oregon.
Chroogomphus loculatus

1.Not completely as above.
2

2.Stem 2 cm wide or more when mature and covered with conspicuous, felt-like, reddish to orangish scales and patches; cap margin often with felty partial veil remnants; gills with olive shades; spore print green; often growing in small clusters; associated with Ponderosa Pine or Douglas-Fir in the western mountains.

2.Mature stem usually thinner than above and lacking conspicuous scales and patches (though sometimes with minutely scaly areas); gills lacking olive shades; often growing alone or scattered; spore print blackish; mycorrhizal association and range various.
3


3.Mature cap not wider than 4 cm; stem with bright yellow shades; found in conifer bogs in northeastern North America; spores 18-29 µ long; cystidia thin-walled; apparently rare.
Gomphidius flavipes
(formerly Chroogomphus flavipes)

3.Not completely as above.
4


4.Cap dry or merely slightly sticky under normal conditions, covered with flattened scales or hairs; hyphae of cap "skin" not gelatinized; western in distribution.
5

4.Cap thinly slimy when fresh and young (later dry and shiny), smooth or with tiny, inconspicuous scales or hairs; hyphae of cap skin gelatinized; widely distributed.
6


5.Cap evenly orangish to yellowish, with the margin more or less the same color as the center; cystidia with thick (2-4 µ) walls; under western hemlock and other conifers in western North America.
Chroogomphus tomentosus

5.Cap yellowish to pinkish or brownish over the center, with a grayish margin; cystidia with thin walls; under western white pine and western hemlock in the Pacific Northwest.
Chroogomphus leptocystis


6.Found under pines (species of pinus, with bundled needles) from the Caribbean to Illinois and VIrginia; cap convex (never conical or bell-shaped), cinnamon brown to purplish brown; cystidia with thick (4-5 µ) walls; spores 17-20 µ long.
Chroogomphus jamaicensis

6.Not completely as above.
7


7.Cystidia with walls 5-7.5 µ thick in places (enlarge the illustration on the linked page).

7.Cystidia with thin walls (under about 1 µ thick).*
Chroogomphus ochraceus
= C. rutilans sensu N. Am. authors

*Despite attempts by several authors to delineate differences (or trends) in cap color between Chroogomphus vinicolor and Chroogomphus ochraceus/rutilus, the thickness of cystidial walls is a more reliable indicator, and "[t]here is no evidence . . . that the pileus coloration is an important character at the species level" (Miller, 2003).




References

Kauffman, C. H. (1925). The genus Gomphidius in the United States. Mycologia 17: 113–126.

Li, Y. C., Z. L. Yang & B. Tolgor (2009). Phylogenetic and biogeographic relationships of Chroogomphus species as inferred from molecular and morphological data. Fungal Diversity 38: 85–104.

Martín, M. P., J. Ll. Siquer, J. C. Salom, M. T. Telleria & G. Finschow (2016). Barcoding sequences clearly separate Chroogomphus mediterraneus (Gomphidiaceae, Boletales) from C. rutilus, and allied species. Mycoscience 57: 384–392.

Miller, O. K. Jr. (1964). Monograph of Chroogomphus (Gomphidiaceae). Mycologia 56: 526–549.

Miller, O. K. Jr. (1966). A new western species of Chroogomphus. Mycologia 58: 855–861.

Miller, O. K. Jr. & J. M. Trappe (1970). A new Chroogomphus with a loculate hymenium and a revised key to section Floccigomphus. Mycologia 62: 831–836.

Miller, O. K. Jr. et al. (2002). Two new species of Gomphidius from the western United States and eastern Siberia. Mycologia 94: 1044–1050.

Miller, O. K. Jr. (2003). The Gomphidiaceae revisited: a worldwide perspective. Mycologia 95: 176–183.

Saitta, S., M. Bianchi & M. Carbone (2020). Tre specie di Chroogomphus interessanti in Italia. Rivista di Micologia 63: 75–93.

Scambler, R., T. Niskanen, B. Assyov, A. M. Ainsworth, J. -M. Bellanger, M. Loizides, P. -A. Moreau, P. M. Kirk & K. Liimatainen (2018). Diversity of Chroogomphus (Gomphidiaceae. Boletales) in Europe, and typification of C. rutilus. IMA Fungus 9: 271–290.

Singer, R. (1949). The genus Gomphidius Fries in North America. Mycologia 41: 462–489.

Thiers, H. D. (1985). The Agaricales of California. 3. Gomphidiaceae. Eureka, CA: Mad River Press. 20 pp.



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Cite this page as:

Kuo, M. (2007, October). The genus Chroogomphus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/chroogomphus.html