Armillaria solidipes, an older name for Armillaria ostoyae, North American Biological Species I, NABS I

Tom Volk's Fungus of the Month for September 2008

by Hal Burdsall and Tom Volk.

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Armillaria solidipes

This month's fungus is the third species of Armillaria to make Fungus of the Month! You may have already heard about our discovery and description of Armillaria nabsnona, honey mushroom number nine, from the Olympic Peninsula in Washington. You may have also already read about the tenth anniversary of the humongous fungus, Armillaria gallica in 2002.

As you read on those pages, up until fairly recently there was considered to be only a single species of Armillaria, namely Armillaria mellea (Vahl:Fr.) Kummer. Until the late 1970s Armillaria mellea was considered by most researchers to be a pleiomorphic species with a wide host range and distribution. It was considered by different researchers to be either a virulent pathogen (in the west) or a opportunistic pathogen (and then not very virulent) in the eastern United States. Its host range was phenomenal, one of the broadest known for fungi, and its morphology was extremely variable.

Armillaria solidipesSince fruiting body morphology proved difficult, other avenues of research were followed. The most productive was placing single spores of different fungi in agar medium and seeing whether they would mate. If they did mate, two specimens were considered to be the same biological species. You can read about the details of how this was accomplished in The state of taxonomy of the genus Armillaria, but the end result was that there are TEN North American Biological Species (NABS) and five European Biological species (EBS), along with many other biological species from around the world. There's a chart of these accepted species here.

NABS I was associated with a specimen of Armillaria ostoyae collected and described (as Armillariella ostoyae) by Romagnesi in France in 1970, mainly because European Armillaria researchers were far ahead of those in the Americas. However, they neglected a species described by Charles H. Peck in 1900, which we show in a recently published paper to be NABS I. Because the oldest name takes precedent, the correct name for NABS I is Armillaria solidipes.

You can read all the details in this paper, which is available here as a pdf file.

Burdsall, H. H., Jr., and T. J. Volk. 2008. Armillaria solidipes, an older name for the fungus called Armillaria ostoyae. North American Fungi 3(7): 261-267. doi: 10.2509/naf2008.003.00717 Published August 29, 2008

Abstract: The name Armillaria ostoyae has been applied for nearly 40 years to the Armillaria species that causes a major root-rot of conifers throughout Europe, the northern United States, much of Canada, and more recently in China. However, C.H. Peck described this species in 1900 under the name A. solidipes, well before the name A. ostoyae was coined by Romagnesi in 1970. Thus, the name A. solidipes must be used for the taxon wherever it occurs.

I recommend you read the paper for all the gory details.

Fungal nomenclature is fun!


Hal Burdsall This month's co-author is Hal Burdsall, who was my mentor at the Center for Forest Mycology Research, which is a part of the USDA Forest Service in Madison, Wisconsin, where I worked from 1989-1996. Hal has had a great career working on wood decay fungi. He retired several years ago, and he and his wife Sandy also raise and show mules!

If you have anything to add, or if you have corrections, comments, or recommendations for future FotM's (or maybe you'd like to be co-author of a FotM?), please write to me at my email address

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