Mushroom Taxonomy: The Big Picture

by Michael Kuo

NOTE: THIS PAGE IS OUTDATED AND HAS BEEN REPLACED (HERE) AS OF FEBRUARY 2011; IT IS MAINTAINED HERE ONLY FOR REFERENCE TO THE PREVIOUS PUBLICATION.

I frequently receive e-mails from frantic biology students who have been asked to discover the kingdom, phylum, class, order, family, genus, and species of a certain mushroom. Here, with the student's typo included, is the most entertaining example I've received so far:

Recently in my biology class we were asked to chose an orgasm. I chose the Armillariella ostoyae. My professor wants us to find the kingdom, phylum, class, order, family, genus, species, and or variety. I know the kingdom, genus and species. I have had difficulty finding the phylum, class, order and family. Do you know of any good sites that can help me with my research. Thank you very much.

Aside from recommending that the student might want to find a new professor, I replied that the taxonomical hierarchy for Armillaria ostoyae is:

Fungi: Basidiomycota: Basidiomycetes: Agaricales: Tricholomataceae: Armillariella: ostoyae

. . . in the traditional, and now probably outdated, system. Armillaria has been reconceived within the past few years, resulting in the elimination of Armillariella, and placing the genus in the Marasmiaceae rather than the Tricholomataceae; also, there is debate about whether or not the kingdom and phylum distinctions should be made at some other level in the hierarchy.

But uncertainty is not what professors want on homework assignments. The problem is that there is no "correct" answer to the professor's question. Or, better said, the answer to the question changes constantly, and has been changing ever since Linnaeus started using Latin names to arrange organisms.

Though it is a fact usually unobserved in introductory biology classes, taxonomy does not represent organisms. Rather, taxonomy represents how we perceive and organize organisms. This is a very important difference. It is the difference, for example, between what happened at the scene of the crime, and what the witness saw happen at the scene of the crime--and anyone who has ever watched a courtroom drama knows how different these two things can be.

In my field (I am an English teacher), the rules of grammar and punctuation are seen by most teachers as unchanging and universal. Students are "wrong" if they omit the apostrophe from don't, or write "Everyday someone gets their lunch." Yet there was a time--not that long ago, from a historical perspective--when dont was perfectly correct, and the time is coming (or is already here) when this use of everyday and their is correct. People of my mother's generation physically cringe when they hear "their" used like this. People of my generation notice a problem, but use it anyway as a substitute for the sexist "his." My students don't even notice. Within my lifetime, the language has changed, as a result of a change in our culture: we became more aware of sexism, and less comfortable using masculine pronouns as universal pronouns.

With grammar and punctuation, however, the rule makers usually lag far behind the general population. This is because the rule makers (the authors and publishers of dictionaries and grammar handbooks) are conservative by nature, and often see themselves as corrective agents, holding back the masses and saving them from their mistakes. But with taxonomy, things are reversed. It is the mycologists, in the case of mushrooms, who are constantly changing things, and the general population that lags behind. Thus, I must provide the biology student above with an answer I know to be incorrect, knowing that her professor is likely working from outdated information.

Once, mushroom taxonomy was an arrangement of mushrooms based on their physical appearance. This one had gills, so it belonged in a group with other gilled mushrooms, while another mushroom, this one with pores, belonged in a different group. For well over a hundred years, advances in mushroom taxonomy simply represented more careful attention to the physical features of the mushrooms--and, importantly, the fact that more and more mushrooms from around the world were being sent to scientists in northern Europe. These scientists began to discover that closer examination revealed other groupings. Some of the gilled mushrooms had white spore prints, for example, and gills that were attached to the stem. New families and genera were named; species were placed in the hierarchy accordingly.

Then, roughly a hundred years ago, scientists began looking at mushrooms with microscopes. Some mycologists had been doing so earlier, but the hegemony of microscope mycology didn't take hold until the 20th century. As a result, new groupings emerged. These mushrooms, for example, had ornamented spores, indicating that they formed a group separate from other mushrooms that looked more or less the same to the naked eye, but had smooth spores. As microscopes got better and better, more taxonomical changes were made.

It is important to recall that the mushrooms themselves did not change during this brief history; what changed was the way we examined them. New technologies and methods of analysis--like studies of chemical composition, mating studies, and (especially) DNA analysis--are in vogue these days, and they are resulting in radical changes in mushroom taxonomy. Groups that we once thought were related, based on physical appearance or microscopic features, are turning out to be unrelated. But it is likely--I would say it is a certainty--that future mycologists will decide something besides DNA is the definitive key to mushroom taxonomy, or that the technology we're now using to see DNA is grossly inadequate, providing an inaccurate portrait. I have already spent a painful hour on the phone listening to one self-righteous DNA mycologist complain that another DNA mycologist was using equipment and techniques so outdated as to be meaningless. (It probably goes without saying that good equipment, in this mycologist's estimation, is the kind that costs so much money that there are only a few labs on earth that possess the technology.)

The taxonomical mess I have been describing is further complicated by the fact that the whole system was set up by fundamentalist Christians who believed that God created a perfect and unchanging universe. I discuss this problem in detail in "The Evolution of a Great Big Headache," but for our purposes here, suffice it to say that the idea that species evolve over time was added to mushroom taxonomy as an afterthought. "These mushrooms have ornamented spores, so they must have evolved together." These days it is fairly easy to see the logical fallacy in this statement, but it was not that easy to see in the 1960's. I would be laughed out of the room, however, if I suggested today that the same logic problem might be involved with: "The nucleotide sequence at the 5' end of the nuclear large ribosomal subunit gene of these mushrooms is statistically the same, so they must have evolved together."

I offer these comments by way of introducing the table below, which represents how mycologists currently see taxonomical relationships between mushrooms. I have culled the information from Ainsworth & Bisby's 2001 Dictionary of the Fungi (see the notes below for a complete citation), and I have included only "mushroom" taxonomy--omitting the details on rusts, yeasts, lichens, molds, and so on. The editors of the Dictionary, of course, compiled information from peer-reviewed papers published in scientific journals; it should come as no surprise that editing such a compilation involves attempting to "standardize" things that have not yet become standards, resolving taxonomical conflicts that are often hotly debated, and so on. Yet Ainsworth & Bisby's Dictionary has become more or less the definitive standard for mushroom taxonomy; for better or worse, the biology student must consult this source to get the "best" current answer to a taxonomy question.

NOTE: THIS PAGE IS OUTDATED AND HAS BEEN REPLACED (HERE) AS OF FEBRUARY 2011; IT IS MAINTAINED HERE ONLY FOR REFERENCE TO THE PREVIOUS PUBLICATION.

NOTE: THIS PAGE IS OUTDATED AND HAS BEEN REPLACED (HERE) AS OF FEBRUARY 2011; IT IS MAINTAINED HERE ONLY FOR REFERENCE TO THE PREVIOUS PUBLICATION.

Notes

I have done my best to avoid typing mistakes in the table above, but I ask you to imagine typing Hypsizgus, Syzygospora, Iodowunnea and the like for hours on end with no recourse to a spell-checker. If you find a mistake, please drop me a line; I will appreciate knowing it.

Use Control/F in your browser to search the name of a genus. If the genus you are searching is not on the page, it may have been renamed, or collapsed into another genus. This often happens; notice for example that the genus Stropharia is not listed in the Strophariaceae (which is named after Stropharia), since it has been found to belong in Psilocybe. It is also possible that a genus not listed in the table has uncertain status according to Ainsworth & Bisby's Dictionary; I have not included these genera.

See also Cantharellus Clade, Lepiotoid Clade, and Physalacriaceae Clade, pages in our "Taxonomy in Transition" series.

I recommend these sources for further information on the contemporary "big picture" of mushroom taxonomy:

Kirk, P.M. et al., eds. (2001). Ainsworth & Bisby's dictionary of the fungi. Oxford: CAB International. 655 pp.

McLaughlin, D. J., et al. (2001). The Mycota: A comprehensive treatise on fungi as experimental systems for basic and applied research. VII: Systematics and evolution (parts A and B). Germany: Springer-Verlag.

Moncalvo, J. M., et al. (2002). One hundred and seventeen clades of euagarics. Molecular Phylogenetics and Evolution 23: 357–400.

Cite this page as:

Kuo, M. (2003, September). Mushroom taxonomy: The big picture. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/taxonomy.html