Sistotrema confluens, an odd tooth fungus in honor of the tercentenary of the birth of
Carolus LinnŠus, the father of modern taxonomy.

Tom Volk's Fungus of the Month for December 2007

by Andrus Voitk and Tom Volk

Please click for the rest of Tom Volk's pages on fungi

Carolus LinnŠus-- Carl von LinnÚ by Alexander Roslin (cleaned up version digitally improved by Greg L)

2007 marks the tercentenary of the birth of Carl LinnŠus, father of the phylogenetic order, binomial nomenclature and the species concept. It's hard to believe it's been 300 years already! We cannot allow this year to come to an end without paying homage to this genius, the Darwin of his day, who classified all living organisms. Ever modest, he lives on for his quip, "Deus creavit, LinnŠus disposuit" --God creates, LinnŠus organizes.

It all started pretty early in life for LinnŠus. Little Carl (later Carl von Lineé, or Carolus LinnŠus in Latin) had a fascination with the names of plants from a very early age, certainly encouraged by his father, who was a pastor as well as an avid gardener. His father, disappointed that Carl did not want to become a priest, sent him off to medical school. In those days, medical doctors had to be well versed in plant identification, since many medicines of the day came directly from plants. Carl spent most of his time studying plants and even took time off from school to study plant in Lapland, in the northern reaches of Sweden. Eventually he went to the University of Harderwijk in the Netherlands to complete his medical degree.

LinnŠus published his first edition of Systema Naturae ("Arranging Nature") in 1735. This was the beginning of his attempts to name every living creature that was known at the time. He made many modifications to this work. In 1753 he published Species plantarum, "Species of Plants," in which he attempted to list all of the plants (including fungi) that were known to European naturalists at the time. Prior to this work, various authors used names containing two, three, ten or more words. LinnŠus was the first to consistently us binomial nomenclature for his names, i.e. the names consist of only two words: the genus name and the specific epithet. Thus all of plant and fungal taxonomy now begins with this publication. In the tenth edition of Systema Naturae in 1758, LinnŠus started using the binomial system also for animals.

After practicing medicine in Sweden for three years, he returned to Uppsala in 1741 where he became a professor, restoring the botanical garden by planting all the plants arranged in the groups in which he had ordered them. He continued to update his books and publish new ones By the time of his death in 1778, he was one of the most widely known and acclaimed scientists in Europe.

Sistotrema confluens fruiting bodies in Newfoundland In honour of LinnŠus, let us describe a mushroom that can give us insight into the species concept in mycology, Sistotrema confluens. Most of the rest of this is written by Andrus Voitk about his experience with this fungus in Newfoundland, Canada.

One day I came upon this cute and fuzzy stipitate toothed fungus, growing in a row (shown to the right). A woody consistency and white spore print may suggest a Phellodon, except we do not have such a Phellodon in Newfoundland (or elsewhere). What else could it be? Well, on returning the a few days later, I found a resupinate form on some birch bark at the end of the row of stipitate toothed fungi (shown below-- the outdoor picture did not turn out, so this picture was taken of the dried specimen, accounting for the ragged look and difference in colour). Problem solved, a resupinate polypore, another Basidiomycota. Or was it?

Well, not quite. First off, I had a difficult time identifying this specimen. Actually, I didn't have the difficulty; unfamiliar with polypores (or most fungi, for that matter), I did not even try. Instead, I shopped it around. Initially with dried material, then, when this ran out, with just the picture. Not much luck. After almost a year of trying, Urmas K§ljalg of the University of Tartu, Estonia, identified it from the photograph: Sistotrema confluens. Fine. Just as suspected, a polypore. Or was it?

a resupinate (flat) form of Sistotrema confluensA quick search on the web turned up a paper about this very mushroom by the same Urmas K§ljalg and associates. No wonder he recognized its portrait! K§ljalg's genetic analysis of genus Sistotrema showed that all members of the genus bore genetic similarity except two, one of whom is S. confluens. This duo was clad in quite different genetic garb from its sister sistotremata.

So what, you say. Happens in the best of families. What do sistotremata do? They decompose wood, like all good resupinate polypores. Except the two outcast sisters. They form ectomycorrhizal partnerships with trees, something nobody in the entire Sistotrema genus would dream of doing. They are different.

How do we decide on the species of an organism? We can consider its looks, macroscopic and/or microscopic (the morphological species concept). We can do mating studies (the biological species concept). We can consider its ecologic behavior (ecologic-physiologic species concept). Lastly, we can compare its genetic make-up with other putative species (genetic species concept). Each of these concepts requires that we make some choices about which of our observations are important and which not.

Looking at Sistotrema confluens morphology, we decided that its resupinate form was more important than its stipitate form in deciding where it belonged. (We took some support for this position by observing that the teeth were not "real" teeth, like those of a Phellodon, but merely the result of some pore walls disappearing, leaving the remainder hanging like wannabe teeth. This phenomenon is seen in other polypores as well, so clearly this is not a Phellodon relative.)

When we looked at S. confluens ecology-physiology, we decided that the little decomposing in which it engages is more important for classification than its mycorrhizal activities. Since no polypore worth its salt engages in mycorrhizal relationships (or do they?), this embarrassing trait had best be swept under the carpet.

Along comes DNA, the supposed boogeyman of the LinnŠan system, the molecule that, pulled up by its bootstraps, will make this classification and ranking method obsolete. Not so for S. confluens. Clearly, in assigning species and ranking to this organism, we made some wrong choices as to what is and is not important, both with respect to its morphologic and ecologic characteristics. We had the information, just didn't know what to play up and what to play down. What the genetic studies have done is help us reevaluate these decisions and make better ones. DNA, just like microscopy and mating studies before it, has not destroyed the system but made it more robust.

In the case of the two outcast sisters Sistotrema, genetically they belong in a clade with genus Hydnum, not with the rest of their clan. In retrospect, what a nice solution! Hydnum species are stipitate, have teeth and engage in mycorrhizal practices, just like these outcasts. Why shouldn't they belong there? Eventually we shall see a reassignment of these fungi to reflect this. The system is still intact, made more accurate by selecting correct characteristics to emphasize. Shoving them in with Phellodon would have been a mess, of course, because there already is a Phellodon confluens. Still, all those of my involuntarily recruited consultants, who suggested my unidentified mushroom was an as yet undescribed Phellodon, my protestations to the contrary, were right. In a way.

Linnaea borealis floweringI am sure LinnŠus would have approved, laughed even. But let this "humble" man, who claimed to put order into God's mess, have the last word. LinnŠus has been preserved in many botanical names, including the very pretty twinflower, LinnŠa borealis L. (shown to the right). Please do not assume from that name that LinnŠus was so crass as to name the flower for himself. This is just not done in polite botanical circles. The genus was named by Jan Frederik Gronovius, a Dutch botanist and patron of LinnŠus, after a trip to northern Sweden. LinnŠus provided the species epithet for this plant. And named another genus, Gronovia, for his patron. Very polite and genteel. Oh, how did LinnŠus react to this honour? With a typical, memorable LinnŠan quip: "The genus Linnaea was named by the famous Gronovius-- a Lapland plant, humble, insignificant and disregarded, flowering but for a brief time- after LinnŠus who resembles it."

We hope you have enjoyed learning something about the interesting tooth fungus Sistotrema confluens and about Carl LinnŠus, as we celebrate his 300th birthday. To celebrate, we suggest you make up a new Latin name for one of your friends.


R. Henrik Nilsson, Karl-Henrik Larsson, Ellen Larsson and Urmas K§ljalg. Fruiting body-guided molecular identification of root-tip mantle mycelia provides strong indications of ectomycorrhizal associations in two species of Sistotrema (Basidiomycota). Mycological Research. 2006. 110:1426-1432.

For more about the life of Carl LinnŠus, please read the very well written page by Ben Waggoner and others.

Andrus VoitkThis month's co-author is Andrus Voitk, a non-professional mycologist (he prefers "mycophile") from Newfoundland, Canada. He is the author of "A little illustrated book of Common Mushrooms of Newfoundland and Labrador." Gros Morne Cooperating Association, Rocky Harbor, Newfoundland. 2007. It's an excellent book and a fantastic model for what a regional mushroom guide should be. The many color photographs are beautiful, the keys are innovative, and the descriptions are very thorough and practical. It's also very useful for people outside the region. I highly recommend this book, especially for the humor and irreverence that Andrus put into nearly every page. I hope to make it to the Newfoundland annual foray someday.

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

This page and other pages are © Copyright 2007 by Thomas J. Volk, University of Wisconsin-La Crosse.

Learn more about fungi! Go to Tom Volk's Fungi Home Page

Return to Tom Volk's Fungus of the month pages listing