What's in a Name?

Meet Ganoderma applanatum.

Not much to look at, is it? Its name isn't very exciting, either – applanatum means flat, and ganoderma means “shining skin,” a name more applicable to its cousin, the reishi (Ganoderma lucidum) for whom the genus was originally erected. It's more commonly known as the “artist conk” because its white underside bruises easily, which lead to a long tradition of fungus-based art among ecologists. Also, and largely due to the reishi's reputation in traditional Chinese medicine, a few biomedical researchers are investigating it for possible avenues in cancer treatment. That's really it, though. As far as mushrooms go, there are easily hundreds that are tastier, better-looking, or simply more interesting than this unassuming shelf fungus. 

So why am I bothering to bring it up? Well, it turns out the scientific history of this fungus, one that stretches back to the very early days of biology in the United States, is much more interesting. It is emblematic of the difficulty of classifying organisms, and the challenges modern researchers face when attempting to organize past research.

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Linnaeus's Big Idea

The story begins with a man named Carl von Linne. Linne was nuts about naming things in Latin, to the point where he Latinized his own, to Carolus Linnaeus. In 1753, Linnaeus sparked a scientific revolution with the publication of Species Plantarum. This book was a list of descriptions of plants along with a two-part name, one representing a genus and the other a species. These were terms borrowed from Aristotle, who had attempted to build a classification system for every object on the base of its shared, general characteristics (genera) and its particular, unique characteristics (species).

Linnaeus's new system was important in two ways: first, it simplified scientific names considerably – what was once a wordy description in Latin was easily condensed to a two-word shorthand. Second, it put forward the idea that organisms could be classified according to relatedness, effectively codifying the idea of common descent a full century before Darwin. Now, a scientific name not only specified features of an organism, but what branch of the tree of life that species occupied.

Linnaean taxonomy caught on quite quickly, to the point where layman and scholars alike were enthusiastically joining “Linnaean Societies” dedicated to the identification and naming of things. With this new naming system, however, came problematic competition among adventurers, explorers, and gentlemen scholars to put as many new Linnaean names on as many things as possible, then get those names to press before someone else did. Over the next century, bulletins, newsletters, and other publications would include lists of hundreds to thousands of different organisms, each with a proposed name and a short description in Latin and not much else. Specimens were to be lodged in herbaria for the benefit of anyone who wanted to take a look at them, but the slowness of communication and difficulty of travel didn't always make them accessible.

North America, chock-full as it was of things unknown to European scholars, proved particularly fertile ground for a biological gold rush. This 18th century naming spree exposed one of the Linnaean system's greatest strengths as also one of its greatest weaknesses. Since the classification of its organism was now inextricably linked to its name, to change an organism's relationship in evolution's family tree meant also changing its name. Since fungi were especially hard to pin down (doing so without a microscope to look at the spores is practically impossible), the process of naming most fungi was not unlike the game of putting hand over hand on a baseball bat to decide who picks first, only the bat in question is several miles high – the debate over Ganoderma applanatum wasn't really settled until 1909, around 110 years since its first discovery. But let us start at the beginning. 

The Beginning

Persoon. Source.

Persoon. Source.

Depending on who you ask, the story of our mushroom starts in either In 1799, with mycologist by the name of Christian Hendrik Persoon, or in 1786 with August Johann Georg Karl Batsch. Persoon recorded a collection of a New World Boletus applanatus, classifying his sample into a species already established in Europe. Batsch, on the other hand, 1786 description called it Boletus lipsiensis. Of the two, Persoon's record appears to have gotten more attention than Batsch's, although it's impossible to be sure that both researchers were looking at the same thing, since all future mycologists had to go by was the similarity of the brief descriptions authored by both men.

In 1801, Persoon had a change of heart and decided that the mushroom was a new species after all, renaming it Boletus fomentarius, but it didn't appear anyone saw that particular memo, since in future publications, the applanatus designation stuck. 

All Heck Breaks Loose

The 19th century saw a strangely large and poorly organized level of interest in the mushroom. In 1833, Karl Friedrich Willhelm Walroth, working from Persoon, renamed the mushroom Polyporus applanatus. Four years later, 1837, a second German mycologist, ACJ Corda, working from Batsch, decided to re-classify the fungus into Polyporus again, this time as merismoides. The French researcher Leveille took a look at the Polyporus applanatus collection in 1846, decided it needed yet another designation under Polyporus, this time as Polyporus megaloma. In 1878, Edward Gillet of Massachusetts, decided that the fungus was actually Fomes (as Fomes applanatus), a genus of hoof-shaped conks, but his work appeared to go ignored in later treatments of the species except for one notable personality that we'll get to in a bit. 1889 was a particularly eventful year, as three researchers, Karsten, Patouillard, and Berlese, decided to take a look. Karsten reclassified our hero into the now-defunct but fun-to-say Elfvingia,   whereas Patouillard put it into a new genus that had been built for shiny, lacquered polypores such as reishi – Ganoderma, as applanatum. Berlese classified it as Fomes gelsicola; he doesn't cite any previous research in his name, indicating that he thought he had a new species.

So, to recap, at this stage in the game, the fungus has at minimum ten different names floating around, at varying levels of recognition and acceptance:

Boletus applanatus
Boletus fomentarius
Polyporus
applanatus
Boletus lipsiensis
Polyporus fomentarius
Polyporus megaloma
Fomes applanatus
Elfvingia applanata
Fomes gelsicola
Ganoderma applanatum

But, it looks like Patouillard nailed it with Ganoderma applanatum, right? Unfortunately, Patouillard's designation was not long for this world. In 1903, the American mycologist William Murrill decided that Ganoderma should only be applied to the shelf fungi that have a shiny surface, and not Ganoderma applanatum, so he returned it to the genus Elfvingia

Atkinson to the Rescue

Finally, in 1908, American mycologist George Atkinson decided to settle this debate once and for all, using the latest in microscope technology. Using his newer tools, Atkinson figured out why the fungus kept getting reclassified (aside from lapses in communication) – some researchers had described the spores as smooth, others as covered in tiny spikes. The reason for this was because the spore had a clear wall which would sometimes collapse when put under the microscope, producing ridges and valleys that looked a lot like spikes. This was a trait shared by the flashier reishi, which suggested that our wallflower of a fungus belonged in Ganoderma after all. So put Patouillard's name back on it and call it good, right?

Well, no. Atkinson decided that Batsch's Boletus lipsiensis was the same species as Ganoderma applanatum after all, and so the more temporally correct species name was lipsiense, not applanatus. He argued further that since Patouillard hadn't looked at the spores, even though he was right, it was for the wrong reasons. Atkinson's name was accepted, and to this day the correct official name is Ganoderma lipsiense.

So why did I spend the entire article referring to it as Ganoderma applanatum? Well, it turns out that, for whatever reason, Patouillard's name proved the more popular of the two in the 20th century, and most researchers, even today, use applanatum and not lipsiense. While Atkinson may have one the argument on technical grounds, it was Patouillard whose name entered common, if wrong, useage.

Photomicrographs showing the spores of Ganoderma lucidum, or reishi. Top: how the spores look under the microscope. Middle: scanning electron micrographs of intact spores. Bottom: scanning electron micrographs of spores whose outer wall has been damaged, showing the columns that often got reported as spines. Reproduced from Basidiospores, Pilocystidia, and Other Basidiocarp Characters in Several Species of the Ganoderma lucidum Complex, Adaskaveg and Gilbertson, 1988.

Photomicrographs showing the spores of Ganoderma lucidum, or reishi. Top: how the spores look under the microscope. Middle: scanning electron micrographs of intact spores. Bottom: scanning electron micrographs of spores whose outer wall has been damaged, showing the columns that often got reported as spines. Reproduced from Basidiospores, Pilocystidia, and Other Basidiocarp Characters in Several Species of the Ganoderma lucidum Complex, Adaskaveg and Gilbertson, 1988.

Epilogue

Ganoderma applanatum's classification away from Fomes didn't sit well with Atkinson's contemporary, Curtis Gates Lloyd. The writings of both men suggest that they had a mild professional rivalry. Notably, Lloyd's Wikipedia page dryly observes that his “views on naming conventions in taxonomy” were “controversial.” In his study, Atkinson can't seem to resist sniping at his colleague's stab at the spore problem.

Wrote Lloyd: “European mycologists have been using the microscope on the spores of Fomes [leucophaeus, a species included in Ganoderma applanatum by Atkinson], and when I sent the plant [fungus] there it was noted that it had smooth spores, while the spores of Fomes applanatus are rough. It was published in Mycological Notes in 1901... which I think was the first time attention was drawn to this popular error which had persisted in American mycology up to that date.”
Replied Atkinson: “In this statement Mr. Lloyd evidently overlooked the fact that Patouillard had published the statement that the spores of Fomes leucophaeus were smooth, in 1889, twelve years before this notice in Myc. Notes 1901.”

Lloyd himself used more colorful language when refusing to surrender to Atkinson's classifications in 1920 (12 years after Atkinson's paper), saying that his colleague's classification was, quote, “a cheap juggle" and insisting that the mushroom belonged in Fomes, this time as longiporus.

Aside from Lloyd's protests, things died down for Ganoderma after Atkinson's publication. In the midcentury the genus was split into two subgenera to recognize the difference between the shiny and dull ones, but resolving those subgenera has still baffled researchers. At present, it's still unknown if Ganoderma applanatum's sister species Ganoderma australe and Ganoderma adspersum are proper species, or merely different subpopulations. As late as 1985, the Norwegian mycologist Leif Ryvarden ended his summary of the Ganodermas with the pessimistic declaration that “chaos is an understatement for the present taxonomic status of the genus.”

Even today, Genbank, a database where scientists put DNA sequences from species they've studied, shows that Ganoderma applanatum is largely polyphyletic, meaning that many individuals that have been identified as Ganoderma applanatum are more closely related to other Ganoderma species than they are to each other.

The distinct, shiny surface of Ganoderma lucidum, also known as reishi. Source. 

The distinct, shiny surface of Ganoderma lucidum, also known as reishi. Source. 

Lessons Learned

A lot of the chaos of the early days of taxonomy was ended by the establishment of international committees on nomenclature, whose responsibility it is to keep track of past names and approve proposals for new ones. Still, despite this improvement, nomenclature continues to be a difficult subject. This tale goes to show that despite the brilliance of Linnaeus's system, the non-human biological world is reluctant to cooperate with how we think. Fungi are especially difficult to pin down, and DNA analysis has largely supplanted the old techniques of comparing physical features, as I discussed in a previous post. Sequencing has lead to massive reorganizations of fungal classification, as we discover that many similar-looking fungi are distantly related, and many closely related fungi are quite dissimilar-looking.

On top of this problem, the social dynamic among researchers can make learning names a nightmare – once someone's memorized one name, they're often really reluctant to learn the new one if a species is reclassified. As fungal reclassification is happening an increasingly brisk pace, both mycologists and guidebooks can be three or four names behind the times. Yet it's also much more challenging to try to talk about organisms in terms of a number or a DNA sequence – our minds work best when we can organize things, even if those things aren't particularly amenable to being organized.