Boletus rubriceps, a new species of porcini from the southwestern USA

It has been a long time coming, but a paper by David Arora and Jonathan Frank that was published yesterday in North American Fungi makes the case that the red-capped king bolete of the southwestern USA deserves to be treated as a separate species from the familiar Boletus edulis of Europe, Asia, and elsewhere in North America.

Boletus rubriceps

Boletus rubriceps, the Rocky Mountain king bolete

Henceforth, assuming this taxonomy is not challenged, it will be known as Boletus rubriceps, of Latin derivation: rubr- (from ruber, L.) = “reddish”; ceps (L.) = “heads/caps”. This will also subsume another older provisional name for the species, B. “pinophilus”, which seems not to have been well accepted due to its differences from the European species of the same name, and should now be deprecated for our local red-capped beauty. Also note that B. luridus var. rubriceps is a distinct and only distantly related species.

By whatever name, it is my very favorite mushroom for the table, along with its cousin, B. barrowsii. I’ve collected it in Arizona and Colorado, and seen collections in the high conifer forests of Utah and New Mexico. I’m going back to the White Mountains this weekend for what will probably be the last flush of the season, following the rains earlier this week.


The porcini (Boletus s.s.) are an economically important group of ectomycorrhizal fungi whose basidiocarps have a white tube layer at first, reticulate stipe, and white flesh.  The type species, B. edulis, is widespread and morphologically variable, with very little genetic variation from Eurasia to North America.  Here we describe a new species of porcini, Boletus rubriceps, from the southwestern USA. Morphological characters and molecular data (ITS and LSU) distinguish this species from the Eurasian B. edulis and North American B. edulis var. grandedulis.


Note — 08-29-2014

Bill Warner has responded to this post today with some very erudite commentary that you’ll want to read if you take an interest in scientific taxonomy. He also enclosed a pic of Boletus luridus to show just how different it is from the new B. rubriceps.


Read your post on Boletus rubriceps today, and the taxonomist in me choked at seeing Arora describe a “rubriceps” given the priority of Boletus luridus var. rubriceps. But, the plant/fungus Code allows homonymy of infraspecific names (although there is a “recommendation” that one should not generate a homonymous infraspecific name in a genus where that name already is present as a valid species).

All of this simply leads to confusion, which is why we “more civilized” zoological taxonomists do not allow homonymy at any rank, and infrasubspecific taxa have no standing. When I saw your previous posts about B. luridus v. rubriceps, my immediate reaction was “NO WAY”–luridus is that red-pored poisonous one–and I rest my case about the plant code bubba-wisdom allowing homonymy! In any event, I am a bit surprised that Arora would create such a homynym, though, because if Boletus luridus var. rubriceps is ever elevated to specific status, Boletus rubriceps Arora & Frank becomes a specific homynym and because it is the newer name it would be dropped and again leave our local bolete without a valid name until a replacement is proposed!

Note that there are at least 5 different red-pored/blue-staining boletes in AZ (and most people incorrectly call all “Boletus satanus”) and they are normally considered poisonous. In checking into the “…var. rubriceps” it was interesting to see that Boletus luridus is eaten in Europe and some in the New World (and even considered “good”), even though it has been shown to contain at least some muscarine. Muscarine has the same anticholinesterase activity as the old organophosphate and carbamate pesticides (and military nerve gasses, Sarin, etc.!), although low levels usually don’t generate much in the way of symptoms unless one’s cholenesterase levels were already low because of medications, etc.

Boletus luridus

(Bill Warner)

I collected a couple Boletus luridus on the way to the Foray (gave one to Chet for the show & tell). It immediately stained deep blue-black after cutting–check out the attached picture of the one from last Friday–that nearly black cut base had only been cut perhaps 2-3 minutes before! The species is very firm & heavy (like a good “former edulus” button)…maybe someday I will get up the nerve to try one. They are uncommon, but present along the Rim & Young roads, as is the also red-pored (but more maroon, like red velvet cake) and very probably poisonous Boletus haematinus–the most beautiful Arizona bolete in my opinion!

Cheers, Bill

About Christopher May

Chris is a radiologist in private practice in Scottsdale. He is married to Barbara May, with two grown children, Megan and Nick.
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11 Responses to Boletus rubriceps, a new species of porcini from the southwestern USA

  1. Max says:

    Am not sure what the objection is to name choice. Boletus rubriceps has never been used as a name according to Index Fungorum, so it was available for valid publication. If B. luridus var. rubriceps is raised to species rank by someone, they will have to choose a different name for it because Boletus rubriceps has already been published. This has happened numerous times in the past with other taxa. The fact that the taxon B. luridus var. rubriceps was published earlier than Boletus rubriceps is not relevant because their ranks (species and variety) are different. Nor is there going to be confusion as Boletus luridus is not a Boletus in the modern sense (i.e., it is not a porcini), and it will be transferred to a new genus in the near future as has been done for species of Butyriboletus, Aureoboletus, Retiboletus, Caloboletus, Exsudoporus. If B. luridus var. rubriceps is then published as a distinct species, the name rubriceps could be used in combination with the new genus name (for example, Luridiporus rubriceps if that name were chosen for the new genus). The process of creating new genera for boletes mimics what happend a couple centuries ago when all gilled mushrooms belonged to Agaricus but were then split into many genera. The splitting process means more names of genera to learn, which may be bothersome at first, but each name will be much more informative than Boletus. For example, the genus Caloboletus indicates a large bolete with blueing flesh and bitter taste, Butyriboletus indicates a dense, yellow-pored bolete with a reticulate stalk, Exsudoporus indicates a red-pored bolete that exudes yellow droplets when young (E. frostii), etc.

    • Debbie Viess says:

      Speaking of cryptic mushrooms, the above response was from a cryptic mushroomer:
      David Arora.

      Why not sign your name to your posts, David?

      Certainly the Colorado red-capped bolete in the edulis group is an easily recognized form. At what point do we start to use the new name? After date of official publication (apparently Aug. 28 of this year), or after this name/concept has been vetted and accepted by myco-nomenclaturists?

      This is on ongoing issue for many newly published species names, not just this one.

      Good to see you and others finally getting some of these well-known species described and even better, published.

      • Bill Warner says:

        Ha, I managed to mildly annoy D.A.–COOL–up to now I have just been buying him a gallon of gas every couple years with the royalties from all the copies of Mushrooms Demystified I keep buying and giving to my kids/relatives/friends! But, Debbie, start using the name now–it is published and official. If in the unlikely circumstance that future data suggest something different, the weight of the evidence (and new publications) will change the name “back” to whatever priority dictates.

        By the way, I too am happy that Arora et al are (finally) putting names on well known edibles that have been widely published in field guides with misapplied European species names for many decades. Given that there is such a large audience and “fan base” for the edible species, it would be great to get those well known ones done sooner than some tiny, obscure woodland things that nobody ever notices–now how about our local Macrolepidiota “c.f. procera,” etc., etc., etc.! 😉

        In any event, more power to ya boys (and girls)!!

        • Debbie Viess says:

          Hey Bill,
          Gotta have a sense of humor in this biz, eh?

          AS to your local “procera,” yes, there is no true procera nor bananas growing in NA. We don’t even get the quasi-procera in CA, alas, cause they are sure a yummy mushroom and I wish that we did! Dr. Else Vellinga is attempting to make some sense of this group. Fortunately, no matter what you call these procera-esque critters, they are all good edibles and easily IDed.

          Else (pronounced L-Zuh) is also one of the few people who is actually publishing new species names, so you might not have to wait too long for some results that you can actually use in your real life.

          But hey, ya call this living? (Old Jewish joke.)

          Debbie Viess

          • Bill Warner says:

            The Macrolepidiota shows up in the Huachuca Mts. in SE Arizona in late July in wet years; I posted some pics on the Mushroom Observer site (see #49830); if Dr. Vellinga is interested in specimens or a sample in 96% ETOH for DNA work, have her contact me and I can make an effort next summer to get material for her.

  2. Bill Warner says:

    Actually, my comment to Chris was because there already WAS confusion and the name HAD been used for a Boletus (Chris did a search for the name Boletus rubriceps and came up with the luridus variety–see previous posts). In animal taxonomy (i.e. ICZN rules) we recognize subspecies as a species group name, but infrasubspecifc “variety,” “form,” or “race” are no longer valid and don’t make it into the lit anymore (hence my facetious sniping). Sometimes those terms (historically) were used as an equivalent to subspecies, and sometimes they have been/can be elevated, but priority and availability rules are still present for homonyms. I was surprised to see when perusing the ICN that infraspecific names could be homonymous with specific names in the same genus, and it was only a RECOMMENDATION that authors do not do so.

    As for the generic limits & splitting, hopefully visible morphological characters (e.g. as you mentioned) will prevail; the “name every node” attitude of some on the zoological side had made a tough mess in some taxa…where one must first determine the species to know the genus within which to place a specimen! And, of course, the nodes on a cladogram shift back & forth like a pebble in the surf with each new gene and each new morphological analysis added to the mix. The search for “knowledge” is starting to give way to the “hope for stability in knowledge.” The fungal crowd has a long way to go for the latter when even common, well known taxa are currently unnamed…and that comes from a coleopterist working on groups where there are only a few dozen people in the world that care about the species he describes!

  3. jonathan girtman says:

    I think Boletus luridus var. rubriceps should be the one changed, since it’s cap(cep) is not really red(rubri.) I recommend Boletus luridus var. rubriporus, since the pores ARE red. 🙂 This is my greatest donation of knowledge to the scientific community, ever. Thank you, and good night! 🙂

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  5. maxfun says:

    Boletus luridus is a distinctly European species recently transferred to Suillellus where it is the type species of that genus. Given that Europe and North America do not share the same mycorrhizal boletes (except for a few circumboreal ones), what you have been calling B. luridus var. rubriceps is almost certainly a different species, perhaps unnamed but likely belonging to the genus Suillellus or possibly Neoboletus.

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