© Steve Trudell
Danny’s DNA Discoveries – Agrocybe of the PNW
by Danny Miller
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Danny’s DNA Discoveries – Agrocybe of the PNW
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Introduction
Agrocybe - somewhat stocky, boring yellow-brown mushrooms with plain brown spore prints that usually grow on the ground, and usually smell and taste strongly farinaceous, and have a cellular cap cuticle. That means that the cells on the surface of the cap are spherical, so the top layer can break in any direction, unlike most mushrooms whose caps want to split radially. That means there is something subtly different about the cap compared to the many other genera in the large Strophariaceae/Hymenogastraceae family, and in the case of Agrocybe, it means the cap tends to crack like dried mud when it dries out, more so than most genera. The Psathyrellaceae, Panaeolini and Bolbitiaceae (Bolbitius, Conocybe and Pholiotina) also have cellular cap cuticles, but they are delicate, fragile mushrooms whose caps tend to wrinkle or sparkle in the sun. Still, Agrocybe are known as fairly non-descript mushrooms that can be hard to recognize. Most species are most common in the spring, which is interesting, although many can also be found in the fall. Cyclocybe - One of the species of Agrocybe that didn't smell strongly farinaceous, Agrocybe erebia, turned out genetically to not really be an Agrocybe, so smell is now a fairly good character of the genus (except for the species with a sclerotium). Agrocybe erebia is now in a genus of its own, Cyclocybe. It is somewhat closely related to Tubaria, but perhaps not closely enough to be in the Tubariaceae family. Time will tell if it gets its own family or not. The other claim to fame of this genus, since it only makes boring brown mushrooms, is that our most common large, urban, spring mushroom is an Agrocybe. abundant common uncommon rare - colour codes match my Pictorial Key and are my opinions and probably reflect my bias of living in W WA. Rare species may be locally common in certain places at certain times. |
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Agrocybe dura UK (=Agrocybe molesta EU?) - this grass species is on a remote branch inside Agrocybe, but multiple genes confirm it inside Agrocybe. Agrocybe praecox EU is found much more commonly in grass than this is, this is only known locally from one WA collection (not photographed), but it matches a bunch of EU and ENA sequences of A. dura. A. dura is reported as a grass species with a scant veil and spores >10u long (A. praecox has spores <10u long). We need more collections with large spores to sequence, because some match A. praecox, and we need spore measurements of this genetic species. Agrocybe praecox EU (=Agrocybe sp. 'IN01', =Agrocybe microspora IL) - This is probably the real thing, the EU species A. praecox, since matching sequences of this are more common across Europe than any other possibility, and because the pale tan colours of this genetic species match the original description of A. praecox better than the cap colours of the other possibilities. This is possibly the most abundant large, urban (wood chips, mulch, grass, or in forest parks that are inside cities), spring mushroom in the entire PNW. Since most people live in urban areas, and large mushrooms attract the most attention, it is probably the most commonly reported spring mushroom in the entire region. The cap tends to crack, it has a ring on the stem (that may be prominent or scant), and it smells and tastes strongly farinaceous. It is not usually very stocky. Agrocybe praecox is said to have spores 8-10u long. However, the holotype sequence of A. microspora IL, with spores 6-8u long, has the same ITS. Agrocybe sp. 'praecox-PNW02' - two collections (from grass in a forest campground and in an urban forest park, with somewhat dark caps) appeared at first to be a distinct genetic species as ITS is not the same as A. praecox. But then some had ambiguous locations making it difficult with ITS only to place collections in PNW02 or PNW03. Then LSU was discovered to be unique in PNW03, but the LSU of PNW02 matches that of A. praecox. What does this all mean? It means this species concept is reserved for those collections with ITS perhaps ambiguously of PNW02 or PNW03, but the LSU of A. praecox. Agrocybe sp. 'praecox-PNW07' - one WA collection with spores 10-11 x 6-7u from grass does have slightly different ITS than anything else known, but it has the same LSU as A. praecox. There is a second collection that like PNW07 has unique ITS that I haven't codenamed yet but I am waiting to see what its LSU is and if I can ever find an ITS match of it. Agrocybe 'praecox PNW03' - this species has a darker cap (often with olive tones), a usually marginate stem bulb, and is usually found in the wild in the spring (but may occur in an urban park or in the fall). The cap appears to crack less often than in A. praecox, and on average it may be a little more stocky. Like A. praecox, it also has a ring and smells strongly farinaceous. Because it is darker capped, it can be mistaken for Cyclocybe, which is not farinaceous. LSU is distinct for this species, so I believe this to be a real species. Note that some sequences have ambiguities, making it difficult to tell PNW03 and PNW02 apart with ITS only. Those collections may look different, and perhaps represent a hybrid. Agrocybe acericola NY - is a similar ENA species to PNW03 (darker cap found in the wild on hardwood debris) with similar spores. I think reports of this represent PNW03, as a half dozen ENA sequences purporting to be A. acericola do not match anything found in the PNW so far. But if you think you find this species for real in the PNW, save it for sequencing. There's one last wrinkle. One mating study showed that specimens from western NA from three different habitats (wilderness, urban wood chips and gardens, and grass) were three separate biological species (could mate with each other but not with the others). However, my study has shown that urban grass and non-grass species can be the same genetic species (the real A. praecox) and I have also seen evidence of hybridization between species, so I cannot explain the fact that somebody found that grass collections and urban wood chip and garden collection could not mate with each other.
Agrocybe praecox © Alan Rockefeller, A. 'praecox PNW07' © Yi-Min Wang, A. sp. 'praecox-PNW02' © Daniel Winkler
Agrocybe sp. 'preacox-PNW03' © Sharon Squazzo and Yi-Min Wang
Agrocybe flexuosipes PA (=putaminum EU, =Agrocybe smithii MA) - A. putaminum and A. smithii (from Europe and eastern North America respectively) are described practically identically - no veil nor ring and a club shaped stem that can be grooved and scaly (from numerous caulocystidia). It was once a rare invasive, but is now almost common in wood chips and gardens. In fact, sequences that purport to be from both species have ITS sequences almost identical. The only stated morphological difference is that A. putaminum has pileocystidia and A. smithii doesn't. We have DNA from CA of a specimen with loads of pileocystidia (it is the specimen in the photo below), and Henry Beker sequenced the type of Hebeloma flexuosipes without pileocystidia and they match. Therefore, he recombined it as Agrocybe flexuosipes. I declare them all to be synonyms since an exact ITS match was made with collections both with and without the pileocystidia, and from Europe, the east coast and the west coast. Somebody may do a multi-gene study and try and see if these species might be different in other genes, but as the ecology is the same, the odds of that bearing out seem slim to me. Agrocybe sp. 'smithii-PNW04' - ITS DNA of 2 collections from WA and 1 from France is 4 bp and 2 indels different in ITS from all the rest (about 1%). This could possibly be a distinct species, but I don't know how to identify it morphologically. The below photograph shows a quite pronounced umbo, but another collection did not have an umbo.
Agrocybe flexuosipes © MO user Byrain (2 images), A. sp. 'smithii-PNW04' © MO user Kavanagh (Thunnus)
Agrocybe sp. 'PNW05' - this recent discovery was quite large with a very long stem (19cm!). No observed veil, and a clavate stem, just like A. flexuosipes. It was found near old growth on the Oregon coast. The spores are 9-12 x 6-7.8u, similar to A. flexuosipes, so I don't know how to differentiate it yet, except for the size and habitat, but the DNA is quite distinct. Agrocybe sp. 'PNW06' - 6 bp different in ITS than PNW05, so it might be distinct, but it is also a very large wilderness species. Sequenced once from ID.
Agrocybe sp. 'PNW05' © Leah Bendlin, Agrocybe sp. 'PNW06' © Ed Barge (2 images)
Agrocybe pediades EU - This European urban grass species (sometimes in sand, gardens or manure) is somewhat small (<5 cm) with a somewhat hemispherical cap shape with a faint veil zone on the stem. Agrocybe subpediades and Agrocybe semiorbicularis are said by many to be the same and the DNA supports this. All three species all around the world have the same ITS DNA. Agrocybe columbiana n.p. - This is a new name being proposed for a local PNW very small species (<3 cm) found in grass, without a veil at all and with smaller spores, a greenish overall colour and rhizomorphs at the base of the stem. Please be on the look out for it so we can figure out what it is!
Agrocybe pediades © Andrew Parker
Agrocybe arvalis EU - This small grass or garden species does not smell farinaceous but grows from a ball or sclerotium at the base of the stem. No veil. Bitter taste. We need local DNA to confirm we have this species, but European and eastern NA DNA match up well, so we probably do.
unsequenced Agrocybe arvalis © Danny Miller |
Summary of Future Studies Needed
