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Danny’s DNA Discoveries – Lactarius
by Danny Miller
Read my introduction to Russula for an explanation of what makes Russula and Lactarius unique among gilled mushrooms. Lactarius are notable for bleeding a latex, often called a milk, when broken, especially from the gills. The milk is usually white, but may be yellow, orange or red (or rarely blue!) and even change colours while you watch. They look somewhat like Russulas, but unfortunately, there's a lot more variety of statures, so you can't as easily learn to recognize a Lactarius on sight as you can a Russula - you may need to break it to see the latex. Not every "bleeding" mushroom is a Lactarius, though. The most common other "bleeders" are much smaller and more delicate Mycenas. Even small Lactarius are not very delicate (although they are fragile, as explained under Russula).
Some common features of Lactarius that might help you spot one are a frequently zoned cap, scrobiculate stem (covered with large, round spots of pigment), and a inrolled cap margin that might be bearded with hairs. Some species don't have any of these features, though. It's very common for them to taste acrid, or somewhat hot like a hot pepper, just like some Russulas. Not many other mushrooms besides Russula and Lactarius have that taste.
L. aestivus © Danny Miller, L. rubrilacteus © Steve Trudell
This clade has coloured milk, instead of the white milk that every other Lactarius will have (although the white milk in other clades might turn yellow in a matter of seconds). Usually you'll find orange or red latex, and the mushrooms themselves are usually orange or red too, often with a beautiful, prominent green staining. The east coast has a common blue Lactarius that bleeds blue blood and I'm very jealous. Most of them taste rather mild, or at most slightly bitter or slightly hot.
Normally there is a subgenus/clade named after the genus, so there "has been/should be/will be again" a clade "Lactarius", but right now its unclear to me why this group, which Hesler and Smith referred to as subgenus Lactarius, is now called "Deliciosi".
L. aestivus - very common bright orange species with little green staining
L. aurantiosordidus - uncommon dingy orange spruce species
L. deliciosus group - the (half dozen?) or so other species have not yet been sorted out, nor do we even know yet how many other species we have. But we at least know that we don't actually have L. deliciosus.
L. rubrilacteus - a very common dingy orange mushroom that turns green significantly
L. barrowsii - a rare white mushroom with red latex
L. rubidus and L. substriatus © Noah Siegel, L. occidentalis © Michael Beug, L. rufus © Steve Trudell
Candy caps are species of Lactarius that smell and taste like maple syrup when dried. They make excellent desserts, something unusual for a mushroom. To eliminate the more typical mushroom flavours from the food, the mushrooms are powdered and mixed into a fat - like cream or butter and used to make ice cream or popcorn or cookies. Unfortunately they are hard to identify because they do not smell or taste that way when fresh (some people use a lighter to burn them to see if they can coax a sweet smell out of them in the field for identification purposes). There also exists an Oregon candy cap "truffle" in this clade.
Mushrooms in this clade are usually small, with caps about 5cm wide and stems <1cm thick, but there are exceptions. They are usually orange-brown to red-brown and bleed a white milk. They are mostly mild or only slightly hot tasting (with one notable exception). (A few small brown or greyish-brown Lactarius that are not in this clade either have a velvety cap or are very slimy all over).
L. rubidus - our common candy cap, mistakenly called L. fragilis. The milk is watery-white like skim milk, as opposed to the thicker white "whole" milk of its lookalikes. The caps are dry.
L. aurantiacus group - more than a half dozen candy cap lookalikes (hard to tell apart from each other): L. subviscidus, L. substriatus (=L. subflammeus?), L. tabidus (=L. theiogalus), L. luculentus var luculentus, L. luculentus var. nov (unnamed variety mistaken for L. luculentus var laetus which is known from CO and may or may not occur here), L. alpinus var mitis (which may not be in the Russularia) and/or other unnamed similar species. Their milk is usually deep white and the caps may be somewhat sticky. They have been mistakenly called L. aurantiacus, but that species does not occur here.
L. atrobadius - a viscid, dark blackish-red capped small, mild species, often mistakenly called L. hepaticus, but that species has been reported here too, so keep an eye out for its dry cap and slightly acrid taste.
L. occidentalis - a dull brown to olive-brown capped small species under alder. (The rare, similar east coast L. carbonicola was reported once from Idaho and needs specimens. It is somewhat brick red with watery milk, and not much is known about its tree associations except it's sometimes found on burned ground).
L. rufus - a larger, brick red species that is extremely hot tasting
L. xanthogalactus - a large, orange capped species with a white stem and white milk that rapidly turns yellow, from OR and CA, may belong in the Russularia. Mistakenly called L. chrysorheus and L. vinaceorufescens.
Plinthogalus Clade - Lactarius fallax group
L. fallax group © Steve Trudell
L. fallax group - we have two common, almost identical species of Lactarius fallax, both mostly mild tasting with a beautiful brown velvety, suede cap. The two species are not separable, as thought, by the presence of marginate gills (dark coloured edges), so var concolor and var fallax (both described from Oregon) are not valid genetic varieties, only forms. There is also a false truffle in this clade in California.
L. pallidiolivaceus - a rare species described from Southern Oregon under pine, but it's also found in California with other trees. It is rumoured to be in this subgenus, because if you look closely, the cap is minutely velvety under a hand lens. We need collections and DNA. It is olive-grey with a very tough stem and scanty milk that stains tissues dark. Most collections are mild tasting but one was very acrid.
L. pallidiolivaceus © Christian Schwarz
Piperites Clade - everything else
This is the largest clade, so I will break them up into smaller groups. Most of them are at least somewhat peppery tasting (and most peppery species are in this clade).
Lactarius milk turning yellow © Danny Miller
Within 10 seconds or so, the milk of these species will turn from white to yellow before your eyes, as shown above.
L. scrobiculatus var canadensis - very common, yellow with a bearded cap margin and yellow scrobiculate stalk.
L. resimus - a rare, whitish capped, with a bearded margin and somewhat scrobiculate stalk.
L. xanthogalactus - possibly in clade Russularia, orange cap, white stalk (no bearding nor scrobiculation). CA and central to southern OR.
Lactarius pallescens © Michael Beug, L. montanus © A and O Ceska, L. aspideoides © R Lebeuf, L. representaneus © Ian Gibson
This reaction may take a few minutes, but the milk will stain the mushroom's own tissues purple. The milk itself doesn't turn purple, nor will the milk turn anything purple except other parts of itself.
L. pallescens - common, white capped species (a similar California species, L. californiensis, is reported from Oregon and needs sequencing)
L. montanus - common grey capped species (the similar L. cascadensis under alder with tan gills is rare and poorly understood and needs sequencing)
L. aspideus/aspideoides/pallidomarginatus - rare yellow capped species, one or more of these are present in the PNW, but we don't know which (L. aspideus group for now)
L. representaneus - rare, yellow cap with a bearded margin and scrobiculate stalk.
L. nectator © Steve Trudell, L. olympianus © Andrew Parker, L. pseudomucidus © Kit Scates Barnhart, L. glyciosmus © Steve Trudell
Summary - rare species marked in pink
A few small species (~5cm caps with stems <1cm thick) somewhat resemble the Russularia.
L. glyciosmus - small, grey, birch species that smells strongly of coconut! A sister species may be in the far north.
L. pseudomucidus - small, dark brown/grey cap and stem, beautifully contrasted with white gills, very slippery all over. It has many close relatives that are not quite as small which will be discussed below.
L. lepidotus - rare, only known from Mt. Rainier alder, nondescript grey-brown scaly cap
The rest of the species are stockier, with caps up to 10cm or so and stems often >1cm thick
L. 'necator'/olivaceoumbrinus - beautifully ugly, dingy dark greenish capped toadstools under birch/conifers. (L. turpis is probably a synonym for L. necator).
L. sordidus - similar east coast mushroom with a more yellow-green cap, rumoured from Idaho
L. pubescens/torminosus - pale/darker pinkish-orange bearded species found mostly under birch. We need to study if there is more than one variety of these.
L. subvillosus - orange, bearded, zoned cap. Scrobiculate stem from southern OR and CA.
L. olympianus (zonarioides?) - orange zoned cap, but not bearded nor scrobiculate. More common.
L. hysginus - be on the look out for this reddish brown Lactarius rumoured to have 2 varieties in the PNW.
L. alnicola - yellowish cap, slightly bearded and scrobiculate, uncommon from the eastern and southern regions.
L. payettensis - rare, apparently sticky capped, pale olive-buff with coarse hairs around the margin that darken in age, very acrid, the milk stains the gills dark and the white stem with ochre spots stains dark yellow-brown on handling.
L. vietus - a northern, grey, birch species with milk that turns grey and stains the gills grey.
Large, pale species
L. 'controversus' - large white Lactarius with pink gills, resembles Russula brevipes and Hygrophorus saxatillis unless you notice the latex.
L. pseudodeceptivus - similar conifer large, white Lactarius with perhaps a slightly bearded margin and without the pink gills. Nothing is known about this rare species, we need specimens.
L. argillaceifolius var megacarpus - very large (~20cm) purplish-grey species with gills that stain brown under oak in southern OR and CA.
Grey species with viscid stems - most need collections and so far don't have DNA records
L. kauffmanii - our most common grey capped species with a viscid stem, larger than L. pseudomucidus, stem paler than cap, described from Idaho. It is unknown if L. kauffmanii var sitchensis from Oregon is distinct or not.
L. mucidus - similar to L. kauffmanii, but smaller, perhaps with a pale cap margin, the milk staining the gills yellow or green. Two rare varieties reported, both need DNA.
L. caespitosus - also in the L. kauffmanii species group, with a buff spore print. Rare, needs DNA.
L. glutigriseus - another group member with the middle of the stem coloured but the top and bottom pale, without DNA yet.
Also with viscid stems, although not always obviously so
L. affinis - a cinnamon orange capped mushroom with a cinnamon tinged stem. No zoning.
L. trivialis - very closely related, but maybe darker in youth. We need collections to study.
L. flexuosus - greyish brown cap with lilac tones, zoned especially near the margin, and with a tinge of colour in the gills. With birch and cottonwood.
L. circellatus var borealis - suspiciously similar, with stronger lilac tints? Needs collections.
This is a separate genus now, of mainly tropical species. We don't have any confirmed species in the PNW, although the European Lactifluus volemus has been rumoured from far northern Alberta and BC. It is big and orange with a dry, minutely velvety cap and a fishy odor.
Summary of Future Studies Needed
Figure out how many species we have in the Lactarius deliciosus group, and give them names.
Figure out the L. substriatus complex and which is the real one, and verify it is the same as L. subflammeus.
Name our L. luculentus var. laetus if it is in fact distinct from the real thing.
Get official sequences of L. alpinus and its varieties, and L. atrobadius. Name our new local species if it is distinct from them as is believed.
Get sequences and collections of L. pallidiolivaceus
Figure out how to tell the two species of L. fallax apart
Get sequences of L. carbonicola and L. lepidotus
Verify what sequences of L. alnicola and L. resimus are and document the unnamed species sequences in this group.
Get specimens and sequences of L. californiensis and L. cascadensis.
Figure out which species are in the PNW of the L. aspideus group (L. aspideoides? L. pallidomarginatus?)
Figure out if we have an additional sister species of L. glyciosmus.
Get sequences of L. sordidus and figure out if it's here.
Figure out if the varieties of L. pubescens and L. torminosus are distinct, and if we have a third species.
Determine if we have L. hysginus and what it is and how many varieties we have.
Get sequences and specimens of L. payettensis
Figure out what L. pseudodeceptivus is.
Sort out L. mucidus and its varieties, L. caespitosus and L. glutigriseus and see if we have additional species.
Verify what L. affinis and L. trivialis are, and if we have an additional species.
Verify what L. circellatus var borealis is and get specimens and sequences.
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