Danny’s DNA Discoveries – Lactarius
by Danny Miller
Russularia clade - Candy Cap relatives
Lactarius rubidus
Our local candy cap species (described from Oregon) has a dry cap, watery-white latex (like skim milk instead of whole milk), and completely mild taste. The cap is somewhat of a dull orange-brown. It will smell like maple syrup when dried, but several almost identical looking species don't. Other species around the world, like L. fragilis and L. camphoratus, look very much the same but are not found here.
Lactarius rubidus © Noah Siegel
There are many candy cap lookalikes. Do not expect to be able to learn to tell them apart by my descriptions below, which are incomplete, as the differences are subtle and often microscopic.
Lactarius subviscidus
This lookalike, described from Washington, has a slightly sticky cap, thick white milk (like whole milk) and slowly turns slightly hot when chewed. The colour is sometimes a deeper orange- or reddish-brown.
Lactarius subviscidus © Noah Siegel
Lactarius substriatus (== L. subflammeus?) group
The type of L. subflammeus (a Smith species from Oregon) is the same as some Smith collections that he labelled L. substriatus, but we don't have his type sequence from Washington yet, so we don't know for sure that they are the same species.
Southern Oregon and California have two additional genetic species in this complex, which probably need new names. But so far, for Washington, we are assuming that we only have one species, and the oldest name is L. substriatus. It is also slightly peppery after a while and can be viscid and somewhat striate on the cap margin. Its milk may eventually stain itself and other mushroom tissue yellow. The colouration is sometimes very close to that of a real candy cap. L. subflammeus was said to differ by its milk not having any yellow staining properties, but if the species are the same, the yellow staining may have been overlooked or not be constant.
Lactarius substriatus © Noah Siegel
Lactarius tabidus (=L. theiogalus, = L. thejogalus)
L. tabidus is usually not viscid and its milk also can slowly stain yellow, like L. substriatus. It is a European species also found once (proven) near Salem, Oregon and reported rarely from OR and BC.
Lactarius tabidus © NAMA and the Field Museum of Natural History
Lactarius luculentus group
L. luculentus var luculentus, from Oregon, has an off-white spore print, a viscid cap and a slightly bitter and/or slightly peppery taste. It has very similar colouration to the others, but is uncommon. It is found under Douglas fir. DNA has been found in WA as well.
Lactarius luculentus var luculentus © Buck McAdoo
L. luculentus 'var laetus', from Colorado under spruce, has a pure white spore print, a somewhat viscid cap and slightly bitter taste. It is usually the brightest orange species. Smith, who described it, says he also found it in Washington, but so far, our common BC, WA and OR species is genetically different than Colorado specimens, and may represent a third, unnamed variety, found with other conifers besides spruce. Lactarius aurantiacus is the name of a European mushroom that we have incorrectly used for some of our false candy caps in the past, especially for L. luculentus. DNA of the true var laetus matching specimens found in CO has not been found here yet.
Lactarius luculentus 'var laetus' © Gabriela D'Elia
Lactarius alpinus var alpinus
This small, east coast Lactarius has a dry cap and is found under alder as opposed to conifers like most other related species. It is said to occur here but so far the DNA has only been found in Newfoundland and Europe.
Lactarius alpinus var mitis
Described from Idaho, this may be a distinct species in the Piperites and not a variety of L. alpinus, as specimens from other places in the Rockies (Montana and Colorado) that resemble its description have DNA that is quite different than var alpinus. We don't have a type sequence to know for sure.
See also the next species description.
Lactarius cf alpinus/cf atrobadius
This unnamed species (which is in fact in the Russularia) was collected twice near Salem, OR during NAMA 2018, and once near Mt. Rainier in WA in 2019. It was probably with conifers and once resembled L. alpinus and once resembled L. atrobadius (see below), but doesn't appear to be either. The sequences had 6 bp differences between them, but looking at the original chromatograms, I found noise in the graphs that showed that 4 of those differences were not real, so with only 2 bp between them, they could be the same species, with the cap colour varying due to age or weathering. More collections need to be made and studied of this species, L. atrobadius and all varieties of L. apinus.
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Lactarius sp. cf alpinus/cf atrobadius © Danny Miller, © NAMA and the Field Museum of Natural History
Other Russularias
These species look different enough from the candy cap that they are easier to identify
Lactarius atrobadius
Often mistaken for the European L. hepaticus, this species described from Oregon has a viscid, very dark blackish-red cap and a mild taste, making it one of the easiest species in this group to ID on sight. It is a conifer or mixed forest species. I am still looking for the DNA of this species to understand how it fits in and if some of our unnamed specimens might be this species.
Lactarius hepaticus
This has been reported locally, so keep an eye out for its dry cap and slightly acrid taste, and save the specimens.
probable Lactarius atrobadius © Noah Siegel
Lactarius occidentalis
A dull brown to olive-brown capped species without strong orange tones found under alder, described from Washington. It also has a mild taste. I need to collect DNA from it to know exactly where it fits in, but the microscopy shows it to be part of the Russularias.
Lactarius carbonicola is a rare, similar east coast species, perhaps in the Russularia, perhaps not. It 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).
Lactarius lepidotus is a rare, similar (perhaps in the Piperites and not in the Russularia) drab little grey-brown mushroom found only at Mt. Rainier under alder so far. It has a scaly cap. We need collections to analyze.
Lactarius occidentalis © Michael Beug
Lactarius rufus
This European conifer species can get larger than most other species, is a brick reddish colour, but most importantly is exceedingly hot tasting and can be identified on that basis alone, if you're brave enough to try it. It is quite common.
Lactarius rufus © Steve Trudell
Lactarius xanthogalactus
This large Lactarius doesn't look like it belongs in this clade, so it is also keyed out under the "milk that turns yellow" group, but it appears to be related. It has an orange cap, a white stem and white milk that rapidly turns yellow. It can taste somewhat bitter or acrid. It has mistakenly been called L. chrysorheus and L. vinaceorufescens. It's a southern species from California also found in Oregon, under oak and Doug fir and in mixed forests.
Lactarius xanthogalactus © Danny Miller
Two small Lactarius may resemble the Russularia, but are actually in the Piperites: L. glyciosmus (grey birch species that smells like coconut) and L. pseudomucidus (dark grey cap and stem contrasted with white gills, very slimy everywhere).