Danny’s DNA Discoveries – Lactarius
by Danny Miller
Deliciosi clade
Lactarius 'deliciosus' group
It is confusing to figure out how many species we have in this group, but some patterns are emerging. We don't have the real L. deliciosus, nor do we appear to have the real L. deterrimus as has been reported (the latter being very similar to L. aurantiosordidus, below, and perhaps that species has been mistaken for it).
1. L. deliciosus var areolatus, from Idaho, is not uncommonly found in the Rockies. It has bright orange latex turning reddish-purple and a cap that may crack. It appears we know its DNA. It could need to be promoted from variety to species level.
2. L. deliciosus var. olivaceosordidus complex, from Oregon, is not uncommonly found in the coastal states. It has muddy or reddish carrot coloured latex and yellow flesh under the cap. We have about 10 distinct local sequences, differing by up to 1% from each other. Perhaps this represents just one species with an unusual amount of genetic variation, or perhaps it will be decided to split this into some number of species. It/they could need to be promoted from variety to species level.
3. We also have an unnamed clade of sequences representing a sister complex to the L. deliciosus var. olivaceosordidus complex. Perhaps this is the mushroom that has simply gone by the name Lactarius deliciosus (it's either a mushroom in this clade or one in the L. deliciosus var. olivaceosordidus complex). This clade has sequences that also vary by about 1%, so it too may be split into more than one species. Clades 2 and 3 are very close to each other and it's even conceivable that they could all be regarded as one species with more than 1% variation in ITS DNA.
4. L. deliciosus var. piceus from Europe has also been reported from here (with spruce, latex turning purplish). I do not know what these reports represent, so we need collections to figure that out. It may turn out to be a duplicate of one of the above.
5. Lactarius aestivus (bright orange with little greening) and Lactarius aurantiosordidus (dingy orange with spruce) round out the group. These two are not confusing and are the best known species and are described in detail below. They were the low hanging fruit of the L. deliciosus group, as their DNA is very distinct, as is their morphology, so it was uncontroversial to name them as distinct species instead of varieties. Continuing to sort out the group will not be as easy.
Besides these species, we also have a handful of individual sequences from Eastern Oregon that are 5% different or more from each other, but it's suspicious that none of those sequences has yet occurred twice. Some sequences could have errors.
As a group, the L. deliciosus group mushrooms usually have zoned caps that are orange with orange latex that may turn reddish or purplish when exposed to air, scrobiculate stems, and they turn significantly green in age or after handling, making them quite remarkable. The taste is usually mild, but some may be bitter (like black pepper, not a hot pepper) and some may show a bit of the hot pepper acrid taste so common in other clades, but not usually found here. You can help us figure out how many species we may have by noting the tree associations (pine or spruce may make a difference and there may be other choices as well), how much they green and the exact colour of the latex and if it changes over time and how quickly. If we can find patterns and get sequences of them, perhaps we can someday figure out how many species we have and how to tell them apart.
Lactarius deliciosus group member © Steve Trudell
Lactarius aestivus
This group member is our most common species, described from Washington, with bright orange colours and latex. It grows with true fir and hemlock but does not turn appreciably green.
Lactarius aestivus © Danny Miller
Lactarius aurantiosordus
This small-ish spruce species is dingy orange, with dingy orange latex. It is a California species whose DNA has occasionally been found in Oregon and BC. Other spruce species without names so far will probably (hopefully) be larger, with brighter cap and milk colouring.
Probable Lactarius aurantiosordidus © Debbie Viess
Lactarius rubrilacteus
This very common species, described from Oregon, has red "blood" or latex, and is an especially cool species. It is a dull orange colour and can turn considerably green. It is a conifer species, under Doug fir and pine, at least.
Lactarius rubrilacteus © Steve Trudell
Lactarius barrowsii
This rare mushroom is very pale, almost white, but may have orange and green splotches. Its milk is red. It has been found in either Washington or Idaho (the report is conflicting), but is more common in the SW (Arizona, Colorado) under pine. It is probably an inland species.
Lactarius barrowsii © Dimitar Bojantchev