Bark Bonnet - Mycena corticola

Good evening, friends,

We return to Beebe Woods a week later and a good bit wetter. We experienced a substantial soaking this past Thursday which kept the woods wet and the fungi fleshy. I found this little bark bonnet (Mycena corticola) growing out of the hole in an oak left by a long-gone limb. Don’t be fooled by the size, the mushroom is small but the ecological impact is quite large — and hardly understood.

Fun Facts

Mycena (aka bonnets) are usually thought of as decomposers, but recent research has revealed the fungi are frequently found in healthy plant roots. This suggests that they can act not only as decomposers, but as mycorrhizal partners and potentially parasites when presented with certain environmental conditions.

Even before some plants have roots, Mycena are on the scene. The seeds of the orchid Gastrodia elata need a Mycena species to help them germinate. Mycena corticola is thought to be a bark decomposer and is theoretically benign to the tree as the mycelium doesn’t impact the vascular system (phloem and xylem). Mycena is a broad genus involved in myriad ecological interactions, many of which we have yet to understand.

One of the identifying characteristics for this mushroom is a coating of crystalline granules on top of the cap when young. I’m not really sure if that’s what’s going on here, I would think they might get washed away by the rain.

The etymology of Mycena comes from the Ancient Greek word for mushroom, mykēs. The species epithet corticola comes from Latin cortic- which means bark and the suffix -cola which means “residing within”.

I definitely already knew this but for those that were wondering: the difference between Ancient Greek and Latin is that Ancient Greek gave way to the Greek language that is written and spoken today, while Latin was the primary language of the Romans (and influenced by Ancient Greek as the Romans took over that part of the world). Latin is no longer spoken but it did inspire the romantic languages of today like Spanish, English, and French.

The little black dots are what appear to be insect frass (excrement). There was a tiny little insect crawling in and around the gills, presumably eating the spores or the gills.

Ecology

The fungus appears to be a benign, early decomposer and usually appears on the bark of standing trees, particularly oak. This particular oak was young and still alive, healthy looking in fact. The mushrooms pop up late summer through winter, with a preference on fruiting during or shortly after cool rains, and seem to have a global distribution.

These mushrooms are also found on conifer, and with such a wide distribution it makes me think this is a species complex. Different genetic species (determined by substrate, geographic location, etc.) that are all housed under the name M. corticola. To confirm the identification we would need to sequence the DNA.

The mushrooms are purplish brown when young, but those vibrant colors quickly fade to the light brown, almost orange you see here. The striations (lines) in the cap are an identifying characteristic.

The mushrooms usually fruit gregariously with dozens of little bonnets filling the bark crevices, but this was a solitary mushroom. I didn’t want to pluck this mushroom since it was the only one, and in the back of my head I kind of wished there was someone else there to share the experience in person.

I was here for an embarrassing amount of time trying to get decent pictures when the opportunity I’d been dreaming of presented itself: someone came walking their dog up the trail.

“Hey there’s a mushroom growing right out of this little hole”

“Okay” he replied without breaking stride nor diverting his gaze.

Another satisfied customer. Always fun to share a find in real life and quite possibly make someone’s day.

Thumb for scale.

Michael Kuo of mushroomexpert.com notes that these mushrooms exhibit marcesence (similar to the marcesence in trees we talked about a couple month ago) which means they can dehydrate and essentially exist in suspended animation. They wait until the next rain to rehydrate and continue to release spores. I might have too much time on my hands because I went back today to see if this proved to be the case. See for yourselves, but this tiny mushroom managed to get even smaller as they bide their time until the next rain.

There’s a full moon on Thursday night. I went to a talk last week from Peter Trull and learned that spotted salamanders (aka mole salamanders, Ambystoma maculatum) emerge from their subterranean dwellings on rainy nights after the March full moon. They head toward freshwater ponds and lakes to breed and lay eggs.

I’m not great at staying up late but I’m going to try and find some of those rascals this spring,

Aubrey

References:

1. Kuo, M. (2006, December). Mycena corticola. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/mycena_corticola.html

2. Harder CB, Hesling E, Botnen SS, Lorberau KE, Dima B, von Bonsdorff-Salminen T, Niskanen T, Jarvis SG, Ouimette A, Hester A, Hobbie EA, Taylor AFS, Kauserud H. Mycena species can be opportunist-generalist plant root invaders. Environ Microbiol. 2023 Oct;25(10):1875-1893. doi: 10.1111/1462-2920.16398. Epub 2023 May 15. PMID: 37188366.

3. Liu JJ, Yang XQ, Li ZY, Miao JY, Li SB, Zhang WP, Lin YC, Lin LB. The role of symbiotic fungi in the life cycle of Gastrodia elata Blume (Orchidaceae): a comprehensive review. Front Plant Sci. 2024 Jan 8;14:1309038. doi: 10.3389/fpls.2023.1309038. PMID: 38264031; PMCID: PMC10804856.

4. https://www.inaturalist.org/taxa/423924-Mycena-corticola

5. https://www.burwur.net/sinns/3etym.htm#:~:text=%2Dcola,%5D%20=%20%22bark%22).