Good afternoon, friends,
This week's mushroom is Agaricus bitorquis, commonly known as the pavement mushroom. This mushroom was found on the west side of the ramble on 6/14/2021.
While this little mushroom may appear rather mundane, boy does it pack some fun facts in that compact cap and stipe. The squat stature is nothing to mock as it has been noted to push up through the cracks in concrete/sidewalks - possibly even creating those cracks. If you look at the photo below you can see the close proximity of this mushroom and the paved path (middle of photo by the fence post).
This mushroom is very similar both in physical and genetic traits to the white button mushroom, Agaricus bisporus, that you see in the supermarket . Like the white button mushroom, the pavement mushroom is edible and cultivated for consumption. However, if you were to forage this mushroom I would suggest you're cognizant of where you're harvesting. This fence line along the west lawn in the ramble is as conspicuous of a canine commode as they come. Each fence post carries an array of odors indicating which pompous upper west side pooch has recently paid a visit. The mushroom is also known to bioaccumulate heavy metals, specifically lead, so while it may not be the most conducive to consumption, you do have to admire its hardiness and resiliency to grow in such degraded environments.
In 2020, research was conducted in Spain that suggested mycelium from the pavement mushroom, A. bitorquis, can be cultivated and used as a form of IPM (integrative pest management) to combat a mite that hampers production of the more commonly cultivated white button mushrooms, A. bisporus. (Reference 4)
Although at first glance it looks like it could be mycorrhizal, growing out of the ground in association with tree/plant roots, but A. bitorquis is saprobic and gets its nutrients from decaying organic matter - in this instance probably buried wood chips. It is found growing in North America, Europe, Asia, and Australia in late spring through summer - and even into the winter in warmer climates. The mushrooms can be found growing in clusters, but I only found one other near this specimen.
In latin, "bitorquis" means 'two collars' and that's in reference to the two rings (or annuli - plural of annulus) that this mushroom has on its stipe. I didn't get a great photo of them above but you can see a better example here. As we've discussed before, the rings are the remnants of membranous veils that protect the mushroom while it grows to maturity. Agaricus mushrooms have a partial veil (attaching from the stipe to the margin of the cap and protecting just the gills) that has two layers of membranous tissue. The two rings are the result of the detachment of both of those tissue layers.
Additionally, this mushroom is subterranean and develops underground. This left me wondering what evolutionary advantage is conveyed by a subterranean mushroom. Perhaps the ability to avoid predation from above ground insects and animals is worth giving up the ability to have wind-blown spores. Maybe it relies on a subterranean organism - perhaps worms - to consume it and subsequently spread the fungal spores throughout the soil.
Let's savor the last full week of January,
1) Kuo, M. (2017, December). Agaricus bitorquis. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/agaricus_bitorquis.html
4) María J Navarro, et al. "Cultivation of Agaricus Bitorquis Mushroom As an Strategy for the Integrated Pest Management of the Myceliophagous Mite Microdispus Lambi." Pest management science, v. 76 ,.9 pp. 2953-2958. doi: 10.1002/ps.5840. Website: https://pubag.nal.usda.gov/catalog/7072145