from the June 26, 2016 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins,
central Yucatán MÉXICO
The rainy season's arrival has very quickly transformed our brown-parched, extremely hot landscape into a humid, super-green and lush one where each afternoon clouds form, keeping sunshine down, and thus keeping temperatures lower. On Tuesday afternoon we had our best rain yet, exactly 50 mm (2in). In other words, mushrooms are up.
At the top of this page you can see some on a rotting log in deep, humid shade at the bottom of the shallow sinkhole, or rejollada, adjacent to the Hacienda. The caps are about 1-¾ inches across (45mm).
Some caps were flat, some concave and some convex, and the caps were smooth and somewhat sticky. The caps spread atop tall, slender stems that were fairly firm but not really tough or wiry, possessed no ring and arose from no cup, or volva, as seen below:
In that picture the dark items among the gills on the caps' undersurfaces are feeding insect larvae. A view of a cap's gills -- which split as they approach the cap's margin -- with some wormlike larvae among them, is shown below:
There you can also see that the gills are separated from the stem's point of attachment with the cap by a small distance. The manner by which gills attach or don't attach to stems is an important field mark, for in many species the gills connect to the stems in various ways, and in some they actually continue down the stem.
Maybe the most important feature for identification purposes, however, is one not shown, and that's the spore color. I brought two caps to the hut, placed them top-up on surfaces of two different colors, and the next morning found beneath the caps patches of pure white, the whiteness caused by white spores that had fallen from the gills during the night. I planned to photograph the spore print but a disturbed anole knocked it onto the dirt floor before I could get to it, destroying it.
First I tried to identify our white-spored, orange-yellow mushroom using the Google image search feature with key words such as "mushroom Mexico yellow," but nothing turned up. That's not surprising, since tropical mushrooms haven't been much studied and documented. So, using field marks mentioned above, and others, I "keyed out" our mushroom at both MushroomExpert.Com and MycoKey.Com. Both keys, which focus on Northern mushrooms, not tropical ones, led me to the "Mycenoid mushrooms" -- species belonging to the genus MYCENA and other closely related genera.
The last serious study of the genus Mycena was done in 1947. It recognized 232 North American Mycena species, and since then the number has increased. If that's the shape of Mycena taxonomy in North America, you can imagine what it is in Mexico. Michael Kuo, the expert at MushroomExpert.Com, says this about Mycena:
"DNA studies that have included mycenoid specimens have made it fairly clear that what we are now calling the genus 'Mycena' represents a pretty incoherent group of genetic entities, and we will eventually wind up with several genera and a much smaller genus Mycena, centered around the type species of Mycena, Mycena galericulata."
Therefore, about the best that can be done at this time is to post our photos and habitat information, with the claim that what's growing in the moist, shadowy bottom of the Hacienda's rejollada, probably is a Mycenoid mushroom.