Toadstool Tuesday
Drought fungi and Cheetah Spots (Whalleya microplaca)
Good evening, friends,
Another dry week, but when life gives us lemons we squeeze them into lemonade and quench our first. Today we’ll look at how some fungi function during drought-like conditions and then we’ll chase that down with a spotlight on Cheetah Spots (Whalleya microplaca). This is a fungus you can find year-round, regardless of rain, in the northeast as long as you can find one of the two host plants.
Fungi During Drought
One study looked at the impact drought had on fungal communities in two separate, one square hectare (100m x 100m) plots of land in the Brazilian Amazon. They used plastic sheeting two meters above the ground to prevent 50% of the rainfall from trickling through to the floor in one plot, while the other was left undisturbed. Though the two plots were 50 meters apart, after fourteen years the rain deprivation in one resulted in different soil compositions between the two that were more indicative of biomes thousands of kilometers apart.
The researchers found that dark-septate fungi (DSF) flourished both in species diversity and overall numbers during the dry season - augmented even more so in the simulated drought plot. DSF are ascomycete fungi (like morels or the Whalleya we’ll look at), that live within the roots of plants. They can wrap around or even within the plant cells.
Researchers also found a decrease in plant pathogens in the water-restricted plot, and particularly where DSF are richest. The researchers suggested the presence of DSF alleviates some of the drought stress in plants and also helps them ward off infection during these dry periods.
Another study in Nature found that mycorrhizal fungi can help plants adapt to drought conditions across various global climates (Reference 2). For all intents and purposes, fungi seem to help plants during drought. It’s truly a shame we can’t see all these profound plant and fungal interactions with the naked eye, in the same way we can marvel at mushrooms, but at least we’re learning about them now.
Cheetah Spots (Whalleya microplaca) Fun Facts
The name Cheetah spots was coined by Juniper from the New York Mycological Society, and that’s indeed what these spots on the wood look like. Cheetah spots only grow on the dead branches of spicebush (Lindera benzoin) or sassafras trees (Sassafras albidum) - two closely related, aromatic plants in the family Lauraceae.
A study out of China suggests that W. microplaca is one of several endophytic fungi that can cause a leaf blight or other foliar diseases in false starwort (Pseudostellaria heterophylla), also known as child ginseng (Reference 3). In some instances these endophytic fungi can help prevent disease, and in others they are the disease? Just when you think you know someone.
I couldn’t find anything concrete about the etymology but I’ll take a stab at it. The genus Whalleya might be named after the mycologist Anthony Whalley. As for the species epithet microplaca, placa could come from the Latin placare which means “to placate” and “micro” would indicate just a little bit of placating? In Spanish, placa is a metal sheet, so “small metal sheets” makes a little more sense. Still unclear.
Ecology
It appears that W. microplaca is an endophyte, living in the plant, that potentially turns into a pathogen, and is eventually a saprobe that helps digest the branch when it dies. You can find the fungus year-round and, per iNaturalist, the fungus only grows in North America east of the Rockies and in Japan. Per Texasmushrooms.org, the fungus can also grow on Yaupon holly (Ilex vomitoria). The black spots are the fruiting bodies of the fungus and can grow to a few centimeters long, but rarely get wider than 1 cm in width.
I emailed Ethan from NYMS about this fungus and he also gave me the heads up that there is another ascomycete, Creosphaeria sassafras, that you can find on both spicebush and sassafras. While W. microplaca grows crust-like on the wood, C. sassafras form small balls that protrude off the substrate. Aside from the substrate, Ethan noted the other distinguishing characteristic is the mustard brown color in between the inner and outer perithecium walls when you cut one of the balls in half. You can see all the intricacies of C. sassafras at Ethan’s iNaturalist observation here.
Nothing else really going on right now, enjoy your week,
Aubrey
References:
Buscardo, E., Souza, R.C., Meir, P. et al. Effects of natural and experimental drought on soil fungi and biogeochemistry in an Amazon rain forest. Commun Earth Environ 2, 55 (2021). https://doi.org/10.1038/s43247-021-00124-8
Cosme, M. Mycorrhizas drive the evolution of plant adaptation to drought. Commun Biol 6, 346 (2023). https://doi.org/10.1038/s42003-023-04722-4
Wang XA, Gao Y, Jiang W, Wang L, Wang H, Ou X, Yang Y, Wu H, Guo L, Zhou T, Yuan QS. Comparative Analysis of the Expression of Resistance-Related Genes Respond to the Diversity Foliar Pathogens of Pseudostellaria heterophylla. Curr Microbiol. 2023 Jul 25;80(9):298. doi: 10.1007/s00284-023-03410-0. PMID: 37490157.
https://www.gmsmicrofungi.org/xylariales/xylariaceae/whalleya/whalleya-microplaca.html
“In Spanish, placa is a metal sheet, so “small metal sheets” makes a little more sense. Still unclear”. In italian it’s the same: “placca” is a small metal sheet, so in the photo you have posted you can see the little black spots of the fungus on the tree.