The genus Hypomycesis a fungal group of mycoparasites. There are around 60 species of Hypomyces but the most widely known species from this genus is Hypomyces lactifluorum, more commonly known as the lobster mushroom. However, I feel as if this species shouldn’t hog the spotlight. Don’t get me wrong, I just love finding these cool red-orange fungi growing on Russula or Lactarius mushrooms. But there are other species of Hypomyces we should be even more aware of, especially if you eat a good number of store-bought mushrooms.
Across North America and Europe, the most cultivated mushroom is Agaricus bisporus, while Asia has a particular taste for oyster mushrooms, (Pleurotus sp.) and shiitake (Lentinula edodes). Agaricus bisporus is so widely distributed that it has many common names. Large individuals are sold as portabella, while smaller individuals have the name crimini. A white variety of the same species are sold as white button mushrooms. If you have eaten mushrooms, chances are, you have definitely consumed Agaricus bisporus. And this is where Hypomyces perniciosus comes into the picture.
Hypomyces perniciosus specializes in parasitizing the tissue of Agaricus bisporus. Many North mushroom farmers are all too familiar with Hypomyces perniciosus, the fungus that causes wet bubble disease. In 2017, Chunlan Zhang and his team carried out a series of experiments to better understand this economically important fungal parasite. Their work has helped us tremendously in grasping the underlying biology of this interaction. By simply inoculating both the mycelia of Agaricus bisporus and the actual fruiting body, the mycological community has gained so much important insight.
As it turns out, Hypomyces perniciosus doesn’t infect the mycelia of Agaricus bisporus. The parasite was only successful if it came in contact with the actual mushroom of Agaricus bisporus. Our mycological knowledge can help us explain this interaction through an evolutionary lens. Mycelia is almost always buried in some type of substrate. Whether that substrate is wood or soil, these fungal threads rarely are exposed to the open air. And this simple idea is the key. Most, if not all species of Hypomyces spread their spores via upwellings of wind currents near the forest floor. For the same reasons many mushrooms extend their spore forming structures above the still boundary layer just above the forest floor, Hypomyces perniciosus too only produces its spore forming structures on areas that have a better chance to interact with wind.
Fungi that spread their spores via wind have evolved mechanisms to extend their spore bearing surfaces past the still air directly above the forest floor. Just a few centimeters above the soil’s surface is all these organisms need to successfully expel their spores vast distances with the help of wind. This goes for Agaricus bisporus with their long stipes, and Hypomyces perniciosus that only parasitized the aboveground structures already past the still boundary layer of the forest floor.