The world’s deadliest fungus may be adapting to spread faster
Over 90 percent of the world’s deaths from eating mushrooms come from the “death cap” — a European species that can also cause kidney and liver damage. Only half of a mushroom contains enough toxins to cause serious harm.
The death cap, Amanita phalloides, is an inconspicuous fungus that can be light green, bronze, or white. It sits a few inches off the ground and is usually found near oak, beech, chestnut, birch, hazelnut, hornbeam, pine and spruce. It has a symbiotic relationship with the trees, depending on the roots for survival.
While not native to North America, the death cap is found in the United States and Canada and is likely introduced into the roots of infected imported trees.
Now, a new paper has made a surprising discovery about the death cap population in North America: They’ve started reproducing in a new way, which could fuel their invasive spread.
This could lead to major problems: young death caps are sometimes confused with edible “puffballs” or Asian paddy straw varieties.
Eating a death cap usually doesn’t trigger any red flags, either, Britt Bunyard, publisher and editor-in-chief of mycology journal Fungi, tells The Atlantic.
“Venomous snakes, reptiles, plants, [and] Fish have aposematic coloration showing they are venomous. not mushrooms. The dangerous ones are all mostly monotonous or brown, green-brown and bronze. There’s nothing in the taste that tells you what you’re eating is going to kill you.”
Currently, an average of one person per year dies in North America from eating death caps, reports the Atlantic.
In 2016, there was an unusually severe outbreak of death cap poisoning that affected 14 people. While all patients recovered, three received liver transplants and one, a child, suffered permanent neurological impairment.
No partner required for reproduction
In Europe, death caps reproduce by combining genomes with a mate. Analysis of 86 fungi collected in California beginning in 1993 and parts of Europe since 1978 suggests that US fungi can reproduce using an individual’s chromosomes.
‘The multiple reproductive strategies of invasive death caps likely facilitate their rapid spread and demonstrate a profound similarity between plant, animal and fungal invasions,’ the researchers say.
While other species of fungus can reproduce unisexually, the death cap was not known to have this ability. Experts say it’s a rare trait not typically seen in fungi outside of a laboratory setting.
This type of reproduction can limit genetic diversity and be harmful in the long term. The authors hypothesize that the fungi could use this strategy to spread further to find a mate.
“Some of the offspring of these fungi mate, some do not, and the cycle repeats,” the authors write.
While it’s not clear whether reproductive adaptation is responsible for the fungus’ rapid spread in states like California, the findings warrant additional investigation.
“I think they’re building a very good case,” Jesús Peña, a mycologist at Harvey Mudd College, told Science.
Thumbnail: image of death cap mushrooms, background edited by Cheryl Santa Maria. (Archenzo/Wikipedia) CC BY-SA 3.0