The world’s most lethal mushroom is likely spreading into new parts of the United States because of an unexpected adaptation. According to a recent study, death caps, which can cause severe kidney and liver damage leading to mortality when consumed, have adapted their mode of reproduction to spur their spread in North America.
According to Brittanica, death caps are responsible for the majority of mushroom poisonings worldwide. The small Amanita mushrooms are native to Europe, where they’re widespread across the continent. Today, they’re found in all continents except for Antarctica. They likely spread to North America on the roots of imported trees.
Recently, researchers say they’ve figured out how death caps have been spreading so successfully to different parts of the United States: Unlike some mushrooms, death caps don’t need a mating partner to reproduce—they can reproduce both sexually and asexually. The ability to reproduce asexually—or “unisexually”—allows for the mushrooms to spread quickly and survive in otherwise isolated areas, while also having the ability to reproduce sexually—or “bisexually”— provides for genetic variation.
In the course of their research, the scientists looked at mushroom specimens collected in California and Europe between 1978 through the present. According to the study, death caps have been able to reproduce unisexually in North America for at least the last 17 years and potentially for up to 30 years.
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“The diverse reproductive strategies of invasive death caps are likely facilitating its rapid spread, revealing a profound similarity between plant, animal, and fungal invasions,” write the study’s authors. “The fungus is both unisexual and bisexual, revealing a previously unsuspected reproductive flexibility in a natural population of death caps.”