The world’s deadliest fungus has changed the way it reproduces as it spreads across the United States

Sci­en­tists have just dis­cov­ered a fright­en­ing rev­e­la­tion about the world’s most dan­ger­ous mold. It is pos­si­ble that the spread to new areas is pro­gress­ing because it is no longer able to breed like before.

Mush­rooms are famous for being poi­so­nous, but in real­i­ty, most of them only tem­porar­i­ly make peo­ple sick.

One extreme Euro­pean death mush­room (Amani­ta phal­loides) accounts for 90% of all record­ed mush­room deaths worldwide.

Researchers have now revealed how this dan­ger­ous plant spreads so quick­ly and eas­i­ly in North Amer­i­ca that it kills many peo­ple think­ing they’re eat­ing it.

A. phal­loides, which live in Europe, com­bine their genomes to cre­ate new generations.

It turns out that death spar­rows don’t need a mate to repro­duce. A study on A. phal­loides led by researchers at the Uni­ver­si­ty of Wis­con­sin-Madi­son in the Unit­ed States revealed that the fun­gus can use the chro­mo­somes of a sin­gle indi­vid­ual to form spores.

The dis­cov­ery is based on the genomes of 86 mush­room species col­lect­ed in Cal­i­for­nia since 1993 and in parts of Europe since 1978.

Of the US sam­ples, death­caps appear to have been able to repro­duce both sex­u­al­ly and asex­u­al­ly for at least 17 years, and in some cas­es 30 years.

Spec­i­mens col­lect­ed at two dif­fer­ent loca­tions in 2014 con­tained exact­ly the same genes and turned out to be the same fun­gus. In addi­tion, there are “indi­vid­u­als” that were col­lect­ed once in 2004 and “indi­vid­u­als” that were col­lect­ed again 10 years later.

“The inva­sive fungi’s diverse repro­duc­tive strate­gies appear to dri­ve their rapid spread, reveal­ing deep sim­i­lar­i­ties between plant, ani­mal and fun­gal inva­sions,” the researchers wrote in their paper. It has become,” he wrote.

Asex­u­al spores are formed by the fun­gus dupli­cat­ing its own set of chro­mo­somes into two iden­ti­cal pack­ages. Sex­u­al spores, on the oth­er hand, are formed when two dif­fer­ent par­ents each donate their own set of chro­mo­somes to their offspring.

Among fun­gi that form mush­rooms, many species are known to repro­duce with both sex­u­al and asex­u­al spores depend­ing on the sit­u­a­tion. No one knew.

Sex­u­al repro­duc­tion enables species evo­lu­tion and adap­ta­tion by intro­duc­ing more genet­ic vari­a­tion into pop­u­la­tions. How­ev­er, hav­ing an asex­u­al mode allows indi­vid­ual mush­rooms to spread rapid­ly and sur­vive for years on their own.

When mush­room spores land on a healthy sur­face, they ger­mi­nate and begin to set fruit. Thus, asex­u­al spores enable the wide­spread dis­sem­i­na­tion of indi­vid­ual mush­rooms with­out the need for mat­ing part­ners or genet­i­cal­ly dis­tinct offspring.

Deathcup mush­rooms are native to north­ern Europe, but in recent decades have been able to invade new habi­tats in oth­er parts of Europe, North Amer­i­ca and Aus­tralia. Asex­u­al repro­duc­tion may be one of the main reasons.

Inter­est­ing­ly, researchers found that the genes of asex­u­al spores col­lect­ed in Cal­i­for­nia between 1993 and 2015 were not sig­nif­i­cant­ly dif­fer­ent from those of the same species pro­duced in the same region.

A the­o­ret­i­cal mod­el sug­gests that indi­vid­ual death cap­sules could sur­vive for years by repli­cat­ing until they find oth­er death cap­sules to mate with.

“Some of these mush­room off­spring mate and some do not, and the cycle repeats itself,” the researchers argue.

While oth­er toad­stools are often bright­ly col­ored and poi­so­nous, death­caps are unre­mark­able and can eas­i­ly deceive humans and pets look­ing for deli­cious food in forests and parks.

Half the death cap is enough. With­out med­ical inter­ven­tion, symp­toms can appear as ear­ly as 6 hours after inges­tion of the fruit­ing body, and liv­er fail­ure can fol­low short­ly thereafter.

It is clear that a dead­ly hut infes­ta­tion pos­es a seri­ous risk to human and ani­mal health. In 2016, 14 cas­es of human poi­son­ing were attrib­uted to the fun­gus dur­ing a par­tic­u­lar­ly severe local death cap out­break in San Francisco. 

There are typ­i­cal­ly only a few such cas­es per year in the Unit­ed States.

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