This Fungus Makes Convincing Fake Flowers From Scratch

The yellow, flower-shaped growths lure in pollinator insects to spread the fungus’ spores

Fusarium xyrophilum fungus and yellow-eyed grass flower
Only the flower on the far left is real. The rest are made of fungus. Kenneth Wurdack, National Museum of Natural History, Smithsonian Institution

Scientists have discovered a type of fungus in Guyana that sprouts fake flowers that are dead ringers for the canary yellow blooms of the grasses it infects—all to trick insects into spreading its spores, reports Priyanka Runwal for Scientific American.

The fungus, called Fusarium xyrophilum, apes the flowers of two species of yellow-eyed grasses found in the savannas of Guyana. The fungus infects the entire plant and, in a more sinister turn, sabotages the plant’s mechanism for producing real flowers so that its imposters are the only game in town, reports Paul Simons for the Guardian.

According to a statement, the fraudulent flowers’ mimicry goes beyond the obvious physical resemblance. To lure in pollinator insects such as bees, the fungus’s spongy florets also contain pigments that reflect light on the ultraviolet spectrum, which bees and other nectar specialists use to find flowers. But the disguise doesn’t stop there.

According to the paper, published in the journal Fungal Genetics and Biology in late 2020, F. xyrophilum also produces a smelly chemical called 2-ethylhexanol that is also found in types of yellow-eyed grasses in the U.S. and is known to attract insects. Per Scientific American, the researchers were forced to make do with these North American relatives of the Guyanese grasses because of the travel restrictions imposed by the Covid-19 pandemic.

For the understandably bamboozled bee that falls for the fungus’ wiles, the anticipated meal of nectar and pollen is replaced by a face full of spores. The spores don’t appear to harm the insects, but F. xyrophilum gets a free ride to unsuspecting new hosts and an opportunity to mix their genetic material with spores from other members of their species, per the statement.

Researchers say this elaborate deception likely evolved to maximize the fungus’ ability to infect new hosts. Because the fungus can reproduce both sexually and asexually, the charade could also help facilitate sexual reproduction, or “outcrossing,” which introduces greater genetic variety and helps the fungus adapt to changing environmental conditions.

“This is the only example that we know of, anywhere on planet Earth, where the false flower is all fungal,” Kerry O’Donnell, a microbiologist at the U.S. Department of Agriculture’s Agricultural Research Service and co-author of the research, tells Scientific American.

Other plant-infecting fungi hijack leaves rather than make their own flowers from scratch. For example, Monilinia fungi infect blueberries and huckleberries and transform the plants’ leaves into flowery-smelling, sugar-secreting and ultraviolet-reflecting enticements for pollinating insects, according to the Guardian.

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