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Delicious but damaging invasive golden oyster mushrooms found decreasing fungal community richness

A popular species of edible mushroom, golden oyster, has spread rapidly throughout the United States since escaping from cultivation into the wild. Now, a new study from researchers at the University of Wisconsin–Madison shows these mushrooms are spreading in every direction from their initial documented escapes in New York, Iowa, Wisconsin and Ohio. The study, in the journal Current Biology, also found that ecosystems invaded by the golden oyster support less diversity of fungal species and smaller numbers of native fungal species.

"The same way that plants and animals can be invasive, mushrooms can also be invasive," says Aishwarya Veerabahu, a doctoral student in the Department of Botany and lead author of the paper.

The study uses data collected from shavings of dead tree trunks in the UW–Madison Arboretum and Madison parks, allowing the researchers to determine what fungal species are present, both native and invasive. It also incorporates observational data from community scientists around the country.

Biodiversity loss is an ongoing problem across the globe, and loss of fungal biodiversity is a young, but growing, field of study. Without diversity in ecosystems, species have a smaller pool of genetics at their disposal to evolve and continue to survive. Since fungi provide ecosystem services in unique niches, loss of native species could dramatically alter how an ecosystem functions.

The study's takeaways included:

• Golden oyster mushrooms are displacing other fungal species, decreasing biodiversity. Trees where golden oyster mushrooms were detected hosted about half as much diversity of fungal species as trees where the golden oyster mushroom was not detected. Loss of native fungal diversity could have implications for the rate of decomposition and carbon storage capacity in forests. It could also deplete fungal species with rich potential for pharmaceutical development.
• Climate models predict that the range of habitability for this mushroom will increase. As the planet continues to warm, golden oyster mushrooms will be able to invade more ecosystems and continue to spread across the country. That could mean more ecosystems will lose fungal biodiversity in the future. In future studies, Aishwarya hopes to explore what traits make the golden oyster mushroom a successful invasive, as there may be an overlap with traits that make it desirable for cultivation.
• Community scientists made tracking the rapid spread of golden oysters possible. The team used visual observations reported on iNaturalist and MushroomObserver to map out the range of the mushroom in the United States. They also used that data to predict where the mushroom might be able to continue its spread.
• Just because there are no visible mushrooms on a tree does not rule out the presence of the golden oyster mushroom. The most recognizable part of the golden oyster, the part people eat, is actually just the fungus's fruiting body. The team tested wood shavings from trees to also look for the presence of golden oyster at a molecular level.