NEW SPECIES ALERT! Agaricus hortusdamarum discovered in Rome, Italy

Ciao, nuovi funghi!

Agaricus hortusdamarum a) holotype on litter of conifers needles; b) bulbous stipe and evanishing annulus; c) appendiculate cap; d) holotype ex situ; e) holotype scraped stem slowly coloured reddish brown.

The next time you stroll through your local park, you might want to take a closer look at what's growing beneath the trees.

A new species of fungi called Agaricus hortusdamarum was discovered in Rome, Italy, according to a paper published last week in the Italian Journal of Mycology. The mushroom was spotted growing on a bed of pine needles and grass under the shade of Mediterranean cypress trees in an area known as Parco dei Daini, "Fallow Deer Park," within the Villa Borghese Gardens—the most popular urban park in Rome.

The first Agaricus hortusdamarum specimen was spotted in November 2020. A year later, five additional specimens were discovered in the same park.

“Parco dei Daini” (Fallow Deer Park) in the Villa Borghese Gardens, Rome Italy, where “Parco dei Daini” (Fallow Deer Park) in the Villa Borghese Gardens, where Agaricus hortusdamarum was discovered.

Researchers from the Institute of Ecology and Earth Sciences at the University of Tartu in Estonia used internal transcribed spacer (ITS) data to determine that Agaricus hortusdamarum is a distinct species. ITS data is the standard for analyzing fungal diversity in environmental samples. This method allows researchers to assign a DNA barcode to each new species.

Agaricus hortusdamarum is most physically and genetically similar to the fungus Agaricus iranicus, a rare species that has only ever been found in the Guilan province in Iran.

Microcharacters of Agaricus hortusdamarum. a) fresh lamella fragments showing the large cheilocystidia and the basidia (in the insert) for comparison. b) dried lamella fragments mounted in KOH, basidia and basidiospores. c) fresh lamella fragments; d) cuticula fragments; e) velar fragments; Bar = 10 µm

"This study reports further evidence of the presence of particular and/or rare fungi in the urban Parks of Rome," the study authors write. "The surprising variety of fungi are probably related with the botanical biodiversity of trees present in the various ancient parks of the metropolis and confirm the importance to maintain and preserve the public green areas of the city."

This study caught my eye for two reasons. First, I love the idea of happening upon a new fungal species in an urban public park. Living in the city can make you feel starved of nature, but this discovery is a reminder that natural wonders are everywhere—you might just need to look a little closer.

Second, I'm currently planning a trip to Rome. I'll be adding a visit to Parco dei Daini to the itinerary. Wish me luck on my quest to spot an Agaricus hortusdamarum specimen, or perhaps a new fungal species of my very own? One can dream...

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