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New Species Discovery at South Mountain Preserve: Will Yaeger’s Leucoagaricus Fungal Find

You never know what fascinating fungi you’ll find at Wildlands Conservancy’s 14 nature preserves, whether it’s a first for science or a first for your very own eyes. 

Just ask Lehigh University alum, ’24, Will Yaeger. His little-white-mushroom find turned out to be a big discovery.

Last August, during one of his regular outings at South Mountain Preserve, Yaeger, a mycology enthusiast who was studying molecular biology and biocomputational engineering, spotted a species that was unfamiliar to him.

“I remember making a note at the time that it really didn’t look like it belonged to any species I recognized, which was exciting. I’ve become pretty familiar with the fungi of the Lehigh Valley, so when I find something I haven’t seen before I get very curious.”

Yaeger’s curiosity for all things fungi sprouted during the pandemic. Spending numerous hours outside acquainted him with countless species as well as an understanding of local fungal diversity. Many mushrooms need Pennsylvania’s diversity of oaks, pines, and beeches, coupled with rain, to merely exist, and destinations like Wildlands Conservancy’s 14 nature preserves provide the ideal environment for nurturing a full array of fungi.

Yaeger found the small white mushroom along the Alpine Street Trail, not far from the preserve’s infamous tiny waterfalls. Like many dedicated community scientists, he uploaded a photo of his observation to the iNaturalist app to record what he had found.

Based on the mushroom’s general characteristics, his best guess on identification was to place it into the order Agaricales, which includes mushrooms with gills. Narrowing its identity down to a specific species, however, would require more advanced methods.

Encouraged by his passion for biodiversity, Yaeger continued looking for an answer. He collected the specimen and sent it off to Mycota Lab, a fungal biodiversity research lab, for DNA testing. Through DNA sequencing and data analysis, Mycota Lab has identified 25,000+ mushroom specimens from across North America.

When the results of the lab’s analysis came back, they were exciting: the DNA didn’t match any known species. 

He explained, “The DNA sequence they got was very different from anything in the fungal databases. The closest match, which was a species in the genus Leucoagaricus, was only 90% similar. In DNA terms, that’s a huge difference—enough to make it clear that this was a new species.”

Only 15 specimens were sequenced, and that was enough to find one species never before documented in scientific study before now.

Since the species Yaeger found had not yet been described by science, it was assigned the temporary name Leucoagaricus “sp-PA01.” The name reflects the fact that it is the first new species of this genus to be found in the state of Pennsylvania. 

For Yaeger, this was also the first time he uncovered a new species.

“It’s very exciting to find a species that hasn’t been documented before right here in our own backyard—and this probably isn’t the only one like it around here. Fungi are so diverse and so understudied that there are almost certainly other mushrooms in the Lehigh Valley that haven’t been described yet.”

A recent NPR article estimates that only 1% of mushrooms are known to science. So, the field for fun, learning, and discovery is wide open when it comes to the wonders of fungus among us! And if you’re like Yaeger, maybe a simple walk in the woods, and some place like South Mountain Preserve, will put you on the path to discovering your own passion for our local natural world.

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