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Unusual discoveries made in the evolutionary patterns of porcini mushrooms

Keaton Tremble, PhD Candidate at University of Utah, and Bryn Dentinger, Curator of Mycology at NHMU and Associate Professor of Biology, recently published new findings from a study exploring fungal genetics. Their study investigated Boletus edulis museum specimens from around the world and found adaptation to specific environments play a significant role in genetic variation.

The species, more commonly known as porcini, is a gourmet delicacy that has been consumed by humans for thousands of years.

It is found beneath the soil and has a mutualistic relationship with trees, engulfing their roots as the fungus assists in decomposition of things in the soil. Symbiotic relationships involving the fungi and tree roots play essential roles in the functioning of ecosystems.

Tremble explained why porcini is a valuable research organism: “Because the porcini mushroom is found everywhere on Earth. It's a good system to understand how are these fungi adapting to their environment? And do fungi that are very closely related, do different things in their environment.”

These researchers set out to look at the broader patterns of genetic variation in Boletus edulis across the world, instead of comparing just several populations, they found surprising similarities across populations.

“And one of our big kind of initial finding is that no matter what porcini looks like, across the entire northern hemisphere, it can interbreed; it is still evolutionarily connected to each other,” said Tremble.

Results have pushed the envelope of how scientists define and study evolution. Often, geographic isolation plays a pivotal role in speciation. These scientists have found environmental adaptations to play a more prominent role, stressing the importance of selective pressures. While specific selective pressures are not known yet, one likely factor is adaptation to local hosts, as they are found underground in mutualistic relationships with trees.

Tremble and Dentinger present provoking evidence on evolution, suggesting porcini are evolving by way of diverse evolutionary strategies. They found one primary genetic lineage dominates European populations whereas several genetically distinct lineages have prevailed in North America, despite movement between populations. Dentinger discussed the implications of this.

“The population in Europe, it is panmictic. So there is no geographic structure across that whole continent. But it's the opposite case, when you get over to North America. And that is a pattern that has never been shown in any organism before, at least in an organism that is still undergoing reproduction, recombination across that range, which we've been able to demonstrate here,” explained Dentinger.

Not only has this research made new strides in the study of evolution, but it has emphasized the importance of museum collections in large scale studies like this one. The Natural History Museum of Utah has a collection of over 1.6 million objects available to researchers. In addition, Dentinger said contributions of citizens across the world play a crucial role in studies of this scale.

“It would be impossible for just two people like us to gather enough individuals in even our lifetime, to be able to conduct a study like this. So we rely heavily on the accumulation of resources over many years of collecting by many people, to gather the numbers that we need to do this kind of research,” Dentinger said.

Their paper was published in New Phytologist in October of this year, visit this link to read further. To learn more about the Natural History Museum of Utah visit nhmu.utah.edu.

Erin Lewis is a science reporter at Utah Public Radio and a PhD Candidate in the biology department at Utah State University. She is passionate about fostering curiosity and communicating science to the public. At USU she studies how anthropogenic disturbances are impacting wildlife, particularly the effects of tourism-induced dietary shifts in endangered Bahamian Rock Iguana populations. In her free time she enjoys reading, painting and getting outside with her dog, Hazel.