Boletus edulis (English: cep, penny bun, porcino or porcini) is a basidiomycete fungus, and the type species of the genus Boletus. Widely distributed in the Northern Hemisphere across Europe, Asia, and North America, it does not occur naturally in the Southern Hemisphere, although it has been introduced to southern Africa, Australia, New Zealand, and Brazil. 

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Researchers at The Dentinger Lab at the Natural History Museum of Utah, USA, have been studying the genetic make up of the porcini mushroom.

Keaton Tremble and Bryn Dentinger, PhD, have suggested that porcini mushrooms have evolved in surprising ways.

Keaton Tremble explained:

“In North America, there is a strong stratification of separate genetic populations in local areas, despite the fact that they aren’t reproductively isolated. Yet in Europe, there is one lineage that dominates from Spain to Georgia to Scandinavia. 

“This paper shows that you don’t need isolation for genetic divergence. The force of ecological adaptation is so strong in Boletus edulis that even though you can disperse spores basically anywhere, there is strong selection to adapt to specific environments.”

According to the research in North America, different genetic lineages exist side-by-side, and despite genetic evidence of intermixing, local ecological factors played the bigger role in maintaining the distinction of these lineages.

Crucial to their research were the collections of mushrooms in natural history museums.

Bryn Dentinger said: “our study was all possible thanks to fungaria.”

Taking samples of the fungi and running statistical software allowed the researchers to genotype 792,923 SNPs (single nucleotide polymorphisms), which are the individual ways in which the 160 porcini genomes differed from one another.

 In the end, Tremble identified 6 major lineages. Feeding his data into mathematical models, Tremble uncovered a complex web of genomic mixing, where lineages remained distinct despite evidence that other lineages had mixed with them. Their modeling and geographical sample data showed that this ability to remain distinct was due to environmental adaptation, not physical isolation.