Although fungi of the genus Piloderma are common, scientists have now discovered five previously unknown species. One of these is one of the most widely distributed species in Northern Europe, while another is found only in old-growth forests. The discoveries, published in Fungal Biology, show that diversity in this genus is much greater than previously thought and that some of its species are at risk of disappearing as old-growth forest is logged.

Many of the fungi of the genus Piloderma are among the most common fungal species in Sweden. They are associated with trees in a form of symbiosis called mycorrhiza, where they help their hosts acquire water and nutrients in return for sugar. This makes them very important to the functioning and growth of forest ecosystems.

Researchers have now discovered five new species in the genus, which are described in a study published in Fungal Biology. With an additional seven new species that they published last year, Piloderma has now tripled in size, and grown from being a small to a medium-sized genus.

“We have seen for a long time how important Piloderma species appear to be in mycorrhizal symbiosis, and that the diversity of species in this genus far exceeds the number of named species. It’s satisfying that we can now, through delimitation and naming, make these species visible and communicate about them” says Martin Ryberg, professor at the Department of Organismal Biology.

Rare species found in old-growth forest
One of the new species described is Piloderma fugax. It appears to be rare and was found close to Gällivare in Sweden and in Trøndelag in Norway. Its ecology deviates from other species in the genus, as it only grows in old-growth forests. Since it is also small and difficult to detect, the researchers have given it the name fugax, which means shy, hidden or fleeting in Latin.

“It’s interesting but also a little frightening to see that in a genus like Piloderma, where we previously thought all species were common, there are such hidden old-growth forest species. They risk disappearing as the forest landscape is transformed from natural forests to plantations. Because of their insignificant size, no one have discovered them. I hope that our research can assist in making more people aware of and marvel at this kind of species and forests” says Sten Svantesson, lead author of the study.

Compared DNA to identity new species
In the study, the researchers looked for new species in Sweden, Norway, Finland and Lithuania. They collected fruiting bodies and went through collections already made in other research projects. Then potentially new species were compared with existing species to establish that they were in fact new.

“Species are deemed to be new if we, based on DNA sequencing, consider that we can establish that they are biologically distinct from existing species, that is, if no reproduction occurs between them. We then use data from soil and root tip samples uploaded into international gene databases from previous studies to obtain more information about their geographical distribution and ecology,” says Sten Svantesson.

Among the five new species found, was also Piloderma luminosum. This very common species was found to be easily recognisable by its almost luminous yellow to orange fruiting bodies. It has been distinguished from a species complex that includes the equally common species Piloderma byssinum. The difference between the two species is small but consistent.

“These two species often grow right next to each other and are commonly occurring in soil and root tip samples. By distinguishing them as different species, their differentiation can now be investigated – whether they have developed different niches or whether other factors have led to one original species becoming two,” says Sten Svantesson.

Contact details
Sten Svantesson, postdoctoral researcher at the Department of Organismal Biology and Museum Curator at the Museum of Evolution at Uppsala University.
E-mail: sten.svantesson@ebc.uu.se
Cell phone number: +46 703095588