About 600 species of divergent fungi that never find a fit along the fungal family tree have been shown to have a common ancestor, according to the University of Alberta-led research team that used genome sequencing to give these bizarre creatures a taxonomic home of their own.
“They don’t have any particular feature that you can see with the naked eye where you can say they belong to the same group. But when you go to the genome, this pops up,” says Toby Sprebel, principal investigator on the project. He is an Associate Professor in the Department of Biological Sciences.
“I like to think of these as the platypuses and squirrels of the fungal world.”
Spribille, Canada Research Chair in Symbiosis, points to Australia’s famous Linnaean-challenging classification system Linnaean monotremes—which produce milk and have nipples, but lay eggs—that have been the source of controversy over whether they are real.
“Although no one thinks our fungi are fake, they are all the same because they look so different.”
Using DNA-based dating techniques, the team found that this new class of fungi is called lichenomycetesIt descends from a single ancestor 300 million years ago, or 240 million years before the extinction of the dinosaurs.
David Díaz-Escandón, who conducted the research as part of his doctoral thesis, explains that these “exotic” fungi had previously been categorized into seven different classes—a higher-order group that in animals is equivalent to the groups named mammals or reptiles.
Working with a team of researchers from seven countries to obtain material from fungi, he sequenced 30 genomes and found that all but one of the classes descended from a single ancestor.
“They were categorized, but they were categorized into such different parts of the fungal side of the tree of life that people never suspected they were related,” says Diaz Escandón.
These fungi include forms as diverse as ground tongues—a strange, tongue-shaped fungus that shoots vertically out of the ground—beetle gut microbes, and a fungus found in tree sap in northern Alberta. They also include some unusual lichens that live in extreme habitats such as the Atacama Desert in South America, the driest non-polar desert in the world.
“What’s really cool is that even though these fungi look very different, they have a lot in common at the level of their genomes,” says Sprybel. “Nobody saw this coming.”
Based on their genomes, which are small compared to other fungi, the team speculates that this group of fungi is dependent on other organisms for life.
“Their small genomes mean that this class of fungi has lost much of their ability to incorporate some complex carbohydrates,” said Spribel. “When we go back to look at each of these fungi, all of a sudden we see them all in some kind of symbiosis.”
He notes that the new research will be important for the broader study of fungal evolution, specifically how fungi inherit important biotechnological traits such as enzymes that break down plant matter.
The new group could also be a source of new information about previous fungal extinctions.
“We think it’s possible that the diversity we’re seeing today is just the tip of the iceberg that has survived. And we don’t have a lot of examples of this kind of thing in fungi.”
The research appears online in the journal Current Biology.