MTPR

140 Years Of Scientific Assumptions Upended By Lichens From Missoula's Pattee Canyon

Sep 9, 2016

Recently, the work of lichenologist Toby Spribille, a research professor based part-year at the University of Montana-Missoula, has upended the idea that lichen are an alliance between just one fungus and one algae. In many lichens, a mysterious yeast is the third player in this symbiosis. 

On a beautiful, sunny September day, a friend and I went climbing on a granite crag in the Bitterroot Mountains. The air was crisp with fall, and the forest floor was accented by a yellow tinge of Oregon grape leaves, signs of the seasonal transition. Something of summer lingered, though: dust with a hint of mud and and an aftertaste of butterscotch from the large ponderosa pines that dotted the canyon.

We decided to climb a favorite route that leads up to the top of a two-hundred foot buttress. As I climbed, my hands moved from hold to hold. Grasping each felt as familiar as shaking hands with old friends. As I negotiated the moves to gain a ledge where I could secure myself to bring up my partner, I was struck by a colorful patch of lichen on the rock face next to me. Even though I’d climbed this route dozens of times, I had never noticed this microcosm of life smeared across the rock.

As I belayed my partner up to the ledge, I examined the colorful world on the rock in front of me. The closer I looked, the more I saw. The small cracks in the mat of lichen surged like huge crevasses in a micro-world, curving and breaking with the topography of the rough granite. The small polygons of green were flecked by a multitude of browns and grays.

I noticed now that there were what appeared to be several types of lichen covering the same spot of rock. Some appeared as a dust of color, others looked like a mishmash of small green bowls. The main patch in front of me was a sharp green acid color, abutting a patch of orange.

A lichen is a fungus that has a symbiotic relationship with a type of algae, or, in some cases, a photosynthetic bacteria. The algal partner photosynthesizes, providing the fungal partner with carbohydrates, protein, and other nutrients to live. In turn, the fungal partner provides protection for the algae (or cyanobacteria), sheltering it from the harsh mountain elements. As lichenologist Trevor Goward says, “Lichens are fungi that have discovered agriculture.”

At least that's what scientists thought - up till 2016.

Lichens live at the edges of environments, in places too hot, too cold, too barren, or in this case, too steep for other life forms. The life of lichens is played out in slow motion, far from human eyes. Some lichens only live on the high branches of giant old-growth trees. They grow very slowly, sometimes only a millimeter a year. Certain types of lichens are even used to date geological events such as the retreat of glaciers.

In order to reproduce, lichens work in various ways, such as cracking and breaking, where each part of the broken lichen can grow into new lichens. Another means is by fungal spores being picked up and deposited by wind someplace where they can germinate and hopefully find photosynthetic partners to cultivate.

Recently, the work of lichenologist Toby Spribille, a research professor based part-year at the University of Montana-Missoula, has upended the idea that lichen are an alliance between just one fungus and one algae. In many lichens, a mysterious yeast is the third player in this symbiosis.

Spribille's team and that of UM professor, symbiosis specialist John McCutcheon, studied the genes of two types of lichen collected in Pattee Canyon outside Missoula in 2011:  Bryoria tortuosa (tortured horsehair lichen) and Bryoria fremontii (wila). Both lichens appeared genetically identical; they consist of the same species of fungus, paired with the same species of algae. But while yellow tortured horsehair lichen is poisonous, brown-colored wila has long been a food source for North Americans. How could two species with such obvious differences look identical under the microscope?

To answer that question, Spribille widened his search beyond the genes of ascomycetes, the type of fungus commonly found in algae. He looked for the genes of all sorts of fungi, including those from a group of yeasts called basidiomycetes. With painstaking research, Spribille began to find these yeasts in the outer crust of species after species of lichen - including Bryoria tortuosa, the poisonous lichen that otherwise looked identical to the edible Bryoria fremontii, which has less of the yeast.

His findings, published in the journal Science in July 2016, confirm that among the large group known as macrolichens, symbiosis requires not two, but three symbionts: ascomycetes fungus, basidiomycetes yeast, and an algae. “There’s been over 140 years of microscopy,” says Spribille. “The idea that there’s something so fundamental that people have been missing is stunning.”

Climbing and science are about more than individual accomplishments; they're about a team of people working together to achieve a common goal. For climbers, this goal is usually about making it to the top of a cliff or a mountain. For scientists, it's about gaining a foothold of discovery on the world's complexities. For lichens, the goal is to exist on an exposed rock face hundreds of feet in the air. For that, they too must work as a team.

"Field Notes" is produced by the Montana Natural History Center.

(Broadcast: "Fieldnotes," 9/13/16 and 9/21 & 22/14. You can hear the program on the radio Sundays at 12:55 p.m., Tuesdays at 4:54 p.m., and Fridays at 4:54 p.m., or listen via podcast.)