Introduction to Lichens: Dr. Klara Scharnagl

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What’s something from the microbial world you can go outside and almost be guaranteed to see? I’ll give you a hint. They are those gray, green, yellow, orange, red, and other colorful splotches on trees and rocks. I once even saw one while I was mountain biking. It was growing on an old boot! Those are lichens.

But what are these things we call lichens? And what are they doing hanging out on rocks and other substrates that don’t move? That’s what we’ll talk about in this episode of the podcast. Lichens fall within the microbial world because they are composed of microbes. You’ll learn from lichenologist Dr. Klara Scharnagl why these organisms are so cool and how to enjoy them for yourself in your daily life. You can think of this as your introduction to lichens, learning from an expert in lichens.

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What are lichens?

You may have encountered lichens before but were unaware. Often those colorful splotches that look almost like paint on trees, rocks, or even your mailbox are actually lichens. Sometimes they are nearly indistinguishable from paint. “I’ve collected splotches of paint off the sides of trees thinking they were lichens,” says Klara. After it rains, lichens can appear even more vibrant and colorful.

“Lichens will grow on any substrate that stands still long enough and doesn’t try to get them off.” Different species are specific to certain substrates. Some only grow on rocks, some on trees. But others grow on numerous substrates.

A lichen is more than one thing. It contains two or more different organisms living together in symbiosis, a fungus and algae or cyanobacteria. Either way, the fungus is always paired with another organism capable of photosynthesis. Symbiosis is when two organisms live together, and often in these relationships, they help each other survive.

The lichen eye

Once you start noticing lichens, you start to see them everywhere. Your eyes are opened, and all of a sudden, you will be surprised how many you’ll notice. It happened to me when I noticed them on my mailbox and thought to myself, how did I not see that before? 

“I call that getting the ‘lichen eye’ because it’s true. Once you see them, you can’t stop seeing them everywhere,” says Klara.

Are lichens extremophiles?

Lichens can survive many extreme conditions — situations like drying out completely without dying — because they sit and wait for conditions to get better. Although it might seem like we should put them in the category of extremophile, we need to consider the definition of extremophile before doing so. 

In a previous podcast episode about extremophiles, Dr. Adrienne Kish made a distinction between extremophiles and extremotolerant organisms. Extremophiles require extreme environments to survive. In contrast, extremotolerant organisms can tolerate extreme conditions but don’t require them.

So, although people sometimes refer to lichens as extremophiles because they can live in extreme environments (salty tide line or very cold of the north and south poles), they are not necessarily extremophiles unless they require those conditions. Lichens generally seem to be able to tolerate extreme conditions. So, the average lichen is extremotolerant rather than an extremophile.

What are lichens doing?

Lichens sit on rocks and trees looking real pretty with their neutral gray and green colors and sometimes vibrant orange and yellow colors, but what are lichens doing? Klara says she’s curious about this question. “Actually, in a way, this is one of the questions that I’m still trying to answer — what happens in the day of the life of a lichen? We don’t fully know.” But one thing is clear. They are “symbiosing,” says Klara. When you find them on rocks, pilings, trees, bones, or cars that have been abandoned, they are living in their symbiotic relationship.

In this symbiotic system, the fungus provides a lot of the structure and some protection to the algae. And in exchange, the algae photosynthesizes and therefore provides sugars to the fungus.

What is clear, though, is that lichens make an impact on the environments where you find them. In the long term, they are playing ecological roles. Many grow on rocks and secrete very small amounts of acid. Over decades and centuries, this acid breaks down the rocks, which in turn contributes to mineral release and soil formation.

In the short term, lichens play roles in the various nutrient cycles. Though they grow slowly, what they do adds up. In their own small way, they contribute to the carbon, water, and nitrogen cycles. For example, certain lichens contribute to the nitrogen cycle because their cyanobacteria can fix nitrogen out of the air.

Do lichens harm surfaces they attach to?

When lichens live on rocks and statues, they secrete acid. But does this acid break down and harm the surface? In general, it’s such a long process that it shouldn’t be a concern, says Klara. 

But in some cases, Machu Picchu, for example, people are taking a more serious approach to the lichens by removing them due to concerns that, given enough time, Machu Picchu would be eaten away by the lichens.

How do they get where they are?

The thought of lichens moving sounds counterintuitive because they are stuck to a substrate. However, they do have ways of moving around in their environments and ultimately reproducing. Here are a couple of strategies that Klara shared.

Like how the seeds of plants are moved by animals, wind, or water, lichens can send off their own seeds that the fungus makes called spores. However, this mode of transportation comes with its own challenges. First, the spores need to land on a good substrate for the lichen to grow on. Then, they need to find an algal partner to start growing with and form a lichen.

A second strategy for movement involves both partners of the lichen. It sends off little “packages” of the fungus and the algae or cyanobacteria. These packages can be soredia, which are fluffy balls of algae and fungal hyphae. Or they can be isidia, which are slightly more solid structures that microscopically (you can see them with a hand lens or under a dissecting scope) look like little fingers. These packages break off and can be taken to a new location by wind, rain, or animals (picked up on their feet while walking on the lichens).

Fruiting bodies of lichens

Lichens display peculiar structures that make them intriguing to observe, especially if you look with a hand lens. Their fruiting bodies can look like mushrooms, cups, golf tees, or discs. Some can even get quite large. And the colors are striking, like the red apothecia on certain lichens.

One group, called script lichens (as in script handwriting), are grouped based on how they look. They form fruiting bodies called lirellae that look like primitive hieroglyphics, says Klara.

These fruiting bodies are the reproductive structures of the lichen. These raised or embedded structures contain spores that are released when conditions are right.

Although lichens are two organisms, they have species names

One concept about lichens that is a bit strange is that they have species names since they are two or more individuals. As it became clear to scientists that lichens were in these complex symbiotic relationships, they debated over the best way to name them.

Naming them is complicated because of how they behave individually vs. together. If you separate the lichen partners and try to grow them in the lab, they’ll grow. But they won’t look anything like the lichen itself, says Klara. And many of the algae grow freely in nature but never form anything that looks like a lichen. Only when they come together, they form this thing we recognize as a lichen. And so, it would make sense to have a name unique for them. But it would also be confusing because it’s a name for two species. 

Lichenologists decided the best solution was to describe them and name the species from the fungal perspective. A reason for this is that the fungus forms most of the structure we see. So, for scripts lichens, they say, “Graphis scripta and its partner such and such algal species.” 

The diversity of lichen partnerships

These lichen symbiotic partnerships can vary, which is discussed in the book Entangled Life by Merlin Sheldrake. They don’t strictly contain one specific fungus and one specific algae that never pair with any others. Basically, every iteration you can imagine has been done by some lichen somewhere. One fungus can form a lichen with both a green algae or a cyanobacteria. And the same species of fungus can associate with different species of algae. 

However, it is to their advantage to be non-specific in their preferences for algae/cyanobacteria because a spore can land somewhere and form many potential partnerships. Otherwise, the chances to form a lichen would drop drastically. So there is some generalism in the association. But for every generalist lichen, there are lichens that require much more specific relationships.

How long do lichens live?

The relationships lichens form are quite long-lived. According to Entangled Life by Merlin Sheldrake, one lichen holds the record for the oldest at over 9000 years old. “In a way, you almost wonder if they can get close to that idea of immortality,” says Klara.

This ability to live for a long time is due at least partly to their tolerance to extreme conditions and tendency to grow slowly. One of the only parameters that limits them is their substrate. If an old tree falls or is cut down, that’s the end. But rocks take a very long time to break down. So, the upper limit of lichen age is unknown at this time. 

Can you see a lichen form?

The beginning of a lichen’s life is microscopic when the fungal spore meets an algal or cyanobacteria cell. Even finding the packages mentioned earlier, small soredia or isidia, after they land somewhere would be extremely difficult. When we see them, they have already formed into a lichen. So, it is a challenge for lichenologists to see them form, says Klara.

And growing them in the lab to watch them form comes with challenges as well because it is an artificial environment. But this controlled setting does give lichenologists a chance to see what might happen when a germinating fungal spore encounters algae or cyanobacteria.

Klara’s journey to becoming a lichenologist

Klara’s interest in lichens began with a passion for fungi in general. Growing up in the subtropical environment of Miami, Florida, with beaches and the Everglades, she had lots of chances to explore outside. Her parent’s backyard was filled with wildlife and lichens. But she didn’t notice the lichens until later after she had developed her “lichen eye.” 

She started noticing fungi when she was around six years old on a family camping trip to North Carolina in the Great Smoky Mountains. In awe of the various shapes and colors of the mushrooms they found, she became a mushroom hunter. Her parents encouraged her passion by giving her a mushroom field guide so she could identify her treasures. This grew into a lifelong passion. But she didn’t know until much later that this passion could also lead to a career as a mycologist (someone who studies fungi). At first, she assumed mushroom hunting was simply a hobby.

However, when she graduated from college and was deciding what to do, her mom reminded her of her passion for fungi, which encouraged Klara to potentially pursue it as a career. She volunteered at the Chicago Field Museum of Natural History and worked with a group that studied lichenized fungi. The passionate graduate students (at the time) Matthew Nelson and Todd Widhelm taught her about lichens and helped her realize this was what she wanted to do with her life. 

“I remember this day where I was sitting with Matt looking at lichens through a microscope and talking about all these cool facts about them. Like the fact that they can live under layers of ice in interior Antarctica and still survive. And he was so enthusiastic, giggling with excitement about how cool lichens are. And again, me a young college student seeing this grad student scientist giggling about how cool something is. I was like, yeah, I think I found my thing,” says Klara.

She went on to get a master’s degree in fungal symbiosis, studying mycorrhizal fungi (a symbiosis between fungi and plants via the plant roots). Then for her PhD, she worked in the herbarium with Alan Praither studying patterns of diversity. The main question she wanted to answer is why do we see lichens where we do?

For many other organisms like plants and animals, the tropics tend to have many species and high diversity, and the north or south parts of the world have fewer species. This pattern is called the latitudinal diversity gradient. And the idea is that the climate in the tropics is more conducive to life and metabolic activity than in the extreme seasons and weather of the north and south. But no one had asked this question for lichens. So Klara wondered if they would be an exception to the rule since lichens can tolerate extreme conditions.

After conducting fieldwork all over the world surveying diversity in the different latitudes, including the boreal forest in Canada to the Amazon rainforest in Peru, Klara found the answer to her question. They do, in fact, follow a latitudinal diversity gradient just like other species. Though she found a lot of species far north, there were even more in the tropics. Another exciting part of this research is that Klara may have discovered some undescribed species.

Studying lichens in the field and the lab

Lichenologists conduct their studies through fieldwork and experiments in the lab. So, Klara shares her experience traveling to tropical rain forests, subtropical forests, temperate forests, and boreal forests to study lichens, as well as studying them in the lab. In some ways, lichens are easier to study than animals because they don’t run away and hide. Once a lichen forms on a tree or a rock, it doesn’t move. So, if you see a lichen on the side of a tree one day, it will be there tomorrow.

Another significant difference from other types of fieldwork is how lightweight the tools are. When a lichenologist goes into the field, they only need a hand lens, a collecting tool (field knife or a hammer and chisel to remove them from rocks), paper packets to put the lichens in, GPS to get coordinates, thermometers, and DBH tape to measure the size of trees.

But what about studying them in the lab? In some ways, the lab environment can be more challenging than the field. Lichens are difficult to grow in the lab, and they grow slowly. Just getting enough for an experiment takes a long time compared to collecting lichens. Other biologists have simple, easy-to-grow model systems like E. coli bacteria, fruit flies, or mice. Lichenologists are still a long way from having a good model system in the lab.

However, one advantage to studying lichens in the lab is the opportunity to study the molecular side of things — DNA and RNA. Klara finds it very exciting to pull lichens apart and see what’s going on inside them.

Is it okay to collect lichen specimens?

Lichenologists collect lichens for fieldwork, but can we collect lichens to collect and explore them at home, maybe under the microscope? Klara shares her advice on enjoying lichens in our daily lives.

“I like to generally follow a convention that was taught to me by some of my earliest lichen mentors, Rick and Jean Seavey, at Everglades National Park. Lichens take a long time to grow. By the time we see even a very small lichen, it could be decades old or at least a few years old.” When considering taking a lichen or even a piece of one, think about what you would be removed from the environment. So, the rule Klara encourages us to follow that the Seavey’s taught her is this: “Always make sure you can see at least one other individual of that lichen you’re about to take. If you don’t, then don’t take it.”

Even in Klara’s biodiversity surveys, where she tries to collect as many samples as possible, she respects this rule. Scientists have a history of collecting other organisms to the point of harming them, says Klara. And so, it makes sense to be mindful when considering taking a sample, especially since we still know so little about lichens. Lichenologists are only just beginning to discover which lichen species might be sensitive or endangered.

So for us amateur lichenologists, here’s Klara’s general advice: appreciate lichens where they are. And bring a hand lens and a camera so you can take a good look at them where they’re growing. But let them keep doing their thing at their very slow pace.

The only exception is when you come across a fallen branch covered with lichens. Since the lichens on that branch will not thrive on the ground and will likely get eaten up by snails and slugs or dry up and die, it’s a safe bet that you can take a sample without worrying.

When it comes to cutting off a piece of lichen, it probably shouldn’t harm it. But the long-term effects are still not known for sure, says Klara. If you’ve left a piece of the lichen there, it should be fine because they are resilient. However, let’s follow the rule Klara gave us to leave the lichens behind so they can continue to grow slowly. And if we’re going to take anything, take it from something like a fallen branch.

Lichen Buddies: furry, felt lichens

One way Klara shares lichens with others is through a project she started called Lichen Buddies. These are felt and pipe cleaner representations of lichens adorned with googly eyes. With a Lichen Buddy, children (or anyone who is a child at heart) can get to know lichens in a cute and cuddly way, says Klara.

They were in part inspired by Giant Microbes, which are stuffed microorganisms (instead of getting a stuffed teddy bear, you get a stuffed bacteria) and part inspired by a Saturday Night Live sketch with Christopher Walken as a gardener who puts googly eyes on his plants. “The only way to know where you stand with someone is to look into their eyes,” says Walken in the sketch. “So, of course, when I made Lichen Buddies, I had to put googly eyes on them. Even though I do have to stress that lichens do not actually have eyes,” says Klara.

These soft, cute versions represent actual lichen species and come with cards that include a photograph and information about the lichen. So, it allows people to get acquainted with lichens while learning about them as they would live in nature.

This project began as a giveaway at science festivals Klara was involved in at the herbarium at Michigan State University. She used them in an activity where kids hunted for lichens in a room representing a miniature environment with lichen substrates like trees and rocks. They recorded the location they collected the lichen from (tree, rock, the ground) and whether it was a north or south part of the room. And when they finished, they took home their lichen buddies. So, they got to try out being a lichenologist and discover a career they might not otherwise encounter.

What it means to be a curator of lichenology

Klara has taken on a new position at the University of California Berkeley Herbarium as the curator of lichenology. Curators are responsible for collections, so she is taking care of a collection of lichens. You can think of it as a library of lichens where many different species are preserved and cataloged. This collection provides an enormous resource for folks who want to learn about taxonomy of lichen species, study certain species, or examine the distribution of species. So, her job will be to maintain and add to the collection, invite researchers to use it, and conduct her own research continuing to ask the questions she’s passionate about. She will also be involved in outreach, helping people to get to know what lichens are through workshops. So, lichen buddies will make an appearance in her work.

At-home microbiology activity

For the at-home microbiology activity, Klara invites us to go on a Lichen Hunt. But this is no ordinary lichen hunt because, as you’ll see below, she tells us what types to search for and how to look at them under the microscope.

Remember that it’s best to enjoy lichens where they are by looking at them close up with a hand lens and taking pictures. But if we want to take a sample, we should do so from lichens on fallen branches that will likely no longer thrive, rather than removing lichens that are firmly in place.

So, step one is to search for lichens – Generally, unless you are in a very polluted part of a city, you can go outside and find lichens on brick walls, trees, rocks, the sidewalk, and mailboxes. Look for them in unlikely places! They will surprise you.

Next, identify what kinds of lichens you find.

Types of lichens

Crustose – crusts, flat, sometimes partially within the substrate; look like splotches of paint

Foliose – large, green, leafy

Fruticose – three-dimensional, bushy, can have little tufts or palms, or even look like tiny trees

Then, figure out what proportions of each type of lichen structure you find. The proportions will tell you a little bit about the environment that you’re in.

Pollution: If you are in a highly polluted area, you will see more crusts. If you have good air, you will see more leafy and fruticose species.

Precipitation: If you have a certain amount of rain or a lot of fog, you will see more three-dimensional lichens. In lowland, tropical forests, you will see mostly crusts on trees because they have to deal with constant saturation.

Lastly, what colors do you see?

Lichens come in fun colors like orange and yellow. And those colors, like the shapes, can tell you about the environment. If you see orange lichens, you may be seeing nitrogen-loving or nitrophilic lichens. They may be there because of air pollution. But orange lichens on a rock could be thriving on the nitrogen from a little animal that uses the rock as its toilet. 

Lichen microscopy

If you come across a fallen branch covered in lichens, you can take home a lichen sample to view under the microscope. 

With a dissecting microscope, you can see much more detail, texture, and even different layers of color. “It’s like going on a safari across the landscape of the single lichen,” says Klara. You can even see tiny critters that live on lichens like springtails, spiders, and pseudoscorpions. 

Using a compound microscope opens up another world within lichens. You can take a look at the internal structure of a lichen. 

How to prepare a lichen sample for the compound microscope: With the lichen laying flat in front of you, take a razor blade and slice straight down once, and then slice straight down again so you have a very thin slice. Then, make a wet mount by placing the thin slice on a slide with a drop of water and a coverslip and take a look under the microscope. (Learn more about using a compound microscope here.) 

What you’ll see: For many lichens, says Klara, you’ll see a thick layer of fungi at the top, and below that, an algal layer with a bunch of green balls. And then, below the algal layer, there will be what looks like loose fungal hyphae and a lot of air pockets. And then, for some, Klara says, you might see a thick bottom layer. If not, it will end at the loose layer. 

Another part of lichens you can look at under the microscope is the fruiting bodies. Using the same slicing approach described above, it’s possible to see the spores inside. Lichenologists, Klara says, use spore characteristics a lot to identify lichens along with the visible characteristics.

With the compound microscope, you can also look at tiny creatures if you soak the piece of lichen in water. Everyone loves tardigrades, and it’s possible to find some from lichen. (Learn how to find tardigrades under the microscope here.)

Links & Resources

• American Bryological and Lichenological Society
• Ways of Enlichenment
• Seavey Field Guides & Subtropical Florida Lichens (Rick and Jean Seavey, Klara’s earliest mentors)
• Entangled Life by Merlin Sheldrake (book with a section on lichens)
• Lichens of North America -Deep dive, big investment, can key out lichens you find; may also find a copy to check out from your local library or university
• Next Time You Go Hikin’ Look For A Lichen (blog post)
• How To View Microbes With A Home Microscope (blog post)
• How to find a tardigrade at home under the microscope (blog post)
• Hand lens (use this to look closer at lichens on your hunts)

Connect with Dr. Klara Scharnagl

Dr. Klara Scharnagl is the Tucker Curator of Lichenology at the University of California Berkeley Herbarium. Klara discovered her passion for fungi at the age of six on a family camping trip in the Smoky Mountains of North Carolina, and many years later discovered her passion for lichenized fungi while working with scientists at The Field Museum of Natural History in Chicago. To her passion for fungi, Klara adds a passion for the study of symbiosis — organisms that live in close contact with one another for part or all of their lives — and the symbiosis continuum from pathogens (enemies!) to mutualists (buddies!). In her free time, Klara enjoys hiking and being in nature, writing poetry, and dancing!

Connect with Dr. Klara Scharnagl: Twitter, website
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