Instant Genius - Lichens, with Kerry Knudsen

Episode Date: May 1, 2022

Lichenologist Kerry Knudsen, from the Czech University of Life Sciences Prague, tells us all about the biology of lichens. Once you’ve mastered the basics with Instant Genius, dive deeper with Instant Genius Extra, where you’ll find longer, richer discussions about the most exciting ideas in the world of science and technology. Only available on Apple Podcasts. Produced by the team behind BBC Science Focus Magazine. Visit our website: sciencefocus.com Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Music just as the artist intended. Visit name audio.com to learn more. From BBC Science Focus magazine, this is instant genius, a bite-sized masterclass in podcast form. I'm Alice Lipscomb Southwell, the managing editor at BBC Science Focus magazine. In this episode, I talked to Kerry Nudson, a like-a-nosepherson. at the Czech University of Life Sciences in Prague. He's a world-leading lichen expert who has discovered dozens of lichen species and currently has 20 more on his desk just waiting to be described.

In this episode, he tells us all about the biology of lichens. So, Kerry, just to start us off, what is a lichen? A lichen is a symbiosis between either an algae or a cyanobacteria with a fungus. Lichens occur on wood, rock, soil, plants, and if you leave a car sitting too long, it'll grow on that too. So if there are a symbiotic association between this sort of fungus and algae, can that fungus or algae exist by itself, or can they only exist within this sort of lichen system? The algae can definitely exist on its own. The fungus has to form a lichenization or it'll die. So how many species of lichen are there? We usually say there's 18,000 described species.

There has to be way more than that. I just am working on a paper right now. I mean, we're working on in the lab here. We have 20 undescribed species from the southwest. Wow, the southwest of the U.S. is that? Yeah. And 7% of the surface of the earth is supposed to be covered by lichens. In the UK there, you have 1,800 species roughly.

Oh, wow. And how many of the lichen species have you discovered? Somewhere between 70 and 75, I've described. I don't keep count. We're busy on this new 20 right now. So you said that lichens can live on lots of different surfaces. Is there anywhere where they're particularly prevalent or anywhere that they can't live? Well, they're, for instance, you won't find them like in really deep shape.

or in the desert, you can go, I work a lot in the desert, you can go through large parts of the desert at low elevations and there's no lichens at all. So they do, each lichen has kind of, some for instance, like are only growing the mountains, some you find just growing in seawater and the tide. So they do have limitations. It depends on each species. Because they do seem to be particularly prevalent around the coast as well, don't they? if you're going for a walk along some cliffs, then you'll see a lot of lichens on rocks and things like there. Well, one thing is there aren't much trees,

but the main thing is there's more humidity, and that allows them, and with the fog and things, this allows them to photosynthesize more. And you said that they might maybe live on those rocks there because there aren't trees, but I mean, are lichens considered parasites of trees? Because that is one area where you see them a lot. Oh, no.

lichens aren't parasites of trees, but if you see a dead tree covered with lichens, or if you'll notice on one or two very large branches that are dead on a tree, you'll see a lot of lichens. That's because there's more sunlight there. Yeah, and you'll find on a really shady tree, you'll find less lichens, and a lot of times you'll find them more on the trunk because the trunk gets more sun, you know. So if I want to start identifying lichens, what's the best way to go about it? The best way to do it is to get a couple picture books and look at them. There in the UK, you've got Dobson's books, which are readily available and cover a lot of species. The main thing is, once you get used to it, once you look at some pictures, you'll probably be able to recognize them pretty easy.

As for identifying them, that's another problem. Because there is a lot of variety in lichens, isn't there? Some are quite tendril, some are sort of cup-shaped, others are more encrusting. Oh, yeah, yeah. That's why it would help looking at pictures, so you get an idea of the growth forms. But none of them, only a very, none of the ones you'll normally see look like mushrooms. So how long have Lycan's been around for then? I mean, they look sort of primitive, but are they? Have they been around for millions of years? Well, we used to think they came about 400 million years ago. A person, Matt Nelson, who had the pleasure drinking some pints with, recently in Prague. He has estimated that they came up 250 million years ago. That would put them in the Permian and extinction period.

And during that time, 90% of the species on Earth became extinct. And in the rock record, there's a giant surge of fungal species in the rock record. So possibly that theory is correct, and they've been around 250 million years. And have they changed a lot in that time or have they stayed quite similar? I don't think they've evolved, of course, but the basic lifestyle form, they have to form a thalus in order to have the algae or cyanobacteria grow within it. And that form has limitations. So I doubt if they may have been taller or bigger at certain periods, but basically they've had

to keep a thalus type form in order to grow the algae or. or a cyanobacteria with them and process the food from them. And could they still be evolving or do you think they've got about as good as they can get now? Oh, no, everything's evolving. So we have in Likens, even now that there's hybridization going on. So, yes, everything's still evolving anyway, even as humans. So maybe not culturally too much, but no, in small ways we are. So how long can lichens live for? Can they be quite long-lived species like corals that can sometimes live for thousands of years? Or are they really quite short-lived? A few are evanescent. I mean, they literally last one season or so, but those are relatively rare. Especially on hard rock, you can see lichens in the mountains or the desert that possibly are hundreds of years old or even thousand. There's an estimate that one lichen in the Arctic is an

I think it was 9,500 years old. But that's done by measuring it. And I think if I imagine that that was estimated on size and stuff. So I don't know how good that. That's pretty old. But a thousand years, I wouldn't be surprised if you could be up in the Alps and see a thousand-year-old lichen growing on hard rock. So how quickly do they grow then if you said you can calculate its age by looking at its size

or is it very much dependent on the species? It's more dependent on the habitat. Okay, so for instance, in the desert, you can, growth could be as little as zero to one or two microns a year. And then in other habitats, and, you know, with more moisture and better habitats, the growth can be in millimeters or maybe a centimeter or two. There are some lichens probably in the Amazon, and there's some reports of clodonias in,

North America, they grow fairly faster than that, but I'm not familiar with them myself. So how do lichens reproduce? Okay, well, they basically, they produce spores, and the spores are ejected into that, usually during rainy periods, because of from hydraulic pressure inside the fruiting body. Anyway, the spores are ejected and land, picked up by the air, wherever they land, They germinate and form a small hypha. The hypha has a very short period of time, depending on the algae around it, which also have short life cycles to lichenize one. And then if it lichenizes one, then it begins the slow process of forming a thalus.

It doesn't happen overnight. But if they can't get an algae, the heifer will die. Can you tell us a little bit more about this thalus? You mentioned it previously, and I wanted to get a better grasp of what it is. Okay. What you see is when you see a light and you'll see whether it's a flat or a bunch of little aerials or if it looks like a leaf or if it looks like a little chest piece. Anyway, that's the thallus.

And the thallus is formed for one reason alone to keep alive the algae. within the thallus, you have the algae forms a layer in it. Usually then there's a connecting to the substrate, there's a connecting area of fungal tissue. And then around the outside is formed a cortex or some kind of surface to protect the algae within. So for instance, when you see algae, when they're dry, they're usually, you can see the colors kind of dark or they might be red or yellow. But when they're wet after a rainstorm, for instance, you'll notice that they're green, greenish-looking. And that's because the cortex, whatever pigments are in the cortex, become translucent when

it's wet and allows sunlight in. Then when it's dry, the pigments help protect against ultraviolet light to protect the algae. But the thalus is there for one reason for that algae or cyanobacteria, to survive. So it can feed the lichen. That's why that's why lichens are not not killing trees. If you see a fungus growing on a tree, you know it's doing something to the tree, maybe eating the wood or something, but the lichen is there. It just needs a place to grow, but it's getting all its food from the algae or cyanobacteria within it. It is very much like a land coral almost,

isn't it? Because you think corals have got these algae within them that they use for food. So yeah, it's like the land version of a coral. Yeah, they are. It's the same thing, a symbiosis. So is there a particular place on the planet that's especially rich for lichens? Well, first off, the lichens are adapted to different habitat. We have lichens growing in the Antarctica. You know, we have lichens growing in the desert. So they vary in habitat. That's not the problem. Almost in any country of the world, you can find at least some habitats, if they're undisturbed of the right kind, you can find 100 to 500 species in. But average, like for instance in California where I did a lot of work, average site had 30 lichens in a relatively small area. Now, we just finished a study with Jan Vondrak here in the Czech Republic.

there was 674 species in 12 hectares. So it just depends, you know, and in the Amazon, I haven't seen figures for that, but you could have quite a few growing in the upper story of the forest. And if you've got that many species all in one area, will they compete with each other at all or not? Oh, yeah, they compete with each other. You can see this on rock. they'll sometimes they'll overgrow each other if they overgrow each other they kill the one

underneath you know and and and lichens they can be quite violent too because there's for instance like a nicholas lichens they begin as a fungus and uh there's four lands on a lichen or their hypha comes up through the through the rock or something and penetrates it from below then they steal the algae from the lichen that's there. So they get it and then, and then they grow out of it in a different shape. So there's a, there's a, there's kind of a period invasion of the body's natural, you know, but there's, there's kind of a period in there where there'll be like, you can see half of the old lichen and half of the new lichen emerging from it. That also, you can see the adaption of that evolutionary wise, because it's pretty hard finding an algae

sometimes, you know. So in that case, they steal it from somebody that's more successful. I can't find my own just snatch it from you instead. Now, we know that funguses, they'll decompose organic matter. Now, can lichens do this too? Well, no, not technically, no, because the lichen is the fungi are decomposing material for their food. Of course, the lichen is getting its food from the algae or cyanobacteria. What eats lichens then? Well, one thing that for sure eats lichens and causes us a lot of trouble in the herbarium if we don't freeze our specimens before we save them is mites.

You'll see mites on a nice wet morning all swelled up crawling around on lichens. And if they come back to the herbarium, even they'll stay alive for a while and eat the lichens in the herbarian. They die, though, if you freeze them. But otherwise, all the stories I've heard of deer or caribou, for instance, eating lichens, they always eat it in a bad time. So, you know, I mean, there's not much nutrition in lichens. But caribus that have been in bad times of the winter that have been cut open,

you have their bellies full of lichens, undigested too in a lot of cases, just to fill them up. Could we eat lichens if we wanted to? Oh, yeah. Well, people have eaten lichens when they're, I'm sure that George Washington in America fed his troops lichens when he ran out of food. They probably weren't too happy about that. The trouble with lichens, though, is they have secondary metabolites in them. So there's some lichens. If you ate enough of them, you could probably get sick in different ways.

But no, there's a, in Japan, there's a lichen that's eaten. But, you know, it's cut up and mixed with probably mixed with other things in rice and stuff. And that's the only one I know that for sure anybody eats. And I don't know too much about that one. So you couldn't sit down have a three-course meal of lichens. Yeah, yeah, no, no. Or if you did, if you did it be, you'd be in terrible situations. Now, everyone sort of thinks that lichens are really beautiful and it can be quite tempting to touch them.

Is it okay to do that when you're in the wild or does it damage them if you touch them? No, no, you won't touch them. They're actually, they're leathery. I wouldn't say this. Leathery maybe is not the right word, but they definitely have a texture to your fingers that is hard. It's not like saw. And there's only some that look like little granules, piles of those. Those you could, by touching them, you'd knock and move them around or something.

But those are not your normal looking lichen. And also you hear these stories that if you see lichens, they can perhaps help you navigate. If you look for them on tree stumps and things like that, is this true? With GPS units now, even the worst ones working, you really don't need lichens. But in different habitats, lichens, for instance, in the desert, you find lichens almost always on the north side. Okay. And then here in Europe, I'm in Central Europe right now. In Central Europe, you usually find them on the south side and the moss is on the north side. The only trouble is I was just in the desert and trying to get using my GPS to check what was the side of the rock the lichens were on.

There was lichens on all three sides. Three of the four sides directions had lichens on them. So yeah, probably not too good for navigating. don't rely on that then if you're lost in the ones. Yeah, only on memory, hopefully. So why did you decide to study lichens in the first place? I mean, there aren't many lichenologists around, so what inspired you to do it? Well, I myself was, I was a construction worker for 25 years and became disabled and was hoping to go back to college, you know, but couldn't because they figured I was too old

and having been a construction worker, I'd be a bad bet to send to a college. So I found out about Lycans, and I knew nobody was working on them in Southern California in the area I was in. So I started studying them. My main interest, though, in studying them or if I had become a botanist, I was interested in the diversity, in recording the diversity of life during this sixth distinction we're in right now. And so for the first 15 years, I worked in Southern California and did a gradient collecting lichens from the desert all the way out to the islands. There's eight islands off the coast of Southern California. That puts us through mountains, valleys, and along the coast, and then out onto islands along the seashore too.

And the reason I did that is in the 20th century, at the beginning of the 20th century, the first lichenologist in Southern California, for 15 years traveled all back and forth across South of California and left a record that's at Harvard of this specimen. So I knew if I built a collection, that could be compared with the 20th century, and hopefully in the 22nd century it'll be of some value. So I was interested in adversity, and actually I'm a taxonomist, so most of the time I'm either describing or revising species. And how much did it change in that 100 years, if you said this like an at the beginning of the 20th century did that trip and then you did it, then almost 100 years later, then how much had changed? Oh, yeah. Well, I've studied that really close. What happened is I've been to

Harvard twice to study the collections there besides my own fieldwork. If you ever see the Hollywood sign in Los Angeles, that's the Santa Monica Mountains. And that stretches from where you see the Hollywood sign down to the coast and then goes along the coast for about 25 miles. And that was his main study area back in those days without cars and stuff. Otherwise, he had to go by train and then horseback usually to go collect lichens. But at that time, he could easily get around that whole area by horse or by walking. In that area, 70 lichens that he collected, we did not find. Now, we found more lichens overall than he did, but we were able to go to areas farther north in the range and that he couldn't, that he normally wouldn't have been able to get into at that time.

We, of course, with a car, were able to drive all over the place, park, and then hike. And California has chaparral. It's kind of a brush. So it's hard to get around in if there aren't trails or cars. But still, in terms of comparing the species, 70 were missing. We figured out part of them had disappeared when they built houses and the highway along Malibu and places like that. They built. houses. They build a highway that runs along the front of the mountains. He could only get halfway up the coast in the front of the mountains. So that destroyed part of them. And then part of them were from farther north. So they must have been there when it was wetter. And since

the beginning of the 20th century, rainfall in southern California has been decreasing. So some of those probably died out because they were outliers and it was dry. But But the main thing that destroyed them, and which surprised me when I first went there, is reading his flora as expecting all these things growing on trees, and especially some rare little small lichens. And when I went there, there was hardly anything on the bushes. And then I found out what I found out later is darting as the Santa Monica Mountains near Los Angeles and Malibu there began to dry out in the beginning of the 20th century, by about 1920 or so, there was massive fires began.

And before that, it was estimated that a fire maybe only happened naturally there every 500 years. So since then, I think there's been 200 fires in the Santa Monica Mountains. Some of them have been very small, but other ones have covered burnt areas, large, large areas. And even the Hollywood sign was recently threatened a couple years ago, was that whole part of the mountain burn for maybe the 20th time. So, and what's causing the fires? Drought. And what's causing drought climate change?

That's probably the biggest cause of lichen loss in California right now, for instance. And now we have it happening here in Europe, Portugal, Spain, fires. We're having them in Greece, Italy. And here in the Czech Republic, which considers they have a drought if it's, doesn't rain one month out of the year. Now they have whole months where it doesn't rain sometimes hardly at all. And we started to have fires here too more often. That's just one effect of climate change. Thank you for listening to this episode of Instant Genius. That was the lichenologist Kerry Nudson. To hear him tell me even more about Lycans and how they are affected by climate

change. Head over to the Instant Genius Extra podcast. The latest issue of BBC Science Focus magazine is out now. a copy and store or visit sitesfocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist focal, name creates high-end audio systems, combining innovation with craftsmanship, so you can listen to music, just as the artist intended. Discover more at name audio.com.

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