SciCafe: Snakes of Madagascar

SciCafe: Snakes of Madagascar - Transcript

Narrator:

You're listening to Science at AMNH.

In this podcast, join herpetologist Frank Burbrink on a journey to the remote forests of Madagascar, where his team recently discovered several new species of reptiles. Hear tales of life in the field and discover how DNA analysis helps identify new species in the lab.

This SciCafe lecture took place at the Museum on May 3, 2017.

This lecture included many original photographs, which can be seen in the video version by visiting the AMNH YouTube Channel, or the SciCafe section of AMNH.tv. To get the latest science lectures from the Museum, subscribe to Science at AMNH and rate us on iTunes, Soundcloud, or wherever you get your podcasts.

FRANK T. BURBRINK: Let me ask you guys a few questions, and be honest. How many people are here on a date? Raise your hands. All right. How many people told their date they're coming to see Neil Tyson? All right. You're not seeing him. You're seeing me.

We're going to talk about species and what species are.

And so this is one of the things I work on in Brazil. This is a monkey frog in Brazil. And the point of putting this slide up here is to remind me to tell you how important the identity of species are for biologists and evolutionary biologists, in terms of—if you were to do this is physics or look at this in physics or chemistry, they are our atoms in biology. They are the things that we study, the things that interact with ecology, interact with the environment, interact with each other. And sadly, they're the things we're losing at a massive, massive rate, right?

So I'm going to show you something here. If this line represents the number of species that we estimate to be on the planet Earth that are fungi, plants and animals—not microbes—it's estimated about 10 million species. In red is about how many species we've pretty much identified so far. And that's from all of human history, from quest for fire to when...I timed this when NWA got into the Rock & Roll Hall of Fame, okay? And that's a good moment, for sure. So we have a lot of work to do, right? And we need to train the next generation and the next generation of researchers.

But what we're facing is this, which...a day before this would have been a pristine rainforest. A day after it is basically nothing, for anything that I study, for reptiles and amphibians. And that's pretty shocking to you, right? So if you live your life, you may see some shocking events in your life. You drive a million miles you're going to see a couple of really horrible car wrecks, right? This looks like a car wreck except if you go into the field and go to the remote parts of the world—Brazil, Borneo, Madagascar—this is daily. This is not the exception. And this really is the world, unfortunately, right? So we're losing a lot of stuff at an unprecedented rate and we need to find it, we need to understand it.

And as a biologist and an evolutionary biologist I'm pretty selfish. I need to understand it because...I mean, this example is a phylogeny, it's an evolutionary tree of vertebrates, from sharks to mammals. And every time we lose something on that tip of that tree, that makes it much more difficult for us as evolutionary biologists to reconstruct and infer the patterns of evolution. And from these phylogenies and these trees, they allow us to understand things like how speciation happens, why some groups are really diverse and some groups are not. What causes speciation and all those elements? But as we lose these, it's almost like you're building a puzzle—that's the Mona Lisa—and you lose 50, 60, 75 percent of that puzzle, and can you tell me it's the Mona Lisa? Can I tell you what the reconstructed history is on Earth? But defining and understanding and delimiting species is quite hard.

So I have a quiz for you. In Row A or Row B there are three species here. Who says Row A has three species and who says Row B has one species? Row A has three species, anybody? No, you guys know I'm trying to trick you, right? Row A are simply rat snakes. You can go right outside New York within 30 minutes and see these guys, all the way down to Florida. They have multiple color variations. Very similar to if you look around the room, all of us humans which all share genes, we're all basically genetically the same, we have color variation as well. Row B are three different species and they look almost cursorily identical. Those are racers.

So it's actually very difficult sometimes to delimit species, especially on Row B, where we have something called cryptic speciation. That is, there are three different species, but looking at them cursorily, their bodies, their anatomy, it's very difficult to tell that those are three different species.

But how we model and understand species and speciation is—you have to kind of know a process. You have to know how this stuff is happening to understand how to delimit it. And I'm just going to show you a very basic diagram of how speciation forms, at least in the majority of ways, at least with vertebrates, how speciation forms.

If you start on this side, you see this blue population of snakes, right? And they may be all interacting, they're sharing genes, they're homogenized...and they spread out over the landscape in the second panel and third panel. And in the third panel, they're in some kind of different environment with some low level of gene flow. So the homogenization that was keeping them together, which is gene flow, keeping them the same species, is becoming reduced, ultimately to the point where it's reduced enough where you have adaptation and divergence. This one adapted to, say, a forest community, and this one to a grassland community, right?

But what is really c ool is we can use DNA and DNA sequencing to reconstruct these events over millions and millions of years, so almost like using, again, DNA as a time machine.

If you watch movies, including things I like, like Marvel movies and Sci-Fi stuff, you always see scientists looking at computer screens with double helices. You ever notice that? I mean, I've sequenced trillions of base pairs; I don't look at this stuff, right? Also, my computers don't make noise, right? You know, they always make little—I mean, unless you consider like, Slayer and NWA the noise that my computer's making. But really, what ends up happening is you see giant strings of DNA. And in fact, we don't even look at this anymore. It's just files; the computers are looking at it for us.

And so when I started sequencing DNA in the early '90s when I was a graduate student at LSU—if you think DNA on the screen is maybe a half a centimeter, one of those base pairs, when I was a graduate student if you sequenced this much DNA, especially at LSU, you had voodoo dolls out, you were happy, you were drinking, going crazy. Now within six weeks—so that amount of data now, within six weeks, I can produce three miles of data in terms of the length, right, of DNA data, getting close to sequencing full genomes.

And now with these data, we can reconstruct these evolutionary events and speciation. And so this is just these tubes representing speciation. You have an ancestral species, and that tube diverges into one species over time, and a second species over time. And the red represents us tracing mathematically the DNA backwards in time. And from being able to do that we can tell how much gene flow has happened through time, when it's ceased. We can tell the timing of when these species diverge. So again, it's the closest thing I think we're going to see in our life to a time machine, right?

And if you pull this back, you can create a phylogeny, which is, every one of those long lines to the tips represent a species, and you can pull this back for 20 and 30 million years to reconstruct the evolutionary history of an entire group and species. And mathematically, we can convert that graph into something that tells us how many species have been forming over a period of time. And this tells us a lot about processes of evolution such as things like adaptive radiation, when species colonize new areas, do they explode in diversity? And we can understand the tempo of speciation and how evolution produces diversity.

So now getting to the most important topic of tonight, which is me...I'm looking at snakes, and I like snakes a lot. And as I said, I've been looking at them since I was three years old. I'm still fascinated with them. They're way more predictable than people. And this is a shot of me working on these things in Madagascar.

And some people...I don't know, how many people don't really like snakes? No, don't like snakes. I said "don't like." Listen up.

Why the hell did you come if you don't like snakes? Right? It's in the title.

Okay, so I always have to try to sell this as like, why snakes are important. Snakes are important because they exist and because they're life on Earth and we should enjoy them aesthetically like you like the paintings at the MoMA, right? But some of these are actually helpful to human beings.

This is a species of copperhead that I found was a unique species of copperhead. You can find them in upstate New York. They're coming out of their dens right now. This species of snake produces a venom that's now being used to digest cancers for breast cancer and targeting them. So really cool stuff, right?

There's other species of snakes, like black mamba, that can—their venom basically neutralizes pain, the same way opioids do, but with no addiction, which is really important right now, and no respiratory distress. People forget that that's another issue with taking morphine.

And then thirdly, anybody here had Lyme disease? Yeah, well, I just got treated for it two weeks ago. That's a fun treatment, isn't it? Turns you to liquid. But basically there's some evidence now that having a healthy snake population reduces Lyme disease, because they're eating the rodents in which the ticks are on. This hasn't been published, but it looks like it's going that way.

So of course I've worked on beautiful snakes all over the world, mostly in the "new world." We still use this term in biology, which is, you know, Christopher Columbus terms, "new world," right, so North and Central and South America. And really wonderful snakes.

But one of the main places that I've been working for the last six years is the island of Madagascar, and Madagascar has some really fantastic properties for biologists. It's like a miniature compact Earth that we can manage and study. So you have an island that's about the size of Texas, where most of the species that we work on are only found on that island.

And I'm going to tell you something about the snakes of that island, the snakes that have one single entrance, one single dispersal to that island, and have diversified into almost all of the ecological niches that it requires every family of snake to fill in the rest of the world. So it's a perfect, what we call a "natural laboratory" for looking at these things.

So you guys know about Madagascar from movies, cartoons...forget that. Lemurs, you know, everybody likes lemurs. And then you see the cute chameleons, right, little bitty guys. That's an adult on the end of my thumb, and these other guys...but you know what? Forget that. That's about snakes. You're not going to see another lemur for this talk, all right? It's about snakes, okay?

So I'm talking about finding new species, and how do you do it? So you guys mind if I take you through what a typical expedition is like when you go out there for four to eight weeks to try to find species of snakes to reconstruct evolutionary history that's dwindling before our eyes? Okay.

Take a 19-hour flight, land in Antananarivo in the wee-wee hours. First thing we usually do is a have a beer with a local tortoise. Get to the hotel room, and get the Wi-Fi password, which is us very, very simple. I don't know why it's written down; I've never had a problem remembering that. You get your stacks of cash, it's a very cash society and it's very Weimar Republic kind of thing, where you have like, wheelbarrows for a single beer, of cash. Go to the local grocery stores, get the illegal Kinder Eggs, because I don't know, for some reason we eat a lot of Kinder Eggs in the field.

Load up the vehicle, and you drive all over the place to get to really, really rare habitats, driving through villages, seeing people—oh, and I lied, there is another lemur—seeing people with weird pet mouse lemurs. That thing bit the heck out of me and everybody in the village thought that was the best thing they'd ever seen. And you do drive through some gorgeous stuff, like the avenue Baobab trees—you know, this is really great stuff—and then past the avenue of colorful hats...

The friendly fossa, does anybody know what this animal is? It's related to groups of—it looks—a mongoose, but...it looks like a cat, and it's pretty giant. I have a really good film of it attacking one of my students, but I'm not going to show it to you.

You get the vehicle on the ferries. You have to cross a lot of rivers, put this thing on ferries, which takes up a lot of time. And all the while, we're catching snakes along the road.

Then you get to the village, you set up the field camp. You hang out with the villagers. You figure out how much it's going to cost to have them help you cook, help you watch the area, and defend you, potentially, against other villagers. So it's cool. You get basically the fort set up, you make the table. You get the DNA collecting materials, which are very simple, which are just these tubes, and chemicals to preserve the DNA, some tissue-taking material like scissors and forceps, and lighters to clean it. So it's very, very simple to do.

You get your field notes ready, you make sure the warm beer is still warm, and then you go out into the field. And it's either sometimes a 30-kilometre hike, straight into the field forever. Sometimes it's boat rides. Sometimes it's this, which is suspension bridges to get from one singhi–these are these kind of montain carse regions that have sort of forests trapped in between them that may yield new species. Yeah, you cross these things. You're not really sure who built them, but we're still alive.

And you know, it's funny, you always see people like Indiana Jones crossing it. Yeah, you cross it, but then you got to get back down, man, and that's not that easy, right? So like, you're scrambling down this, and wow, you're scrambling down this. you're also looking at all those cracks for lizards and snakes.

But you're in great places. You're, you know, at the top of the world in Madagascar, few places anybody has ever done research. And we're getting a lot of cool animals, nocturnal geckos, iguanians, some of the only places they occur in the old world. A bunch of lizards. Sometimes these things climb on you out of the blue.

But let's be for real, we're after snakes. And we catch a lot of them, and we find a lot of them for DNA stuff. So I'm going to just show you a few field shots. There's this beautiful Lycodryas Citrinus. These don't have really good common names. Bumblebee-colored, just gorgeous, do not bite. Different boids we find. Going sometimes to really degraded habitats and finding incredibly rare species that have never been sampled genetically, this guy, which we found within five minutes.

Doing a little bit of outreach, getting the kids involved. There are no venomous snakes in Madagascar, and so the kids hopefully will learn to like the animals instead of hate them and kill them.

And then ultimately with all that genetic data, produce these giant evolutionary trees, right? And this is sort of pared down. The normal number has 732 species for genomic-scale data for these guys. What I've done here is colored in red. This should be a little bit shocking. Those are all the new species we've found that are yet new to science, right? So about 40 new species that are awaiting description, and you guys are going to be some of the first people to actually see them. That green line marks the oldest species on there that hasn't been described, and it's about seven million years old. So we're still finding snakes that are at least seven million years old that have not been described.

And so some of these are spectacular, right? And so this was in the New York Times. This is Madagascarophis lolo, the "ghost snake." And I'm going to give a shout-out to Sarah Ruane, Dr. Sarah Ruane. She was the finder and lead author of that paper, and she was my doctoral student and is now a professor at Rutgers. So the snake madness continues. It's like the coils are wrapping around the United States of researchers.

And then finding other new species, these are new species of snakes. Different hognose snakes. This thing I love, called an Ithcyphus. A lot of people hate them in Madagascar. They believe they fall out of trees with their tails pointed down, and spear you and kill you. They don't, they don't, they don't do anything to you; they just sit there.

And great semi-fossorial aquatic snakes, more hognose snakes, crazy arboreal snakes, new species that have—again, are waiting to be—some of these, waiting to be named, that you only find at night and high-up in trees, more of their congeners and all this kind of stuff. A whole bunch of new species of cat-eyed snakes that come in multiple colors, but the colors lie to you; they don't tell you who's a different species or not.

And then my favorite, this Langaha, which is one of the few snakes on the planet Earth that have these weird nasal projections, and males have different ones than females, and we still do not know—it's 2017, I have no idea what they do with those noses and we're trying to figure it out.

So you've seen this, you've seen the species numbers, you see where we're getting. You know, it's like, you're talking, you know, me and our crew about six years collecting this stuff, and you're talking about 10 to 15 people. That is a lot of effort to find, you know, 30 to 40 new species of snakes. So we really do need the next generation of scientists, local scientists in Madagascar and locally on the planet Earth, to help find and describe all of this new stuff.

[Applause]

Narrator:

Thanks for listening to Science at AMNH. If you liked this episode, subscribe to Science at AMNH and rate us on iTunes, Soundcloud, or wherever you get your podcasts. To listen to our archive of podcasts, visit AMNH.org/podcasts.

The SciCafe series is proudly sponsored by Judy and Josh Weston.

SciCafe: Ghost Snake Stories in Madagascar, and related activities are generously supported by the Science Education Partnership Award (SEPA) program of the National Institutes of Health (NIH).