Pinning Down The Origin Of Butterflies

IRA FLATOW: This is Science Friday. I’m Ira Flatow. One of the things that gives me the greatest enjoyment when I’m outdoors is watching butterflies. You catch a glimpse of a delicate, colorful butterfly flitting about. It’s like a mobile flower.

But it turns out that the evolutionary history of the butterfly has been a matter of scientific debate. Where did the first butterflies come to be? Writing this week in the journal Nature Ecology and Evolution, a team of researchers crunched the genetic data on butterflies from over 90 countries to try to put a pin on the butterfly origin. Joining me now to talk about the work and what they found is Dr. Akito Kawahara. He’s professor, curator, and director of the McGuire center for Lepidoptera and Biodiversity at the Florida Museum of Natural History in Gainesville. Welcome to Science Friday.

AKITO KAWAHARA: It’s a pleasure to be here.

IRA FLATOW: Nice to have you. There are lots of species, right? 19,000 species of butterflies around the world. But there is a question about where they evolved.

AKITO KAWAHARA: That’s right. Until now, we really didn’t know where they came from. Scientists had thought that they might be originating in Australia or Asia, but we didn’t really have a very good idea until now. Using the DNA data, we used fossils, and geographic information, and also plant data as well, what kind of plants butterflies feed on, tried to trace the history of how butterflies evolved on this planet.

And what we discovered from this is that butterflies likely originated either in North America or Central America and spread throughout the world, starting in North or Central America and then going into what is now South America, crossing various oceans and crossing over to Asia and to Australia, and, eventually, going into Africa and Europe.

IRA FLATOW: Wow, really interesting. Well, now that you have the geography pinned down, let’s talk about the evolution. Where do butterflies come from, evolutionarily speaking?

AKITO KAWAHARA: Butterflies come from moths. They’re actually a group of day-flying moths, so moths are hundreds of millions of years old, probably 300 or 400 million years old. And they came from aquatic insects. They’re related to these insects called caddisflies. And what we think happened is that these first moths came out from the ocean and started to feed on these very, very kind of primitive plants.

And then when angiosperms, these flowering plants, took over the world, moths started to take advantage of that. And then we think one group of moths somehow became day flying and just took advantage of the flowers that were available during the day.

IRA FLATOW: So how do you trace back where that event occurred, where the moths and butterflies separated a bit?

AKITO KAWAHARA: Yeah, so for this study, what we did was we went into museum collections, so we have about 100 authors that were part of the study. And we obtained tissues DNA tissues from museum collections pin specimens in the collections. And we took the DNA from these specimens with, of course, their permissions and so forth, and we traced their evolutionary history. We built what’s called a phylogeny, a family tree, of butterflies from thousands of specimens.

And then once we had that, we also included fossils, and that gives us a time point on when particular events took place. So once we have that, then we have a pretty good idea of how old butterflies are. And so our analysis led to the conclusion that they’re about 100 million years old. And then with that, we included geographic information from present day butterflies and then traced that back on to the tree, and when you do that, you can figure out where they came from and how they spread across the world.

IRA FLATOW: Wow, that’s cool. You mentioned museum collections. You see the dried pin displays of butterflies. Is there enough DNA there for you to sample and use in your research?

AKITO KAWAHARA: Yeah, the technology has gotten so much better in the last 10 years or so that we can now take DNA out of these dried, old museum specimens and get pretty good DNA sequence data that we weren’t able to do in the past. So in this study, one of the oldest specimens is from the 1940s, but we’ve done other studies where we can take– that we’ve shown to take DNA data from specimens dating back into the 1800s and so forth.

IRA FLATOW: Do you use live butterflies at all, going around catching them with a net like we see people running around?

AKITO KAWAHARA: Yeah, this project was really fun. It involved traveling to museum collections to obtain museum specimens, but it also involved going out into the field, too. So when we first started this project in 2015 or so, one of the first things we tried to do was go look for butterflies. So with the proper permissions and so forth, we went to different places around the world to look for particular butterflies that we could sample to include in the study, and we were able to do so.

IRA FLATOW: You mentioned that you also looked at fossil butterflies, but this isn’t a Jurassic park DNA and Amber situation, is it?

AKITO KAWAHARA: That’s right. It’s more compressed fossils, so butterflies that have happened to be preserved in layers of dirt or clay are the ones that we have included in the study. But compared to other organisms, like mammals, butterflies aren’t– they don’t have very hard parts, so they don’t preserve very well in the fossil record. So we had to use what we could. And we used about 14 fossils in the study.

IRA FLATOW: Are there species that you really wanted for the analysis but you didn’t have so you had to go hunting for them?

AKITO KAWAHARA: Yeah, one of the butterflies that has been this enigma or just an incredibly interesting butterfly, it’s called Baronia brevicornis. It’s this butterfly found in Mexico, and it’s been my kind of childhood dream to see this butterfly alive. It’s the so-called ginkgo of butterflies. But we were able to go and get a specimen of for this study, and it’s a very, very unusual swallowtail butterfly that’s very different from what we think– that we typically see in modern butterflies. But it’s still around in Mexico.

IRA FLATOW: Let’s talk about this evolutionary leap. Can you actually see in the records of butterflies and moths where it happened? Is there a definite a little mark there?

AKITO KAWAHARA: Different studies have shown that butterflies have come from moths, so I think there’s a pretty strong scientific agreement that that’s what happened. And almost all modern butterflies are day flying. There are exceptions, however. There’s a very, very interesting group of butterflies. There’s only about 30 species of these butterflies, but they’re found in the neotropics, so in South America and Central America.

And they are very cool because they are actually night flying. And what’s even more interesting about these particular nocturnal butterflies is that they have ears or hearing organs in order to hear predatory bats at night.

IRA FLATOW: No, really?

AKITO KAWAHARA: Yes, it’s really, really interesting.

IRA FLATOW: Because the bats are– they’re food for the bats.

AKITO KAWAHARA: That’s exactly right. They’re food, so they have to protect themselves. And they have these ultrasonic hearing organs on their bodies that allows them to hear the bats when they’re hunting.

IRA FLATOW: And so the daytime butterflies, they don’t have those.

AKITO KAWAHARA: That’s correct. Some daytime butterflies have ears, but they’re not ultrasonic in the sense that they can hear things like footsteps, or low frequency sounds, animals or predators potentially approaching them. They can hear those kinds of things, some of them can. But the ones during the day do not have these sophisticated hearing organs that a lot of moths have and these nocturnal butterflies have.

IRA FLATOW: Is there something that you personally don’t know about them or maybe science in general that you’d really like to know, something like the next big butterfly mystery that needs to be solved?

AKITO KAWAHARA: I’d say we’re in a time where we’re doing a lot of research on the genetics of butterflies and moths, and one of the things I’d really, really like to know more about is how they’re able to see. So the vision of butterflies is an area that scientists are very interested in. And also how they smell and how that’s genetically programmed, I think that’s an area of research that’s very up and coming. And a lot of it is we’ll a lot more in the very near future.

IRA FLATOW: Do we know that, since they go to flowers like bees do, is their eyesight anything at all like a bee’s eyesight?

AKITO KAWAHARA: Yeah, so butterflies are really interesting because they have what are known as compound eyes. So instead of one big single eye, they have millions of these tiny lenses or what one could call facets. And these all functioned together to be able to see the world around them. And each one has a photoreceptor that can sense a particular color. So with this assembly of different colors that they can perceive, they can put together this mosaic that they see from the outside world into a single image. And they can do this in ultraviolet as well.

IRA FLATOW: People have this image of butterflies as sweet, pretty things on the wildflowers, but they’re not all like that, are they?

AKITO KAWAHARA: That’s correct. There’s a lot of butterflies that are brown and kind of drabby looking. And the opposite is true for moths as well. There’s many, many moths that are out there that are extraordinarily beautiful, I would say even more beautiful than most butterflies, and most people are extremely surprised when they find out that it’s actually a moth. So moths are extraordinary.

IRA FLATOW: I was surprised to learn– we’ve talked about bees previously– that some bees are meat eaters. Are some butterflies, perhaps, meat eaters, too?

AKITO KAWAHARA: Yeah, it’s funny you ask this question because a lot of people think that butterflies come to flowers, and that’s what they do. And they pollinate, and that is true. However, a lot of butterflies also come to different kinds of things.

So some butterflies only come to things like tree sap. Others only come to decaying material. Others come to feces. We did, actually, a field expedition to Africa, and there’s this particular group of butterflies that are extremely cool. They’re very, very fast. You can’t actually really catch them in flight because they’re just so fast you can’t even see them.

But the one time you see them is when they land on the ground, and they love poop. They love baboon poop. So you have to be kind of standing around in front of this– in front of the poop, waiting for these butterflies to show up. And then that’s when you actually see it, and that’s when you have a chance to catch one if you’re trying to catch one.

IRA FLATOW: Were you as surprised as I am now listening to this when you discovered that?

AKITO KAWAHARA: Yeah, it was fascinating and pretty smelly expedition. But it was a lot of fun.

[LAUGHTER]

IRA FLATOW: When people go to these live butterfly exhibits, the butterflies sort of land on you. They must be– is there something on you they are looking to eat?

AKITO KAWAHARA: Yes, the butterflies, when butterflies land on you, it’s typically because they are looking for minerals. They are actually attracted to sweat. And if you look very closely, oftentimes, you’ll see their mouth part, which is a little straw called a proboscis, probing around, looking for things to drink. So it’s likely that they’re attracted to your sweat.

IRA FLATOW: So like the salt, the salt in your sweat, or–

AKITO KAWAHARA: Exactly.

IRA FLATOW: –other minerals.

AKITO KAWAHARA: Salt and other minerals.

IRA FLATOW: Really?

AKITO KAWAHARA: Mm-hmm.

IRA FLATOW: So they like salt also. They like mineral– well, obviously, they’re animals. They need those kind of minerals, too.

AKITO KAWAHARA: That’s right.

IRA FLATOW: We talk about species of plants and animals that are sort of living fossils that haven’t really changed much over time. I’m thinking like sharks, and the animal kingdom ferns, and the plants. Are they’re butterfly species that fit that category?

AKITO KAWAHARA: Yeah, some butterflies have not, at least, we think have not changed that much. The Baronia butterfly from Mexico is certainly one of them that has not appeared to have changed that much. They have very unusual features that almost no currently existing butterflies have. In the moth world, too– and remember, butterflies are really just a derived group of moths– there’s some really, really ancient moths that seem to have not changed. They still feed on ferns and very primitive plants, and their behavior seem to have not changed for millions of years, hundreds of millions of years.

IRA FLATOW: That is fascinating. I’m Ira Flatow, and this is Science Friday from WNYC Studios. So how did you get into this? What made you start to study butterflies?

AKITO KAWAHARA: Well, it’s funny. When I was a kid, I grew up in Japan, and I was really fascinated by insects. And it was driven mainly by my father, who was an artist, but he also had an appreciation for natural history and thought that kids should be able to go outside, and look for nature, and study nature, and so forth. So I feel very fortunate that he provided me with that opportunity because, every weekend, we’d go to collect butterflies and look for butterflies.

And that just– it became, eventually, a profession. I realized that I could actually be a professor to do this, and I just followed that dream. And here I am.

IRA FLATOW: So that shows the importance of bringing kids outside, getting into nature.

AKITO KAWAHARA: Yes, I think it’s extremely important, something that I’d say we all know as scientists should be doing. The world is changing pretty quickly, and natural environments are disappearing or changing. And I think appreciation is really important and getting our kids out there because kids, in general, they’re innately interested in the living world.

And with insects and butterflies, you just have to look in your yard, and they’re there. And just stop and see, and they’re just fascinating and beautiful. And there’s so much to learn from them.

IRA FLATOW: And what I hear you saying about nature changing is get the kids outside to look at the butterflies while the butterflies are still here to look at.

AKITO KAWAHARA: That’s right. The butterflies are still here to look at, but I guess I would say that some of them are disappearing. And that’s something we need to be aware of. And there’s a lot of things we can do to prevent that from happening, things like planting native flowers and plants that are used by butterflies, creating habitats that are good for them. I think these are just really simple things that we can all do, and if all of us do it together, I think it will have a big impact.

IRA FLATOW: Is it harmful to grab a butterfly by the wings like we try to do in the garden?

AKITO KAWAHARA: So butterflies have scales all their wings, and there–

IRA FLATOW: Is that right?

AKITO KAWAHARA: Butterflies and moths are in this group of insects called Lepidoptera, meaning they have scales on their wings. So when you touch the wings, the scales can oftentimes come off, so you have to be pretty gentle when you do so. And you don’t really want to hold the butterfly by the body because that can harm them. It can hurt their legs and so forth. But typically, holding them by the wings gently is OK as long as you don’t rub too many of the scales off.

IRA FLATOW: So now that butterflies started in North and Central America, does that change our understanding of them at all?

AKITO KAWAHARA: Yeah, definitely. I think now that we know that they came from North and Central America, how they spread across the world is very different from what we had thought before. These certain group of butterflies that only feed on particular plants that are found in places like Siberia, or South America, or wherever it is, and so getting this broad geographic understanding now gives us an insight into how butterflies spread across the world.

IRA FLATOW: Do you have a favorite butterfly we could share with our audience? Or is it like children? You say, I have so many of them, I can’t narrow it down.

AKITO KAWAHARA: Yeah, I’d say one of my favorite butterflies is this butterfly called the sunset morpho butterfly. And it’s this butterfly that’s only found in the Amazon jungle, and I have seen it multiple times on field trips. And growing up in Japan, I read about this butterfly when I was a kid, and I’ve always wanted to try to see one up close.

And I’ve only seen them from far away. And one day, I think I’ll be able to see one up close. But it’s a beautiful, big butterfly that’s orange, and white, and black, and extraordinary. It’s a very, very slow-flying butterfly but just beautiful and something I’d love to come close to one day.

IRA FLATOW: Well, we wish you good luck in finding that butterfly.

AKITO KAWAHARA: Thank you very much.

IRA FLATOW: Thank you very much for taking the time to tell us all about this. This was fascinating.

AKITO KAWAHARA: Thanks again. It was great.

IRA FLATOW: Dr. Akito Kawahara, professor, curator, and director of the McGuire Center for Lepidoptera and Biodiversity at the Florida Museum of Natural History that’s in Gainesville, Florida.

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