The secret powers of flowers

[MUSIC PLAYING] IRA FLATOW: Hi, it’s Ira Flatow. And you’re listening to Science Friday. We’re waiting impatiently for signs of spring beneath the melting snow. I mean, I’m looking for you, crocuses and daffodils. These colorful blossoms would surely brighten all of our moods. But my next guest argues that flowers are not just beautiful. They are critical to the diversity of life as we know it and to food and agriculture.

Let’s learn all about that with Dr. David George Haskell, biologist and author of How Flowers Made Our World– The Story of Nature’s Revolutionaries. He’s based in Atlanta, Georgia. Welcome to Science Friday.

DAVID HASKELL: Thank you, Ira. It’s a delight to be with you to chat about the world-changing power of flowers.

IRA FLATOW: One of my favorite topics because I grow a lot of them. So let’s get right into this. Because when I think about the evolution of life on Earth, flowers are not typically front and center in my mind. So tell me what we have been getting wrong all these years.

DAVID HASKELL: Yes, we think of Earth’s evolution, often, we’re thinking about Tyrannosaurus and animals and maybe microbial revolutions billions of years ago. And I think flowers belong in that pantheon of revolutionaries because they were late arrivals on planet Earth. They evolved maybe 130 million years ago. After they evolved, they swiftly took over most of the habitats on the planet and are the foundation of most rainforests, prairies, seagrass meadows, mangroves all over the world now.

So they truly are revolutionaries. They opened opportunities for other animals and created most productive ecosystems on the planet. So we think of them as ephemeral and merely ornamental, but in fact, flowers are extraordinarily powerful world-changers.

IRA FLATOW: Let’s talk about that because I’m wondering, does the fact that flowers are pretty and they smell good, does it distract us from seeing them as evolutionary powerhouses?

DAVID HASKELL: Perhaps. I mean, there’s nothing wrong with enjoying flowers as pretty, as ornamental, as enjoying their aromas. It’s an important part of our individual and cultural expression. And those aromas and the colors that we’re so attracted to are also the source of much of flowering plants’ world-changing power. It was through experiences of beauty connecting to bee aesthetics and butterflies and beetles and so on that flowers drew other species into cooperative networks, and through that cooperation, then revolutionized the world.

So in a way, we think about revolutions in a human context, often through violence and domination, authoritarianism. Flowers offer an alternative view of how the world can be changed and transformed, and that is through interconnection, often mediated by interspecies’ experiences of beauty.

IRA FLATOW: Now, if I remember correctly from my biology, non-flowering plants came first, like ferns. So that raises the question, why did flowers emerge? And when did flowers first come onto the scene? What happened?

DAVID HASKELL: Yeah, absolutely. I mean, mosses, ferns, cycads– there are lots of non-flowering plants. And they were around building the Earth’s forests and creating habitats for hundreds of millions of years before flowers came along. And then what flowers did was have a– there was a convergence of innovations. Some of them were about attracting pollinators into the flower itself, using petals and aroma as visual signals, combining male and female into the same flower, which is a much more efficient way of pollinating the flower, of transferring pollen from one flower to another.

But they also revolutionized botanical motherhood by enclosing their seeds inside fruits. Some of those fruits are fleshy. Some are protective. Some are wing-like to catch the wind. And so, through a series of different innovations, flowers quickly became some of the dominant creatures on the planet. And by some estimates, it only took a handful of million years after they evolved for them to become the dominant vegetation around much of the planet. And then they catalyzed the evolution of whole new animal groups, like bees and butterflies, and, later, grazing mammals, and even humans. We wouldn’t be here without flowering plants.

IRA FLATOW: So was this evolution quite rapid?

DAVID HASKELL: Yes, they exploded onto the scene. And Darwin, back in the 19th century, called it an abominable mystery, how flowers appeared so late and so explosively in the fossil record. Now, of course, Darwin didn’t know anything about modern genetics, and so we have some insight now that he didn’t, that flowers have these genetic superpowers– they are especially genetically nimble– within themselves that allowed them to diversify very, very rapidly.

And the Earth changed from a planet covered mostly in cycads and mosses and various forms of ferns and other non-flowering plants into one where, first, the understory and then the overstory of most forests were dominated by flowering plants. And that’s still the world we live in today. Before flowering plants, there were no rainforests, prairies, steppes, or mangroves. So flowering plants were not only innovative, they were– to use a jargon from human economics, they would disrupt us. They came along and overturned many ecosystems and created enormous opportunities for other creatures.

IRA FLATOW: One really interesting idea I learned from your book is that grasses are considered flowers. I didn’t think I ever thought of my lawn as a sea of flowers.

DAVID HASKELL: Yes, so lawns are kept in a state of perpetual youth. We erase all signs of sex and death from them, creating this ecological illusion, which, of course, you go out into a forest, mostly what you see is sex and death. And so a lawn is a strange, strange thing, a reflection of parts of our psyche maybe.

But if you were to not mow your lawn or go out to a natural area where the grasses are free to grow, of course, later in the season, the grass would send out flowering stalks. And grasses are pollinated by the wind, not generally by bees or other insects. So they have very inconspicuous small flowers. But anyone with hay fever knows that grasses can make quite a lot of pollen. That pollen drifts through the air and is received by other flowers.

And then the amazing thing with grasses is that after fertilization, the little embryo grows, and the mother grass supplies an enormous amount of food that goes along with the embryo, which is why grass seeds, when you plant them, whether it’s grass for your lawn or wheat or maize or rice, can explode. It’s like rocket ships taking off from the soil. Because they’ve got these amazing storehouses of food. And that’s another innovation of flowering plants, is to give many of their embryos little food hampers to give them a boost as they start off their lives.

IRA FLATOW: After the break, the integral role of grasses to human evolution. Don’t go away.

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IRA FLATOW: So grass has played this huge role in human evolution. And because we’re talking about rice, which is a flower– which I didn’t really think about– and wheat is– they’re grasses?

DAVID HASKELL: Yes.

IRA FLATOW: Right?

DAVID HASKELL: If you count up all the calories that humans eat worldwide, 2/3 of those calories come from just three species of grass– wheat, maize, and rice. And a lot of the rest of the calories come from sugar cane and oats and barley and millet. And then if we’re eating grass-fed beef, for example, well, that [CHUCKLES] cow is also made from grass. All flesh is grass, the sacred texts tell us. And that’s a sort of an ecological truth, as well as having some theological overtones.

And so in the present-day, we are sustained by grasses. But our evolution was also catalyzed by grasses. Because why did we or our ancestors come down from the trees? Our ancestors were living happy lives up in the trees in tropical forests, and a few of them decided to come down from the trees and become bipedal primates in grasslands. So without the grasslands and the savannas, there would have been no incentive for early pre-human hominins to evolve.

And then the diet of those pre-human ancestors was also mostly grass-based, either eating the grass and grass seed directly, or eating a lot of the animals that were feeding on that grass. So yes, we are grass apes, Homo poacaeae, if we were to name ourselves for the family of plants that sustain and created us.

IRA FLATOW: That is really interesting. I’m a big fan of orchids, and I know you devoted a large chunk of your book to orchids. I grow them on my windowsill. What can they tell us about the relationship between flower and pollinator?

DAVID HASKELL: Absolutely. Orchids are the apex of the complexity of relationships with pollinators. Of course– and we’re attracted to them. I mean, you keep them on your windowsill. I’ve got a whole load on my windowsill here. Orchids have magnificently, often, very large and conspicuous displays with their petals and their sepals. Some of them are aromatic.

But the sexual parts are actually miniaturized. They only produce a tiny little bit of pollen. And the egg is buried right in the center of the flower there, and the stigma receives the pollen from other orchids. And orchids lure and manipulate and bribe all sorts of different insects to come and pollinate them. If you think about the orchids on your windowsill, that usually there’s a central portion which is often tube-like or a little bulbous lip that encourages the bee or other pollinator to pass in and receive the pollen.

Now, some orchids are doing this, quote unquote, “honestly” by offering nectar rewards to reciprocate with the pollinator. But others are a lot more devious. Some orchids look like they’ve got pollen and nectar, but in fact, have none. Others look and smell and feel just like female insects. There’s one, the bee orchid, that looks and feels and smells just like a female wasp. So amorous male wasps try to mate with these orchid flowers and, of course, just get a little dab of pollen put on their head– complete waste of time for the male wasps. But the orchids are then pollinated.

So orchids take a deliciously varied approach to pollination, and it’s often very specific to individual pollinators, which then leads to a powder keg for evolution. When you get specificity between pollinator and a flower, a slight genetic change in the flower or pollinator can cause that species to split, which is why there are tens of thousands of species of orchids around the world, often with very small–

IRA FLATOW: Yeah, more than any other flower, I think. Yeah.

DAVID HASKELL: Yeah, it depends how you count it, either them or the sunflowers.

IRA FLATOW: You talked about specific pollinators and, specifically, about the orchid. I remember getting an orchid. I think it was called Darwin’s orchid–

DAVID HASKELL: Yeah.

IRA FLATOW: –because it had a huge bulb at the bottom. You know what I’m talking about?

DAVID HASKELL: Yeah.

IRA FLATOW: And there had to be a moth that could stick its nose all the way into the bottom.

DAVID HASKELL: Yes, this is an orchid from Madagascar that, at first, Western scientists only knew about the flower. And it had this big, long spur with nectar in the end. But no one knew what pollinated it. And Charles Darwin said, I predict that there is a moth out there with a proboscis of exactly the right length to fit into this flower. And of course, this was after he died. He never lived to hear the end of the story.

But 20 years after he died, Western scientists found the moth, described the moth, and there was an almost perfect match between the moth and the orchid, which, at the time, was sort of a triumph for the predictive power of evolution, because there were some creationists who, at the time, were arguing, look, this moth is– disproves Darwinian evolution. And of course, Darwin had the last laugh on that one.

IRA FLATOW: Right, so I mean, to be so specific for a pollinator that there could only be one pollinator just is an amazing thing.

DAVID HASKELL: Yeah, it’s extremely efficient. It means that the orchid is not giving nectar to pollinators that aren’t going to be diligent and faithful couriers of its pollen. But it’s also very– it’s a risky strategy in terms of long-term evolution, because if your pollinator goes extinct, or the habitat changes and your aroma doesn’t carry quite so well, you’ve put yourself at risk compared to a flower like, say, a magnolia flower or a rose that welcomes all kinds of pollinators.

IRA FLATOW: So to wrap up and looking toward the future, is it silly to ask if flowers are endangered by climate change or changing world?

DAVID HASKELL: Not at all. 50% of orchids, 50% of magnolias, as far as we can tell, are threatened with extinction. And then, on the other hand, there are flowering plants that are extremely nimble and are adapting to the various changes, whether it’s climate or salty soils or increasing drought, so that as flowering plants always have done, they’ve adapted.

But we are having such an extraordinarily powerful effect on the planet that we are, indeed, pushing many flowers towards extinction, which is improvident, to say the least, because flowers made our world, created the most productive habitats on the planet, including human agriculture. And so to cause so many of them to become threatened and endangered is not treading a very cautious path.

By partnering with flowers, we can find solutions. And that’s the great genius of flowers, is to draw animals into cooperative partnerships. We have been and we can be even more one of those cooperators working towards a better future with flowering plants.

IRA FLATOW: Last question– do you have a favorite flower?

DAVID HASKELL: Oh, I’ve got lots of favorite flowers. I mean, one that really, in writing–

IRA FLATOW: It’s like asking about your children, right?

DAVID HASKELL: Yeah. Yeah, and the one that really shocked me– I learned a lot about in writing this book– were the seagrasses. They look very inconspicuous, unremarkable. These are flowering plants that flower literally under the water, in the seawater. And they are–

IRA FLATOW: No kidding.

DAVID HASKELL: They’re incredible at storing carbon, storing sediment, stabilizing the edges of continents, providing habitat for marine animals to breed in and to feed in. And until recently, we knew very little about seagrasses. And they, too, are also in endangered. Their populations are in decline. But there are some amazingly inspiring stories about restoration of seagrasses.

So I like them because they’re obscure, they’re not very conspicuous, and they have this great story about humans working with flowering plants to solve some of the problems that we’ve created. So they’re one of my many favorites.

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IRA FLATOW: I’m glad I asked. I learned so much today, Dr. Haskell. Thank you for taking time to be with us today.

DAVID HASKELL: Thank you, Ira. Always a pleasure to chat. Thank you.

IRA FLATOW: Dr. David George Haskell, biologist and author of How Flowers Made Our World– The Story of Nature’s Revolutionaries. He’s based in Atlanta, Georgia. If you like flowers, you’ll love this book– even if you don’t like flowers. Shoshannah Buxbaum produced this episode. I’m Ira Flatow. We’ll see you again.

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