The Hour is Blue

From the Archive: Dr. Dolph Schluter on Evolutionary Biology

This interview was first broadcast on February 25, 2021 on The Blue Hour on CiTR 101.9 FM at the University of British Columbia in Vancouver, Canada.

Dolph Schluter is an evolutionary biologist at the University of British Columbia and one of the world's leading authorities on ecology and the divergence of new species. His research spans speciation, natural selection, adaptation and adaptive radiation, including decades of work with Darwin's finches in the Galapagos Islands and threespine sticklebacks in British Columbia.

At the heart of our conversation is the question that has animated evolutionary biology since Darwin: how do species form, diverge and persist? Near the end of our conversation, Schluter describes Charles Darwin's closing passage in On the Origin of Species as his favourite passage in all of literature:

"There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."

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The Blue Hour, hosted by Farha Guerrero, airs live every Tuesday at 2 p.m. PT on CiTR 101.9 FM at the University of British Columbia in Vancouver, Canada.

Transcript

Transcript lightly edited for clarity and readability while preserving the substance and natural rhythm of the original live conversation.

Farha: Dolph Schluter writes, "Since the Big Bang, not much has happened in the universe more interesting than the diversification of life on Earth. Most of life's current diversity is wrapped up in the genetic and phenotypic differences between species, between the communities of species they form, and between the higher taxonomic groups that species make up, such as families and phyla. For this reason, the study of the origin of species, speciation, and its consequences tells us a great deal about how this extraordinary diversity of life arose, how it's distributed across the globe, how it's presently maintained, and how it has changed through billions of years of Earth's history."

Welcome to The Blue Hour. I am Farha Guerrero. Tonight I speak with Dolph Schluter, an evolutionary biologist from the University of British Columbia who studies adaptive radiation, the evolution of ecological diversity in groups of organisms that are multiplying rapidly.

He's one of the world's leading authorities on ecology and the divergence of new species.

But first, let's start the night with a favourite song of his, Bob Dylan's "Stuck Inside of Mobile with the Memphis Blues Again."

[Music]

Dolph Schluter, I want to congratulate you on receiving the Killam Professorship last month at the University of British Columbia.

Dolph: Thanks, Farha.

Farha: You have pursued the origin of species on Earth with passion and creativity, research that spans decades of inquiry into a broad range of topics, including speciation, natural selection, adaptation to new environments and species diversity.

But your passion in evolutionary biology has early beginnings. You spent your childhood outside the suburbs of Montreal, roaming through fields, woods and ponds, often bringing home frogs and snakes and bugs.

Tell us about this early fascination with the natural world.

Dolph: I did enjoy being outside and collecting things, bringing them home, bringing home snakes, bringing home frogs to feed to the snakes, even catching birds in my backyard, which my parents forced me to release.

Farha: And then in your teen years, you would take some skeletons from your high school biology class, is that right? You would dissect them and then put them back together?

Dolph: Yes. I brought one home and I dissected it to try to remove as much of the flesh as possible, and my mother helped me boil the remnants with a plan that I would reassemble the skeleton, but it didn't turn out very well.

Farha: Is it also true that you had saved some of your pocket money to buy a small fishing boat where you spent many hours fishing?

Dolph: That's true. I spent a great deal of my hours outside of school catching fish in the St. Lawrence River, close to where I lived. So I bought myself a boat using my paper route money.

Farha: You were out in the woods, so to speak, as a young person. You were out in the elements, and as I've learned, that continued with you throughout your life, and I believe probably still does.

Dolph: That's how it ended up, yes. As a kid, I imagined that maybe someday I would get a job that would require me to go fishing and that I would be paid for it. In many ways, that's what happened.

Farha: Let's bring us back to Bob Dylan's song that we heard at the start of The Blue Hour, "Stuck Inside of Mobile with the Memphis Blues Again," and how it helped you land your first job in biology.

Dolph: I was a huge Bob Dylan fan, and as an undergraduate student in biology at the University of Guelph, I'd had a couple of summer jobs in labs, but I was really hoping to get a field job for one of the summers when I was an undergraduate.

I applied to a lab to be the assistant of a PhD student who was doing work on snapping turtles in Algonquin Park. The graduate student had chosen me as the favourite candidate, but the supervisor had chosen someone else as the favourite candidate.

I had my interview with the supervisor, which I can't remember very much about, but afterwards he took me down to meet some of the students in his lab. We sat around and talked, and I learned that he was a huge Bob Dylan fan.

At one point in the conversation, I was leaning against the counter awkwardly to one side while they chatted amongst themselves. He said, "Do you know there's a mistake in one of Bob Dylan's songs?" I just blurted out the answer.

It was a mistake in the Blonde on Blonde recording of "Stuck Inside of Mobile with the Memphis Blues Again."

Anyway, I got the job.

Farha: That's a great story.

As you continued in your interest in biology, you met a man named Bob Montgomery, is that correct? He was perhaps your first exposure to someone studying evolutionary biology in a field setting?

Dolph: It was. My Bob Dylan story is one example of how some random event changes your future. This was another one.

I skipped class to go to a seminar by Montgomery at my university at the recommendation of my mentor, the supervisor who had hired me. I went to this lecture and it was really interesting. It was about the evolution of territorial behaviour in hummingbirds.

His field site was in Mexico. I was taking an evolutionary biology course at the time. I was fascinated by the topic of evolution.

Up to that point, the only exposure I'd really had to research in evolution was reading books by people like Richard Dawkins and Stephen Jay Gould and Ernst Mayr. These are stupendous writers.

Reading their works, one gets the impression that how one studies evolution is by sitting in a room and thinking very deeply about the problem and then deducing the correct answer to large questions.

The seminar by Montgomery gave me exposure to another way of researching evolution, which is through fieldwork to ask questions about how things evolved. It was a revelation. I went to talk to him afterwards.

He told me his work was finished down there. He was a finishing PhD student in the laboratory of Peter Grant, who was at McGill University. He suggested I write to Peter Grant.

That's what I did. He was carrying out field studies of finches on the Galapagos Islands. I applied to do graduate studies with him.

He accepted me as a student. It was not long after that I headed to the Galapagos.

Farha: You were drawn into the idea of working on big ideas like natural selection rather than the basic biology of a species.

Dolph: My thoughts weren't so organized yet at that stage, but I knew that I was interested in processes in evolution. Also, my background was more ecology. I was very interested in the ecological processes that give rise to evolutionary change.

This project on the Galapagos finches got me excited. It allowed me to think about the things I was interested in and start to apply them to a real system. It was thrilling.

Farha: Let's pause for a moment.

Charles Darwin, who we all know, stepped ashore on the Galapagos Islands in 1835, where he encountered a group of small brown birds, which he called finches. He didn't think much of them at the time, but back home in London, his ideas about evolution began to take shape.

Let's listen to a brief introduction to Darwin's finches produced by FuseSchool Global Education.

[Audio clip]

Narrator: What are Darwin's finches and why are they so important to biologists? The study of finches led to the development of one of the most important scientific theories of all time.

But how did this come about?

In December 1831, a naturalist called Charles Darwin boarded the HMS Beagle, bound on a surveying voyage to South America. Whilst the ship and crew carried out coastline surveys, Darwin was free to explore the islands en route.

In 1835, the Beagle arrived at the Galapagos Islands near Ecuador. What Darwin found there surprised him greatly.

As well as giant tortoises and marine iguanas, Darwin collected and preserved a variety of different songbirds called finches. Upon returning to the UK, he examined them together with ornithologist John Gould and made some fascinating discoveries.

The scientists observed that the birds were all similar to a single type of finch found on mainland South America, suggesting that these mainland finches had originally colonized the islands.

However, the Galapagos finches were all slightly different from the original mainland species, and they were also different from each other. The finches on each island showed distinct variations in their overall size, beak shape and claw size.

These differences were attributed to the differing food sources available on the various islands of the Galapagos. Some of the birds had long, thin beaks and sharp claws suited to catching and eating insects, while others had large, powerful beaks suitable for cracking open nuts.

Because of the distances between the islands, breeding between different species of finch was unlikely, and Darwin concluded that the finches must have evolved over time from the original mainland species to suit the conditions found on each individual island.

In all, 13 of the birds brought back by Darwin were identified as being entirely new species, all similar to each other, but with definite variations from their common ancestor.

Darwin proposed that the variations seen both within and between the finch species arose by chance. Variations which gave any individual a competitive advantage made them more likely to survive and therefore reproduce, outcompeting those with less advantageous characteristics.

Darwin called this theory natural selection, and he published it in his book On the Origin of Species in 1859. Evolution by natural selection is now widely agreed to be the most accurate theory to explain the origin and diversity of all life on Earth.

Farha: Dolph Schluter, you essentially followed in Darwin's footsteps, travelling to the Galapagos some 140 years later.

Because Darwin wasn't able to test any of his ideas about natural selection and the origin of species, you were on a quest to do these sorts of experimental tests to understand why different species of finches became modified for different ends.

How did it feel to go to the Galapagos and, in almost a surreal way, continue Darwin's work so many years later?

Dolph: It was tremendously exciting, that idea of going to the Galapagos, the birthplace of many of Darwin's ideas that led to his theory of evolution.

It was indescribably thrilling to actually be there, probably the place in the world that I would most want to go.

It was also exciting for a couple of other reasons. First, I'd never been further south than Boston before, and here I was now headed to the tropics, and for months.

The third reason it was amazing was that it was probably my first true wilderness experience.

Most of the time that I was down there, my first field season was about five months long, and the first four months were spent on an uninhabited island with just one other person, with boats coming every four weeks or so to replenish our freshwater supply, bringing food and mail.

So we were completely isolated from the rest of the world, no radio contact, nothing. All of this was incredibly neat to me.

Farha: And there were species abound, I can imagine.

Dolph: It was amazing to see the finches first because, well, they're Darwin's finches. But secondly, they were wonderful to work on because they were so tame.

It was possible to observe individuals and what they were feeding on simply by approaching fairly closely, looking through a pair of binoculars.

We'd been advised to bring binoculars that could focus very closely, at very short distances, because it was so easy often to approach the birds. So it was wonderful to work on.

Farha: You used field observations coupled with computer modelling to study why these species of ground finches in the Galapagos evolved from a common ancestor, is that right?

Dolph: That's right.

The question I was interested in was, how did competitive interactions between species for foods produce the diversity of beak forms that we see today in the finches?

As part of that project, I did comparisons between populations of finches on islands where sometimes you'd find two species together, and other islands where only one of those two species would be present alone.

Often they would then have a beak size and a diet that was intermediate. It was thought that this pattern was produced by competitive interactions.

I was really interested in this problem because the basis of that idea was that if you could imagine a world in which there was no competition, then all the finches, if there were multiple species at all, would all have the same beak size.

What I attempted to do was build an evolutionary model on the computer that first took all of the seed measurements that I and others had obtained from multiple Galapagos Islands.

We collected soil samples and we'd sifted through and counted seeds and determined their size and their hardness. That allowed us to build, on the computer, a landscape whereby we could imagine how successful a finch of a particular beak size would be if it were on that island.

I was able, using the program, to say what its beak size would be if there were no competitive interactions versus what it would be if we did incorporate competition for food, for seeds, in the evolutionary model.

The result of that exercise was that a computer model that incorporated competitive interactions could successfully predict the beak sizes of finches that had evolved on Galapagos Islands, whereas the alternative model that left out a role for competitive interactions was unsuccessful.

Farha: What surprises did you come to in your research when you were actually there working in the field with these finches that you had read about in books prior?

Dolph: A lot of the work that framed the field studies that I carried out were ideas that David Lack in particular had written about in his book Darwin's Finches.

He had proposed a strong role for competitive interactions, for example, between species. Most of the work that I conducted while I was down there was really testing this idea.

So it was not coming up with brand new ideas, but rather trying to test these ideas against alternatives.

I guess the surprise was that I believe we were largely successful in showing that David Lack's ideas, over and over again, had proved correct.

But I did come away from the islands also with other ideas about how new species formed in the first place, and about the role that genes played in determining which directions evolution had proceeded in the finches on the Galapagos Islands in comparison with other directions that might have taken place but did not.

Those ideas became more important in the work that I carried out after completing my PhD and coming to Vancouver.

Farha: David Lack is one of your heroes. Most people who've taken a biology course in the last 50 years are familiar with his work, but few might actually remember his name.

As you mentioned, his classic 1947 book called Darwin's Finches had a big influence on you and many others.

Let's listen to a little description of David Lack. This is a short clip by an author named Matthew James, who wrote the book Collecting Evolution: The Galapagos Expedition That Vindicated Darwin.

[Audio clip]

Matthew James: Charles Darwin was vindicated by the 1905-06 expedition in several ways. One of the most notable ways was through the birds called Darwin's finches. But at the time, they were just known as Galapagos finches.

The specimens collected by the California Academy of Sciences were used by David Lack, an Englishman who went to Galapagos to do his own fieldwork.

Then he went to San Francisco for three weeks to work on the specimens collected in 1905-06, and he wrote a landmark book, a book called Darwin's Finches.

Arguably, we all know about Darwin's finches today because of David Lack's work. David Lack's work was really only possible because of the 1905-06 expedition.

So I would say that the expedition from California in 1905-06 was the most important expedition in Galapagos history that no one has ever heard about.

I hope that by telling the story of that expedition, scientists in the islands, anyone interested in Darwin, and others interested in the history of evolution and the history of science will be able to now know about this unknown chapter in Galapagos history.

It's not only unknown, but it's extremely significant. I think that when the further understanding of this expedition is possible, people will marvel at how important it was.

It had several levels of vindication of Darwin. It has made the California Academy of Sciences the centre of gravity for specimen-based studies to this very day.

On multiple levels, the expedition was significant. It's unfortunately not known, but I think that it will become much better known.

Farha: Just like David Lack, and prior to that Darwin, you were on the Galapagos Islands working with finches.

It's extraordinary to think that that was something you did in the early beginnings of your doctoral studies. Those experiences were something that carried you through all of the things that you've done, which we're going to talk about.

But I'm curious if you could bring us back to the Galapagos again.

I've read a story about you being on one island called Los Hermanos, and the sea was furious. It was too rough for a boat to dock.

You had some interesting experiences with being thrown in the waves as you were trying to swim and gather your data books, which were your most precious cargo.

Can you bring us back to that moment?

Dolph: The trip to Los Hermanos was so much fun. I went with Trevor Price, who's another student in my lab, and a third fellow, Stephen Millington.

This island hadn't been visited, I think, since that expedition we just heard about.

It was an important island because the small-beaked ground finch was there alone, without the medium-beaked ground finch, and it had evolved to a larger size on that island in the absence of its presumed competitor.

David Lack had described this pattern, and we wanted to go there and confirm it, and also to make observations about the diets of the birds while we were there.

But to get on the island proved to be more challenging than we had anticipated.

There was a great swell, and we weren't able to land in the usual way. The usual way of landing was we'd get into a little rowboat, and the rower would approach the rocks at the shore, and one at a time we would jump out onto some sort of rocky landing that we managed to approach.

But the swell was so great on this trip that we were unable to do that.

The only way we could get on the island was to jump in the water and swim to it.

Trevor also brought a line of rope, and he climbed to the top of the island above a shelf of rock and lowered the rope down.

That's how we managed to pull everything up to the top of the island and set up our camp. Everything, food, you name it, including, I think, maybe three dozen eggs, none of which was broken by this experience.

We stayed on the island for several nights. We brought mist nets and so on, so we were catching birds and measuring them and observing them.

Then we had the same problem getting off the island. We ended up lowering everything down to the same shelf and throwing everything into the sea, and then the rowboat would retrieve it.

Finally, to get off the island ourselves, we had to leap from this cliff and into the water ourselves.

Farha: Wasn't there a time where your back was scraped quite badly by the barnacles?

Dolph: The swell, when you're trying to land on the island, would pick you up and hurl you against the shore and then drag you back down. So we were left scarred by that experience, mostly from the sharp barnacles on the rocks.

Farha: You wanted to find a system where you could do experiments on natural selection beyond the rare species of finch in the Galapagos, where you could do experimental trials to measure natural selection and evolution in action.

Your research in the Galapagos then brought you to an entirely different species, the threespine stickleback, a small fish common to the Pacific Northwest and among the younger species on Earth, which makes it easier to follow their evolutionary tracks.

Let's listen to a short clip from The Making of the Fittest, produced by HHMI BioInteractive, and how stickleback fish have adapted to live permanently in freshwater environments.

[Audio clip]

Narrator: For tens of thousands of years, much of North America lay buried under ice up to a mile thick. Then the massive ice sheets receded.

In what is now Alaska, ocean-bound streams and rivers emerged, opening up new possibilities for countless species.

One of the animals that came calling was the threespine stickleback. Common to the northern ocean, this little fish spawns in freshwater.

There were now lots of new spawning grounds to explore. But as the ice-free land began to rise, streams and the fish in them were cut off from the sea.

Isolated populations of sticklebacks faced a survival challenge. Could they adapt to full-time life in a freshwater lake?

Ten thousand years later, they're still there. But they have been transformed.

Stickleback bodies changed in many ways as they adapted to life in post-glacial lakes. They got smaller, their colouring changed, and most strikingly, even their skeletons changed.

As we begin to learn exactly how stickleback bones evolved, we're learning about a lot more than just fish. We're learning about how all animal bodies evolved.

Farha: Dolph, because sticklebacks, as we learned, evolved repeatedly, you were able to do comparative work and experiments that tested the role of natural selection and the origins of species at UBC.

Tell us about the beginning of your postdoctoral research and what became 30 ponds on the UBC campus, where you were able to watch, so to speak, evolution in action with these wonderful stickleback fish.

Dolph: After the work on the Galapagos, I did some work on finches on continental regions. I did some fieldwork in Africa and in the southwestern U.S., but I started to look around for a system in which it would be possible to do experiments.

We learned so much about the causes of evolution on the Galapagos projects just by making comparisons between islands.

What I was hoping I would someday find would be some kind of island system with a fairly low number of species that had evolved relatively recently, that would allow me to take the questions I was interested in and take them further to the experimental stage.

The idea of doing experiments on Galapagos finches is just impossible, or finches at all.

When I came to the University of British Columbia as a postdoc, I learned about these stickleback in small coastal lakes off the coast here.

It was a professor, Don McPhail, who discovered several lakes along the coast that had two species of threespine stickleback in them, in comparison to most other small lakes that had just a single species.

All of these forms, all of these populations, had originated through a process of species origination, speciation and adaptation in freshwater, all from the same ancestral form, the marine threespine stickleback, which is still out there in abundance in the coastal waters.

I realized that this was a system in which it would be possible to do experimental studies.

I began to hunt for funds to allow me to build a series of experimental ponds on UBC South Campus.

The sorts of things I was interested in at first in attempting to address were, how has natural selection on a species changed? When a second species is added to its environment, will they compete for food? Will natural selection drive them apart? If so, how strong was that process?

These are questions I was interested in as a PhD student, but could not address without experiments.

That's how the stickleback project began.

These populations are amazing. The lakes themselves are only 10,000 years old or so.

Especially these lakes that contain two species, they don't occur anywhere else except in these lakes that are 10,000 years old.

This makes them among the youngest species on Earth in any system.

They proved to be relatively abundant, easy to catch, easy to keep in the lab and easy to raise in numbers large enough that we could actually carry out these pond experiments.

They are an amazing study system, and they're in our backyard. It's relatively simple to work on them. The permitting procedure is much easier than getting permits to work in the Galapagos.

We don't have to cross borders with specimens. There are so many things about it that seemed promising that I began to work on them, and I'm still working on them because they just keep on giving.

Farha: For years, you and your students have been crossing and combining varieties of sticklebacks and putting them into these ponds and keeping track of all of your observations, watching natural selection take its course.

The sticklebacks blossomed into many varieties in their new freshwater homes.

Tell us about some of the things that you witnessed, how their heavy armour plates that would protect them against ocean predators might have changed, or how they might have lost their belly spines that proved a handicap for them.

There are all these different variations, and some of them, with time, their colour might have changed compared to their marine counterparts.

Give us a glimpse of some of the things that you saw that you were able to observe in a relatively short period of time.

Dolph: In a very short period of time.

The kinds of changes that we see in freshwater are some of those that you mentioned and were mentioned in the previous recording.

Bony armour in freshwater evolves downward. They lose their bony armour plating down the side of the body. They lose their bony spines on their bellies, and the spines they do retain are shorter.

That transition is associated with reduced predators in freshwater.

But we also think that it's associated with not just reduced predators, but the greater cost of producing bony armour in freshwater, which is a much lower-ion environment than the sea.

We also think that the genes that influence bony armour do other things.

We haven't got a complete list of what those other things are. But, for example, one of the major genes that is responsible for the reduction in bony armour plating also affects schooling behaviour of fishes.

Some of these genes have manifold effects, and all of those changes are also under natural selection, and we're continuing to try to understand them better.

They've changed in colour, some of the freshwater populations.

In your typical stickleback, the males develop a red throat during the breeding season, and that's alerting to other males and attractive to females.

Males build nests in which females lay eggs. The males fertilize the eggs, and then they tend them and look after the young in their first few days of life as well.

They even change colour, they become more blue. Some freshwater populations have evolved a black nuptial coloration instead of the usual red.

They've changed their shape.

The marine stickleback is constantly swimming against the tide. The tide comes in, they face one way and tread water, basically to stay in the same place. When the tide turns, they turn around and tread water again to stay in the same place.

They are evolved for swimming distances and swimming against the current. They have a small head, they're very fusiform, more like tuna.

But in freshwater, all that's gone.

They have evolved much larger heads and changes in the size and shape of the mouth, changes in musculature.

All this has happened not only in a short period of time, but also repeatedly in different lakes.

One feature that attracted me to these pairs of species, these lakes that contain two species, is that it looks like each of these pairs of species has evolved independently.

It's almost as though the same pair of species has evolved over and over again, repeatedly and independently, in different lakes along our coast.

That's wonderfully interesting because it allows us to start to make progress in understanding the natural selection pressures that lead not only to differences in armour and differences in head size and shape or colour, but also the evolution of traits that cause new species to form.

The traits that underlie barriers, we call them, to gene exchange between species. The traits that cause individuals of one species to look at members of the other species as foreign objects, nothing you would want to mate with.

Farha: You have jokingly said that this big apparatus of ponds that exists on the South Campus is a kind of evolution accelerator, is that right?

Dolph: We call them that jokingly because our facility is close to the TRIUMF facility at the University of British Columbia.

We sometimes meet physicists out for a walk and we've had the opportunity to give them a tour and explain what we're doing.

We've described them as evolution accelerators.

They are evolution accelerators because when we carry out experiments, we can make crosses between existing populations and existing species.

We can produce almost any shape or form of stickleback that we want simply by carefully choosing the wild parent population that's already out there and then crossing them to produce intermediate forms.

We can breed these intermediate forms to produce populations that are also highly variable for the traits that differentiate the parent populations.

Often when we do experiments, we use these experimental hybrid populations because they have so much variability, which we generated ourselves, and that speeds things up.

It allows us to measure natural selection more easily, to measure its strength more precisely.

Farha: In terms of actual time, the lifespan of a stickleback fish is about one to three years, is that correct? How long does it actually take to see these changes that you've described to us?

Dolph: The generation time of a stickleback is much longer than, say, a fruit fly.

When we do experiments in ponds, we have to think ahead. We have to think, what are we going to be doing in two years' time?

Let's make the initial crosses now, and then we'll keep them in the lab for a year or more, a year or two, before we introduce them to the ponds.

On the order of two years to generate the crosses that we're interested in.

Then we would sample individuals from the ponds periodically, measure them and genotype them, depending on the experiment.

We would track the changes over one or two more generations, so one or two more years.

If we have enough foresight and make the crosses that we need ahead of time, then it's possible for a student to pick up a project and carry it all the way through in a period of maybe three to four years, which is the duration of a PhD.

The generation time isn't a complete barrier, but it does require waiting longer than you might have to for other kinds of organisms. We can get them to breed in one year.

Farha: It was ambitious to peer inside the stickleback's DNA, given that most genetic experts work with, as you said, fruit flies or bacteria.

Dolph: It was.

At one point, after I'd been working on stickleback for more than a decade, I was approached by a group of biologists at Stanford University who were interested in uncovering the genes responsible for natural variation in nature.

David Kingsley was the head of the lab, and he'd done work on mouse genetics in the past.

Most of the genetics work had focused on understanding the effects of random mutations, usually harmful mutations that had popped up in their laboratory populations or that they'd hastened along using mutagens.

But he thought that we could learn a lot about the genetics underlying variation, not just in fishes or vertebrates, but including humans, by finding a system in which it was possible to understand the mutations that were responsible for natural variation, adaptive variation.

Variation of the kind where one population, like the marine, is fully armoured with these bony plates down the side of the body, and where in freshwater those bony plates had been lost or much reduced over and over again.

Here was a genetic problem where the differences had actually been favoured by natural selection rather than popped up as a deleterious mutation in a mutation screen.

So we began to collaborate.

I was skeptical at first just because of the one-year minimum generation. These are not fruit flies, as you are aware.

But the work was at such an early stage. Nothing was known at that time about the genetics of stickleback variation. His group was really starting from scratch.

Once the first year was over and we were making genetic crosses, the generation time was no longer the rate-limiting step.

There was just so much hard, basic genetics bench work that needed to be done that we had more than enough genetic crosses available for them to work on before long.

This collaboration turned up some really fundamental things.

One gene they discovered responsible for the reduction in bony armour is called EDA, or ectodysplasin.

It's a known gene in humans. Mutations in the gene in humans produce usually boys that have little or no hair, bad teeth, no sweat glands.

But here we have a natural population mutation that's actually favoured by natural selection.

Another example is the loss of the belly spines in this population on Texada Island, with the so-called benthic species in one of the lakes there that has the species pair.

The benthic has lost almost all its armour, including these belly spines and this sort of armour plate.

The gene responsible for that, PitX1, turns out to be a really interesting gene because we crossed a population that lacks it entirely, has the mutation that eliminates the pelvic bones, to the marine ancestor, which is fully armoured and has this belly spine and plates.

They figured out that it was PitX1.

It's an interesting gene because it's not a gene that makes anything. It doesn't make skin or muscle or bone. It's sort of an administrator gene.

It tells the tissue around it what to do. When it switches on, it says, make the bones in this part of the body. It doesn't turn on anywhere else.

What's cool about this belly spine, this pelvic spine, is that it's the evolutionary ancestor to the hind limb in four-limbed vertebrates, including ourselves.

So it's a gene that turns on in us and is responsible for the normal development of our legs, and in hind limbs in other tetrapods.

David's work also produced evidence that the same gene was probably involved in hind limb loss in manatees and whales. Other people have shown that it's probably involved in hind limb loss in snakes as well.

So it proved to be an interesting gene because it told us a lot about not just fish, but about all animals, as the previous recording we played said.

Farha: Our understanding of the role of natural selection in speciation has come a long way, but there is still much to explore.

It sounds like this is a fascinating time to be studying evolutionary biology, to be studying genetics, to be studying all these intersections between these fields.

But my sense is that at the heart of your research, one thing stands out. You are, without any doubt, interested in the purest of questions initially posed by Darwin, the origins of our species.

Although evolution can help us understand how to better preserve species in this changing world of ours, you're primarily interested in the roots of it all.

Essentially, you want to know how species form, how they become different over time, and how these species allow many species to persist.

Let's listen to Charles Darwin, the last few sentences from On the Origin of Species, which still gives you goosebumps today. Is that right?

Dolph: That's my favourite passage in all of literature.

Farha: Here we go.

[Audio clip]

"There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."

Dolph Schluter, it's been a wonderful pleasure to speak with you today.

My final question to you is, what do you see when we reach the bicentennial of Darwin's famous book? Where do you think we'll be in our understanding?

Dolph: Good question.

I think probably still a lot of the advances will come from genetics.

We'll have a much better understanding of how natural selection produced the diversity of forms that we see, and especially how natural selection on traits caused changes in the frequencies of genes, and then how those genes also directly or indirectly led to the origin of new species.

I think we'll have a much better idea.

For me, I'm not a geneticist. I collaborate with geneticists and I've learned a great deal.

But for me, the main use of genetics in my work is that it helps me to understand what features of environments are causing natural selection on organisms, and why they have changed in the particular ways that they have, and what features of environments have ultimately led to the origins of new species.

Knowing something about the material basis of these traits that differentiate populations allows us to carry out more precise experiments, more directed experiments that answer those fundamental questions, that answer those big questions.

Farha: Let's end the show with a song that was filmed on the UBC research ponds titled "I Am a Pond."

Why don't you set it up?

Dolph: This particular video was made by a group of graduate students in our unit.

There's an old tradition in my department, in our Biodiversity Research Centre, where every Christmas the students put on a production of skits that make fun of the faculty.

It's quite a production. It usually includes live drama, but over the years they have also incorporated videos.

So this is one nutty video that a group of students put together and filmed down at the experimental ponds.

Farha: Thank you again, and best of luck in all of your future endeavours. I'm sure you still have a lot of unanswered questions that you're still pursuing.

Here we go. Let's hear "I Am a Pond."

[Music]

Explore Further

Learn more about Dolph Schluter and his research at the UBC Department of Zoology, or visit the Schluter Lab for publications and current research.

Read Charles Darwin's On the Origin of Species, first published in 1859.

From the conversation