JOHN FITZPATRICK: Good afternoon. Thank you all for coming out on this beautiful Monday. I'm John Fitzpatrick. I'm Director of the Cornell Lab of Ornithology. It's lovely to see you all out here as spring sets in.
This is a really momentous day for the Lab of Ornithology. It's our inaugural Paul C. Mundinger Distinguished Lectureship. And we are very pleased on this occasion not only to have a very distinguished lecturer, but also the entire Mundinger family here. And you'll hear from Tom in a minute.
But I wanted to acknowledge right off the bat the generosity of the Mundinger family for remembering the late Paul Mundinger, who was a very avid recorder of bird sounds and a very distinguished scientist in his own right, with this lectureship. And I want to acknowledge and ask if they're willing to stand. Mary Mundinger, as well as Paul.
Paul, Jr. and Ann and Elizabeth Mundinger. Thank you all.
The Mundigers are all Ithacans. They were here as kids, along with Mary and Paul, when Paul was getting his PhD here. And they have, as you might hear from Tom in a second, some fond memories of the old Lab of Ornithology Building. Paul taught at Queens College in New York City as a distinguished bird recordist.
A major part of his life's work on tape has been donated by the Mundinger family to the Macaulay Library. We just took a look at it, and it filled half of a whole library shelf, all those wonderful tapes. Mary is a former Dean of the Columbia School of Nursing. She has a very distinguished career in her own right-- winner of numerous awards, sitting on panels and boards having to do with public health, with health policy, and with academic health.
So it's a very great privilege to have the entire Mundinger family here for this inaugural Mundinger lecture. And it's a pleasure to introduce Tom, who's going to say just a few words about the family. And Tom is in the Department of Medicine at the University of Washington, Seattle. Tom.
TOM MUNDINGER: Thank you very much. As Dr. Fitzpatrick said, we're all from Ithaca. In the 1950s, my dad and his wife Mary started their family here. All four of the children were born at was then called Hopkins County Hospital. So Ithaca is a home to us, to all of us. And that's part of the reason that we wanted to be remembered with-- my dad's legacy to be remembered with a lectureship here.
A little bit about this lecture series. And with this being the first in the annual lectureship-- so this is annual. We hope to see you all and a couple of your friends back here with a couple of extra seats next year in the years to come. But he felt a very strong connection to the city of Ithaca, the University of Cornell, and especially the Lab of Ornithology.
He received his PhD from Cornell in the mid-'60s and, as Dr. Fitzpatrick said, went down to the New York area and did his post-doctoral fellowship at Rockefeller University and then went on to Queens College. But in his professional life, my father was both a teaching professor as well as a researcher. And in his research, he worked both in the lab and in the field. And we're going to be hearing a lot of exciting fieldwork here this evening.
And again, his work was in animal behavior. His index of animal behavior was birdsong. And my dad felt it was a great honor to have his professional or anyone's professional legacy associated with a lectureship like this. So he would be very proud to have members of the Ithaca community, to have students, both graduate and undergraduate, to have faculty, fellows, staff-- to have a lectureship that includes all of this in this educational endeavor.
So on behalf of the family, we'd like to thank you all for being here and for your attention. And we'd like to thank Cornell University and especially the Lab of Ornithology for being host to this lectureship that honors my dad's professional legacy. So we're in for a real treat this evening. And thank you very much, and enjoy the evening.
JOHN FITZPATRICK: Thank you, Tom. And now it's my great pleasure to introduce Irby Lovette, who's the Nancy and Larry Fuller Professor of Evolutionary Biology and the head of the Fuller Evolutionary Biology Lab at the Lab of Ornithology, who will introduce our speaker.
IRBY LOVETTE: Thanks, Fitz. I think I have the easiest job of the evening, because you all know why you're here. I think this is an introduction for someone who basically needs no introduction to any audience that is paying attention to the history of evolutionary biology in the last 40 or 50 years.
And I could stand here and give you a very, very long list of professional honors won and papers published and books written. If you'd like to see that, go online. Look at the Wikipedia entry. It's vast.
What I'm going to do instead is I think give you just a couple of anecdotes that I think might frame Rosemary's talk in a slightly larger context. And one thing I want to acknowledge is that this very room that we're in right now is steeped in the discussion of Rosemary and Peter's studies of finches. This is the room where, for more than 20 years, we've taught evolutionary biology to many, many thousands of Cornell students who've gone onto illustrious careers of their own.
And so the example of Daphne finches has been covered in this room-- I think it's probably still echoing off the walls in here in various ways. I know many of you here are actually in that class right now or maybe alumni of that class in recent years. And so this is a special treat. This is the first time we've actually been able to bring the source of that information into this context.
And I think pretty much every evolutionary biology class around the country does something like that. So we're not special in that regard, but I will say, it doesn't stop at the college teaching level. Just this past weekend we were turning around a group of 20, I think, junior undergrads from 20 different colleges around the United States.
And they were seeing the posters about Rosemary's talk, and they were saying, Rosemary Grant is coming into Cornell? And I said, yeah. And I thought to ask them, just kind of on the fly, how many of you 20 students heard about natural selection and Darwin's finches not in college, but in high school? 19 hands went up.
And so this touchstone example of natural selection happening in the wild has really permeated, I think, all of our thinking at all levels about how natural selection actually functions. And so it's not just professional audiences and the ivory tower folks that have learned about evolution through these examples. It's basically our entire culture across the United States, and maybe even across the world.
So that's the context by which Rosemary is coming to talk to us. But the kind of iconic example that I think most of those students would have heard about in their high school biology classes was only the beginning of a really, really long and very, very impactful set of studies that Rosemary and her husband, Peter, who's here today as well, did over the course of more than 40 years. And so the example that you may think you know if you took high school biology or college level biology a while ago has only gotten better over time.
And I think Rosemary is going to bring us somewhat up to date on that tonight. And I just want to close with a personal anecdote. I had the very, very good fortune myself of seeing a job advertisement when I was 20 years old to serve as a field assistant for Rosemary and Peter on Daphne. And I answered that advertisement, and they chose me as their field assistant.
So I've actually spent six months on Daphne, chasing finches, under the tutelage of Rosemary and Peter. And so I have kind of a front row seat to the way in which they do their science, which I think is unusual. Many people know about their science, but few have seen it in practice. And I want to just point out that, for me, it really is almost a magical combination of the greatest theoretical broad-based consideration of fundamental principles married with something that I got to see first hand-- a really, really deep understanding of the study systems in which they work.
And it's not just the finches. I remember being tutored in plants, like portulaca and khakibos, and ipomoea, the seeds that are so important to those finches, and a whole bunch of other things. And so I want to say that Rosemary is not only an extremely exceptional and enormously influential scientist, but she's also a consummate naturalist. And I think it's that marriage of traits that has made her work so impactful for so many people. And with that, I ask everyone to join me in a rousing Cornell welcome to Rosemary Grant.
ROSEMARY GRANT: Well, thank you very much. Thank you very much for the introductions. And this is just a huge honor for me to be here today on behalf of both Peter and myself to be giving the inaugural lecture. We've had a really enjoyable morning so far, speaking to lots of students, post-doctoral fellows, and faculty members. And I just thank you very, very much for the invitation to come and to talk to you today.
So I chose this title with "Evolution of Darwin's Finches-- Integrating Behavior, Ecology, and Genetics," because Paul's very innovative research in a number of species of birds really did integrate behavior ecology and genetics. And this is where Peter and I have followed in the same footsteps as Paul.
By Paul integrating behavioral ecology and genetics, he was able to show-- and this is, I think, one of his papers that I most enjoy reading. He was able to show that song learning involves an interaction between experience and genetically determined neural circuitry. And this is a really innovative piece of work that he and his colleagues did.
Now, Peter and I, the way we think of it is, I think, the same way Paul does. We think that genotype variation is translated into phenotypic variation, translated into fitness, all under the influence of the general environment and the social environment. And this is the environment of other species in the same area and also the interaction of individuals within the same species.
Now, all of us, I'm sure, in this room, whether we are hiking in the Alpine meadows or we are traveling in the Amazon jungles or diving beneath the surface of the sea, are just amazed at the diversity of life on this planet. How is all this biodiversity generated? How and why do species multiply? How do we even go about studying this process of speciation?
Well, we know from a lot of people's works-- and I'm thinking of not only Dolph Schluter, but many other people-- that much diversity arises from adaptive radiations. And that is a rapid diversification of lineages of species from a common ancestor. One of the most spectacular, of course, is the Hawaiian honeycreepers, with their enormous plumage differences, their bill shape differences. And over 50 species of these have evolved from a common ancestor in the last 6 to 7 million years. But unfortunately, many, many of them have now gone extinct.
Now, Darwin himself suggested that, actually, young radiations-- he didn't put it quite that way, but that's really how we would translate it today-- that young radiations might be the best place to observe this. And there are many young radiations. There's the cichlid fishes, the char in Iceland.
But we chose Darwin's finches as our young radiation, and we know now that this radiation occurred in the last 1 to 2 million years, where there are now 15, possibly 16, species that have all been derived from a common ancestor. And we thought it was this radiation where it might be possible to observe and to measure phenotypic changes in contemporary time. And the reason was that it had several things that were helpful for this.
First of all, they occur in the Galapagos archipelago. These islands differ from each other ecologically and impose different selection pressures on the finches. So it might be possible to see how these different finches have adapted to this. The other thing is that these islands, many of them are close to being pristine, never having been inhabited by humans. And such so that if we were able to observe and measure any changes, then it would be the result of natural conditions and not human-induced conditions.
And finally, they are very dynamic. They occur astride the equator, and as such, they are subject to the El Niño Southern Oscillation phenomenon, which means that there are some years when there's enormous amount of rainfalls in these islands. El Niño years, and this huge productivity of plants and also finches, or land birds. And then this is interspersed with years that sometimes can last as long as 2 and 1/2 years, where no rainfalls at all, it's a complete drought, and many of the land animals die. And it's in this sort of situation where we actually see changes in phenotypes.
Darwin himself thought that the speciation might occur-- and this is purely a cartoon. So he supposed that finches probably arrived from the mainland, arrived on an island in the Galapagos, met completely different ecological conditions, changed through the process of natural selection and evolutionary responses to natural selection events, built up a population, moved to another island with yet different ecological conditions. Step one and step two is repeated over and over again until eventually they came together in secondary contact.
Now, if the birds had been changed quite a bit during this process, they could be completely different species. If they had not changed very much, they might interbreed. Or, as Darwin thought, if they had only changed a small amount, then there might be competition for food, and there could be subsequent divergence in what we now call character displacement. And I'll be coming back to this later.
Now, another way of looking at this is that the fiches' divergent population could diverge here, that one line could go off onto another island with different ecological conditions. And they would diverge to a point where they would differ and that the lineages would be diagnostically different in morphology. And these divergence would continue until they got to a point where even if they did come together, they would be genetically incompatible.
Now, the point is here, we know from Wilson's work, that this point from lineage has been diagnosably different. The point when they really can't interbreed for reasons of genetic compatibility can last as long as, on average, 32 million years in birds, in fish, and in reptiles. It's an order of magnitude less than mammals.
But Darwin's finches, only 1 to 2 million years old, would lie around about this point, where lineages are diagnosably different, but long before the point when they're kept apart by genetic incompatibility. So we'd expect at this point that they're kept apart by what we call pre-mating barriers to interbreeding, things like differences in song, and in other birds differences in plumage-- not so in Darwin's finches about the plumage. But it would be pre-mating barriers to interbreeding.
Now, Peter and I have done work on-- we've visited all the islands in the archipelago. But we've done in-depth studies on two islands. One of them is Genovesa in the north, and the other one is Daphne, here in the center of the archipelago. And it's a story of Daphne that I'm going to tell you today.
Now, we can think of Daphne as a microcosm of evolution. When we first went there in 1973, there were two populations of finches. One species was a Geospiza scandens, a cactus Finch, which is a cactus specialist. It feeds on pollen and nectar from opuntia flowers and also the seeds.
And then there's this other very interesting finch, Geospiza fortis, which is a granivore and much more generalist granivore, with a much blunter beak than scandens. Now, we were particularly interested in fortis, because as David Lack had explained in his book, fortis is highly variable in build dimensions and in body size. The sort of variation that we see in human height is just about the same amount of variation.
And we thought, well, this might be a very good species to examine changes that might occur. So the outline of my talk is, how do new phenotypes arise in response to changes in the environment? What is the source of the genetic variation that allows this, and how is it maintained? And then I'm going to tell you about one of the most exciting parts and absolutely unexpected findings in our study, and that is the origin of a completely new lineage, which we followed from its inception up through six generations. And then I'll bring this all together in a couple of [AUDIO OUT] that's given us insight into three models of speciation.
So this is this variable Geospiza fortis, so the medium ground finch. And one of the first things we did is we banded a lot of birds. We watched how they fed and found out that the small members of the population-- this is an example of the small one, and this is an example of the large one. Same species, same population on Daphne.
The small ones fed exclusively on small soft seeds, whereas the largest members of the population were able to eat large, hard tribulus seeds. And they also took a few small- and medium-sized seeds as well. And then the medium-sized birds ate the small and medium seeds.
Now, over the 40 years, there has been an enormous change in beak depth in this population. So we began in '73. This is the average beak depth of the population at that time. And these lines on either side are the 95% confidence limits on either side of the mean. And so we had this enormous change here, when there was an increase in bill depth.
And then it went along for about eight years or so, and then it dropped down again to where it was before. Then it continued low for the next 20 years, and then there was this precipitous drop here. Now, I'm going to tell you about all these three points. The common denominator of all these changes has been a drought, when large numbers of finches die. So during that drought, 80% and sometimes as many as 90% of the finches die.
So we knew that if we looked at evolution by natural selection, there have to be three factors. There must be heritable variation in the trait of interest. Our traits of interest were bill size and shape, and body size.
As the result of an environmental perturbation-- in our case, it's going to be drought-- there was mostly differential survival. And very importantly, in the next generation, the offspring of the survivors must resemble their parents in the trait of interest. And they will do this, of course, if the traits were highly heritable.
So again, one of the first things we did early on in our study was we caught the birds, banded them, measured them, and then also their offspring. Waited until their offspring had grown up to adult size and measured their offspring. Then looked at the association between offspring and parents to get their heritability. And we found that their heritability was extremely high in all the traits.
And I've just given you bill depth here for fortis and bill length here for scandens. And you can see the heritability is 0.72. Zero would be no heritability. One would be complete heritability.
But this heritability is very high. And again, if they were to do this with human height, human height comes out as a heritability about 0.7. So we didn't have to wait long for the first perturbation. This is just one part of the island.
This is what it looks like in a normal wet year. And then this is what it looks like in a drought, when there's not a blade of grass, no vegetation at all, and the finches have to scrabble around in the rocks to find the remaining seeds. This was a drought in 1977.
What happened is that the small seeds quickly went out, leaving the big seeds. So birds began to die. Over 80% of the birds died. And as the small ones went out first until the end of the drought, we were left with just a few birds, and they were all the large birds in the population. Very few of the small birds had survived.
And the reason was that the large, hard seeds of tribulus were the only ones remaining at this time, which only the large finches could crack. So this was a natural selection event, but natural selection alone is not evolution. Evolution is a change across generations because of the heritability.
So when the rains came back again, the few large finches that had survived bred and produced offspring, which when they grew up were large like their parents. So this was an evolutionary response to a natural selection effect, for the reasons that it's the large birds that could eat the large hard tribulus seeds. So the population went up to this point here in bill depth, and it would look like this if I used body size as well.
And it went on for about 10 years, when large birds produced large offspring. And then along came a perturbation in another way. And this was an El Niño event that produced a huge amount of rain. It produced over a meter of rain on this small island.
And this was the largest and most severe El Niño effect in 400 years, and we could tell this by coral core data. And it completely changed the island from a large, hard seed producer to a small seed producer. And I'll just show you this in pictures.
So this is what the island looks like in a normal wet year. And these plants on the ground, they need tribulus plants, which produce these large, hard seeds, which made the difference between survival and non-survival in the previous drought that I told you about. But it went on raining for eight months. The birds actually bred for eight months.
And these tribulus seeds were smothered by grasses and other herbs. It rained some more, and they were covered by vines. Vines grew up over cactus bushes. They grew up over trees. And in the next year, after it had stopped raining, you could still see the trees and the cactus bushes draped with these vines that covered the islands.
And now [INAUDIBLE] data showed that the island had gone from a large, hard seed producer, in green, to an abundant supply of small, soft seeds. So when the drought came two years later, this time it was the smaller birds who had the selective advantage. And it was them that survived, and we plummeted down to back where we were in bill depth. But when we look at bill shape, a very interesting thing happened.
At this point, there was this incredible difference in bill shape, where these birds had all got blunt beaks. These were much more pointed beaks. And if we look at this in another way, you can see when you look at bill length and the bill depth-- this is for the whole 40 years. We started down here.
We went up to this point here in that 1977 drought, when only the large birds survived, and came down here and went across here. And it's this that we get this change of allometry. So why did the birds suddenly have sharp, pointed beaks?
Well, the answer is gene flow between scandens and fortis at that point. And this was a result of hybridization between the sharp-billed scandens and blunt-beaked fortis and then backcrossing to one or other of the parental species. So there was a trickle. Only about 1% of hybrids were formed, but nevertheless this was enough to get a trickle of genes going from one species to the other.
So what was it that caused this rare hybridization between fortis and scandens? And why did some hybrids between fortis and scandens survive the backcross in 1986 and not before? Well, to answer this, we've got to find what is the pre-mating barrier to reproduction between the species? And why did it leak at this time?
So in all Darwin's finches, there is no plumage difference. Males are black. Females are brown. They produce these dome nests. They have similar courtship displays as far as we can see, but they differ very much in song and morphology.
And so we recognized song and morphology. But can the birds-- we had to ask, can individual birds discriminate between their own and another species purely on the basis of morphology in the absence of song? And can they do it by song in the absence of morphology?
So to find out whether they could discriminate between their own and another species on morphology, we took stuffed museum specimens. We put a female fortis on one side of a pole, female scandens on another, took it into the territory, and asked, can the male territory owner discriminate between a female of its own species and a female of another species, even though it was just a stuffed museum specimen? And the answer was a resounding yes. They vigorously courted, as you can see here, a female of their own species and completely ignored the other, even though it was only a stuffed museum specimen.
And, of course, we did this many times, and we did it with a control. And then we asked, can they tell the difference by song? So we recorded song, played that fortis song. Fortis came into the loudspeaker. Scandens went on feeding or doing whatever it was doing.
And played back scandens song. Scandens came in. Fortis went on feeding or doing whatever it was doing. And we did this many times with controls. So just as we can distinguish between the species, the song and morphology, so can the birds.
Now, the songs are very different. Fortis song is a modulated song, here. And then scandens song is a repeated note song that is individual variation, but always on a very species-specific song theme.
Now, we know from work by Bowman that song-- because he was able to do work with captive birds. You can't do that now, but he was able to do this in the 1950s. And he was able to show that song is learned from the father in association with appearance during a very short, sensitive period of time, between day 10 and day 40 after hatching.
Now, this time corresponds with the last few days when the birds were in the nest and when they're out of the nest, being fed by their parents. And all this time the male is singing. So it's not too surprising that they learn almost perfect renderings of their father's song. And once learned, this song is retained for life.
We have recorded song repeatedly through the lives of the birds, and it has not changed. And as adults, they pair according to their species song. So this constitutes a pre-mating barrier based on song, which is learned and culturally transmitted, and morphology and particularly beak and body size, which I've shown you is genetically transmitted.
But we can ask, how robust is this barrier? Because after all, it is vulnerable to disruption if a young bird hears and learns the song of another species during this short, sensitive period of time. And this does happen.
It happens rarely, about 1% of the time. And it happens for different reasons, but one reason is if the male dies and the female is left to rear the offspring. And then females don't sing. And if the natal neighbor is another species, then the birds in both those nests will learn that natal neighbor's song, and so they will grow up learning the other species' song.
Now, we had a few birds produced like this, actually from the very first time we went to the island, just one, at the most 2%. But it happened every breeding season. So we had a few hybrids that we could follow between fortis and scandens. And none of the hybrids in the first 10 years of the study survived the dry season to breed.
We thought maybe this was because they didn't have enough of the appropriate food. Lots of birds were dying at this time, anyway. But we also thought maybe we could see the beginning of genetic incompatibility. But actually, the first was right, that the birds, with their intermediate beak size, there was not enough food available for them. Because after the El Niño in 1983, when there was this large production of small, soft seeds, then the hybrids began to survive.
And they backcrossed to either one or other of the parental species, according to the song they had learned. So fortis and scandens-- again, this as a plot of bill depth and bill length. But it shows you that for the first 10 years of our study, fortis and scandens were completely separated. And then when there was this trickle of gene flow from fortis into scandens and scandens into fortis, the populations started to converge on each other. And this convergence continued for the next 30 years.
So this was what was producing-- the fortis was gaining genes from scandens, which contributed to the sharp-pointed-- a more scandens-like profile on fortis. Now, we had followed the integration of genes from fortis into scandens and scandens into fortis using microsatellite genetics. But then we have since collaborated with Leif Andersson, who was able to look at whole genome analysis.
And we asked him-- we still had these blood samples. And we asked him, would it be possible to find specific alleles that could have been introduced from scandens into fortis that could have contributed to more pointed beak? We know that genes went in, but were there any specific ones?
So we sent our blood samples over to Leif Andersson-- and Leif is here-- and his group. And they found a very interesting gene, a transcription factor. There were other genes, but one stood out as being very important, ALX1.
And when he looked at across all the finch species, he found that those ones that had very blunt beaks, like magnirostris and conirostris from Española, had the blunt form or the blunt haplotype of this ALX1. Whereas all the other finches, including scandens, had a sharp-beaked haplotype. So he said the pointed haplotype and the blunt haplotype.
This gene is highly conserved. You find it in fish and in mammals, as well as birds. And it's associated with craniofacial development. And actually, a mutation in the ALX1 causes cleft palate in humans.
So what we did is we sent over-- also, we found it in fortis. Fortis had both. We had the measurements of all these birds. So we sent blind over to Uppsala, the blood samples. We sent 62 blood samples over.
And we found out that those that were homozygous for the pointed ALX1 had more pointed beaks. Those that were homozygous for the blunt ones had blunt beaks. And the heterozygous ones were intermediate.
So this showed us that-- and I'm cutting a long story short. But it showed us that genes from scandens, the ALX1 pointed haplotype, was moving into the fortis population and was contributing to the sharp-beaked fortis, which is now becoming more pointed, more scandens-like. But the genetic exchange also goes both ways. The blunt beak haplotype was going into scandens. And from that point onwards, the scandens was becoming blunter-beaked and more fortis-like.
So in both populations, in both fortis and scandens, both the genetic and morphological variation increased to a noticeable extent. So these three photographs were taken of scandens in 2012. The scandens at the top has a pointed beak, very similar to the scandens, before introgression, before gene flow, between scandens and fortis. And the two at the bottom have blunted beaks and are more fortis-like.
So we can move on now to the third part. What is it that caused this huge drop where fortis became much smaller in actually body size and in beak size? So the same thing. This time it was a 2 and 1/2 year drought, where over 90% of all birds on Daphne died.
So there was the drought, but there was one other factor that was different. Daphne in the meantime had been colonized by magnirostris. This came in actually during this huge El Niño event of 1983. The population gradually built up until, by the time we reached 2003, there were well over 200 magnirostris on the island.
Now, magnirostris is a close relative of fortis. It's an extremely dominant bird, very aggressive. And it loves tribulus. So during this drought, when all the seeds that were left with these large, hard tribulus seeds, the magnirostris outcompeted the large fortis, leaving behind the very few-- they were dying as well, but the ones that were left behind were the smallest fortis.
So this was a character displacement event, where the morphological distance between magnirostris and fortis was increased because magnirostris outcompeted the large fortis. So again, we went back to Leif and said, were there any genes underlying this character displacement event? And they found one, which was, again-- well, it was a transcription factor facilitator, HMGA2. Once again, highly conserved, found in mammals and fish and reptiles.
Now, we had many of these birds banded. We had the blood samples from them before they went into this 2 and 1/2 year drought. So we took 70 of these, where we knew the measurements, sent them blind over to Uppsala, and once again asked them, can you genotype this? And this HMGA2 comes in two forms.
One variation was for large beaks, the other for small beaks. And once again, out of these 70, the results came back that the homozygous small haplotypes were small. Those with large were large. And the heterozygous were intermediate.
So we said, taking these, how many survived during the drought? Now, this wasn't just one gene. There were other genes as well, but this was a most dominant gene that we found. And so out of the large haplotypes, out of the 20 birds, 14 of them died, whereas out of the small haplotypes, out of 19 birds, only five of them died. The HMGA2 large haplotype, which was associated with large beak size, was at a strong selective advantage through this selection event. And it facilitated this phenotypic shift.
Now, not only was there a morphological change that occurred, but, quite unexpectedly, there was also a behavioral change. Now, to tell you a little bit about the song, the magnirostris has a loud song, sung in the same frequency bandwidth as fortis and scandens song. So this is what a magnirostris song looks like.
Sometimes there are two notes, sometimes three notes. And over the 40 year study, we've had eight fortis and two scandens that learned and sang a magnirostris song. So here's a normal fortis song, and this is one of the fortis that sang a magnirostris song; a normal scandens song and one of the scandens that sang a magnirostris song.
Now, none of these birds bred with the magnirostris, so why was this? The reason was when these poor little birds opened their mouths, sang a magnirostris song, a magnirostris, which is twice its size, whipped in as if from nowhere and just beat it to bits. So it never got anywhere.
So it seems that when the size difference between species is large, the barrier to reproduction is robust. Even learning a magnirostris song didn't lead to mating. But then an extraordinary thing happened, and we almost could hardly believe our ears when it happened. But the songs of fortis and scandens after magnirostris had really built up began to change.
So this is before, when there were only very few-- I think there were one, two, three, four, five-- magnirostrises in green-- magnirostris males on the island. This is what the scandens songs, up here in red, and fortis songs look like in acoustical space. And then after magnirostris built up until there were well over 200 of them on the island, then these birds, both scandens and fortis, began to sing more notes per second, so that it was almost as though the song was compressed.
So instead of getting songs like this, we got more songs like this. And I say, we could almost hardly believe our ears. And we started to wonder, had there been a change in the equipment we used? So we went back and we re-analyzed all our songs from before. And no, it was truly a change that we were hearing.
And so we wondered why there had been this change. Now, Jeff Podos had written this very influential one about beak size and shape influencing song production. So we thought, oh, perhaps this is what we're seeing. But we analyzed our work, and we saw absolutely no association between beak size and shape and the song production.
So clearly, it wasn't this was going on. And then we wondered-- well, we started various things, but then we came down to, could it have been competition for acoustical space that resulted in song divergence? People would have shown this in blue tits and in other birds, such as the antbirds.
And there have been several papers that have shown this change in acoustical space as a result of a bird entering a new environment. And so we wondered if this change had occurred as adults, but it hadn't. The adults had not changed their song. We recorded them every year. And the song change occurred during the short, sensitive period of learning.
So we looked at the father's song, and we found that the copying of father's song was still-- son's still copied the father's song. And you can see this by the red progression line. But if you look at the solid points above a slope of one, it is an indication that son sang more notes than their father.
So this seems to have been what was going on. And we saw this both in fortis and in scandens. So this was really very interesting to us, because it answered, or helped to answer, another question that we had for many years, which is why on all the different islands in the Galapagos fortis and scandens and other birds were singing different songs.
So, for example, this is fortis song on Daphne and scandens song on Daphne. But on Santiago, Pinta, and Santa Cruz, for example, fortis is still singing a modulated song, but with completely different notes. Scandens still sings repeated note song, but with completely different notes.
And on any of these islands, if you look at the acoustical space, then all the birds-- for example, there are over nine species of finches on Santa Cruz, but they all sing in their different acoustical space. So they're separated acoustically on the different islands, just as they were on Daphne. So this gives a clue that there must be some interference in acoustical interference.
So now, I'll move on to the origin of the new lineage. Now, we had already shown with integration between fortis and scandens populations that there had been this increase in morphological genetic variation. And we had actually written, having found this, that in a new environment this could lead to evolutionary change along a different trajectory because of the huge increase in both morphological and genetic variation.
But we never, ever dreamed that we could see such a thing. But what happened is that a bird arrived on Daphne, at a time when all the birds on the island were banded. Trevor Price was a graduate student at this time. And he caught the bird, and he measured it.
And it was a large bird. It was 28.5 grams, whereas a normal fortis is 17 grams. So it's a giant. And it was a young bird when it arrived. And then when it started to sing as an older bird, it had a completely unique song, never before heard on Daphne.
Now, at this time, we had microsatellites, and Peter and I went back to the island. We took a blood sample from this bird, and we matched it up with every bird on Daphne. It clearly was not born in Daphne. It couldn't possibly have been this.
But it came out with 95% confidence in an assignment test that it was a fortis/scandens/fortis backcross born on Santa Cruz, the nearest big island. This made quite a bit of sense. I mean, the island is only five miles away, and it could possibly have flown over from Daphne.
But soon we published this. How wrong we were, because with Leif's group, when they were able to look at the whole genome, they found that this bird was a conirostris from Española. Now, Española is well over 100 kilometers away, but it came out as a perfect conirostris.
So what it did is that it took a long time to breed, but when it did breed, it bred with a fortis/scandens/fortis backcross born on Daphne. And this to us at the time made perfect sense, because we thought it was a fortis/scandens/fortis backcross on Santa Cruz. And again we were completely wrong.
It produced a few of offspring, but none of them survived. Then it bred eventually with the fortis and produced some offspring which did survive, and this was the only outbreeding that occurred.
We followed all these offspring. We took blood samples from them. All of them showed genetic transmission from 5110. And this was seen from microsatellites.
All males sang a 5110 song, which was-- I should say we banded this bird 5110. All males sang his song, which had been passed down from father to son. And so we were following this, and then along came this 2 and 1/2 year drought, where 90% of the birds died.
All these birds went out, except for these two, an inbred brother and sister. When the rains came back, this inbred brother and sister bred with each other and produced 26 offspring. All but nine of them survived. We had a daughter breeding with her father, a son breeding with his mother, and the rest of the sibs breeding with each other to produce more offspring, which bred with each other to produce more offspring, which bred with each other.
All birds showed genetic transmission from 5110. And now we have complete genome sequencing of all these birds, and they all show an absolute genetic transmission from 5110. All males sang the 5110 song, and all were large. And, of course, the inbreeding from whole genome analysis increased each generation, from generation one up.
When it first started, there was quite a lot of heterozygosity because it was a hybrid. And then as they were mating, with the brother and sister mating and all the offspring, the inbreeding got more and more intense. And what also happened was that there was an allometric shit.
So this is fortis in green, conirostris in red. And this is what we call the big bird lineage from 5110, is displaced in this allometric shit. Now, this is really interesting, because it has a small-- it has a small body. It has a large beak.
So it has a large head or large beak on a small body. And this makes it really efficient at feeding on tribulus. It is absolutely omnivorous. It feeds on everything that fortis and scandens on the island feeds on. But it's particularly efficient on these large, hard tribulus seeds.
It's just as efficient as magnirostris, but being smaller, it requires fewer seeds to survive. So if there's another drought and tribulus is abundant in another drought, it could do very well. So is this new lineage behaving like a separate species? It's much larger than its nearest relative fortis.
In morphological space, it lies between magnirostris and fortis, and this was the gap that increased when magnirostris outcompeted the large fortis during the character displacement event I told you about. And the big bird population moved right in. This is three generations of the big bird's song.
And this is a normal fortis song, a normal scandens song, and a normal magnirostris song. It breeds in one part of the island. Irby will recognize this part of the island.
The blue dots are the area before the drought; the red dots, after the drought. They hold territories that are contiguous with each other, which they defend against each other. But these territories are very large, and they overlap with the territories of fortis, scandens, and magnirostris, who they ignore and who are ignored by them. So in all respects, the new lineage is functioning as a separate species.
Will it die out through inbreeding depression? Well, you can see it's quite highly inbred, but it's still not completely inbred. We see no sign of inbreeding depression so far. But, of course, it might die out because of that.
Will the genetic variation be augmented through genetic exchange? It might be, but so far we've not seen any sign of that yet. So whether it survives or not, this new lineage gives us insight into how a new species could arise and either persist or become extinct.
So in summary, we went to the island when there were two distinct species, fortis and scandens. And so after this enormous El Niño event of 1983, which was the largest in 400 years, then the hybrids began to survive, and fortis and scandens began to converge on each other. Magnirostris came in, outcompeted the largest fortis, and the big bird lineage moved right in here.
So this gives us insight into three models of speciation. There's the allopatric model of speciation, the kind that really has been called this, but Darwin actually first envisaged this. And this we saw between fortis and magnirostris, where there was no interbreeding on second recontact, a character displacement event led to the morphological divergence, and we saw competition both for morphological space and for acoustical space, which led to song divergence.
But there's this under-appreciated role of introgression, gene flow between two different species. And we had speciation could lead to speciation by fusion, where interbreeding between fortis and scandens on Daphne led to one unique lineage of mixed genetic composition very different from fortis and scandens on other islands in the archipelago. And then speciation by introgression with conirostris, eight conirostris coming into Daphne.
And in a completely new environment, led to the development of a unique lineage, which we call the big bird lineage. So I think we all know this diagram, Darwin's only diagram, which was in his notebooks, where he was pondering over the relationship between species and drew this sort of treelike diagram and wrote, "I think."
Would he now join up some of these branches and write "I now realize"? I don't know. But we think many graduates, post-doctoral fellows, our collaborators, and daughters. And one of these we think very much, Irby, who spent six months' hard work on this island; the Galapagos National Parks and Charles Darwin Station for logistic research; and our funding agencies.
But anybody, and I'm sure I include Irby in this, too-- anybody who has worked on the Galapagos, I'm sure, will want to leave you with two messages. One, a conservation one, that environments and populations are dynamic. They're constantly changing. And for a sustainable environment or a sustainable globe, we must keep them both capable of further natural change.
The other one-- and I think this is directed to the young people in the audience-- we live in very exciting times. The genomic data are rapidly accumulating. Changes are happening every year. And this can really enhance our field studies.
But reciprocally, a reliable interpretation of genetic data really requires a deep understanding of ecology, evolution, and behavior in the natural environment. So I think it is very important to remember this. But thank you very much.
IRBY LOVETTE: Are you willing to take a few questions from the audience?
ROSEMARY GRANT: Absolutely, yes.
IRBY LOVETTE: Does anyone have any questions for Rosemary?
ROSEMARY GRANT: [LAUGHING] Yes.
AUDIENCE: How do you gain permission to go on the island in the first place? I've always wondered how you just go on and start--
ROSEMARY GRANT: Oh, OK. You know, I almost thought of showing a little video about this, because we've got to be very careful when we go on. Because, well, it requires quite a lot of permits, but also nowadays we have to go through a quarantine process.
So we have to make sure that everything we take on is scrupulously clean. All the food that we take on-- so that goes into quarantine. All the food that we take on has got to be checked.
So for example, with things like rice and flour, we freeze them for 96 hours before we take them on. And everything is sprayed and inspected and put into large bags and taken onto the island then. I think this has changed a little bit since Irby went, but we were partly responsible for making this very-- we're talking to the parks to make it like this. And they now do this for all islands in the Galapagos. Yeah.
IRBY LOVETTE: One over here. Blue shirt.
AUDIENCE: How do you think the natural selection of plants affected the birds themselves?
ROSEMARY GRANT: Yeah. That's a super question. We have also looked at this a little bit, and we found evidence of this in one plant, which is cordia lutea, and we have published this. But also, I think what you're particularly referring to, which we've also thought about, is the tribulus.
How has that actually increased in size? Now, Mark Johnson is looking at this right now, and he's looking to see whether the tribulus had changed at all. We started to do this, but we thought it was-- it got a little bit difficult, because it's a perennial plant. It grows in different parts of the island, and it is extremely variable.
And I think a lot of variation is due to just the soil it is in and the amount of water it gets at that time. But Mark is actually looking at this really thoroughly now and looking at it across many populations in many different islands and actually in different parts of the world. So there might be change.
And we certainly in cordial lutea, between the population that occurs on Genovesa and also on Española-- the size of the seeds very much reflect the birds' beaks. So in magnirostris on Genovesa, they take the bottom third of cordial lutea around that. And the cordial lutea has a great big sea like a cherry stone, a big cherry stone there.
On Española, the cordial lutea are exactly the same species. It's much smaller seed, but there, conirostris takes it. And the conirostris is a smaller bird, but it also takes the bottom third. So it looks as though there has been selection on the seeds. Yeah.
IRBY LOVETTE: [INAUDIBLE]
ROSEMARY GRANT: Yeah. This question up here? Yes?
AUDIENCE: Many of these changes are external and behavioral. But there are also changes in the [INAUDIBLE] and anatomical legacy [INAUDIBLE]
ROSEMARY GRANT: Yes. What I've just told you about is, as you say, the external phenotype. What we hope to, with the Uppsala group's help-- it may be time to find out some of these. But there must be some really strong physiological changes in some species of finches.
For example, difficilis, which is a sharp-beaked finch-- there's populations that live high up in a sort of cloud forest. And they must be very different from the ones that live lower down in the arid climate. And it would be really nice to know the physiological differences there.
You see the same in the warbler finches. There are two warbler finches, Certhidea. And they're genetically very different from each other. They look identical, but they're genetically very different.
One of them only lives high up, the other in the arid part of the environment. And it would be really nice to know the physiological differences there. And I could go on and on, but yes, you're absolutely right.
And we hope not us, because we're really quite old now. But if we could live another many years, that would be what we would look at. And we are starting to do this with Leif. That's a great question. Yes?
AUDIENCE: [INAUDIBLE] observational differences, or did you also look into the genetics? Did you actually analyze the genetics of the different types of birds?
ROSEMARY GRANT: Yes. We've looked at genetics. We've looked at the behavioral differences. We've looked at the genetic differences.
And we're trying to actually get even longer reads of the genotypes, so that we can actually see if there are any things like inversions going on like this. So that, again, is work in progress. Yeah.
IRBY LOVETTE: One last question.
ROSEMARY GRANT: Yeah.
IRBY LOVETTE: Rosemary, [INAUDIBLE].
ROSEMARY GRANT: Yeah?
AUDIENCE: Hi. This is more based on just your research experiences. When you're performing long-term ecological research on very specific [INAUDIBLE] for many decades, I want to know how you stay motivated in staying in that same research environment, and perhaps during times where the data isn't necessarily pointing you in any sort of direction?
ROSEMARY GRANT: OK. Yes. I mean, there have been long periods of time when-- I've shown you this-- where they're all the same. I mean, I just showed you beak depths. That's all the same.
But actually, by living on the island with-- there are constant questions every single day. There were many things that I haven't talked about, of course, because I had an hour to talk. And so I had to pare down everything.
But it's a very exciting place still to be. And when you're actually living amongst the birds yourself, you're just bombarded with questions every day. Even if it's not the birds itself, it's questions-- like the one I got over here is, are the plants changing.
So we've done other little experiments, like pollination experiments on opuntia and things like this. But there is so much going on that you're just bombarded with questions, and so it's a very stimulating place to be. And I can honestly say, and I'm talking for Peter as well, I'm sure, that there has never been a moment where we have been bored.
And in fact, we've taken books down and not read them. You get really exhausted, because you have 12 hours of light only. And it's amazing how long you-- you're so exhausted, because, of course, it's very hot, that you sleep very well at night, even though it's on a rocky slope. The only thing I will say that is nice when you finally get back is that first fresh water shower is just wonderful.
But otherwise, no, you never get bored.
IRBY LOVETTE: On that note, let's give Rosemary one more big round of applause.
ROSEMARY GRANT: Thank you very much. Thank you.
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Dr. Rosemary Grant is a hero to generations of students and scientists in the field of evolution. Her work (along with husband Peter) on the finches of the Galapagos Islands provided one of the first and clearest demonstrations of natural selection occurring in real time, and is a foundational example for this subject in every high school and college biology classroom. Featured in the Pulitzer Prize-winning book The Beak of the Finch, she showed that bill size in different populations of finches can change over very short periods—as little as two years—driven by environmental conditions and food availability. The findings turned the world of evolutionary biology on its head, as such changes were previously thought to take hundreds or even thousands of years. In her talk, Rosemary will cover many of the highlights from her work on Darwin’s Finches and discuss the complementary insights she has gained from decades of exploring their behavior, ecology, evolution, and genetics.