Evolutionary Adventures

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Gary Galbreath is a detective and an adventurer. But the mysteries he solves are evolutionary, and the treasure he seeks is the ever-elusive new species.

Galbreath, Northwestern University distinguished lecturer in biological sciences, uses genetics to study relationships between species and how mammal populations have migrated across the globe over time. Science in Society asked for some highlights.

You’ve studied the origins of Cambodia’s national animal, the kouprey, which you weren’t even sure was a true natural species. What sparked your interest?
I was curious about its place in nature. Little had been done with DNA in regard to origin of any of the Asian wild cattle, particularly the kouprey.

I was able to obtain some hairs from another kind of wild cow—the banteng—which is also found in Cambodia. I was interested in the possibility that the kouprey might actually have started out as a race of hybrid human-raised cattle that escaped back into the wild. I thought if we looked at the mitochondrial DNA, which is maternally inherited, of a banteng, it might help us out. A portion of the mitochondrial DNA of the kouprey had just been published by someone else, so this was the first time that a comparison could be done. It turned out that, as we predicted might be the case based on morphology, there are notable DNA similarities between kouprey and Cambodian banteng.

I do much of this work with John Mordacq, another lecturer here in biological sciences. I tend to obtain the specimens, and he does the very difficult work of getting good DNA sequences out of them. To my delight, there turned out to be a very strong resemblance between the Cambodian banteng and the kouprey. John and I published a paper noting this, and we listed three hypotheses that could be used to explain it. But our favorite was that the kouprey had never really been a natural species, but was a hybrid between domestic zebu cattle like you find all over east Asia and the banteng, and that’s why there was a similarity in mitochondrial DNA.

What changed your minds?
Not long after that, I became aware of a fossil kouprey skull. That was the end of my favored hypothesis. The dating isn’t perfect, but [the skull is around] ten thousand years old or more —well before the domestication of cattle by human beings.

I think everybody who is interested in this now agrees that what happened was sort of the other way around. That, due to ancient hybridization events, kouprey DNA got into the banteng [population] in southeast Asia. So, in a very broad sense, the banteng populations that you find at least in Cambodia are the hybrids, not the kouprey.

It’s still scientifically interesting, because this is one of those instances where mitochondrial DNA of one species has become broadly fixed in widespread populations of another.

In a way, I feel sadder that [the kouprey] was a real species, because it means they were a real species that humans have driven extinct. I should mention that the kouprey sample was from a museum specimen. No one has certainly seen a kouprey for more than a decade now, and it is probably extinct.

What other species classifications have you investigated using genetics?
There’s the Gobi bear. It’s actually a form of grizzly bear, but they live in the hills along the edge of the Gobi desert. Russian researchers have tended to treat it as a separate species, and other people were treating it as a unique subspecies. I had a strong feeling—and the great field biologist George Schaller actually had indicated this already, so I don’t want to imply that this was my own idea—but I agreed with his initial impression that [Gobi bears] were probably the same as an animal from the Himalayas, the Isabelline bear.

We managed to get a hair sample and run a comparison, and sure enough it’s almost identical. It’s appearance is the same. It’s a little smaller, but it lives in a habitat that’s terrible for grizzly bears, so you would expect it to be small. Adult size in bears is heavily dependent on diet when they’re growing up, so we concluded that this is simply an outlying population of Isabelline bear. So that solved a little mystery.

You’re currently finishing a long-term study on the migration of moon bears, and the project started through a really interesting coincidence. What happened?
Way back in the late eighties, I found this very odd-looking bear—it was sort of a village mascot—in Yunnan province of China. He was very friendly and mostly blond in color, which moon bears aren’t supposed to be; they’re supposed to be coal black. He had a dark mane, and some other dark patches on his body, but mostly he was blond, so this was something new. At the time I couldn’t do anything about it except take some pictures.

Roughly a decade later, my friend Sy Montgomery told me that a fellow who was in the forestry department in Cambodia, whom she had met at somebody’s birthday party in New England, had told her about a strange blond bear that had been captured in Cambodia. Of course, this clicked with me— though [Cambodia is] a long distance from Yunnan province of China. I ended up seeing pictures that he had, and he saw my pictures, and it was clear that it was the same animal. So I thought we had to find out if it was a new species.

[The three of us] ended up doing quite a journey across Cambodia. The bear, at this point, was in captivity on a palm oil plantation that was owned by a guy you could perhaps call a warlord. That made just getting in to see the bear, let alone getting hairs from it, not the easiest thing in the world to do. But it all got managed, and we ended up getting hairs from not only that animal, but from another blond bear we found at a zoo in Thailand and a number of other moon bears in captivity. We found some that were partially blond and partially black—there are some real intermediates.

By this time, I was realizing that this was probably color variation within a species (not a new species). We collected all of the hairs anyway and [confirmed] they are all one species of bear. But I did realize that there’s a lot of genetic variation, and the samples fall into several groups of mitochondrial DNA haplotypes (a set of genes inherited from the maternal parent), so I realized there was probably a biogeographic story in all this. So that started this whole project.

How has the project evolved?
We’re trying to work out the relationships and past migrations across a good deal of the Asian continent of moon bears.

I started gathering DNA specimens from moon bears all over southeast Asia, preferably from animals where we had a reasonably good idea where they came from. After a while, I expanded out, and we’ve been getting data as far apart as Pakistan, Siberia and Japan, so we’re actually able to look at large-scale migratory phenomena. It’s kind of like the out-of-Africa story in human beings, but in bears instead, you might say.

How far did the moon bears spread?
There are bears that look a lot like moon bears from as far away as Europe in the fossil record. I’m not sure if that’s because they’re the same species, or because moon bears are, with reference to most other bears alive today, relatively primitive bears in their structure.  If you were to look at the skull of the common ancestor of most of the old world bears, it would look a lot more like a moon bear than any other living bear. That makes it difficult to tell fossil bears that are simply extremely primitive from those that are actually moon bears, because we can’t see their soft anatomy and the shape of their ears and footpads—things that we use for species identification.

How have historical species classifications changed as new genetic technology has become available?
Every now and then, you get a real blockbuster that changes a classification. Honestly, and happily, most of the time [genetic data] doesn’t change the classification very much. I think in a way everyone, without saying so, was holding their breath in the 1980s and 1990s as it became possible to do this for lots of groups of organisms. It was a real test of all of the classifications and phylogenies done just based on things like skulls and teeth.

For the most part, in animals in general, things have held up well. So that’s very pleasing. It means that what biologists thought they were seeing in nature was for real. Occasionally, something jolts the world view of scientists. But often, even then, if you look back at the literature, there was somebody who was insightful and made the argument on morphological grounds earlier, and was sometimes ignored. But this is the way science is supposed to work: we come up with competing hypotheses and test them. In the end, DNA has tested the different morphological models, and most of them have come up looking pretty good.

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