Suzanne Estes: Talking Evolution

Evolutionary biologist Suzanne Estes is so modest that it’s easy to overlook her accomplishments. “Suzanne’s major flaw is indeed that she is too self-effacing,” says Patrick Phillips, her graduate adviser. But conversations with Phillips and other admiring colleagues make it clear that she should not be underestimated as a scientist or mentor: Estes’s drive and intellectual curiosity have made her an up-and-coming genetics researcher and influential mentor to tomorrow’s scientists.

Estes studies the genetic evolution of Caenorhabditis elegans, the roundworm. “They have a very rapid generation time for an animal–about 4 days,” she says. This means she can take the worms through many generations in a short time and watch evolution in action in her laboratory.

Mostly, she’s interested in the genetic mutations handed down from one generation to the next. Natural selection favors members of a population whose mutations improve survival–say, by giving them longer beaks or more fur. This phenomenon is a key to the long-term health of any species, and it plays out well in large populations, in which relative fitness is often tested.

But when population numbers dwindle, as in the case of a threatened species, negative mutations can become a problem. Estes showed this in the lab by passing each generation of worms through a single-worm bottleneck, ensuring that mutations became fixed. As a result, the populations declined in fitness over time. This scenario is plausible in very small populations in the wild and “is one of the reasons why conservation biologists are so afraid of small populations,” Estes says.

During her doctoral research, Estes discovered that conservationists had less to fear from small population sizes than was generally thought. As soon as Estes returned her worm populations to a regimen of large population size, they quickly recovered from the accumulated, deleterious mutations. “We surmised that this was due to the fixation of secondary mutations that compensated for the effects of the original deleterious mutations,” she says. Next, she showed that even small populations could efficiently purge deleterious mutations and maintain their overall level of fitness. These were fundamentally important discoveries, says Patrick Phillips, a biology professor at the University of Oregon (UO), Eugene, and Estes’s thesis co-supervisor.

The results, she says, really come into play in the minimum effective population size calculations used by conservationists to manage threatened and endangered species. “None of those take into account the fact that compensatory mutations are possible,” she says. Although Estes doesn’t advocate lowering the effective population size used in species management, she does think that her work bodes well for a speedier recovery of managed populations.

Now, Estes is digging deeper into the research and looking at the question of repeatability. “One of the big questions in evolutionary biology has been if you rewind the tape of evolution, as Stephen Jay Gould put it, are you going to see the same outcome every time?” she says. “We also have the tools now to identify these compensatory mutations that ameliorate the effects of the bad mutations.” Phillips says that her move toward more genomic approaches should produce many more exciting results from her lab in the next few years.

Worm keeper

Estes never set out to become a keeper of worms, but the natural world fascinated her from childhood. The future evolutionary scientist grew up in Ada, Oklahoma, the birthplace of Oral Roberts. She spent much of her childhood roaming the rolling hills about 130 kilometers south of Oklahoma City. She liked being outdoors and took an interest in living things and how they operate.

Her parents–mom was a social worker, dad a highway patrolman–supported her interest in nature and her desire to pursue her education, but they knew little about the academic world. When it came time to select programs or colleges, Estes relied on instinct more than guidance from anyone around her. She loved natural science and did well in high school biology. So when she enrolled at East Central University (ECU) in Ada, biology was an obvious major.

While a student at ECU, she attended a minisymposium on ancient DNA at the University of Oklahoma. “I was completely fascinated and started getting really interested in population genetics and evolution,” she says. The genetics teacher at ECU didn’t believe in evolution, but Estes didn’t let that stop her. Her interest grew, and she began researching graduate schools on her own. She had many good teachers at ECU but little guidance about graduate studies, she says.

A break came in 1997 when she was chosen to be a McNair Scholar. Named after Ronald McNair, an African-American astronaut who died in the Challenger, the McNair program awards grants to promising undergraduate students from disadvantaged backgrounds to encourage them to pursue graduate degrees.

The opportunity was life changing and mind changing, Estes says. It provided a paid summer internship at the local Environmental Protection Agency laboratory, where she analyzed water samples and interacted with scientists. The scholarship also paid for a trip to UO to visit Michael Lynch’s population-genetics lab in the Department of Biology’s Ecology and Evolution Group.

Work and family

Estes found her first meeting with Lynch “really intimidating” and had “only had a nebulous idea of what I was getting into,” but she applied and was accepted as a doctoral student in Lynch’s lab. More intimidating still was telling her parents that she planned to move 2400 kilometers away to continue her studies.

A reshuffling of the UO biology department in the fourth year of Estes’s doctoral studies led Lynch to leave the university and threatened to wipe out years of hard work. By then Estes had put down roots in Oregon. She had married when she was 21. Her husband, Nick, and Sarah and Charles, Nick’s children from a previous relationship, moved with her from Oklahoma to Oregon. By the time Lynch left, the children were attending school in the state, and Estes didn’t want to uproot them. Instead of following Lynch to Indiana, she stayed in Eugene. “Oftentimes that doesn’t work out for graduate students, but the absolute perfect co-adviser, Patrick Phillips, was hired,” she says. “I ended up finishing in his lab, and it could not have worked out better.”

It worked, Phillips says, because the chemistry was good and everyone was determined to make it work: “We both maintained a good relationship with Mike and produced some good papers together.”

In 2002, Estes moved up the Willamette Valley to Oregon State University in Corvallis, taking a postdoctoral position studying snake mating systems with zoology professor Steve Arnold. It was a departure from worm work, but her stepson was about to graduate from high school, and she didn’t feel right about moving far. Because Arnold was “one of the top evolutionary biologists around,” the opportunity was too good to pass up.

Luck or hard work?

Once her stepson graduated and Estes completed the postdoc, her family was ready to move anywhere. She applied broadly and was offered her top job choice–and it was practically right down the street. She’s now in her second year as a tenure-track assistant professor in the biology department at Portland State University.

Estes invokes serendipity to explain her success. “I’ve been really fortunate,” she says. “My entire career could be characterized as just being one serendipitous event after another.” But Phillips says luck has nothing to do with it. “Suzanne is one of the hardest working scientists I know. For roughly 3 years straight, she had to transfer a large set of worm populations every 4 days, no matter what. She performed absolutely huge fitness assays all by herself. She never complained and generated extremely high quality–and important–data,” he says. “Grad school is an exciting time, but there is a lot of grind-it-out stuff that needs to be done. Those who succeed are those who do the work.”

A natural mentor

One student who floated through a previous Estes office is Beverly Ajie, who worked with her as an undergraduate when both were in Eugene. Ajie is now pursuing a doctorate in population biology at the University of California, Davis. “Suzanne was a natural,” Ajie says. “She was always available for questions and easy to approach. We spent a lot of time talking about the pros and cons of alternative career paths and how they fit into one’s overall life goals. I think this is something too few graduate students feel comfortable discussing with their advisers.”

Now that Ajie has herself taken on the mentor role, she appreciates Estes’s skill and guidance all the more. “Having Suzanne as a mentor was key to my seeing graduate school and academia as realistic and exciting options,” she says. “Keeping sight of the big picture and the detail at once, I learned, is important to actually doing great science because on a day-to-day basis it’s often tedious and repetitive and yet on a grander scale it’s, well, the best.”

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