Bree Rosenblum

A Kind of Communion

Erica Bree Rosenblum listens closely for the answers

For Erica Bree Rosenblum, PhD ’05 Integrative Biology, the study and teaching of ecological genomics has always been as much about a spiritual connection with her subjects as an academic one. In the field, “you don’t just bring your intellect to bear. You’re in a kind of communion with the landscape, getting a sense of the interesting questions.”

A groundbreaking evolutionary ecologist and educator in the College of Natural Resources, Rosenblum has focused her research on two linked, yet outwardly opposing, biodiversity questions: How do new species arise, and why 
are we now losing so many at such an alarming rate? Rosenblum believes that her weightiest findings, based on analyzing lizard speciation in New Mexico, reinforce insights into how the earth has come by its wealth of plant and animal life, a process still underway across the globe. “Little environmental changes can lead to new species forming,” she says. “Taken over many millennia, that’s how we ended up with this phenomenal amount of global diversity.”

She first sought answers to the new-species question in the early 2000s as a grad student on a road trip. “I didn’t choose my dissertation project by reading a stack of books to select a study system,” says Rosenblum, now an associate professor of global change biology in the Department of Environmental Science, Policy, and Management. “As a graduate student, I drove across the country waiting to find a place that said, ‘Pick me.’ That’s how I chose the White Sands system I’ve been studying for 20 years.”

How species begin and how they end

What Rosenblum found in New Mexico’s 275-square-mile White Sands National Monument, the world’s 
largest gypsum dune field ecosystem, were three lizard species that are common across the Chihuahuan Desert: the little striped whiptail, the lesser earless lizard, and the eastern fence lizard.

Ordinarily these three species are dark-skinned. But during an evolutionary finger snap of perhaps 2,000 to 10,000 years, pale-skinned offshoots arose in the dune fields, replacing their darker ancestors. As evolutionary theory might have predicted, against the pale backdrop of the dunes, mutants that were even slightly lighter were less visible to predators—birds such as the greater roadrunner and the loggerhead shrike—and thus more likely to survive and reproduce. Their darker cousins likely became meals.

“Doing cutting-edge, top-notch research without harming the populations we’re studying brings the whole program into alignment with my values.”

Over thousands of generations, this natural selection process led to dune fields populated by light-skinned lizards displaying two hallmarks of speciation that Rosenblum’s research has uncovered. Not only is their DNA different from their ancestors’, but they also exhibit distinctly different mating behaviors.

To answer the question of how species die out, Rosenblum has been examining several varieties of frogs threatened with extinction by the fungus Batrachochytrium dendrobatidis. Studies suggest that the deadly form of this ancient organism appeared within the past century and then spread worldwide, piggybacking on the global pet trade and exported goods such as agricultural products.

“While this aspect of globalization has implications for human health, it also has huge implications for wildlife, because we’re moving around pathogens of agriculturally important plants and ecologically important animals,” Rosenblum says.

She’s studied fungus-affected frogs from Panama to Madagascar to California, where the mountain yellow-legged frog, once the Sierra Nevada’s most common vertebrate, is now a federally listed endangered species.

With funding from the National Science Foundation, the National Park Service, and the U.S. Fish and Wildlife Service, Rosenblum and her research partners across institutions are learning how to protect the few remaining populations of mountain yellow-leggeds. Bug eaters in the middle of their ecosystem’s food chain, the frogs—as well as their eggs—are food for larger predators such as birds, snakes, and coyotes, making them a key species.

Bree Rosenblum in the lab

Rosenblum and her collaborators are learning which groups of mountain yellow-legged frogs are more fungus-resistant, and thus a better choice for repopulating hard-hit areas. A 2016 study she co-authored—published in Proceedings of the National Academy of Sciences of the United States of America—showed that in Yosemite National Park some populations of the frogs are recovering, seemingly more resistant than previously thought.

She’s also looking at other questions: Do different parts of the world host different strains of the fungus? Do any specific genes make some fungus strains deadlier than others? And are there specific genes that protect frogs or make them more susceptible?

One recent piece of good news: According to a March 2018 Science article that Rosenblum co-authored, some Panamanian frogs, once exposed, appear to develop greater resistance to the fungus. It’s not yet known if that resistance can be passed on genetically.

First do no harm

Rosenblum’s frog research is hopping onto the latest genome-collecting advance: gathering “wild” DNA from, for example, pond water. Picture a frog swimming through a small pond and leaving a few cells in its wake. If the frog were infected with B. dendrobatidis, a few fungus cells might also be present.

“We can filter some of that water, sequence the environmental DNA—known as e-DNA—and use computer algorithms to help us identify the living things that passed through the water, whether bacteria, fungal pathogens, or frogs,” Rosenblum says. “It’s an amazing time in scientific history; we can now use technological advances better in line with our conservation ethos.”

The pond-water scenario is just one example of nondestructive sampling, a research approach that couldn’t be used to its full potential back in 2000, when Rosenblum began her PhD studies at UC Berkeley. At that time, it took months to analyze a single gene. And to get a usable tissue sample, she had to snip off a lizard’s tail or a frog’s toe.

“Little environmental changes can lead to new species forming. Taken over many millennia, that’s how we ended up with this phenomenal amount of global diversity.”

But since then, dramatic technological advances have made it possible for Rosenblum and other researchers to gather DNA information from multiple species in the same amount of time without injuring them.

“I had let animal deaths turn into data points,” Rosenblum says. “And that didn’t feel comfortable anymore, because there are a lot of other ways to get data. Now we can literally take a Q-tip, rub it on a frog’s belly or stick it in a lizard’s mouth, take it back to the lab, and gather genomic information from it.”

Researchers studying a wide array of other creatures are also excited about nondestructive sampling. “Bird folks can get DNA from a dropped feather,” Rosenblum says. “Bear folks can get DNA from a bit of fur left in a tree by a bear scratching itself, and seal folks can get DNA from seal poop.”

As she notes, answering genomic questions with such tiny samples requires partners that are able to analyze ever-smaller specimens and crunch ever-larger amounts of data. But Berkeley is blessed with several, including the two she frequently works with: the Vincent J. Coates Genomics Sequencing Laboratory and the Computational Genomics Resource Laboratory.

White sands national monument

White Sands National Monument.

PHOTO: Erica Bree Rosenblum

Answering an “inner call”

Nondestructive sampling brings Rosenblum’s research techniques into alignment with her love of nature. It’s a bond she’s cultivated since she was a toddler growing up near the Brooklyn Botanic Garden in New York. “I spent a ton of time playing in that patch of nature, on the little stone fox statues, in the pine needles, and watching fish in the ponds,” she remembers.

Rosenblum’s road from the Brooklyn of her childhood to White Sands—the New Mexico dune fields of her dissertation research—was a winding one. At Brown University, where she completed her undergraduate studies, biologist David Rand’s evolutionary genetics class captivated her. She eventually became an undergraduate assistant in his lab, where, she says, her passion for research was born.

But after graduating in 1996—having earned a bachelor’s degree with honors in ecology and evolutionary biology—Rosenblum chose adventures other than grad school. In Chicago, she helped design exhibits for a children’s museum. She then taught high school science in South Africa, conducted research and led safaris in Botswana, and led an international summer student-exchange program in Togo. In Alaska, she worked as a naturalist and a teacher.

In San Francisco, she slowed down and for two years taught science to children at a private school. During weekends and summers, she pursued big-wall mountain climbing.

Contemplating the disparate threads of her life, Rosenblum eventually applied to grad school at UC Berkeley. “Maybe I could do all the things I like in one job,” she recalls thinking. “I could teach, adventure, and do research all at once.”

Bree Rosenblum in the classroom
PHOTO: Julie Gipple

Rosenblum added another thread in graduate school: immersion into the ethos of the 110-year-old Museum of Vertebrate Zoology. It’s more than a specimen collection, she says, and its emphasis on classic natural history research techniques seeped into her personal values and her teaching methods.

“When museum scientists went out to the field, they spent each day in deep observation of different environments and the life in them,” she says. “That was what was passed down through the museum to me.” Rosenblum practices what those previous generations of natural historians preached. “I go to the study system and walk around and camp and listen and journal and meditate. That’s not weird; that’s just good natural history,” she says.

At Berkeley, Rosenblum reconnected with her future husband, a climber and professional environmentalist she had met at Brown. They now have two children: a daughter, 11, and a son, 7. Nature is a big part of their family life, which includes camping, climbing mountains, and sharing a four-generation Berkeley household with Rosenblum’s mother and 102-year-old grandmother.

Rosenblum also considers the earth’s nonhuman inhabitants, especially those that are endangered, part of her extended family, which sums up why nondestructive sampling exemplifies her approach to being a scientist.

“There’s the inner call: ‘I don’t want any animals harmed in my research because I value life and it means something to me at a personal level,’” Rosenblum says. “But the other part is that I study a lot of endangered species, and one of the key motivations of my life is conserving biodiversity. If we can do cutting-edge, top-notch research without harming the populations we’re studying, that just brings the whole program into alignment with my values.”