Scientists Get Close Look at Evolution
On a rocky slope in the Santa Ynez Mountains, Cristina Sandoval grabs a branch and beats it like a punching bag.
“Aha!” she cries as a few wriggling insects spill into her lap. “Aren’t they adorable?”
The squat, beady-eyed bugs may have faces only a biologist could love, but researchers say they are offering a rare glimpse into the mystery of evolution.
For the past 13 years, Sandoval, an evolutionary biologist at UC Santa Barbara, has studied stick insects in the Santa Monica and Santa Ynez mountains. She has collected hundreds in the wild, analyzed them in the lab -- and even discovered a dozen new species.
Now she says one of those, named Timema cristinae in her honor, is in the process of splitting into two separate species. These insects, which are either green or green-striped, may be born on the same bush, but only the best-camouflaged survive.
As a result, the striped insects are now living on chemise bushes, where they blend in, and those without stripes inhabit blue lilac, where they are nearly invisible.
Males can no longer coax females of the other pattern to mate because they seem to have forgotten a crucial bit of insect foreplay -- how to properly tickle a female’s antenna to get her in the mood. Also, mating between the striped and non-striped produces offspring that stand out and are easy prey for birds, Sandoval said.
“Somehow adapting to the plant with their color and body shape makes them less likely to mate with walking sticks of another color,” she said. “Natural selection is a beautiful, powerful process, and the walking stick is in the middle of it.”
Scientists have long believed that new species evolve in extreme isolation, but they now think they may have a ringside seat to the drama of speciation, or the development of a new animal through evolution.
“In our case, we didn’t need isolation,” Sandoval said. “They needed only a few feet between bushes and they needed predators.”
Sandoval, working with other scientists, published her findings last May in the journal Nature and was featured in Smithsonian magazine. One of her fellow researchers, Patrik Nosil of Simon Fraser University in British Columbia, sees a pattern in how separate species develop.
“The first thing that happens is a population finds a new habitat and then adapts through natural selection to that habitat,” he said. “Then they no longer interbreed with the others. By this point they look different, smell different and behave differently than they did.”
John Endler, a professor of biology at UC Santa Barbara and a world-renowned expert on the evolution of color patterns in animals, said the insects seem to be changing into new species by moving to other plants.
“It is completely surprising,” he said.
Sandoval’s work with stick insects began in 1988 when she was a student at UC Santa Barbara.
The Brazilian-born biologist had studied spiders in the Amazon rain forest before coming to the United States to work on natural selection under Endler.
He told her to go out and find some animals. She wanted something plentiful that wouldn’t sting or bite and had different colors.
Armed with just a butterfly net, she began combing the brush for bugs. Somewhere off California 154 outside Santa Barbara, an odd green insect dropped into her net.
She measured and examined it in her lab and soon realized she had discovered a new species. A scientific board certified the finding and named the insect after her.
Since then, the 41-year-old Sandoval has identified 12 new walking stick species and named five others. She has traveled up and down the coast from Baja to Oregon, sometimes camping out in her car for weeks, to study insects.
“Being able to uncover the secrets of an organism’s life is a beautiful thing,” she said.
Sandoval devised simple field experiments to show the importance of coloration in animals. In one study, she put stick insects on different-colored backgrounds to see which one a bird would eat first. The predators immediately ate the one that didn’t blend in as well.
“She was one of my best students,” Endler said. “There is a myth that you need to have high-tech methods to do research, but in this case technology wasn’t needed.”
Sandoval’s work has made her a recognized authority on stick insects.
She once received a specimen in the mail from John Coffman of Rattlesnake Junction, Ariz. His chickens were eating the odd-looking things, and he feared they would die.
“We named it after him -- Timema coffmani.” she said. “The town was very excited.”
Timema monickus was named after the Santa Monica Mountains, where it was found. A species found last year on Mt. San Jacinto, near Palm Springs, has yet to be named.
Sandoval said there are probably hundreds of species waiting to be discovered.
“We haven’t found a new butterfly in 20 years because butterflies are so pretty and many people study them,” she said. “When you go toward moths and grayer creatures, not as much is known because they aren’t attractive.”
Sandoval is now director of UC Santa Barbara’s Coal Oil Point Reserve, a wildlife refuge near the campus. She lives with her husband and two children in a house overlooking the ocean but still loves her fieldwork.
On a recent drive high in the Santa Ynez Mountains, she pulled off the road, charged up a small trail and began swatting a bush.
The flightless stick insects tried their best to remain still and pretend they were leaves but soon fell into her lap.
“This is the emotional part, finding the littlest of the season,” she said. “Most live their entire life on one bush.”
She hiked to the summit and looked over the valley to the sea miles away.
“I think we are continuing Darwin’s work here,” she said. “It’s important to learn about what we have, because only then will we know what we are losing.”
