In 2001, Drs. Bill Bradshaw and Christina Holzapfel at the University of Oregon became the first scientists to prove that recent global climate change is causing genetic adaptation in certain organisms. Their research over the past 30 years has focused on the pitcher plan mosquito and its changing response to the length of sunlight in a day. Changing Planet is produced in partnership with the National Science Foundation.
Changing Mosquito Genes
ANNE THOMPSON, reporting:
From warming ocean temperatures, to melting glaciers, to bleaching coral reefs, many of the impacts of our warmer climate are visible on a global scale. But incredibly, some impacts are happening in places that are invisible to the naked eye, among the very building blocks of life: genes.
Dr. BILL BRADSHAW (Evolutionary Geneticist, University of Oregon): We discovered that indeed that recent rapid climate change has resulted in a genetic shift.
THOMPSON: In 2001, the scientific journal PNAS published a paper that presented the first evidence of genetic adaptation caused by climate change. The scientists that wrote the paper showed this through a long-term study of the pitcher plant mosquito.
BRADSHAW: It was so astounding to see this genetic shift.
Dr. CHRISTINE HOLZAPFEL (Evolutionary Geneticist, University of Oregon): We now know that genetic change that is driven by climate change is a reality.
THOMPSON: Doctors Bill Bradshaw and Christina Holzapfel are evolutionary geneticists and have been working together for more than thirty years. Based at the University of Oregon, much of their research is made possible by the National Science Foundation. The road that led them to their revolutionary discovery started in 1972 with their mutual love of swamps and mosquitoes.
BRADSHAW: Odd as that may sound, we like the sight, smell, sounds of bogs and swamps. And somehow intrinsically interesting are carnivorous plants and we found out that this mosquito actually lives in a carnivorous plant.
THOMPSON: Bradshaw and Holzapfel began collecting data on the Wyeomyia smithii, more commonly known as the pitcher plant mosquito, because it lives for much of its life inside the purple pitcher plant. The pitcher plant is a carnivorous plant that lives in wetlands along the entire east coast of North America, from the panhandle of Florida, all the way to Newfoundland, Canada.
RUDY BOROWCZAK (Graduate Student, University of Oregon): We're out in this kind of mucky, wet environment and the pitcher plants love it here, it's a bog. And they grow on these sphagnum mats that you see around us.
THOMPSON: The pitcher plant traps spiders, beetles, even small toads, with tiny hairs inside its pitcher tube. The pitcher plant mosquitoes grow in the water that sits inside.
BOROWCZAK: It's a pretty ingenious strategy if you live in an environment that captures and kills other insects then you're pretty safe from other insect predators that may try to munch on you instead.
THOMPSON: Pitcher plant mosquitoes have a unique ability to identify the changing length of daylight, which triggers dormancy during the shorter days of fall and winter, and a return to life in the longer days of spring and summer. This trait, called photo-periodic response, is genetic, and passed on from generation to generation.
HOLZAPFEL: Wyeomyia is astutely sensitive to the length of day, and length of day therefore is what they use, since it's such a reliable cue, to tell them about the appropriate time to enter a resting phase.
THOMPSON: Photo-periodic response is the only environmental clue that the pitcher plant mosquito uses to tell it to go into dormancy. As larvae, the dormant mosquitoes are able to survive the winter living inside the pitcher plant. But in recent years, due to rising global temperatures, winters in the North have been getting shorter, and as a result, the mosquito's growing season is lengthening.
HOLZAPFEL: As growing seasons are becoming longer, it is advantageous for organisms to take advantage of as much of that good growing season as they possibly are able.
THOMPSON: After twenty-four years of studying and recording the mosquito's photo-periodic response, Bradshaw and Holzapfel began to question whether recent changes in climate would be reflected in their reams of data.
HOLZAPFEL: We had piles of data of these experiments from a number of years. We sat down with calculators just around the kitchen table and did a couple of quick and dirty calculations
BRADSHAW: And that is when we discovered that indeed that recent rapid climate change has resulted in a genetic shift in the seasonal timing mechanism in our mosquito.
THOMPSON: As their eventual study would document, the mosquitoes were going into dormancy later, thus their photo-periodic response, a genetic trait, was changing. The research, they say, proves that climate change can have an impact at the genetic level. Even more surprising is the fact that this evolution is happening rapidly.
BRADSHAW: We were able to detect a genetic shift in as short a time period as five years.
THOMPSON: Five years for mosquitoes to adapt at a genetic level. Those in the North were showing a photo-periodic response more like mosquitoes from the South, where the winters are shorter and warmer. Today, with the latest genetic instruments and technology available, with the help of their students, Bradshaw and Holzapfel are hard at work trying to locate the specific gene that controls photo-periodic response.
HOLZAPFEL: There are no genes that are known to control the photoperiodic mechanism in any animal in the natural environment. No genes, nobody knows anything about this. So we are using a group of approaches to try to answer that question.
THOMPSON: Identifying this gene, they believe, could not only provide a better understanding of genetic adaption due to climate change, but may offer tools to help humans, plants, and animals adapt and cope with the coming changes.
HOLZAPFEL: Once we know what those genes are, then we are able to actually do manipulative things to modify crops to actually modify the vectors or the carriers of disease and actually make some applications that may help or mitigate the effects of climate change.
THOMPSON: By studying the unique traits of the pitcher plant mosquito, Bradshaw and Holzapfel are helping us prepare for an evolving future as the world gets warmer, and its impacts are felt all the way down to the genetic level.
There’s a very confusing exchange in "Through the Looking Glass" by Lewis Carroll: “'When I use a word,'” Humpty Dumpty said, in rather a scornful tone, “'it means just what I choose it to mean — neither more nor less.'”
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