COSAM E-newsletter, May 2011
Professor, Students Studying Dragonflies as Climate Messengers
Students Nene Ugbah (l-r), Megan Ziegler, Mira Samara and Shane Johnson
collecting dragonflies on the Central Coast. Ugbah, Samara and Johnson
will participate in the National Geographic study this summer.
SAN LUIS OBISPO -- One Cal Poly biology professor and her students are turning their eyes to dragonflies to tease out relationships between global warming, development and species survival.
Biology Professor Shannon McCauley will be taking three Cal Poly students to the Georgian Bay national park in Canada this summer to study that topic thanks to a $15,000 grant from the National Geographic's Committee for Research and Exploration.
The park, in Canada’s Great Lakes region, is the largest freshwater archipelago in the world and offers a unique place to study large and small aquatic insect populations, according to the professor.
McCauley has been studying dragonflies for the past 10 years. The jewel-colored riparian creatures were the focus of her doctoral thesis at the University of Michigan. With some 4,000 species of dragonfly in the world and 72 in California, there are a lot to study.
Facts sure to win a party game: dragonfly larvae live in water only and can look a lot like underwater potato bugs. In a fish-heavy environment, some species grow longer spines to make themselves painful to eat. The eject-and-retract mouth a larval dragonfly uses to grab tadpoles, small fish, mosquito larvae and other food was the inspiration for the “Alien” jaws in the Sigourney Weaver movies. Depending on species, they can spend six months to six years in larvae stage. Their adulthood lasts from a few weeks to a few months – it’s a stage in which mating is job one.
Some species do and an adult dragonfly can travel up to 100 miles a day, and may travel up to 1,000 miles total to mate. What makes a dragonfly decide to head south (and south it almost always is)? Becoming an adult early in the season.
“If you’re a fast grower, you can go south to breed early,” McCauley explained. That gives an individual dragonfly an evolutionary advantage over individuals that mature later.
Professor Shannon
McCauley
To understand more about the movements of dragonflies, McCauley and previous students have raised dragonfly larvae and numbered their wings when they emerge as adults, then studied their movement in Napa County. (Best thing for marking a dragonfly’s wings? A black Sharpie.)
What McCauley and other scientists are learning about dragonflies is that they are heavily influenced by environment and temperature. No matter the species, dragonfly larvae growing up in warmer water will be smaller. Because of that, they’ll also be less likely to disperse long distances, and be more easily caught by predators such as birds.
In California, where temperatures are predicted to be four to five degrees warmer by 2050, that could have a big impact on the ability of dragonflies to move and follow the shifting conditions as the global climate changes. The professor is hoping to continue her research at Cal Poly and in Napa after returning from Canada. She’s seeking the funding to do it. Her Cal Poly students gathered larvae from ponds and reservoirs across campus Winter Quarter. They are currently feeding and raising them in a lab in the Fisher Science building. A grant or private support would let McCauley and the students run a wider variety of temperature and growth experiments, as well as migration monitoring. The professor would like to emulate those estimated 2050 temperatures and see what happens to her dragonfly subjects.
“We’ve always just assumed that species would adjust to the warmer conditions,” that they would migrate to their preferred climate zone as global warming takes effect, McCauley said. But that may not be possible. Her research has found small size makes dragonflies less able to cross barriers like forests or urban areas in search of new rivers, creeks, ponds – and mates.
“Dragonfly populations have always winked on and winked off again in different places. They will disappear, then reappear,” McCauley said. “Their ability to migrate has been key to their survival."