Bernie Roitberg

For the past 25 years, entomologist Bernie Roitberg has been using insects to study evolutionary biology.

Bugs also look better at closing time

November 13, 2008

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By Diane Luckow

Have you ever wondered about those unlikely pairings at closing time in the singles bar, when an attractive woman reluctantly departs with a fellow who just isn’t, or vice versa?

Entomologist Bernie Roitberg can explain such behaviour in his six-legged subjects. He can even trigger it among aging parasitic wasps. It’s a phenomenon he glibly calls the "singles-bar effect".

"As the wasps get closer to the end of life—or people approach the end of an evening in the bar—the less choosey the wasps become about which hosts they’ll lay their eggs in and the less choosy people are about who they leave the bar with," he explains.

"Of course, it isn’t quite that simple but it is clear that people and other animals, insects included, make decisions when carrying out tasks based on their perception of how much time remains."

Roitberg and his colleagues have spent the last 25 years developing mathematical theories about how such phenomena as sibling rivalry, irritability, suicidal tendencies, tolerance, obesity and parent/offspring conflict can drive the evolution of behaviour. And they use insects to test their predictions.

"In our lab, the experiments are not that different from what goes on in a psychology lab or any other evolutionary biology lab, except that we assume no cognitive processes on the insect’s part," he says. "Using insects, some of which have 15 or more generations in just a year, lets us observe evolution as it happens."

Roitberg is now researching senescence, or how we approach the end of life. He tricks healthy wasps into perceiving their end is near by changing the barometric pressure in specially built chambers to mimic an approaching storm. Another group of wasps is in a chamber with steady barometric pressure like a balmy summer day. He introduces low-quality hosts into both chambers to see if those who perceive imminent death will lay their eggs indiscriminately. They do, while those enjoying a stable summer day won’t.

"They’re just tiny little animals tracking their own expectations of life and habitat," says Roitberg. "Their problems aren’t that different from human problems in a general sense."

Over the years, Roitberg’s extensive research has generated significant advances in understanding the behaviour and evolutionary ecology of insects and their natural enemies. In October, the Entomological Society of Canada recognized his research with a 2008 gold medal and a ranking as "one of Canada’s international science stars."
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