SFU BIOLOGIST DRIVES AUSTRALIAN OUTBACK TO SOLVE EVOLUTIONARY 'PARADOX'

July 22, 1996

While insects are an essential part of our environment, few of us would go out of our way to find them.

But SFU biologist Dr. Bernie Crespi does. In fact, he goes looking in the blazing Australian desert for small plant-eating insects called 'thrips'.

Crespi is a behavioral ecologist. His particular interest is in solving a mystery that also intrigued Charles Darwin. "Evolutionary theory says that every living thing competes with every other one," Crespi explains. "Yet we see co-operation at work throughout nature.

"Darwin noted that co-operation among animals seemed to contradict 'natural selection'. So, this is a true paradox. I want to know under what circumstances co-operation evolves out of selfishness. For example, some of the insects I study in Australia actually give up their ability to reproduce in order to help others of their species."

Crespi's most recent expedition occurred in February-March of this year and was supported by a visiting fellowship from Flinders University of South Australia in Adelaide.

Soon after arrival, he and several colleagues headed north into the desert in search of thrips. Thrips belong to the insect order Thysanoptera, and range in length between a half-millimetre and 15 millimetres. Gardeners know them as the tiny insects that can infest roses and house plants.

But why go half way around the world in search of thrips?

"Most scientists studying the evolution of co-operation and altruism have focused their efforts on ants, bees and wasps," he explains. "But the thrips in Australia survive in incredibly hostile conditions by making shelters out of phyllodes, which are leaf-like structures on Acacia trees. These shelters, called 'galls', suggest co-operation among thrips.

"Thrips are products of a special genetic system called haplodiploidy. Male thrips are 'haploid', which means they develop from unfertilized eggs and therefore inherit characteristics only from the mother. They receive just one copy of each chromosome. Yet, female thrips are 'diploid'. They develop from fertilized eggs and inherit from both parents. Accordingly they have two copies of each chromosome."

This, Crespi points out, creates some interesting circumstances regarding the relationship of individual thrips to one another. "For instance, because of haplodiploidy, a female thrips ('thrips' is both singular and plural) is genetically closer to her sisters than to her own offspring. So, it may be to her advantage in some situations to forgo her own reproduction and, instead, help her mother to produce more of her sisters."

Survival of the human species, it would seem, is never far from the minds of Crespi and his colleagues either, as they cross the almost trackless expanses of the Australian Outback in search of thrips. "We drive at 110 kilometres-an-hour for vast distances along dusty trails, searching for Acacia trees with gall-forming thrips. The temperature ranges up to 45 degrees Celsius. The bush flies are terrible. You breathe dust half the time. On our March trip, we were nearly stranded for days between flood-swollen rivers, as our four-wheel drive vehicle slipped and slid across clay gumbo."

Despite the challenges, Crespi and the others on the expedition returned with enough data on thrips (including a number of previously unstudied species) to keep labs at SFU and in Australia busy for years.

"What we learn about the evolution of co-operation and altruism in these tiny insects," says Dr. Crespi, "has implications for just about every type of social animal, including human beings. In other words, we are using these insects to test general theories about how all animals behave."

Crespi's research has been supported by major scientific agencies, such as the Natural Sciences and Engineering Research Council of Canada and the National Geographic Society.