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Past Winner
2007 NSERC Award of Excellence

Graham Bell

Evolutionary Biology

McGill University

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Preserving biodiversity is one of today's most important social and scientific challenges. Evolutionary biologist Graham Bell stands at the front line of that battle through his research into the way species adapt and evolve in response to changes in their environment.

Dr. Bell's internationally acclaimed work takes place on several fronts. In the lab, he conducts cutting-edge experiments that isolate specific factors in order to determine their impact on adaptation and evolution. His field work serves as a real-world testing ground for discoveries made in the lab, as he studies how species diversity is maintained in nature. Finally, he conducts theoretical research, largely based on computer simulations that model ecological communities with respect to overall diversity, food web structure and evolution.

"One of the most important evolutionary questions is: when a certain environmental change will occur, how likely will the population adapt to it?" he says. Some organisms are versatile enough to deal with change without adaptation. Others pack up and move to a friendlier environment. The rest must adapt or die. Dr. Bell's job is to determine how factors such as population size, the severity of stress, or the pace of change affect adaptation and survival.

While some biologists express skepticism about the usefulness of controlled laboratory studies when it comes to understanding the evolutionary mechanisms that govern populations living in complex, variable ecosystems, Dr. Bell is adamant about their value. By using microorganisms as subjects, he says he can, in effect, create a miniature ecosystem that is representative of the real world, but moves through many generations very rapidly thanks to the short life cycle of its inhabitants.

"There are some things you obviously can't study with microbes," he agrees, citing questions specific to multicellularity or sexuality. In general, though, microorganisms are subject to the same laws governing natural selection and adaptation as larger plants or animals. "What is true for E. coli is true for elephants, only more so" he says, quoting Nobel Prize-winning biochemist Jacques Monod. In other words, given the same environmental influences, the degree of adaptation or mutation from one generation to the next will be the same for any organism.

That fact has enabled Dr. Bell to predict what could happen to plant life if levels of carbon dioxide continue to build in the atmosphere. Using Chlamydomonas reinhardtii, a single-celled alga that reproduces every six to eight hours, he conducted a study that spanned thousands of generations, each one exposed to slightly higher concentrations of carbon dioxide.

Given that plants need carbon dioxide to survive, it came as no surprise that the algae grew faster as concentrations rose. However, because of the abundance of carbon dioxide, they also eventually lost the ability to capture the gas on their own and move it to the right place in order to photosynthesize it. It was as if they had grown used to being force-fed, and could no longer feed themselves. "They don't adapt so as to become better at high carbon dioxide levels," explains Dr. Bell. "Rather, the devices they normally use for coping with low carbon dioxide become ineffective."

Another area of his research seeks to understand how various means of reproduction affect an organism's ability to adapt and survive. Reproduction is necessary in order to carry on the species, of course, but it also costs individual organisms energy and resources that reduce their own chances of survival. "The more intensely you reproduce, the more likely you are to die before being able to reproduce again," he says. The extreme example of this fact is found in species such as salmon, which die immediately after reproducing.

Sexual reproduction carries yet another limitation, in that only half of each partner's genes make it through to the next generation. The half that is discarded could contain useful characteristics that would help the next generation survive. From an evolutionary perspective, that makes it inefficient, which Dr. Bell says means there must be another advantage to counterbalance the lost genetic information.

The answer, he says, lies in the fact that sexually produced offspring are diversified, while asexually produced offspring are identical to the parent. "The crucial ecological advantage is that you should make offspring different from their parents when the environment is likely to change radically from time to time," he says. "Sex facilitates adaptation because it makes it possible to combine mutations."

Computer modeling has played an increasingly important role in developing and testing theories related to evolution and biodiversity. Designing programs that can simulate complex ecosystems and yield useful data is a challenge, but has become easier as technology has improved. Part of the problem is that each species can be viewed as an overall population, but attempts to model its behaviour cannot ignore the fact that it is composed of individuals that are able to act independently. Dr. Bell's lab has developed an electronic ecosystem, dubbed Uqbar, which attempts to mimic these realities as closely as possible.

One conclusion of his modeling efforts, which he was able to support with laboratory experiments, was to demonstrate that biodiversity reaches its maximum when overall biological productivity is at an intermediate level. Too much biological productivity, such as when a lake experiences an algal bloom, means that one species ends up dominating the others.

When he isn't studying biodiversity and evolution, Dr. Bell is promoting it. He is the Director of McGill University's Redpath Museum, which is dedicated to preserving natural history, with a particular focus on geological, biological and cultural artifacts. He is also the founding President of the Canadian Society for Ecology and Evolution, a non-profit organization that promotes awareness, study and research related to ecology and evolution.

Dr. Bell's expertise is also routinely sought by other biologists. His extensive list of publications includes an impressive seven articles in the prestigious journal Nature, and he has written three influential books on evolution.

While he knows his research cannot prevent the environmental stresses that are threatening biodiversity, he says it can provide a benchmark for such factors as the population levels of various organisms that are required to ensure survival. From there, he hopes the information will be used to guide policies and practices aimed at minimizing the loss of biodiversity.