Past Winner
2007 NSERC Doctoral Prize

Patrik Nosil

Biology

Simon Fraser University

Patrik Nosil

The importance of biodiversity usually comes up in the context of protecting species that are at risk of going extinct. Biologist Patrik Nosil researches the other side of the biodiversity coin – the processes by which new species originate – and he has uncovered fascinating details about the factors that influence interbreeding between populations as they diverge to form new species.

Charles Darwin proposed some 150 years ago that natural selection was the main driving force behind evolution. Since then, the challenge has been to find concrete evidence for each of the many factors that might make a species evolve in a particular direction, such as adaptation to habitat, reproductive success or the ability to find food. Dr. Nosil has added a new item to that list of evolutionary influences: the ability to avoid predators.

Focusing on tracking evolutionary changes in populations of Timema cristinae (walking-stick insects), Dr. Nosil's thesis work has earned him a 2007 NSERC Doctoral Prize.

Through a diverse combination of laboratory experiments, molecular genetic analysis and extensive field studies, Dr. Nosil found some of the first concrete evidence that avoiding predation influences species development. He also demonstrated that a single population can evolve in two separate directions, thereby promoting the formation of two species from one. It had previously been widely assumed that members of a species located in a specific geographical area would all evolve in the same way.

Field studies of T. cristinae revealed that two sets of adaptations had taken place in one group based on which of two potential host plants the insects preferred to feed on. Reproductive preferences and survival rates of offspring gradually led to better adaptation to one plant species or the other, further weakening reproductive compatibility between populations adapted to different plants. Moreover, if insects that were adapted to one plant moved to the other type, their survival rates dropped, partly as a result of being more exposed to predators. These types of adaptations eventually led to the formation of a new species. DNA evidence confirmed that the changes related to adaptations to different plant species, as opposed to random genetic changes, promoted the formation of new species.

For Dr. Nosil, one of the main lessons of his research is that maintaining an overall level of biodiversity is crucial. Using the example of a population of T. cristinae splitting into two species based on the choice of host plant, he notes, "If that plant wasn't there in the first place, then we wouldn't have had the new insect."

"Diversity begets diversity," he adds. "The more diversity of one type you have, the more likely you can have other types of organisms adapt to that environment and form a new species."

Loss of biodiversity, in contrast, hits an ecosystem twice. Not only does it decrease the survival chances of existing species, but it also reduces the system's ability to generate new species.

Dr. Nosil's work has attracted significant attention from the evolutionary biology community. He has published in some of the top journals, including Nature and the Proceedings of the National Academy of Sciences, and won the American Society of Naturalists Young Investigators' Prize in 2006.