Nosil helps prove Darwin's theory of evolution

May 19, 2006, vol. 36, no. 2
By Stuart Colcleugh

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It's pretty heady stuff for a graduate student to be compared with Charles Darwin, but Patrik Nosil may have to get used to it.

Nosil, in the final year of his biology doctoral studies at SFU, has helped contribute something to Darwin's theory of natural selection that has been missing since the renowned scientist first espoused it in his pivotal book, On the Origin of Species, almost 150 years ago:  documented confirmation.

Nosil and biologists William Etges at the University of Arkansas and project leader Daniel Funk at Vanderbilt University have produced the first authoritative evidence that adaptation to environmental changes can lead to the evolution of new species across all species types and habitats.

“This idea has been generally accepted for about 100 years but without much evidence,” says Nosil. “What our research does is provide fairly strong evidence that it is actually correct. It's been shown previously in a few specific taxa, or pairs of species, like the Timema walking stick insects I've been studying. But that's just one species.

“No one had ever collated data from hundreds and hundreds of species that represent major different groups of plants and animals and then tested whether this association was always positive. And we found that it is.”
Led by Funk, who conceived and initiated the study, the trio spent several years comparing the ecology and genetic diversity of 500 species including plants, fish, frogs, birds and insects. They published their findings recently in the Proceedings of the National Academy of Sciences.

Their research found that ecological divergence, the term for two populations of a single species adapting to different environments, is directly linked to reproductive isolation, the extent to which they can still interbreed, which is a key factor in the formation of two separate species.

Previous research established that species formation results from reproductive isolation over time, says Nosil.

“The question we wanted to answer was, what else matters? Are there factors that increase the rate at which these reproductive barriers evolve beyond the rate just based on pure time?” For each species pair, the researchers analyzed published data on diet, habitat and size, using a statistical technique to control for time.
The idea was to determine whether the degree to which species pairs differed from each other in these ecological variables was positively associated to the degree in which natural selection had caused them to diverge in their ability to interbreed.

They found that the association was positive with a remarkable level of confidence, with a one-in-250 possibility that their findings were a matter of chance, compared to the one-in-20 odds that scientists typically require to confirm such a relationship.

“The bottom line,” says Nosil, “is that in almost all cases when ecological differences increase, the amount of reproductive isolation increases.”

In the future, Nosil hopes to use the same database he and his colleagues have compiled to determine whether, for example, the same species eating on different trees in the same area could evolve into different species.

Meanwhile the young biologist has a doctorate to finish. Helping to confirm one of the most influential theories in the history of science “was a lot of work,” he sighs. “But it was worth it in the end.”

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