A current debate in the field of evolutionary biology is whether adaptation to new environments is the result of changes in many genes, each having a relatively small effect, or large changes in just a few genes.
Canadian researchers, along with evolutionary geneticists in Switzerland, studied how threespine stickleback fish adapted differently to lake and stream environments in British Columbia, using high-resolution genomic methods to test for genetic differences at thousands of positions scattered across the fishes' genome, McGill University in Montreal reported Tuesday.
Genetic differences between lake and stream stickleback were discovered at more than a dozen positions, considerably more than expected under the alternative "few-but-large" change hypothesis, researchers said.
Examining independently evolved lake-stream population pairs, the researchers found increasing divergence between the populations involved genetic differences that presented at more and more positions on the genome.
Previous perceptions of adaptation as being a genetically simple process may have been the result of a bias resulting from previous lower-resolution genomic investigation methods, the researchers said.
"I suspect that as more and more studies use [high-resolution] methods, the tide of opinion will swerve strongly to the view that adaptation is a complex process that involves many genes spread across diverse places in the genome," McGill researcher Andrew Hendry said.