Evolution Diary

VANCOUVER — A tiny, prickly fish is helping B.C. researchers understand how organisms evolve in response to new or changing environments.

Scientists say that’s a key factor in forecasting how different species might deal with climate change and other human-imposed environmental conditions.

The difference between freshwater and marine stickleback, a minnow-sized fish found in lakes, rivers, streams and oceans across Canada, is the focus of a University of British Columbia study that adds genetic proof to evolutionary theory.

Rowan Barrett, a PhD student at UBC’s Zoology department, is part of a team that transferred marine stickleback from a salt-water lagoon to freshwater ponds at the university, and then studied the subsequent changes.

The results were surprising.

“Being able to quantify the speed with which populations are able to adapt to these sort of selection pressures is essential for formulating comprehensive policy about climate change,” said Barrett, co-author of the study published Thursday in Science Express.

Stickleback originated in the ocean but made their way into freshwater bodies of water after the last Ice Age about 20,000 years ago.

Since then, the freshwater fish have lost the marine fish’s characteristic bony armour on their sides.

True to Darwin’s theory that favourable traits passed from parent-to-offspring become more common in successive generations, scientists say changes in these fish have occurred independently across Canada.

Barrett said researchers recently pinpointed the gene that’s responsible for the change in the armour.

There’s a mutation in the genes, otherwise known as an allele, that’s rare in ocean stickleback, but common in the freshwater variety, he said.

To figure out what advantage the mutation may have in freshwater, Barrett and a research partner sorted through over 35,000 marine stickleback pulled from a B.C. lagoon in 2006 and transported the less-spindly ones - about one in 100 - to ponds at UBC.

Then they waited for the fish to breed by the thousands in order to track how often the mutation occurs in the offspring.

It didn’t take long before researchers had what they needed.

“That’s the great thing about stickleback. They don’t require much prodding to produce a lot of offspring,” Barrett said.

The researchers found that fish carrying the mutated version of the gene, which reduces armour, also grew faster. That made them more likely to survive the winter and breed earlier to produce offspring with the gene.

While Darwin’s theory of natural selection, which supposes that all species evolved from common ancestors over time is nothing new, Barrett said the prickly fish study adds a genetic understanding to that work.

“These ideas about natural selection and how that affects evolution have been around all the way back to Darwin 150 years ago, but what he didn’t have was any knowledge of genetics,” Barrett said.

“We’re only now getting to the stage that we can pinpoint the genes that are responsible for morphological traits that help a species survive and deal with changing environments.”

Barrett said the study will lead the way for researchers to look at the genes responsible for species adaptation and how they deal with a new environment.

It’s also a start in determining how many years it may take different species to adapt to climate or environmental changes caused by human development, he said.

“We really need to actually put numbers on these things,” he said.

“If we exceed those thresholds the species is going to be in trouble, and it’ll go extinct.”

This week marks the 150th anniversary of Darwin’s first publication of his natural selection theory, a milestone not lost on Barrett.

“It’s fantastic. It’s really nice to be following in his footsteps and hopefully contributing something new and useful to his ideas.”

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