Ancient snakefly fossil discovery ‘deepens mystery’ of species’ evolution

The discovery of four previously unknown species of snakefly - a type of long flying insect - has thrown what natural historians know about the evolution of these predatory insects into disarray.

Paleontologists who found the fossils in British Columbia and Washington State, have said their finds have “deepened the mystery”, about the way the species has adapted and moved around the world.

The fossil species are from snakeflies which lived in what we now know as North America, 50 million years ago.

Today, snakeflies are a predatory species which are native to the Northern hemisphere, but are conspicuously absent from tropical regions.

Scientists have long believed there was a simple reason for this - that the snakeflies required cold winters where temperatures dipped below 0C, or colder, to trigger their development into adulthood.

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As a result, higher equatorial temperatures would have prevented them from moving south.

But the new fossil findings come from places where the ancient climate does not fit with this explanation.

“The average yearly climate was moderate like Vancouver or Seattle today, but importantly, with very mild winters of few or no frost days,” said Bruce Archibald of Simon Fraser University in Vancouver.

“We can see this by the presence of frost intolerant plants like palms living in these forests along with more northerly plants like spruce.”

The fossil sites where the ancient species were discovered span 1,000 kilometers of an ancient upland from Driftwood Canyon in northwest British Columbia all the way to the city of Republic in northern Washington State.

According to Dr Archibald, the paleontologists found species of two families of snakeflies in these fossil sites, both of which had previously been thought to require cold winters to survive. Each family appears to have independently adapted to cold winters after these fossil species lived, the researchers said.

“Now we know that earlier in their evolutionary history, snakeflies were living in climates with very mild winters and so the question becomes why didn’t they keep their ability to live in such regions? Why aren’t snakeflies found in the tropics today?”

Previous fossil insect discoveries in these sites have shown connections with Europe, Pacific coastal Russia, and even Australia.

Dr Archibald said that understanding how life adapts to changes in the climate by looking deep into the past helps explain why species are distributed across the globe today, and can perhaps help foresee how further change in climate may affect that pattern.

“Such discoveries are coming out of these fossil sites all the time,” he said.

“They’re an important part of our heritage.”

The research is published in the journal Zootaxa.