Bees Narrowly Survived What the Dinosaurs Couldn't

The asteroid that took out the dinosaurs may have also caused the mass extinction of bees, according to a new study.

Because many of the plants that bees were pollinating went extinct around the same time, scientists have long suspected many species of bee went along with them, but fossil records of insects from so long ago are sparse and haven't provided enough evidence to confirm that hypothesis.

To get around the absence of fossil records, Sandra Rehan, of the University of New Hampshire, used a process known as molecular phylogenetics. Rehan rounded up samples of 230 species of carpenter bees from around the world, sequenced their DNA, and looked for similarities in four separate regions of their code.

What became clear is that the bees had a clear common ancestor long ago. Using fossils from about 45 million years ago, Rehan was able to confirm that their ancestor had come from before that point.

"We combined the current DNA with the few fossils we do have and used it to inform what we were looking at," she said. "We were able to look at speciation over time and found that there was no genetic change for a really long time, and that is consistent with a mass extinction event."

Along with the dinosaurs, a huge number of wildflowers and plant species died out, creating what we know as at K-T boundary—the end of the age of the Cretaceous and the beginning of the Paleogene periods. There is not enough evidence to pinpoint exactly why the bees died out, but it's likely that the chaos during the period affected them as well. The fact that carpenter bees from all around the world—they are found on all continents except Antarctica—shared huge swaths of DNA also suggests there was a chaotic event that spread them throughout the world.

"Major ecological changes at the time disturbed all species. We don't know exactly what the climate was or what species died, but we know when there's huge change, all species are affected," she said. "Something scattered them at the time, and that's consistent with what we're finding."

So why study bee extinction from 65 million years ago, especially when they can't make cool websites or leave behind fancy fossils for museums?

If you've been paying attention to the news, you'll know that there has been a huge, mysterious decline in honeybee populations over the past several decades. That decline has also extended to other groups of bees, such as bumblebees and carpenter bees, Rehan says. Today's decline clearly hasn't been caused by an asteroid impact, but understanding their demise in the past may help us protect them in the future.

"It's a different cause, but any information we can learn about how bees lived in the past can be used to inform us today. We still don't know a lot about most bees on the planet," she said. "With the study of their DNA like this, you can learn how they're related, and every little bit helps."