Scientists say there was a widespread extinction of bees 66 million years ago, at the same time as the event that killed off the dinosaurs. The demise of the dinosaurs was almost certainly the result of an asteroid or comet hitting Earth. But the extinction event was selective, affecting some groups more than others. The team used fossils and DNA analysis to show that one bee group suffered a serious decline at the time of this collision. The researchers chose to study bees within the subfamily known as Xylocopinae, which included the carpenter bees.
This was because the evolutionary history of this group could be traced back to the Cretaceous Period, when the dinosaurs still walked the Earth. Previous studies had suggested a widespread extinction among flowering plants during the Cretaceous-Paleogene (K-Pg) extinction event 66 million years ago. It had long been assumed that the bees which depended upon these plants would have met the same fate. Yet, unlike the dinosaurs, "there is a relatively poor fossil record of bees," said Sandra Rehan, a biologist at the University of New Hampshire in Durham, US. This has made the confirmation of such an extinction difficult.
The impact that wiped out the dinosaurs created opportunities for other animals. However, the researchers were able to use an extinct group of Xylocopinae as a calibration point for timing the dispersal of these bees. They were also able to study flower fossils which had evolved traits that allowed them to be pollinated by bee relatives of the Xylocopinae. "The data told us something major was happening in four different groups of bees at the same time," said Dr Rehan. "And it happened to be the same time as the dinosaurs went extinct."
The findings of this study could have implications for today's concern about the loss in diversity of bees, a pivotal species for agriculture and biodiversity. "Understanding extinctions and the effects of declines in the past can help us understand the pollinator decline and the global crisis in pollinators today," Dr Rehan explained.