Leafcutter Bee Fossils Found at La Brea Tar Pits Offer Clues about Ancient Climate Conditions

When it comes to fossils, the biggest creatures seem to get all the attention. But the little guys offer plenty of important information on the ancient environment as well, as evidenced in a recent study of leafcutter bees at the Rancho La Brea Tar Pits.

The La Brea Tar Pits in Southern California are best known for their iconic fossils of mammoths, saber-toothed cats and dire wolves, but the site is a treasure trove of other scientifically significant specimens, including a vast insect collection.

Anna Holden an entomologist at the Natural History Museum of Los Angeles County, studied the collection of leafcutter bee fossils at La Brea, revealing new insights into the local habitat and prevailing climate toward the end of the last Ice Age.

By conducting a micro-CT scan of the fossilized bee nests, Holden and her collaborators found that each nest contained a fossilized and intact pupae.

By examining the ancient infant bee's physical characteristics and the architecture of its cell next, the researchers determined its species to be Megachile gentilis, a bee species that is still living today.

According to the Natural History Museum of Los Angeles County, most insect specimens recovered at the Tar Pits are, in fact, still living today.

After analyzing what they know about the bees today and what they knew about the climate then, the researchers determined that M. gentilis lived in a moderately moist environment that occurred at a lower elevation during the Late Pleistocene.

"Based on what we know about them today and the identification of fossilized leaf fragments, we know that their habitat at the Tar Pits was at a much lower elevation during the Ice Age," Holden told LiveScience.

Leaf fragments collected close to recovery point of the fossil specimens indicate that there was a stream or river nearby a wooded habitat, the researchers said in a statement.

"Because this is a fossil of rare life-stage, it's an exceptional find in itself," Holden said. "But it's just the tip of the iceberg, we know that insects offer a vivid portrait of the prehistoric conditions of this area, and there are literally thousands more to study."

Another recent study conducted at the La Brea Tar Pits has linked climate change as a trigger for evolution in Ice Age predators.

A research team from the Page Museum at the La Brea Tar Pits analyzed fossils from dire wolves and saber-toothed cats and found significant changes over time in the shapes and properties of the ancient animals' skull, which they attributed as morphological changes brought on as a evolutionary response to a changing climate.