Leafcutter Bee Fossils Reveal Ice Age Environment at La Brea Tar Pits

Main Point:

Bee fossils aid understanding of climate of Southern California during Late Pleistocene.

Published in:

PLOS One

Study Further:

Fossilized leafcutter bee nest cells reveal new insights into the local habitat and prevailing climate at the La Brea Tar Pits toward the end of the last Ice Age, according to a recent study published in the open-access journal PLOS ONE on April 9, 2014 by Anna R. Holden of the Natural History Museum of Los Angeles County (NHM) and colleagues.

One of the world’s richest and most important Ice Age fossil localities, the La Brea Tar Pits are well known for their collection of saber-toothed cats and mammoths. The site also contains an equally vast insect collection. Scientists examined the physical features of the bees, the nest cell architecture, and used environmental niche modeling to best match the ancient Ice Age specimens to Megachile gentilis. The study used micro CT scans to reconstruct images of the nest cells and bees.

Since M. gentilis still lives today (as is the case with most insects excavated from the tar pits), the team linked records of its restricted climatic range to late Ice Age environmental conditions at Rancho La Brea. The results suggest that M. gentilis lived in a moderately moist (mesic) environment that occurred at a lower elevation during the Late Pleistocene. The identification of nest cell leaf fragments, which were collected in close proximity to the nest site, indicate a nearby wooded or habitat with a stream or river.

“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.”

“Insects often serve as important paleoecological indicators, but these specimens are particularly significant. Because the bees were excavated from their original nest site, have unique nest-building behavior, and only occur within specific environments, we reaped a lot of information regarding prehistoric climate and habitat from a single species.”

Citation:

Holden AR, Koch JB, Griswold T, Erwin DM, Hall J (2014) Leafcutter Bee Nests and Pupae from the Rancho La Brea Tar Pits of Southern California: Implications for Understanding the Paleoenvironment of the Late Pleistocene. PLoS ONE 9(4): e94724. doi:10.1371/journal.pone.0094724, http://dx.plos.org/10.1371/journal.pone.0094724

Financial Disclosure:

The Annie M. Alexander Endowment provided funding for Diane M. Erwin. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interest Statement:

The authors have declared that no competing interests exist.

Contact:

Press release adapted by PLOS ONE from Kristin Friedrich of the Natural History Museum of Los Angeles County, kfriedri@nhm.org; 213.763.3532, cell 323.449.7370

Kristin Friedrich (Director of Communications) kfriedri@nhm.org; ph: 213-763-3532; cell: 323-449-7370; Anna Holden, aholden@nhm.org, ph: +1 (213) 763-3225

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