The workhorse of the insect world, the honey bee, stepped into the spotlight today. A newly discovered amber-encased fossil pushes back the date that bees began pollinating by millions of years. On a different front, researchers reported their first analyses of the 236-million-base genome of the honey bee, Apis mellifera. Together, the reports provide key insights into the evolution of the 16,000 species of bees.
The honey bee is the fifth insect sequenced, and 170 researchers worldwide have had a hand in interpreting its 10,157 genes. This consortium provides an overview in the 26 October issue of Nature. And dozens of related papers, including three in the 27 October issue of Science, appear today. In them, researchers describe new genes and regulatory regions important to the evolution of social behavior, as well as to other aspects of bee life. They find that the bee has more olfactory receptors than other insects and have evolved a whole group of proteins dedicated to making royal jelly--the food used to nourish developing queens (Science, 27 October, p. 578). "Sequencing the honey bee genome has had an enormous impact on research progress," says Katherine Aronstein, who studies bees at a U.S. Department of Agriculture lab in Weslaco, Texas.
Relatively few bee fossils exist, leaving large gaps in our understanding of how the bees evolved from their ancestor, a predatory wasp. So Bryan Danforth of Cornell University was thrilled when he heard that entomologist and amber aficionado George Poinar of Oregon State University in Corvallis had purchased a piece of amber with a mosquito-sized bee in it. The amber came from the Kachin state in northern Burma (Myanmar), in beds that geologists estimate to be 100 million years old. When Danforth, who studies the evolutionary relationships of bees, got a close look at the specimen, he discovered that it was the earliest known bee pollinator, making it a missing link to modern bees, he and Poinar report in the 27 October issue of Science.
The fossil bee is a bit squashed, but its legs, body, and head are distinguishable. The fossil seems to be part wasp and part bee: It has wasplike spurs on its middle pair of legs. But it also has branched hairs on its head, legs, abdomen, and thorax--a few holding pollen grains--that are beelike. These hairs suggest that this bee was capable of pollinating flowers. Furthermore, these features indicate that beelike traits appeared 40 million years earlier than researchers had evidence of, says Danforth. This bee is sized to pollinate the tiny flowers typical of 100 million years ago, suggesting that it and its relatives may have helped spur the diversification of flowering plants, he adds.