Honeybee Genome May Shed Light on Social Evolution
Monday, October 30, 2006
Bees and people have a lot in common.
We both live in groups and snuggle with others when cold. We both know that staying clean helps prevent disease. We both prepare food for others and leave home to get it even when we aren't hungry. We both can communicate through dancing.
Of course, there are differences.
Bees are an inch long. They copulate while flying. Each winter, the females kick the males out of the house to die.
So to what extent do genes explain our two wildly different evolutionary journeys? Biologists now have a better way of exploring that question, and a whole lot of other ones.
Last week, the Honeybee Genome Sequencing Consortium announced that it had finished copying out the genetic message of Apis mellifera , the world's most important pollinator, maker of nature's best-known sweet food, and object of human fascination and delight for eons. The honeybee becomes the third insect to have its genome fully transcribed, preceded by the fruit fly drosophila and the malaria mosquito anopheles. A flour-eating beetle, an aphid and a wasp are next in line.
The work was done by 150 people in about 20 countries over the past three years. The huge mass of data -- along with that from the other species -- will help sketch a picture of what it means to be an insect, as well as what it means to be a honeybee.
Insects are the most diverse group of animals on Earth, with about 925,000 identified species. The genetic exploration may eventually shed light on the biology of togetherness and cooperation, which bees and people both discovered in the 600 million years since they last shared a common ancestor.
"We can use this genome to go looking for any and every gene that might be involved in the evolution of sociality. But that is down the road," said Hugh M. Robertson, an entomologist at the University of Illinois at Urbana-Champaign.
In a long paper in the journal Nature and several shorter ones in Science, Robertson and his colleagues describe their initial insights on the honeybee genome, which is full of both surprises and confirmed hunches.
The honeybee has 10,000 to 15,000 genes arrayed on 16 chromosomes, compared with humans' estimated 24,000 genes and 24 chromosomes (22 regular ones and two sex chromosomes). Comparisons with the fruit-fly and mosquito genomes suggest that bees evolved more slowly than either of those other insects. Curiously, some bee genes -- notably the ones responsible for internal "clocks" and circadian rhythms -- are more similar to mammals' genes than flies'.
But the most interesting insights so far come from discoveries of what parts of the bee's genome have been enriched, ignored or discarded by the evolutionary force of natural selection.