Origins, spread of honeybees determined

Sequencing of honeybee genome could allow better breeding to assist pollination

Irvine, Calif., Oct. 25, 2006 -- The honeybee, a species that contributes billions of dollars to the world's agricultural economy each year through pollination, originated in Africa and is evolving in surprising ways in the Americas today, according to a UC Irvine researcher. The findings could have significant implications for honeybee breeding and the crucial role these creatures play in farming worldwide.

According to Neil Tsutsui, assistant professor of ecology and evolutionary biology, a worldwide analysis of the honeybee, or Apis mellifera, has yielded new information about the origins and spread of honeybees throughout Europe, Asia, and North and South America. For example, researchers have found that the bees did not arise in Asia, as previously expected, but came out of Africa. They then spread twice into Europe and Asia, creating two distinct genetic lineages, one of which includes the widely cultivated Italian bee, a subspecies used extensively for agricultural pollination. These European subspecies are now breeding with Africanized bees in North and South America, and resulting in genome-level changes that are surprising and unexpected.

The research, reported in the current issue of Science, was based on genetic markers identified in the sequencing of the full honeybee genome, which is being reported in this week's issue of Nature.

"The sequencing of the honeybee genome, as well as our findings about the species' origin and spread, could have considerable applied applications," said Tsutsui, senior author of the Science study, and one of the authors of the Nature paper. "We need to understand the bees, where they came from, and what is happening to them today to ensure they continue their vital work of pollination, which is so crucial to the world's economy."

Among the researchers' findings was the discovery that the introduction of Africanized ("killer") bees into South America in the 1950s affected the genomes of pre-existing honeybees in unusual ways. The genes that originated from some subspecies appeared to be replaced by African genes, while genes derived from other subspecies were more resistant to this replacement.

This finding, according to Tsutsui, is important because the spread of Africanized bees northward from South America in recent years has had some negative consequences; not only are these bees more dangerous to humans because of their propensity to sting in large numbers, but they are also difficult to rear commercially for pollination and the production of honey and other products. The information gained from this study can be used to compare markers between Africanized and non-Africanized bees, which would allow for the identification of genes that lend these "killer" bees their aggressive characteristics. Once those genes are identified, the more dangerous bees can be bred to lose those characteristics.

The National Research Council recently issued a report stating that pollinators, such as the honeybee, are on the decline, and one reason is the encroachment of the Africanized bee into the U.S. According to the report, in order to bear fruit, three-quarters of all flowering plants rely on pollinators for fertilization. For example, in California alone, it takes about 1.4 million colonies of honeybees to pollinate 550,000 acres of almond trees.


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Tsutsui collaborated with colleagues from several universities on the Science study, including Charles Whitfield, first author of the paper, from the University of Illinois, Urbana-Champaign. The study was funded by the University of Illinois, the U.S. Department of Agriculture, and the California Department of Consumer Affairs -- Structural Pest Board.

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