"Every honey bee alive today had a common ancestor in Africa" is one conclusion drawn by a team of scientists that probed the origin of the species and the movements of introduced populations, including African "killer" bees in the New World.
"Our analysis indicates that the honey bee, Apis mellifera, originated in Africa and spread into Europe by at least two ancient migrations," said Charles W. Whitfield, a professor of entomology at the University of Illinois at Urbana-Champaign who is the lead author of a paper to appear in the Oct. 27 issue of the journal Science.
"The migrations resulted in two European populations that are geographically close, but genetically quite different," Whitfield said. "In fact, the two European populations are more related to honey bees in Africa than to each other."
To explore the movements of bee populations, the researchers used simple variations in DNA called SNP (single nucleotide polymorphism) markers. "An SNP marker can tell you a lot about which bee is related to which bee, and where a particular bee came from," said Whitfield, who is also an affiliate of the Institute for Genomic Biology at the U. of I.
While previous studies relied upon a handful of markers, Whitfield and his collaborators used the recently sequenced honey bee genome to locate and compare 1,136 markers. The vast increase in markers provided a level of detail never before possible in the genetic analysis of honey bees.
The genus Apis is composed of 10 species, nine of which are confined to Asia. The one exception, A. mellifera, is distributed from sub-Saharan Africa to Central Asia to Northern Europe, and has more than two dozen distinct geographical subspecies.
In the New World, introductions of the western and northern European subspecies A. mellifera mellifera began in North America as early as 1622. This was followed by introductions of at least eight additional subspecies from different parts of Europe, the Near East and northern Africa.
In 1956, a subspecies from the savannahs of Africa, A. m. scutellata, was introduced to Brazil in an attempt to increase honey production. The descendants of these African honey bees rapidly spread northward and southward from Brazil, hybridizing with and displacing previously introduced European honey bees.
"Clearly, these African 'killer' bees are more aggressive and exhibit other traits that beekeepers and bee breeders dislike," Whitfield said. "By studying variation in the honey bee genome, we can not only monitor the movement of these bees, we can also identify the genes that cause the variations -- and that will allow us to better understand the differences."
The study was conducted by Whitfield and colleagues at the U. of I., Cornell University, Texas A&M University, the University of California at Irvine, the University of Kansas, Washington State University, and Bee Weaver Apiaries in Navasota, Texas.
The study was funded by the Institute for Genomic Biology and the School of Integrated Biology at the U. of I., the University of Illinois Research Board, and the California Department of Consumer Affairs.
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