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DNA Research Finds Low Genetic Diversity Among U.S. Honey Bees

Contact: Autumn Canaday
Email: Autumn Canaday

February 15, 2023

U.S. agriculture owes many thanks to the honey bee (Apis mellifera L.), as it plays the crucial role of pollinator within the nation's food supply. Some of the nation's food industries rely solely on the honey bee, and it's estimated that the economic value of its pollination role is worth well over $17 billion each year. With this fact in mind, ARS researchers recently studied the U.S. honey bee's genetic diversity to ensure that this crucial pollinator insect has sufficient diversity to overcome the growing number of stressors such as parasites, diseases, malnutrition, and climate change.

What they found is alarming: the U.S. honey bee population has low genetic diversity, and this could have a negative impact on future crop pollination and beekeeping sustainability in the country.

The research, recently highlighted in Frontiers, was accomplished by analyzing the genetic diversity of the U.S. honey bee populations through a molecular approach, using two mitochondrial DNA (mtDNA) markers (DNA specifically from a mother). Researchers studied approximately 1,063 bees from hobbyist, and commercial beekeepers in 45 U.S. states, the District of Columbia (D.C.), and two US territories (Guam and Puerto Rico). The data showed that the nation's managed honey bee populations rely intensively on a single honey bee evolutionary lineage. In fact, 94 percent of U.S. honey bees belonged to the North Mediterranean C lineage. Data reflected that the remainder of genetic diversity belongs to the West Mediterranean M lineage (3%) and the African A lineage (3%).

"It's important that we have a realistic and accurate estimation of the honey bee's genetic diversity because this indicates the insect's ability to respond to disease, adaptation to environment, and productivity," said ARS Research Entomologist Mohamed Alburaki. "Without this pollinator insect, we will witness a drastic decrease in the quantity and quality of our agricultural products such as almonds, apples, melons, cranberries, pumpkins, broccoli and many other fruits and vegetables that we're used to purchasing. We can't wait until a domino effect slowly takes place and affects our food supply."

Map of North Mediterranean C lineage
93.79 percent of U.S. honey bees belonged to the North Mediterranean C lineage. The percentage of this lineage is displayed for each state.

The lack of genetic diversity creates a vulnerability for U.S. honey bees to survive in shifting climates that are now wetter or drier than usual. There is also concern that a honey bee's inability to fight off disease or parasitic infection could negatively impact beekeeping sustainability.  The challenge of U.S. honey bees' weakened immunity has become an economic burden to bee producers and beekeepers. In the past, U.S. beekeepers suffered less honey bee colony losses and treated against varroa mite (a ferocious honey bee parasite) once per year. In 2023, colony losses and winter mortality are at a high peak and varroa mite requires multiple treatments per year to keep it under control.

 "As a honey bee researcher, what worries me the most is that 77 percent of our honey bee populations are represented by only two haplotypes, or maternal DNA, while over hundreds of haplotypes exist in the native range of this species in the Old World, or the honey bees' native land of evolution," Alburaki said. "Many of these haplotypes have evolved over millions of years in their native lands, and have developed astonishing adaptation traits that we should consider incorporating in our US honey bee stocks before it is too late."       

These complex factors are driving Alburaki and his ARS research team to develop a solution that's sustainable for the entire nation.  The research team is currently evaluating the paternal diversity of the previously analyzed populations to acquire a full and accurate picture of the overall genetic diversity of the U.S. honeybee populations. Researchers are also interested in the possibility of diversifying breeding stations with honey bee queens from various genetic backgrounds.

Alburaki's research also identified and named 14 novel haplotypes in the three evolutionary lineages. These haplotypes have never been reported before and can provide new insights into the U.S. honey bee's evolution since its importation to North America in the 1600s. There is hope that the researchers can use this information to locate and enhance the numbers of these rare and novel US haplotypes, which could speed the process of reaching a healthier diversity within the nation's honey bee population.  

The Agricultural Research Service is the U.S. Department of Agriculture's chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in U.S. agricultural research results in $20 of economic impact.