- Fruits: apples
- Nuts: almonds
- Animals: bees
- Animal Production: livestock breeding
- Education and Training: demonstration, on-farm/ranch research, workshop
- Production Systems: holistic management
With the recognition that agro-ecosystems are highly interconnected and multifaceted, a major challenge facing agriculture is preserving and improving honey bee health. Stress associated with transportation, nutritional consequences, various diseases and pests have all been recognized as potential factors in honey bee decline. However, intracolony genetic diversity has been shown to result in increased colony survival and productivity through various mechanisms. At the population level, genetic diversity serves as the raw material for selective breeding in agriculturally important plants and animals, including the honey bee.
Honey bees are native to the Old World and only a small fraction of this original population was ever introduced into the U.S. The importation and founder events associated with the establishment of honey bees in North America represent a series of genetic bottlenecks that have limited the diversity of introduced honey bee populations. These bottlenecks include: the limited size of founding populations, parasitic mite reduction of U.S. honey bee populations (managed and feral), and ongoing production of queens from a small number of queen mothers.
The goal of this project was two-fold: perform a comprehensive analysis of genetic diversity of Old and New World honey bee populations, and secondly, educate beekeepers (from backyard beekeepers to large-scale commercial operations, and major queen producers), through a variety of outreach tools, regarding the benefits of genetic diversity in honey bee populations. Our results indicate that although U.S. honey bee populations are less genetically diverse than their Old World progenitors, losses in alleles through time were mitigated by the incorporation of Old World germplasm, thereby increasing overall allelic richness of U.S. queen producer populations.
Taken together, these results indicate the Old World could not only serve as a genetic reservoir to access additional genetic diversity, but could allow for the long-term adaptability of honey bees by providing a broader genetic basis from which to select and breed for more locally adapted bees with improved apicultural traits.
Honey bees are at the center of modern agricultural production, contributing 14.6 billion dollars annually in pollination services alone (Morse and Calderone, 2000). As a single crop, almonds represent $2 billion annual industry in California and production relies almost exclusively on honey bee pollination. As such, nearly half of all managed colonies must be seasonally transported across the country to meet the demands required for successful pollination. Under natural conditions, honey bees are highly polylectic and visit a variety of floral types. Shifts in agricultural practice toward ever larger monocultures, sequential placement on crops, and reduced alternative foraging opportunities, however, has led to major seasonal dietary limitations for the honey bee.
Although honey bees are now distributed worldwide, the species (comprised of 28 recognized subspecies) is endemic to the Old World (Meixner et al., 2011; Sheppard and Meixner, 2003; Sheppard et al., 1997). A small number of these subspecies were imported to North America, primarily between 1622 and 1922, and formed the genetic underpinning for current U.S. honey bee populations (Sheppard, 1989a).
Genetic diversity of the honey bee at the colony level has been shown to play a key role in colony fitness and overall health. Increased colony diversity is associated with lower disease intensity, increased disease resistance, greater workforce productivity, and thermoregulation stability (Mattila and Seeley 2010; Hughes et al., 2008; Seeley and Tarpy, 2007; Jones et al., 2004; Tarpy 2003). Unfortunately, the importation and founder events associated with the establishment of honey bees in the U.S., coupled with the current queen production methods, represent a series of genetic bottlenecks that have reduced honey bee genetic diversity at the population level. These bottlenecks include: the limited size of founding populations introduced into North America; mite-mediated reduction of North American honey bee populations and elimination of feral sources of genetic variation; and annual commercial production of queens from a small number of queen mothers (Schiff and Sheppard, 1995; Delaney et al., 2009; Seeley, 2007). The U.S. Honey Bee Act (1922) established restrictions on the importation of honey bees into the United States, resulting in over 90 years of domestic bee breeding without the incorporation of significant new genetic material. Only with the exception by the United States Department of Agriculture (USDA) can honey bees be imported for experimental or scientific purposes (Public Law 94-319).
Recent improvements in the long-term storage and cryopreservation of honey bee semen has led to the successful instrumental insemination of honey bee queens. As permitted by APHIS and USDA, the Sheppard Lab has been involved in the collection of Old World germplasm since 2008, and its experimental use in breeding has been underway over the last few years. The suplementation of Old World cryopreserved germplasm in a select few U.S. queen producers is currently underway as a means to increase genitive diversity of their populations.
Microsatellites can be used to assess genetic diversity within and among honey bee populations (Delaney et al., 2009; Bourgeois et al., 2008; Shaibi et al., 2008; Solignac et al., 2003). Based on previous research findings, it is hypothesized that honey bees in the New World will be less genetically divers than Old World populations, and thus, could provide additional genetic diversity for long-term sustainable U.S. honey bee breeding efforts.
To perform a comprehensive analysis of the genetic diversity of Old and New World honey bee populations and develop an outreach plan to communicate these findings, three main objectives were addressed over the course of this project.
Objective 1. Assess the genetic diversity of honey bee populations from a representative sampling of Old World honey bee subspecies sampled from their native range and compare this to “strains” currently available in the United States:
The genetic diversity of three Old World subspecies (A. m. ligustica, A. m. carnica, and A. m. caucasica) originating from Italy, Slovenia, Georgia, and Turkey were assessed using microsatellite analysis. These subspecies are a realistic representation of what was originally brought to and established here in the U.S. To analyze U.S. populations, honey bee samples from major commercial queen production operations in California and Hawaii were assessed in addition to several feral populations.
Objective 2. Assess the genetic diversity of New World honey bees spanning three decades and following recent germplasm releases on commercially available queens:
Honey bee samples from several major commercial queen production operations in California and Hawaii were sampled in 2015. Previous estimates of genetic diversity in commercial stock by Delaney et al. (2009) used samples collected from 1993-1994 and 2004-2005. Specifically, queen producer populations sampled in 2015 (QP 2015) will be compared to those used by Delaney et al. (2009) in 2004 (QP 2004) and 1994 (QP 1994) to determine if there has been a change in allele frequency over time. Additionally, as permitted by APHIS, several California commercial queen producers have incorporated Old World germplasm into their breeding programs in recent years. Therefore, samples from 2015 include both queen producers who have incorporated Old World germplasm into their breeding programs compared to those that have not. These two populations will also be compared as a means to evaluate the impact of germplasm releases on genetic diversity and sustainable bee breeding.
Objective 3. Bring awareness to the genetic diversity of honey bees and its importance in sustainable agriculture and beekeeping practices:
We will distribute our findings through our extension program, local and national meetings, WSU workshops and beekeeping short courses, and publication via peer-reviewed journals and interviews and fact sheets.