People have domesticated many different plant and animal species to utilize for food, fiber, or other resources. To domesticate a plant or animal people deliberately breed individuals that have valuable or desirable traits – big ears in corn, longer shelf life in vegetables, less fat (unfortunately) in pigs, large, dry flavorless breasts in chickens. The value and desirability of these traits are in the eye of the beholder.
Organisms cannot excel at everything. Breeding to enhance one trait inevitably diminishes another trait. This is called a trade-off and occurs in most domesticated plants and animals. Crops bred for greater yield often have lower resistance to pests and diseases. Animals often have the same problems; bred for rapid growth domestic pigs, chickens, cows often have lower immune function or resistance to disease.
Honey bees have been on the world stage for several years since beekeepers have experienced higher than normal colony losses. Despite all the attention and even affection honey bees have received many people are surprised to learn they are domesticated, exotic, animals just like other livestock. And, as with other domesticated animals, bees have been bred for traits such as honey production, overwinter survival, and easy handling.
As animals are domesticated the genetic diversity of the population often declines. Genetic diversity can help individuals and populations survive environmental stress and disease. In a new paper, Margarita Lopez-Uribe (former postdoc from the Tarpy, Dunn, and Frank labs now faculty at Penn State) and co-authors compared genetic diversity of feral and managed honey bee colonies. In a previous paper, Elsa Youngsteadt, Holden Appler and others reported that feral honey bees had greater immunocompetence than managed honey bees.
In the new paper, we looked to genetic diversity as a possible mechanism. Feral colonies had less genetic diversity than managed ones. However, transcription of immune related antimicrobial peptides increased as genetic diversity increased in feral colonies but not managed colonies. This suggests that the genetic diversity that does exist in feral bees, perhaps due to natural selection for optimal genotypes and immune variants, improves their immune function. Genetic diversity in managed colonies, from artificial selection for desirable traits, does not improve immune function.
Thus, there may be a trade-off between having bees with traits desirable to beekeepers and bees that can fend off the constant onslaught of diseases to which honey bees are subjected. Scientists and beekeepers are working from every angle to improve honey bee health and sustainability. They should look to feral bees, that survive in the wild without the pesticides and medicines used in managed colonies, for novel genetic variation that could improve disease resistance.
López-Uribe, M.M., Appler, R.H., Youngsteadt, E., Dunn, R.R., Frank, S.D., Tarpy, D.R. (2017) Higher immunocompetence is associated with higher genetic diversity in feral honey bee colonies (Apis mellifera). Conservation Genetics. doi:10.1007/s10592-017-0942-x
This study was funded by the CALS Dean’s Enrichment Grant from North Carolina State University (to DRR, SDF, and RRD) and a National Science Foundation (NSF) Postdoctoral Fellowship (1523817 to MMLU).