Over the past few weeks, there has been a lot of scrutiny of the topic of bee breeding vs natural selection. I found this interesting:
> Two different levels of diversity within a colony were compared for the prevalence of pathogens and diseases. Lower genetic diversity was obtained in the colonies in which the queens were inseminated with semen collected from drones originating from a single colony, while greater was obtained in the colonies with queens inseminated with semen from drones of thirty different colonies.
> Unexpectedly, there were significantly more mites in colonies from the MCS [mixed colony semen] group which consisted of the same genotypes but combined in a single queen. This unexpected data could be explained by the occurrence of heterosis in MCS colonies which was confirmed by more brood throughout the year. (Dariusz Gerula, 2023. J. APIC. SCI.)
Harpur et al. showed that US honey bees were more genetically diverse than the original European stock:
> We found that managed honey bees actually have higher levels of genetic diversity compared with their progenitors in East and West Europe, providing an unusual example whereby human management increases genetic diversity by promoting admixture. ... Beekeepers may be, intentionally or unintentionally, selecting hybrid colonies, which tend to have higher fitness at some colony-level traits. (HARPUR, et al. 2012. Molecular Ecology)
My thoughts: The honey bee breeding system favors outcrossing. The above citations show that greater diversity in colony genetic makeup has positive effects, including producing larger colonies. These are in turn more susceptible to varroa buildup. On the other hand, less diverse lineages may produce smaller colonies with lower varroa levels.
This could account in part for why feral colonies harbor lower varroa levels. These colonies are smaller because they pick small cavities, swarm often and perhaps they are more genetically homogenous. Close selection by breeders and small isolated populations can both lead to lower genetic diversity, possibly leading to smaller colonies and lower varroa levels.
The question is: do we want to sacrifice colony size and the associated vigor and productivity in order to get bees that are less susceptible to varroa. In other words, throw the baby out with the bath water. I suggest this is exactly the direction that these alternative approaches to beekeeping may be headed.
Keeping bees in small hives and encouraging swarming (suggested by Seeley), narrowing the genetic base (as suggested by the local bee breeding crowd), etc. Contrast this with conventional beekeeping which favors bringing in outside stock to increase diversity, the use of large hives and unrestricted brood nests, as well as maintaining young prolific queens, etc.
This may be a recipe for rapid varroa reproduction but by all other measures, it creates better colonies, especially if combined with effective miticides. "You've got to ask yourself one question: 'Do I feel lucky?' Well, do you?" (Eastwood, 1971)
***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html
|