Marc;
Your comments simply do not agree with a) the
experience of the thousands of beekeepers who are already doing this worldwide or b) the recent scientific studies that have been coming out from the likes of Thomas Seeley. Here in the UK the general bee population has a reasonable background resistance level, such that beekeepers who choose to give up treatments tend to have stable and productive apiaries (without excessive losses) within 3 to 5 years. Suggesting that this is impossible because the resistance traits are not present is directly refuted by those like me who are out there and already doing it.
Furthermore the implication in your posts is that it is only possible to develop resistance to disease through long and carefully managed breeding programmes. The reality is that these costly and intensive programmes, selecting for single traits such as VSH, produce results comparable or less good than those observed by beekeepers who simply stop treating altogether and breed from survivors. There are a number of factors behind this:
Restricted, closely related, drone breeding disrupts the benefits associated with expression of multiple phenotypes in the hive, through natural open mating. Restricted mating, for example through AI or the use of isolated mating yards, is one of the main methods used in these directed breeding programmes. Use of restricted mating imposes automatic fitness penalties on the subsequent colonies.
Extreme polyandry improves a honey bee colony’s ability to track dynamic foraging opportunities via greater activity of inspecting bees
Directed breeding programmes assume a single trait solution (eg VSH) while ignoring the potential for other minor traits to form powerful synergies. When we select for VSH, for example by intensive inspection of the colonies, we are using a proxy rather than observing the hives actual ability to cope with mites. The observed reality is that there are many many possible routes to varroa tolerance which can be expressed in a single colony and that obsession with fixing single traits actually hinders the expression of the diverse methods which hives show when natural selection is used instead. If you get away from the idea of finding a golden bullet and look instead at enhancing the mix of beneficial genes in the overall genepool then you can end up with more of a spectrum of tolerance - some hives have multiple strong traits expressed, others have just one or two, some have none.
Here is a list of some of the known mechanisms which contribute to bees developing tolerances to varroa - some have been observed in practice, others are hypothetical, and some others are observed in other Apis species which are affected by varroa:
VSH
Grooming
Biting
Social Apoptosis - infested drone larvae sacrifice themselves
Social Apoptosis - workers carrying phoretic mites leave the hive and do not return.
Uncapping infested cells
Chewing/removal of infested larvae
frequent swarming
smaller nest sizes
resistance to viruses - (viral superposition with DWV Type B)
varroa reproduction suppression
entombing varroa in the cells with larval shed skins
brood breaks during dearth
local adaptation to nectar flows/seasons (affects overall colony efficiency)
In any one hive multiple traits can be expressed, potentially as a result of breedings with multiple drone fathers. No human directed breeding programme can select for such a broad mix of gene combinations.
On top of this, natural selection on the mites themselves comes into play. When we treat hives we kill around 95% of the mites. These mites have a strong evolutionary incentive to breed rapidly and to spread from colony to colony. When hives are not treated, and mites have an evolutionary incentive to NOT crash their host colony, there is pressure for mites to become less virulent (virulent strains of mites die out with their host colonies).
You state that a breeding programme in bees needs thousands of hives. In theory I can see where you are coming from. However this only holds if you view yourself in total isolation from the wider bees populations; your queens breed with drones from other beekeepers and feral colonies. Personally I manage about a dozen hives, however I know of half a dozen feral colonies within a few hundred meters, there are easily 300 managed hives within 5 miles, and I know for certain that one beekeeper near me has 100+ hives that have been kept treatment free for ten years. My genepool includes all of those hives. On that basis, by riding the process of natural selection across a whole landscape, I can make progress on the level of my individual smaller apiary.
References that you might find interesting:
Locke, B. (2016). Natural Varroa mite-surviving Apis mellifera honeybee populations. Apidologie, 47, 467–482.
https://doi.org/10.1007/s13592-015-0412-8
Neumann, P., & Blacquière, T. (2016).
The Darwin cure for apiculture? Natural selection and managed honey bee health. Evolutionary Applications.
https://doi.org/10.1111/eva.12448
Seeley, T. D. (2007). Honey bees of the Arnot Forest: a population of feral colonies persisting with Varroa destructor in the northeastern United States. Apidologie, 38(1), 19–29.
https://doi.org/10.1051/apido:2006055
Villa, J. D., Danka, R. G., & Harris, J. W. (2016). Selecting honeybees for worker brood that reduces the reproduction of Varroa destructor. Apidologie, 47(6), 771–778.
https://doi.org/10.1007/s13592-016-0433-y
Yanping Chen, ଝ, Evans, J., & Feldlaufer, M. (2006). Horizontal and vertical transmission of viruses in the honey bee, Apis mellifera. Journal of Invertebrate Pathology, 92, 152–159.
https://doi.org/10.1016/j.jip.2006.03.010
BREEDING MITE-BITING BEES TO CONTROL VARROA. (n.d.). Retrieved from
http://www.beeculture.com/breeding�mite�biting�bees�to�control�varroa/
Arechavaleta-Velasco, M. E., & Guzm�n-Novoa, E. (2001). Relative effect of four characteristics that restrain the population growth of the mite Varroa destructor in honey bee ( Apis mellifera ) colonies. Apidologie, 32(2), 157–174.
https://doi.org/10.1051/apido:2001121
Le Conte, Y.,
de Vaublanc, G., Crauser, D., Jeanne, F., Rousselle, J.-C., & Bécard, J.-M. (2007). Honey bee colonies that have survived Varroa destructor . Apidologie, 38(6), 566–572.
https://doi.org/10.1051/apido:2007040
Loftus, J. C., Smith, M. L., Seeley, T. D., Meconcelli, S., Pieraccini, G., Pradella, D., … Ellis, J. (2016). How Honey Bee Colonies Survive in the Wild: Testing the Importance of Small Nests and Frequent Swarming. PLOS ONE, 11(3), e0150362.
https://doi.org/10.1371/journal.pone.0150362
Mattila, H. R., Reeve, H. K., & Smith, M. L. (2012). Promiscuous Honey Bee Queens Increase Colony Productivity by Suppressing Worker Selfishness. Current Biology (Vol. 22).
https://doi.org/10.1016/j.cub.2012.08.021
Mattila, H., & Seeley, T. (2014). Extreme polyandry improves a honey bee colony’s ability to track dynamic foraging opportunities via greater activity of inspecting bees, 45(3), 347–363. Retrieved from
https://hal.archives-ouvertes.fr/hal-01234731
Page, P., Lin, Z., Buawangpong, N., Zheng, H., Hu, F., Neumann, P., … Dietemann, V. (2016). Social apoptosis in honey bee superorganisms. Scientific Reports, 6(1), 27210.
https://doi.org/10.1038/srep27210
Mordecai, G. J., Brettell, L. E., Martin, S. J., Dixon, D., Jones, I. M., & Schroeder, D. C. (2015). Superinfection exclusion and the long-term survival of honey bees in Varroa-infested colonies. The ISME Journal, 10(10), 1182–1191.
https://doi.org/10.1038/ismej.2015.186