>There is at least one trait/mechanism of resistance to varroa that is well identified, heritable, apparently present in most honey bee populations, and it produces declines in mite populations of colonies. 

Reminds me of the following paper:

Parallel evolution of Varroa resistance in honey bees: a common mechanism across continents? (https://royalsocietypublishing.org/doi/10.1098/rspb.2021.1375)

From the abstract:

'The near-globally distributed ecto-parasitic mite of the Apis mellifera honeybee, Varroa destructor, has formed a lethal association with Deformed wing virus, a once rare and benign RNA virus. In concert, the two have killed millions of wild and managed colonies, particularly across the Northern Hemisphere, forcing the need for regular acaricide application to ensure colony survival. However, despite the short association (in evolutionary terms), a small but increasing number of A. mellifera populations across the globe have been surviving many years without any mite control methods. This long-term survival, or Varroa resistance, is consistently associated with the same suite of traits (recapping, brood removal and reduced mite reproduction) irrespective of location. Here we conduct an analysis of data extracted from 60 papers to illustrate how these traits connect together to explain decades of mite resistance data. We have potentially a unified understanding of natural Varroa resistance that will help the global industry achieve widespread miticide-free beekeeping and indicate how different honeybee populations across four continents have resolved a recent threat using the same suite of behaviours.'

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