Couple things of note about this study, that lead me to question their conclusion that north vs south doesnt matter, that colony weight does....re-posting link to paper... https://academic.oup.com/jee/advance-article/doi/10.1093/jee/toy377/5251959

First, the players.... 14-16 colonies each of VT stock, WV russian stock, FL Pol-line Italian VSH stock, and mystery southern stock from TX.  

Most interesting finding to me: lumping northern and southern together, 73% of northern stock survived (about 20/28) (with avg of 6 frames of honey stored), and 67% of southern stock survived (about 19/28) (with avg of 9 frames of honey stored). See appendix for honey stored, discussion for survival by north vs south. Sadly number of frames of bees for north vs south was not given.  Kind of seems like a north/south bee source benefit for surviving on less honey is hiding in there...  though Discussion says this difference in frames of honey is not significant?  "There was no difference in honey stores in July according to stock [F(3, 52) = 2.342, P = 0.084]."
   
Key summary paragraph, upon which the party line is based:  "The mean weights of survivor and nonsurvivor colonies [when assessed in Oct] were 29.59 ± 1.33 and 15.96 ± 2.02 kg, corresponding to 18.44 ± 0.79 and 9.71 ± 1.19 frames of adult worker bees, respectively. Since they had received supplementary nutrition in the fall, we also examined the relationship between colony weight and survival within the Russian stock and found that survivors (59.2 ± 5.5 kg, N = 10) were significantly heavier in October than nonsurvivors [29.4 ± 7.8 kg, N = 5; F(1, 13) = 9.691, P = 0.008]."  

Especially looking at frames covered with bees for survivors vs not survivors, seems like they were documenting Parasitic Mite Syndrome there...though many find that their heaviest and biggest colonies die of mites, which isn't what was shown here.  Though "biggest colony" assessment by most beeks may be done in August, rather than Oct.  I wish the number of frames covered by bees in Aug was also mentioned for survivors vs not.  

Note that suddenly weights jump from AVG survivor weight being 29 kg, to the Russian survivors avg weight being at 59 kg.  Also the weights in the appendix range from 22 to 29 kg when sorted by stock, and range from 53 to 58 kg avg weight when sorted by region.  That does not make sense.  I'm not missing something obvious?  avg weights when sorted by region shouldn't be double than when sorted by stock?  No, I'm not missing something - raw data is shown in Fig 2 of colony weight, location and survival, and the max weight is 59 kg.  Oops in there somewhere...and Apiary A apparently is more deadly.

I think it is safe to conclude that their management for Varroa resulted in 33% losses over the winter, irrespective of stock origin and colony weight.  That's newsworthy, right?  They managed Varroa by 1) treating their packages (VT stock, FL VSH stock, TX stock, so 1 north and 2 south groups with 15 per group) with OAD upon arrival, and the nucs (Russian stock from WV) got nothing; and 2) treating with MAQS in AUG based on mite drops being over 20/day; and 3) treating again with MAQS in Sept based on sugar roll results.  I'm assuming their October mite loads are based on the sugar roll.  

Survivor colonies had mite counts of 12 via sugar roll (I'm assuming it's out of 300, and not mite drop, not specified which in Methods nor in Appendix table), and colonies that died had mite counts of 9 (again I'm assuming out of 300).  Current best practices say that sugar roll results of over 3% (so over 9/300) require immediate treatment during the "dormant no brood" phase (based on HBHC https://honeybeehealthcoalition.org/wp-content/uploads/2015/08/HBHC-Guide_Varroa-Interactive-PDF.pdf) and these authors did not appear to adhere to this.  Kind of a testament to the stock that any survived... unless others commonly find acceptably survival with counts of 12/300 with the sugar roll in Oct? 

I got nothing on the genetics component... I don't yet speak genetics.

I am left wondering if Northern stock truly survive more often on less honey, as their weights in the Appendix and reports in the Discussion are in conflict.  Oh well.  The debate will have to rage on....

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