The discussion moved from the original topic to level of inbreeding in
the US commercial population. Here are a couple of papers with actual
standard population genetics metrics- a step up from speculation or
reciting statements from authorities:
Genetic diversity of a small sample of Italian queens from Italy vs.
the US:
Summary
Declines in the numbers of breeder honey bee queens and the concomitant
loss of genetic diversity could potentially result in
inbreeding, and increased susceptibility to pests and diseases. Genetic
diversity of commercial Italian bee colonies in the United
States and Italy was assessed using six variable microsatellite DNA
loci.Worker bees were sampled from colonies of queen
breeders in both countries (USA, n = 18; Italy, n = 24). Overall,
allelic richness (mean alleles/locus), gene diversity (heterozygosity),
and FIS (inbreeding coefficient) did not differ between the two groups.
A total of 48 alleles were present among all colonies. Sampled
colonies from each country had a total of 38 alleles, although alleles
were present that were unique to each group. There were a
total of 10 unique alleles among USA bees and 10 among Italian bees.
Estimates of the level of genetic differentiation based on
different allele frequency patterns among the USA and Italian bees were
measured with the population genetic parameter FST. These
estimates showed that bees from the USA and Italy were measurably
distinct relative to the frequencies of the microsatellite alleles
present in samples from each country. Overall allelic diversity levels
were sufficiently high indicating that inbreeding does not appear
to be an immediate threat to existing honey bee populations.
https://www.ars.usda.gov/ARSUserFiles/60500500/PDFFiles/401-500/455-Bourgeois--Comparison%20of%20microsatellite.pdf
Genetic diversity in the Russian bee program in the US:
Technical Abstract: A genetic stock identification (GSI) assay was
developed in 2008 to distinguish Russian honey bees from other honey
bee stocks that are commercially produced in the United States.
Probability of assignment (POA) values have been collected and
maintained since the stock release in 2008 to the Russian Honey Bee
Breeders Association. These data were used to assess stability of the
assay and the diversity levels of the contemporary breeding stock
through comparison of POA values and genetic diversity parameters from
the initial release to current values. POA values fluctuated throughout
2010-2016, but have recovered to statistically similar levels in 2016
(POA(2010) = 0.82, POA(2016) = 0.74; P = 0.33 . Genetic diversity
parameters (i.e., allelic richness and gene diversity) in 2016 also
remained at similar levels when compared to those in 2010. Estimates of
genetic structure revealed stability (FST(2009/2016) = 0.0058) with a
small increase in the estimate of the inbreeding coefficient (FIS(2010)
= 0.078, FIS(2016) = 0.149). The relationship among breeding lines,
based on genetic distance measurement, was similar in 2008 and 2016
populations, but with increased homogeneity among lines (i.e.,
decreased genetic distance). This was expected based on the closed
breeding system used for Russian honey bees. The successful application
of the GSI assay in a commercial breeding program demonstrates the
utility and stability of such technology to contribute to and monitor
the genetic integrity of a breeding stock of an insect species.
Bourgeois, A.L., Beaman, G.D. 2017. Tracking the genetic stability of a
honeybee breeding program with genetic markers. Journal of Economic
Entomology. 110(4):1419-1423.
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