> While on the subject of varroa reproduction, can someone offer an explanation of how varroa maintain genetic health while constantly inbreeding? 

I think I elucidated this when I brought up the obliquely related topic of mouse inbreeding. Inbreeding does not create problems, it reveals them. In normal heterosexual species, there are recessive traits that get masked and therefore passed on. It is only when the recipient is homozygous for this trait (cystic fibrosis, for example) that the defect is manifested. In mouse, they inbred them for hundreds of generations and weeded out the recessive defects. In clonal species ( aphids are clonal, produced asexually by parthenogenesis) a genetic flaw cannot become recessive, normally it would cause immediate harm, the individual would drop out of the gene pool, and the mutation would not be passed on. Varroa mites are virtually clonal.

¶

> Charles Darwin married a first cousin, Emma Wedgewood. Darwin suspected that close inbreeding in his family might have been the major cause for the health problems of his children, and this suspicion reinforced his research on inbreeding. ... However, under certain circumstances, inbreeding may purge populations from a high load of deleterious recessive mutations. ... A substantial part of the earth’s biological diversity consists of organisms that reproduce only asexually so far as we know, or reproduce sexually very rarely or with extreme inbreeding so that they are effectively asexual or clonal. ... Many asexual eukaryotes and prokaryotes are medically important parasites, agricultural pests, or invasive species. 

SOURCE: Lost sex. The evolutionary biology of parthenogenesis. Schön, I., Martens, K., & van Dijk, P. (2009). 

PLB

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