Researchers have found the survivor bees in a forest around Ithaca, New York. To find out how they coped with the advent of Varroa, the scientists compared the genetics of the wild colony population with the DNA of specimens collected in the same forest in 1977.
And here is what they found: The bees changed in several different ways. One of the most interesting changes in the bee population was in a gene related to a dopamine receptor which appears to be involved in hygienic behavior of the bees, with bees grooming each other to get rid of the mites.
The researchers also found many changes in genes associated with development. Mites reproduce and feed on the bee during the bees’ larval stage, so the researchers suggest that the bees evolved to disrupt the mites’ reproduction process. Also, there were physical changes. Today's bees are smaller than the older bees and their wing shape is different.
Alexander Mikheyev, lead author of the study and professor at the Okinawa Institute of Science and Technology in Japan, concludes: "These findings identify candidate genes that could be used for breeding more resistant bees, such as the dopamine receptor gene. More importantly, it suggests the importance of maintaining high levels of genetic diversity in domestic bee stocks, which may help overcome future diseases."
The Museum Sample
Such a comparative study is extremely rare, especially with bees. Few people collect them, and even fewer collect in a way that is good enough for a population level study. Luckily, Cornell Professor Tom Seeley, co-author of the study, had worked in this area during his Ph.D., and deposited his samples in the Cornell University Insect Collection. This is the first time scientists have been able to observe genome-wide changes after a specific event like the mite invasion.
The study titled “Museum samples reveal rapid evolution by wild honey bees exposed to a novel parasite” by Mikheyev, A. S. et al. was published by Nature Communications, an open access journal for high-quality natural sciences research. It was picked up by the online platforms of the science and bee communities: