Ever since introduction of the Varroa mite in 1987, the press has become sensitized to the fact that the bee population is being threatened by this parasite. As with most issues of this sort, reports range from the sublime to the ridiculous. Some have been justifiably criticized for their lack of investigative rigor and sensationalistic fervor. Although wild honey bees are being lost, commercial agriculture continues to prosper because treated, managed colonies are still available for pollination. The beekeeping industry should also be gratified that honey bees are at last getting some of the respect they have so long deserved as pollinators in helping to produce a bountiful food supply.
Lost in most of these reports is a major effect the reduction of the feral bee population may have on genetic diversity of the managed honey bee population. Nature has built into honey bee behavior elaborate mechanisms to prevent a narrowing of the genetic base. Most significant is the fact that queens mate with 10 to 17 drones in the air over a short period of time. Effectively controlling mating activity has been a goal of many queen breeders, but often is impossible unless some degree of isolation is established. This usually has been accomplished on islands.
The United States’ production of honey bee queens and package bees like many crops is based on a few individuals. Because of this, genetic variation in the drone population provided by wild or feral nests has been considered beneficial. It keeps the genetic base in commercially available queens and bees from becoming too small. With less genetic material generally available, however, the probability of inbreeding increases. The consequences of this have been well described in other crop- and animal-breeding systems. They include susceptibility to diseases and pests, expression of harmful recessive traits, or a general lack of vigor. In humans, the possibility has led to prohibitions in most cultures of marriage within immediate families.
In honey bees, there is also another risk when the genetic base narrows. It is known that as inbreeding occurs there is more chance for diploid drones to be produced. These individuals are homozygous (have the same gene form or allele) at the sex locus; only those with different alleles become females. All diploid drones are destroyed by the colony in the larval stage and the queen is then obliged to lay another egg to replace each. Colonies suffering this condition, called “inbreeding depression,” may have 50 percent less developing brood. As a consequence, they cannot build enough population to produce surpluses, and in some cases may not survive.
Dr. Marion Ellis estimates that the entire United States’ commercial queen population is the result of five hundred individual breeder queens (September 1997 Bee Tidings, Nebraska Cooperative Extension Newsletter). If this is so, there is the possibility that inbreeding depression may be reaching epidemic proportions, and some of the weaknesses seen in bee populations attributed to a variety of causes may in fact be due to this condition. Unfortunately, little is known about the genetic history of many queen mothers used in commercial operations. Nevertheless, it is important to know about the situation and its possible implications. It is fiendishly difficult to breed honey bees and this makes it not only complicated but expensive.
As inbreeding becomes more probable, the concept of making the 1922 bee importation law more relevant to current conditions takes on greater significance. The beekeeping industry may have to accept more risk in importing bee stock in exchange for widening the genetic base of commercially available queens and bees. One program at Washington State University seeks to import honey bee material to broaden the genetic base.
Almost unknown is how drones figure into genetic diversity. Research is continuing into how drones locate queens to inseminate. A part of that is the importance of what are called drone congregation areas. At least one initiative is being developed looking more deeply into what is called “the dance of the drones.
