APIS – Volume 16, Number 10, October 1998
Copyright ©1998 M.T. Sanford “All Rights Reserved”
THE THREATENED AFRICAN HONEY BEE (AHB):
To those in the Western Hemisphere, the idea that the African honey bee (AHB), Apis mellifera scutellata, is a threatened species may seem to be an oxymoron. Could this be the same insect that has taken much of South and Central America by storm? One that not only is extremely defensive in deterring predation, but also tolerates the Varroa mite without chemical treatment in the New World. The answer is yes, but in the same breath it must be said that so far this is only occurring in its South African homeland. The bizarre tale is eloquently told by Sue Cobey in Bee Biz (Issue 8, July 1998, pp. 7-10), who recently visited South Africa on invitation from those beekeepers interested in learning instrumental insemination to help them confront this dilemma.
It turns out the AHB is being overrun by its own version of a Trojan Horse, the hollow wooden statue that hid the Greek army as a ruse, and was given to the Trojans leading to the fall of their fair city (see images of the trojan war myth). The honey bee rendition of this is territorial incursion by Apis mellifera capensis, the native bee of the South African Cape of Good Hope, into AHB country. Unlike other honey bees, the Cape bee has a high degree of thelytoky. This is the capacity for laying workers to produce fully functional queens from unfertilized eggs. Although rare, it is present in other stocks as noted by G. DeGrandi-Hoffman and colleagues (Bee Science, Vol. 1, No. 3, pp 166-171, May 1991).
This characteristic apparently developed in response to the windy conditions prevalent on the Cape of Good Hope, according to Ms. Cobey, where virgin queens may have to wait long times before being mated and often can be lost. The latter would normally result in laying worker colonies, which under most circumstances could produce only drones and be doomed. Ms. Cobey, however, explains that Cape bee laying workers emit queen-like pheromones and thus exert reproductive control over their sisters. Hives with these so-called “false queens” can survive for long periods, eventually reverting to the normal queenright situation. Although those in the Cape manage their bees like beekeepers elsewhere, colonies of Cape bees are notoriously difficult to requeen, according to Ms. Cobey. Thus, beekeepers routinely make increases by simply splitting colonies and allowing them to do what comes naturally, raise their own queens.
Ironically, the Cape bee, not isolated geographically from other areas, was first thought to be endangered by gene flow from outside its natural range, Ms. Cobey says. But the situation turned topsy-turvy when the insect was moved northward by migratory beekeepers about 1992. In relatively few months it was observed that AHB queens disappeared or were rejected, brood patterns became irregular and scattered, multiple eggs appeared in cells, and fighting increased while foraging decreased. In addition, minor beekeeping problems became serious, brood was abandoned, and housekeeping and hygienic behavior ceased. Half the commercial AHB colonies (estimated at 50,000) were dead within a year, and the losses continue to this date.
Cape worker bees, according to Ms. Cobey, use their queen like pheromones to control both AHB workers and queens. They are treated like queens and quickly assume a colony’s reproduction, ousting AHB queens. Worse, they invade nearby colonies and the phenomenon quickly spreads. Colonies taken over by Cape bees, Ms. Cobey concludes, will not accept AHB queens, dwindle and die. Management practice has also unknowingly helped the problem as most beekeepers split colonies and/or hive the plentiful swarms in the region, allowing them to simply requeen themselves. There is no queen-rearing industry in South Africa, Ms. Cobey says, a major reason she was invited to share her considerable skills in that area. Thus, the managed and feral populations are essentially the same, and this allows continued flow of Cape honey bee genes into the AHB population.
Governmental programs dedicated to eradicating the Cape bee have not been successful, according to Ms Cobey. Quarantines did not work. There is no beekeeper registration, and numerous hobby and sideliner operations exist. These small-scale operators were not easy to educate about the problem. A governmental subsidy to help rebuild affected operations was established, but has since been rescinded. The problem is not easy to diagnose as the two bee races look very much alike, something reminiscent of problems seen elsewere in trying to distinguish African and European races in the New World . The only way to tell them apart is by counting ovarioles after dissection.
The search for solutions to this complex problem continues, Ms. Cobey says. Research is needed on a wide variety of topics, including the cytological basis of inheritance, role of odor in regulating colonies, and the effects and consequences of hybridization. The latter has also been a focus of research in the New World with reference to AHB.
Because maintaining both stocks is critical to finding a solution, Ms. Cobey says, stock reservoirs are being established. The Kruger National Game Preserve has been selected for AHB and the Cape Point Nature Preserve for capensis. Beekeepers are also modifying their methods, including minimizing contact between apiaries, restricting the number of supers given to colonies during a honey flow, and sensitizing themselves to possible situations that might favor the spread of the phenomenon. The situation also cries for developing a viable controlled queen-breeding program, Ms. Cobey says, along with learning new techniques such as instrumental insemination.
A complicating factor in South Africa is the introduction of both tracheal (1996) and Varroa (1997) mites, according to Ms. Cobey. And American foulbrood has recently been detected for the first time. Knowledge that tracheal mite resistance has developed elsewhere and AHB tolerates Varroa well in some parts of the New World is encouraging. However, colonies weakened by mite infestation or other stresses may be less able to resist Cape bee takeovers.
The South African situation is ironic, Ms. Cobey concludes, when compared with that in the United States, where the AHB is considered less than desirable for many reasons. In its homeland, the AHB is prized as a good honey producer thriving on erratic, marginal flows and is otherwise well adapted to a semi-desert climate with periodic severe droughts. The phenomenon is yet another piece of evidence that purposeful introduction of honey bee stock is fraught with unknown consequences.