Bee Culture – October, 1986
By ERIC H. ERICKSON, JR.(1), BARBARA J. ERICKSON(2), and ALLEN M. YOUNG(3)
In Part I of this series we presented our experiences with “Africanized” bees in Costa Rica along with interpretations of our observations. In the following article we discuss some important beekeeping principles which govern the approach(es) that may be taken to effectively manage the problem of African bee gene flow into the United States. We then present realistic management approaches for this problem.
Before developing management strategies for the “Africanized” bee it is essential that we keep in mind that domestic honey bees in the United States are characterized by the following:
1. The honey bee queen normally mates with from 8 to 15 drones, hence, each colony is necessarily a heterogenous unit composed of numerous and more homozygous step- or sub-families with varying degrees of relatedness. The queen contributes 50% of the genes of the whole colony but individual workers and daughter queens do not receive exactly the same complement of genes from the queen – only a sample of all the queens genes. Each drone mate contributes 50% of the genes of only the subfamily he sires. Thus, the queen imparts variation within a subfamily, drones impart variation between subfamilies while both impart variation within a colony and between colonies. Out of the genetic mixture called a colony, one must know the parentage of the queen and that of each of her mates in order to correctly classify the total phenotype of a given colony (e.g. % AB vs EB). Obviously, each colony (as well as workers and worker subfamilies within each colony) will be phenotypically and genotypicaly different.
2. It has been shown (at Madison) that worker honey bees recognize differences between subfamilies and worker bees preferentially raise queens from their own subfamily. Hence, in the case of AB, at any given point in time, supersedure queens may have a higher probability of coming from either an “Africanized” or from a “non-Africanized” sire. (Note: it is logical to assume that both “Africanized and “non-Africanized” queens will have mated with both AB and EB drones.)
3. “Domesticated” honey bee stocks (breeds) have been artificially selected to a far greater extent than most people realize and that this selection pressure is manifested to a lesser extent in feral populations as well. Domestic strains of honey bees are usually, but not always, maintained phenotypically through continued artificial selection and “controlled” matings. Significant variability in behavior (e.g. iracibility, etc.) is evident among these strains.
4. Colonies with restricted space for rearing drones produce fewer drones but do not produce more workers. Colonies that swarm produce more drones than those that do not swarm: A small portion of these drones come from laying workers and hence will be genetically different from those produced by the queen. The number of laying workers increases particularly during periods of queen rearing.
5. “Domesticated” honey bees are kept in highly artificial (evolutionarily speaking) and environmentally inadequate domiciles (hives).
Hence, an apiary is roughly analogous to a dairy wherein one or more selected breeds are maintained, with some interbreeding opportunity, in poorly ventilated, uninsulated (unheated or uncooled) artificial domiciles that are rarely if ever cleaned. Drugs may or may not be used to control disease. The animals are fed while confined but allowed outside to forage and defecate at “optimal” times. Finally, the cows are milked or bred too frequently and their diet is sometimes inadequate. To be sure, there is great variance in the quality of management among dairy farms and the same is true for beekeeping operations.
Our objective in relating the above is to point out that a honey bee colony is a poorly defined and highly variable unit which is kept in a hive that is very different from its natural domicile. Relatively little is known about the adaptive significance of particular traits and subtraits of honey bees within the natural enviromnent (i.e., not within artificial hives). Whether EB or AB, there’s a need to understand the complete natural history of honey bees under specific sets of environmental conditions. Breeding procedures to develop strains of domestic honey bees are not unlike those used to develop strains of domestic house and farm animals. Moreover, diversity exists in the management practices of beekeepers. We must recognize these variances at the outset when developing management strategies for “Africanized” bees, acarine mites, protection from pesticides or any other problem.
African bee phenotypes are adapted through natural selection, and probably have a broad genetic base. Domesticated “European” bees have a narrower genetic base. African bees are more adaptable (probably) and hence, the process of “Africanization” is a process of increasing genetic variability. Because of their behavior and local circumstances (perhaps including climate and beekeeper abandonment of previously “European” colonies) the AB phenotype frequently does not suit the needs of beekeepers.
Beekeepers must bear in mind that they are manipulating a “black box” in which not all the desired results can be attained through selection. Of all we believe that we have leamed about “Africanized” bees, we still don’t know precisely how much behavior is governed by environmental variance versus genotype. Of particular interest here would be knowledge of interindividual interactions and behavioral variance over time. In regard to the latter, it is noteworthy that one of the most frequently stated problems regarding the defensive behavior of AB is the unpredictability of defensive response. Most experts seem to agree that a given colony may be docile on one occasion but irascible on another. Apparently, no scientific explanation of this phenomenon is available.
As stated in Part I, we saw no behavioral traits in so-called “Africanized” bees that we haven’t already seen in bees in the United States, and particularly in the breeding program at Madison. The only thing found to be unique was that most of the behavioral characteristics were combined in a single strain of bees. We believe that all are independent, heritable traits that will be muted by our temperate climate or can be selected out or retained, at will, in conventional breeding programs. We, and others, believe that there is no genetic link between defensive behavior and industry/productivity. Artificial selection procedures designed to increase yields of honey, increase brood production, reduce defensive behavior, and optimize other parameters favorable to the honey industry, may be in the opposite direction from natural selection which adapts wild colonies to the prevailing environment. Finally, we would predict, as some have already shown, that some AB will be shown to have greater resistance than EB to many parasites, pathogens, and toxins, because of their natural genetic variability. Similarly, other desirable traits such as productivity may be uncovered in AB because of their ancestry.
We believe that the problem of “Africanization” of honey bees can be better understood with the following analogy:
Let’s assume that a large, long established cattle ranch in Texas is involved in the production of gentle polled (hornless) herefords produced by artificial selection. This ranch is bounded on the south by a vast uncultivated range with an expanding population of wild longhorn cattle. To the north are many other smaller cattle ranches all raising polled herefords produced via any of several breeding lines.
One day the southern fences of the large ranch are breached by unknown numbers of wild cattle that quickly mix with the polled population. Though identifiable (initially) by their appearance and behavior, the first of the wild cattle cannot be easily rounded up and removed. Hence, they mate extensively with the polled population and vice versa. Moreover, the pressure of the wild population continues to break down the antiquated fence about as fast as repairs are made. The progeny of Wild X Polled matings produce offspring of variable appearance and behavior: Many of these cannot be differentiated from the pure polled stock. Now one must assume the role of the rancher — what are the options?
1. Do nothing. Result: ultimate reversion of all progeny to the wild type.
2. Sell all polled stock and go out of business. Result: accelerated reversion to the wild phenotype.
3. Develop new knowledge of the genetics of mating, migratory and defensive behavior of cattle. Result: meaningful long term contributions to basic understanding of bovien anatomy, genetics and behavior but no solution to the immediate problem. The likelihood of a long term solution to the problem is uncertain at best.
4. Corral all uninseminated cows and bulls that can be identified by brand as original stock. Result: limited initial success but long term results must rely on the quality of questionable fences.
5. Build stronger fences. Rogue out undesirable phenotypes. Result: reversal of gene flow.
6. Replace individuals lost through roguing with animals of known breeding from other ranches. Result: expensive but effective immediate revitalization of business and accelerated dilution of wild genes.
It is intuitively obvious to us that while some avenues of AB research are worthwhile, they are not likely to contribute a solution to the immediate problem. Unfortunately, beekeepers and lay persons are being misled into believing that research will magically solve the problem. We must change this impression.
In our opinion, the problem of “Africanization” is not an invasion, rather it is a gene flow problem. Solution to the problem of “Africanization” will come about through beekeeper directionalization of gene flow — achieved by maintaining positive selection pressure favoring desirable phenotypes. Fortunately, we have the mechanism for this process (requeening and possibly drone confinement) already in place. What we must do is insure that existing techniques are applied uniformly at all levels throughout the beekeeping industry. In our opinion (and that of many others), African bee management strategies to reverse the flow of “African” genes may be subdivided into six relatively simple objectives.
1. Develop a program of honey bee selection and breeding that specifically addresses the needs and capabilities of commercial queen and package bee producers: One that they can readily implement. We must recognize that the burden for the day to day work that will solve the AB problem in the United States must necessarily rest with beekeepers and queen breeders (public institutions/scientists are too few in number to accomplish this objective). If done correctly, we will minimize the effect of undesirable behavioral traits, take advantage of desirable AB traits and thus build a stronger bee industry than we have had. Adjustments in existing breeding programs will be necessary.
2. Provide new or improved ways of maintaining colonies that are reasonably free of “African” genes (assistance in meeting objective 2 above). Here, implementation of the concepts presented in options 4-6 of the polled hereford analogy is clearly the only way to procede. Research should be focused on improving efficiency in these areas. This should include:
a. Develop more precise colony evaluation techniques for field identification of undesirable phenotypes. Note: Expensive, time consuming analytical procedures will be of little use, except to researchers once AB genes are in the United States (actually these genes have been here for many years).
b. Develop improved methods of queen finding, queen introduction and regulation of drone populations. If a suspect colony is found, requeen it and put a queen excluder over the entrance to prevent drone escape. Alternatively, a trap can be used to capture all drones for the balance of the season.
c. Have experienced beekeepers assist less well informed peers in a & b above.
d. Provide reliable sources of desirable stock (here we find the importance of closed populations and other sources of AB gene free stock).
3. Develop the necessary beekeeper educational programs for implementation of 1 and 2 above and emphasize the need for beekeeper participation at all levels.
4. Develop necessary programs to insure continuation of a strong beekeeping industry, both hobbyist as well as commercial. Maximal numbers of colonies headed by queens with desirable behavioral traits will serve to offset the AB gene flow. The reversal of gene flow can be further accelerated by encouraging maximum drone production by colonies in AB areas and by requeening whenever necessary. Note: our discussions with Costa Rican University and Extension personnel suggest that the “Africanized” bee problem there has been exacerbated by the retirement of numerous hobbyist and sideline beekeepers (see options 1 & 2 of the polled hereford analogy).
5. Develop a program for public education that emphasizes the problem solving approaches above. Included here is emphasis of the need to maintain a strong, extensive hobby and commercial beekeeping presence (a high density of colonies with desirable phenotypes) to reduce or stop the spread of bees with undesirable traits. Emphasize also the implementation of this program prior to introgression of AB genes to North America. Its essence must be stressed to the public. One of the most counterproductive events would be the loss of existing base phenotypes (apiaries) and their respective drone populations.
6. Assure good overall colony/apiary management. Beekeepers at all levels must be prepared to make difficult adjustments in their management practices and, perhaps, develop new beekeeping skills.
Finally, we must recognize that under concepts of gene flow, some genes of the so-called “Africanized” bees will not be confined to the southern states.
The authors wish to acknowledge the Milwaukee Public Museum, the USDA-Agricultural Research Service and the American Cocoa Research Institute for their support. The authors also wish to thank Drs. Harry H. Laidlaw, Robert E. Page and Ms. Maria Spivak for their counsel and suggestions and for reviewing this manuscript.
(1) U.S. Department of Agriculture, Agricoltural Research Service, Bee Research Unit, Department of Entomology, University of Wisconsin, Madison, Wisconsin 53706.
(2) Department of Entomology, University of Wisconsin. Madison, Wisconsin 53706.
(3) Invertebrate Zoology Section, Milwaukee Public Museum, Milwaukee, Wisconsin 53233.