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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.
Predisposing Factors
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.
An Analogy
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.
Recommendations
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.
Acknowledgments
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 manuscnpt.
REFERENCES
(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.
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