Africanized Honey Bees_

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Africanized Honey Bees?




I
In 1990, a honey bee swarm unlike any         EHBs and create a hybridized, or Afri-            Many experts expected that the farther
before found in the United States was         canized, honey bee.                            from a tropical climate AHBs spread, the
identified just outside the small south          This has always been a major ques-          more they would interbreed with EHBs.
Texas town of Hidalgo. With that identi-      tion for researchers—what, if any, type        But it appears that interbreeding is a
fication, Africanized honey bees were no      of interbreeding would happen between          transient condition in the United States,
longer a problem we would have some           AHBs and EHBs and how would this               according to ARS entomologist Gloria
day. Africanized honey bees had arrived.      affect honey bee traits that are important     DeGrandi-Hoffman. She is research
   Beekeepers, farmers who depend on          to people, such as swarming and                leader at the Carl Hayden Bee Research
honey bee pollination for their crops,        absconding, manageability for bee-             Center in Tucson, Arizona, and ARS
land managers, emergency responders           keepers, honey production, and temper.         national coordinator for AHB research.
like fire and police, and the public all                                                        “Early on, we thought the mixing
wanted to know what they would be fac-                                                       would reach a steady state of hybridiza-
ing as Africanized honey bees began to        SCOTT BAUER (K11074-1)
                                                                                             tion, because we knew the two groups
spread.                                                                                      of bees can easily interbreed and produce
   Now, 14 years later, scientists with the                                                  young,” DeGrandi-Hoffman says. “But
Agricultural Research Service and else-                                                      while substantial hybridization does oc-
where have uncovered many answers,                                                           cur when AHBs first move into areas
but they have also come upon some new                                                        with strong resident EHB populations,
and unexpected questions.                                                                    over time European traits tend to be lost.”
   Africanized honey bees—melodra-
matically labeled “killer bees” by                                                           A Mighty Adversary
Hollywood hype—are the result of honey                                                          DeGrandi-Hoffman and Stan Schnei-
bees brought from Africa to Brazil in the                                                    der, a professor of biology at the Uni-
1950s in hopes of breeding a bee better                                                      versity of North Carolina at Charlotte,
adapted to the South American tropical                                                       have been collaborating the past 3 years
climate. These honey bees reached the                                                        to figure out why AHBs replace EHBs
Brazilian wild in 1957 and then spread                                                       rather than commingling.
south and north until they officially                                                           “We’ve found six biological and be-
reached the United States on October 19,                                                     havioral factors we think are responsi-
1990.                                                                                        ble for making AHBs such successful
   Actually, all honey bees are imports                                                      invaders,” Schneider explains.
to the New World. Those that flourished                                                         First, AHB colonies have faster
here before the arrival of Africanized                                                       growth rates, which means more swarms
honey bees (AHBs) are considered                                                             splitting off from a nest and eventually
European honey bees (EHBs), because                                                          dominating the environment.
                                              Entomologist David Gilley is part of the
they were introduced by European              team investigating the usurpation of              Second is that hybrid worker bees
colonists in the 1600s and 1700s. EHBs        European honey bee colonies by swarms of       have higher amounts of “fluctuating
that escaped from domestication are           Africanized honey bees. Because queenless      asymmetry”—small, random differenc-
                                              colonies are particularly susceptible to       es between the left and right wings—than
considered feral rather than wild.            usurpation, the team maintains a group of
   Africanized honey bees are so called       queenless colonies to lure usurpation          African honey bees have, even when
because it was assumed that the African       swarms into their apiary to be studied.        raised in the same hive.
honey bees spreading out from Brazil          Gilley is shown here requeening one of these      “Imperfections like fluctuating asym-
                                              “bait colonies.”                               metry that increase with hybridization
would interbreed with existing feral

4                                                                                                      Agricultural Research/March 2004
                                               First found in southern
                     WHERE ARE                 Texas in 1990,
                                               Africanized honey bees
                     THEY NOW ?                are now found in most
                                               of the Southwest.




may end up reducing worker viability           destroy rival queens that are still devel-       Finally, some African traits are genet-
and colony survival,” says DeGrandi-           oping. African virgin queens are more       ically dominant, such as queen behavior,
Hoffman. “But this is a controversial          successful fighters, too, which gives       defensiveness, and some aspects of
factor right now, and it will take long-       them a significant advantage if they en-    foraging behavior. This doesn’t mean that
term studies of African, hybrid, and           counter other virgin queens in the colony.  EHB genes disappear, but rather that
European colonies in the same habitat to       DeGrandi-Hoffman and Schneider also         hybrid bees express more pure African
truly understand its influence.”               found that workers perform more bouts       traits. The persistence of some EHB
    But the third factor is undeniably true:   of vibration-generating body movements      genes is why the invading bees are still
EHB queen bees mate disproportionately         on African queens before they emerge        considered Africanized rather than
with African drones, resulting in rapid        and during fighting, which may give the     African, regardless of trait expression,
displacement of EHB genes in a colony.         queens some sort of survival advantage.     she points out.
This happens because AHBs produce                 AHB swarms also practice “nest usur-          A coincidence may have contributed
more drones per colony than EHBs, espe-        pation,” meaning they invade EHB col-       greatly to an overwhelming takeover by
cially when queens are most likely to be       onies and replace resident queens with      AHBs in areas they’ve invaded. Just as
mating, DeGrandi-Hoffman explains.             the swarm’s African queen. Nest             AHBs began their spread throughout the
    “We also found that even when you          usurpation causes loss of European SCOTT B                       Southwest, the U.S.
                                                                                          AUER (K
inseminate a queen with a 50-50 mix of         matrilines as well as patrilines. “In              11071-1)


African drone semen and EHB semen,             Arizona, we’ve seen usurpation
the queens preferentially use the African      rates as high as 20 to 30 percent,”
semen first to produce the next genera-        says DeGrandi-Hoffman.
tion of workers and drones, sometimes
at a ratio as high as 90 to 10,” she says.
“We don’t know why this happens, but
it’s probably one of the strongest factors             An Africanized honey bee
                                                       (left) and a European
in AHBs replacing EHBs.”                               honey bee on
    When an Africanized colony replaces                honeycomb. Despite
its queen, she can have either African or              color differences
European paternity. Virgin queens                      between these two bees,
                                                       normally they can’t be
fathered by African drones emerge as                   identified by eye.
much as a day earlier than European-
patriline queens. This enables them to

Agricultural Research/March 2004                                                                                                     5
feral honey bee population was heavily          takeover by AHBs. Bill had a great deal      ever documented. It’s even interested
damaged by another alien invader—the            of foresight to take these samples,” ex-     some as a model of how modern humans
deadly Varroa mite, an Asian honey bee          plains geneticist J. Spencer Johnston,       may have interacted with the European
parasite first found here in 1987.              who is with the university.                  population of Neanderthals.
   “Varroa mites emptied the ecological            The data showed that within 3 years          “Alan Templeton, a professor of biol-
niche of feral honey bees just as AHBs          of the arrival of AHBs in the refuge there   ogy and genetics at Washington Univer-
arrived,” says DeGrandi-Hoffman. “If            was a turnover from predominantly EHB        sity in St. Louis, has been looking at
they hadn’t been moving into a decimat-         to predominantly AHB. From 1997              AHB spread as a demonstration of his
ed environment, AHBs might not have             through 2001, the mixture stabilized,        model of Homo sapiens’ evolution and
replaced EHBs so quickly.”                      with an average of 69 percent of the col-    spread, which holds that there have been
                                                onies made up of African queens mated        three major migrations out of Africa,
Keeping Tabs on the Invaders                    with EHB and AHB drones and 31 per-          with large amounts of genetic inter-
   An extensive record of the AHB in-           cent composed of EHB queens mated            change among groups,” Johnston says.
vasion was created by now-retired ARS           with AHB and EHB drones. This pro-           Honey bee generations are short enough
entomologist William L. Rubink, who             duced a genetic mixture rather than a        that you can actually follow the invasion
was in the ARS Bee Research Unit in             replacement of EHBs by AHBs. Addi-           and the gene flow, unlike humans, ex-
Weslaco, Texas. From 1990 to 2001,              tional sampling and more analysis of         plains Johnston.
Rubink continuously sampled honey bee           existing samples will be needed to see
colonies in the Welder Wildlife Refuge,         whether this mixing continues or whether     Where Did They Go?
about 30 miles north of Corpus Christi,         the Africanized proportion increases, as        Just how far and how fast AHBs have
Texas.                                          has been predicted.                          spread in the United States may be one
   Once Rubink retired, researchers from                                                     of the most surprising factors in the
Texas A&M University agreed to pre-             Human Parallels?                             whole issue.
serve and analyze his samples. “We have            In many ways, the spread of AHBs in          Some experts predicted the bees
about 25 square feet of frozen bees that        the Southwest has been one of the most       would spread throughout the country;
represent the only real unbroken sam-           successful in- SCOTT BAUER (K11073-2)        others thought they’d reach only as far
pling of a wild area before and during its      trogressions                                 north as the latitude of Houston. Most
                                                                                             expected there would be a southern zone
SCOTT BAUER (K11073-1)
                                                                                             where AHBs would predominate, a
                                                                                             northern zone where EHBs would
                                                                                             maintain a climatic advantage, and a
                                                                                             large transitional zone between the two.
                                                                                             And everyone expected AHBs to spread
                                                                                             across the southernmost tier of states.
                                                                                             But, as of January 2004, AHBs have been
                                                                                             found only in southern California,
                                                                                             Arizona, New Mexico, Nevada, and
                                                                                             Texas, as well as Puerto Rico and the
                                                                                             U.S. Virgin Islands.
                                                                                                Why AHBs haven’t progressed east-
                                                                                             ward into Louisiana—though they were
                                                                                             expected there years ago—is a mystery.
                                                                                             So ARS entomologist José D. Villa be-
                                                                                             gan looking at factors that might corre-
                                                                                             late with where AHBs have spread. It
                                                                                             isn’t just minimum winter temperature
                                                                                             that limits AHB spread, as many be-
                                                                                             lieved, says Villa, who is in the ARS
                                                                                             Honey Bee Breeding, Genetics, and
Technician Mona Chambers measures the dimensions of an Africanized honey bee wing,
one of the traits that differentiate these bees from European bees. Inset: Closeup of the    Physiology Research Unit in Baton
wings Chambers is viewing.                                                                   Rouge, Louisiana.

6                                                                                                      Agricultural Research/March 2004
    “What immediately jumped out at me         has for beekeepers to manage their hives        This defensiveness is probably the bees’
was the correlation with rainfall,” he         in AHB areas.                                   best-known trait. All honey bee behavior
says. “Rainfall over 55 inches, distribut-        But requeening is a lot of work for          runs the gamut from very defensive to
ed evenly throughout the year, is almost       commercial beekeepers who maintain              very docile and can change depending
a complete barrier to AHB spread.”             thousands of hives. DeGrandi-Hoffman            on temperature, humidity, cloud cover,
    Total annual rainfall alone isn’t a bar-   and Schnieder are currently trying to           and food supply. But when provoked,
rier; AHBs have been found in areas of         discover what triggers AHBs to usurp a          AHBs do tend to sting in greater numbers
the Tropics with higher rainfall. But in       hive. They suspect it could be a                than EHBs.
areas with high rainfall distributed           pheromone.                                         “But they’re not anywhere near the
throughout the year, Villa’s pattern of           “If we can find out what tells an AHB        type of threat that Hollywood has made
AHB spread fits perfectly.                     swarm that this EHB nest can be taken           them out to be,” DeGrandi-Hoffman
    Villa is quick to point out that this is   over or that a colony or queen is strong        points out.
simply a mathematical correlation and          and cannot be easily usurped, then we
not proof of cause and effect. But, he         should be able to develop a chemical ‘no-       Living with AHBs
says, “you do find that 55-inches-of-          vacancy’ sign to help beekeepers keep              While beekeepers obviously do not
rainfall point right at the edge of where      AHBs out,” DeGrandi-Hoffman says.               want to work with “hot bees,” people in
AHBs stopped moving east about 10                 While AHBs do make honey and                 the Southwest have simply learned to live
years ago.” He’s planning experiments          pollinate plants, two traits make them          with AHBs. While many will never come
that may uncover the behavioral or physi-      undesirable for beekeepers: Colonies            in contact with the bees, others have had
ological mechanism that explains why.          regularly abscond from hives, and they          to learn new precautions.
    How much farther AHBs may spread           are often too defensive to be easily               Retired ARS entomologist Eric
is still unknown. But if you apply the 55-     tended.                                         Erickson, who was with the ARS bee
inches-of-rainfall limit, there are still         Because of AHBs’ genetic dominance           center in Tucson, pioneered many safety
niches that the bees may fill, mainly in       there has been little dilution of their         methods in areas where people and
southern California. Southern Florida          strong defensive reaction to threats to         AHBs collide. He developed the first
would be hospitable to the bees given its      their nests, explains DeGrandi-Hoffman.         instructions for fire departments—often
temperature and rainfall, but regulatory
vigilance could keep them out, since the
area isn’t contiguous with the other ar-       JACK DYKINGA (K7937-10)

eas of AHB spread. Alabama, northern
Florida, Louisiana, and Mississippi are
unlikely to be troubled by AHBs if the
55-inches-of-rainfall barrier holds.

Keeping on Beekeeping
   One of the greatest challenges for
Southwest beekeepers has been main-
taining their EHB hives when they are
surrounded by AHBs.
   Once AHBs spread to an area, bee-
keepers can no longer allow nature to
take its course in honey bee reproduction.
ARS has always recommended that
beekeepers regularly requeen their hives
with queens of known lineage to keep
AHB traits out of their apiaries. But,
given the African bees’ strong ability to
genetically usurp hives, the recom-
                                               Northwest Fire District’s Captain John Estes of Tucson, Arizona, uses a wide spray of water
mendation is now to requeen with queens        and chemical wetting agent as a means of subduing Africanized honey bees. Looking on is
that have already mated with EHB               ARS entomologist Eric Erickson (retired), who taught this control method to fire
drones. It’s the best way ARS currently        departments throughout Arizona.

Agricultural Research/March 2004                                                                                                         7
                                               SCOTT BAUER (K11076-1)
the emergency responders in stinging
incidents. Most firetrucks already carried
a surfactant, a soapy liquid that helps put
fires out. Such soaps also kill honey bees
when sprayed directly on them. Erickson
also worked out ways to quickly convert
a firefighter’s basic turnout gear into a
protective bee suit. Fire departments all
over the Southwest are now trained in
Erickson’s methods.
   Erickson also developed instructions
for homeowners to help them deal with
AHBs, such as how to prevent honey
bees from taking up residence inside
house walls and how to kill unwanted
bee colonies. (It is safer, though, to call
an experienced exterminator if at all
possible.)
   Swarm traps invented by entomolo-
gist Justin O. Schmidt, also at the Tucson     Entomologist Justin Schmidt examines an ARS honey bee trap used to lure Africanized bee
bee center, have been a boon.                  swarms and prevent their establishment in walls of buildings. Captured swarms are easily
                                               removed or destroyed with soapy water.
   “We developed a simple, inexpensive
trap with a pheromone lure to attract
swarms looking for new nest sites. That’s
how we’re able to track honey bee colo-
                                                                                             SCOTT BAUER (K11075-1)
nies as they spread out,” Schmidt says.        Varroa mites. But that rate varies
   The traps are also used as prophylactic     dramatically.
barriers around golf courses, airports,           “I’ve looked at about 40 colonies.
schools, and botanic gardens, or any-          Some have very few mites, and others
where else AHBs might take up resi-            are loaded,” Eischen says. “But if these
dence and conflict with people. The traps      had been EHB colonies without treat-
lure swarms away from high-traffic areas       ment, they all would have died long ago.”
and make them easy to remove.                     He is trying to isolate which mechan-
                                               ism provides the protection from Varroa
Not All Bad                                    mites. He has already ruled out hygienic
   People usually think only of AHBs’          behavior—the time it takes worker bees
downside, but they also represent a po-        to clean out mites. But if he determines
tential positive. ARS entomologist Frank       what AHBs do differently, it might be
A. Eischen at the Honey Bee Research           possible to breed that desirable trait into
Unit in Weslaco, Texas, has been study-        EHBs.—By J. Kim Kaplan, ARS.
ing AHBs for their resistance to Varroa           This research is part of Crop Produc-
mites.                                         tion, an ARS National Program (#305)
   Eischen maintains an apiary in a re-        described on the World Wide Web at
mote part of southern Texas. “Maintains”       www.nps.ars.usda.gov.
may not be the right term, because he             To reach scientists mentioned in this
simply leaves hive boxes out and lets the      story, contact Kim Kaplan, USDA-ARS           Judith Hooper assists David Gilley with a
bees fend for themselves year after year.      Information Staff, 5601 Sunnyside Ave.,       gas chromatography/mass spectroscopy
All the honey bees in the apiary have          Beltsville, MD 20705-5128; phone (301)        procedure for analyzing volatile
long since been Africanized.                   504-1637, fax (301) 504-1648, e-mail          pheromones from Africanized honey bees.
                                                                                             Pheromones appear to be an important
   His AHBs, which are never treated,          kaplan@ars.usda.gov. ★                        component of successful nest usurpation.
have a slightly better survival rate against

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Description: Honey, insects, bees, nectar from the flowers of flowering plants collected from the brewing of honey in the hive. Taken by the bees from the flowers, the water content of about 80% of the nectar or secretions deposited in his second stomach, the role of the body converting enzyme spit it out after 30 minutes of fermentation, back to the hive, hive temperature maintained at about 35 ℃, after a period of time, water evaporation, moisture content of less than 20% of the honey stored to the nest hole, sealed with beeswax. The composition of honey in addition to glucose, fructose species also contains various vitamins, minerals and amino acids. 1 kg of honey contains 2940 calories. Honey is a supersaturated solution of sugar, low temperature crystallization, crystallization is generated glucose does not produce the crystalline part is mainly fructose.