APIS Volume 12, Number 7, July 1994
In this issue
- African Bee Advance in Texas Stalls
- Tracking Bee Ancestry Using DNA
- Status of the U.S. Beekeeping Industry
- Nosema Control
- More on Bee Attractants
AFRICAN BEE INVASION RUNS OUT OF STEAM?
Reports of African honey bee (AHB) colonization of western Texas continue, but the movement appears to have slowed significantly. And in neighboring New Mexico and Arizona, confirmed finds may be from swarms moving across the Mexican border, rather than migrating westward. The biggest question mark concerns California which has yet to be officially invaded by this insect, although there have been confirmed finds near the state line.
In east Texas as well, the AHB has not advanced as far as previous predictions indicated. The insect has yet to reach Houston and it's now been over three years since the first colony was found in the state. Has the invasion indeed run out of steam, and if so, why? These questions as yet have no answers, but already the press is writing about the phenomenon.
There are some intriguing reasons for the slowdown suggested by Mr. Laurence Cutts, Florida's Chief Apiary Inspector, and others examining the situation. The weather in the region has been generally unfavorable (colder winters, later springs) for feral bees. The bees may be approaching their climatic limits; the present distribution when compared with that predicted by Dr. Orley Taylor over a decade ago shows great correspondence. Texas is a very large state; perhaps the AHB will take some time to reach saturation in certain areas before the invasion can continue.
In addition, the AHB wave from Mexico has also met a challenge that it didn't face in that country, the Varroa mite. Nor can the potential ravages of chalkbrood, the foulbroods and tracheal mites on wild populations be discounted. There is more than a little bit of irony in the realization that the beekeeping industry's nemeses might become allies in stemming the AHB tide.
Another suggestion is that the imported fire ant, well entrenched in southern Texas, is responsible for predation on AHB colonies. Nests in scrub are quite near the ground and migrating swarms are small. There are reports that these ants are also becoming more effective predators on managed European colonies in Florida.
And what of the consequences of hybridization? Increased rate of genetic crossing among AHBs, feral European bees and those managed by Texas beekeepers could be responsible for restraining the migration. The situation is quite different than in tropical areas of Mexico and Central America. There, bees of European origin had not formed large feral populations, providing limited competition to the invaders, and over time, those in managed colonies were almost completely replaced by AHB. Hybrids that developed between European bees and AHB in the wild did not appear to persist (See February and March 1990 APIS).
Unlike in more tropical areas, a population of feral European bees already exists in Texas. This means greater competition for the AHB in the wild. It will also be a continuing source of genetic material above and beyond managed colonies to produce hybrids. And the resultant hybrid population might persist longer in these temperate regions than was the case further south. However, they could still be at some disadvantage. Hybrids may not be so migratory, one of the reasons suggested for AHB resistance to mites and pathogens. This fact, along with addition of European genetic material, could make them more vulnerable to a host of problems than are AHBs.
In the end, no single cause is probably responsible for checking the bees' advance. However, all of the above reasons taken together could make a formidable barrier keeping AHB populations at bay.
TRACKING HONEY BEE ANCESTRY
Even a cursory review of the apicultural literature reveals that over hundreds of years honey bees have been imported from all over the world. The results of this activity have been variable. Among the successes would be introduction of the Italian bee (Apis mellifera ligustica) which materially improved commercial bee stocks, and is in general use today throughout the country. A notable failure was the Cyprian bee (Apis mellifera cypria), considered too defensive by most beekeepers. It has almost been eliminated from the U.S. gene pool. In 1922, legislation to control importation effectively reduced genetic immigration. However, legal and illegal introductions have continued.
Considering the sheer number of importations, the question arises concerning the eventual fate of these bees in the U.S. Dr. Eric Mussen posed this question in his latest newsletter, From the UC Apiaries, while reporting on a study by N.M. Schiff and W.S. Sheppard in the Journal Experientia, Vol. 49, pp. 530-532, 1993. The study's authors did not address Dr. Mussen's specific question. Their purpose was to look at the genetic variation of feral populations in the southern U.S. and find out if the AHB invasion could be adequately monitored using existing European genetic markers. They did this by analyzing mitochondrial DNA (mtDNA).
There are two primary sources of DNA in multicellular animals. The one most heard about, often touted by the press as the best crime fighting tool since the fingerprint, is from the nucleus of the cell. This DNA is the chemical information that determines the form of the organism and much of its behavior. It is inherited from both the mother and the father and can effectively be used to make unique identifications.
But there is another kind of DNA. It is found in small energy-producing capsules outside the nucleus of the cell. These organelles are called mitochondria (the singular is mitochondrion). In multicellular animals, DNA associated with the mitochondria is only inherited from the mother. This provides the means to track maternal ancestry . All bees in a colony have the same mtDNA, inherited from one single individual, their queen. Pioneering studies on mtDNA by Drs. Glenn Hall at the University of Florida and Deborah Smith, University of Kansas, provide evidence that feral swarms of African maternal lines were primarily responsible for AHB migration in the tropics. Study of human mtDNA also gives rise to the provocative idea that all humanity descended from a single Eve.
The Experientia study looked at 422 feral bee colonies sampled from areas not undergoing AHB invasion. The bees came from nine states (Florida was not included). Collection was restricted to wild colonies, including those relocated, but not requeened by beekeepers. The results are as follows:
State Mitochondrial Types Total
African Mel/Ibr Car/Lig
AL 1 14 24 39
GA - 4 28 32
LA - 10 41 51
MS 2 14 31 47
NC - 3 27 30
NM - 7 54 61
OK - - 3 3
SC - 21 59 80
TX 1 19 59 79
Total(%) 4 (0.9) 92( 21.8) 326 (77.3) 422Mel/Ibr refers to two European honey bee races (Apis mellifera mellifera and Apis mellifera iberica). The former is the German or dark bee, while the latter is the Iberian bee, native of the Spanish peninsula. These are grouped together and considered "western" races. The "eastern" races include A. mellifera carnica (Carniolan bee) and A. mellifera ligustica (Italian bee), designated above as Car/Lig; both are thought to make up the majority of the present U.S. commercial honey bee stock. The eastern and western groups have been separated on the basis of mtDNA structure. The African mtDNA was from the Egyptian honey bee, Apis mellifera lamarckii, not Apis mellifera scutellata, considered to be the ancestor of the AHB.
When analyzing the results of this study, it is important to understand that the percentages noted above are only of mtDNA types found in wild U.S. honey bees. They do not necessarily translate into bee types. For example, even though four colonies were found with African mtDNA, the authors identified the individual bees as "European" using morphometrics. Thus, no bees determined to be "Africanized" are present in the above samples. This is problematic. Presence of lamarckii mtDNA is a certain indication of African ancestry.
Is it reasonable to correlate percentages of a certain mtDNA type to a specific population? One school of thought says no, because mtDNA really may have no effect on a bee's structure or behavior which are considered superior measures of identification. However, different mtDNAs may result in different capabilities. Enzymes coded by mtDNA are responsible for energy production in the cell and must interact with those coded by nuclear DNA. These functions may contribute to the differences in metabolic capacities of African, European and hybrid honey bees discovered by Drs. Glenn Hall at the University of Florida and Jon Harrison, Arizona State University (see June 1993) APIS. In addition, because mtDNA is inherited as a total package from the mother, its presence means that it came from an unbroken maternal lineage. In the case of the lamarckii mtDNA identified in the Experientia study, the time line could reach as far back as the 1860s.
It is tempting, therefore, to make a correlation of mtDNA types with bee populations. Dr. Mussen surrendered to this in his article, concluding: "It will be interesting to see if the 22% of feral bees with 'non-commercial' lineage can survive the competition of AHBs for their feral territory."
STATUS OF U.S. BEEKEEPING
F.L. Hoff and L.S. Willett have just released their study entitled The U.S. Beekeeping Industry. It is Agricultural Economic Report Number 680, published by the USDA Economic Research Service, 69pp, May 1994. This document is required reading for anyone interested in the changes taking place in the apicultural industry.
The introduction states in part: "This report updates information on honey production, pollination and the relationship of the U.S. beekeeping industry to agriculture and the environment. The study was mandated in the Committee report that accompanied the Agriculture, Rural Development, and Related Agencies Appropriation Act of 1987. The mandate resulted from concern by beekeepers and members of Congress about problems, issues, and challenges that emerged during the 1980's with the potential to significantly alter the beekeeping industry. These concerns included northward migration of the Africanized honeybee, infestations of colonies by tracheal and Varroa mites, the widespread use of highly toxic pesticides, increasing honey imports, and efforts to discontinue the honey price support program."
This report is an extremely valuable lobbying document. The authors should be congratulated for providing the industry with these facts and figures. The beekeeping community now has plenty of ammunition to back up its arguments for public support in many arenas. However, the time and expense to produce this document will go for naught, if those in the beekeeping industry do not actively use the information to its fullest potential. To obtain a copy call toll free 800/999-6779 in U.S. and Canada (other areas 703/834-0125) and ask for AER-680. The cost is $12.00 payable by Visa or MasterCard. To order a copy by first-class mail, send a check for $12.00 ($15.00 for Canada or elsewhere) made payable to ERS-NASS, 341 Victory Drive, Herndon, VA 22070.
NOSEMA CONTROL
Mr. Glen Stanley, Retired Iowa Apiary Inspector, provided some advice in a recent letter to the American Bee Journal. It was simple. If one controls nosema this helps the bees overcome other obstacles like tracheal mites. In other words, asks Mr. Stanley, "...why not begin fighting the battle where it would do the most good by getting bees cleared of nosema first." Another basis of good beekeeping, he says, is to remove all old, black combs (his emphasis), the source of bacteria, fungal spores and other materials the bees might unintentionally collect. Mr. Stanley's message must continually be kept in mind by beekeepers interested in getting the most from their colonies. Adhere to the fundamentals of beekeeping and the bees will take care of the rest.
Malcolm T. Sanford
Bldg 970, Box 110620
University of Florida
Gainesville, FL 32611-0620
Phone (904) 392-1801, Ext. 143 FAX: 904-392-0190
INTERNET Address: MTS@GNV.IFAS.UFL.EDU
