Status of breeding practices and genetic diversity in domestic U.S. honey bees

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Chapter 4
Status of Breeding Practices and Genetic Diversity in Domestic U.S. Honey
Bees
Susan W. Cobey1,2, Walter S. Sheppard2 and David R. Tarpy3
1. University of California, Davis, CA 95616, USA (e-mail: scobey@mac.com);
2. Washington State University, Pullman, WA 99163 (e-mail: shepp@wsu.edu); 3. North
Carolina State University, Raleigh, NC 27695 (david_tarpy@ncsu.edu)
Abstract The many problems that currently face the U.S. honey bee population has underscored the
need for sufcient genetic diversity at the colony, breeding, and population levels. Genetic diversity
has been reduced by three distinct bottleneck events, namely the limited historical importation of
subspecies and queens, the selection pressure of parasites and pathogens (particularly parasitic
mites), and the consolidated commercial queen-production practices that have reduced the number
of queen mothers in the breeding population. We explore the history and potential consequences
of reduced population-wide genetic diversity, and we review the past and current status of the
reproductive quality of commercially produced queens. We conclude that while queen quality is
not drastically diminished from historical levels, the current perceived problems of “poor queens”
can be signicantly improved by addressing the ongoing genetic bottlenecks in our breeding
systems and increasing the overall genetic diversity of the honey bee population.
Introduction
The decline of honey bee colonies (Apis mellifera) in the USA and Europe, in both managed
and feral populations, is of signicant concern. Historically, there have been periodic high losses
of managed European honey bees (vanEnglesdorp and Meixner, 2009). Although colonies are
challenged by numerous interacting factors, parasitic Varroa mites (Varroa destructor) and
associated diseases play a major role. The current impact of Varroa is augmented by the worldwide
spread of honey bee pathogens, the accumulation of miticide and pesticide residues in beeswax, and
malnutrition (vanEngelsdorp et al., 2009). Colony losses have neither been signicant in Australia
(where Varroa is absent) nor in Africa and South America (where African and Africanized bees,
respectively, exhibit high survival without treatment for Varroa mites).
The selection, development, maintenance, and adoption of highly productive European
honey bee stocks that can both tolerate Varroa and resist diseases offer a sustainable, long-term
solution to these ongoing problems. However, developing such a suite of traits has been elusive.
Bee breeding is subject to unique challenges, including high labor costs, often slow progress
toward breeding goals, and little economic prot. The primary importations of honey bees into
North America took place between the early 17th through 20th centuries, with severely curtailed
importations of additional genetic stock over the past 90 years. The limited importation of honey
bees from areas of endemism, coupled with a queen production system that annually produces the

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majority of US commercial queens from a relatively small number of queen mothers, represent
potential genetic bottlenecks (Figure 1). Such bottlenecks could reduce genetic diversity and may
limit our ability to select strains of bees that can both tolerate Varroa mites and be commercially
productive. Here, we examine the historical importation of bees, the genetic effects of founder
events and queen breeding practices, and assessment of queen quality in U.S. populations in an
effort to provide insights into current reports of declining honey bee populations.
A Brief History of Apis mellifera in the U.S.
As with many animals of agricultural importance, the honey bee (Apis mellifera) is not
native to the U.S. or Australia. The original distribution of the genus Apis was restricted to Africa,
Asia, and Europe. The colonization of the North America and Australia by European immigrants
also led to the introduction of the European native honey bee. In those early times, the honey bee
was primarily of importance as a major source of sweetener and wax.
With the development of “modern” agriculture, the primary importance of honey bees from
a human perspective shifted to their role in providing pollination services. In the U.S., perhaps
the most striking example of the current role of honey bees as pollinators in modern cropping
systems is the magnitude of the population of honey bees required to pollinate the almond crop.
California alone produces about 80% of the almonds consumed worldwide on more than 300,000
hectares of almond orchards. In 2011, an estimated 1.3 to 1.5 million hives of bees will be needed
to pollinate the almond crop (Flottum, 2010). This single agricultural crop, therefore, requires
physical placement into California almond orchards of almost 60% of the 2.5 million colonies of
bees currently managed in the United States. Similar stories, although involving fewer colonies,
could be told of the pollination requirements for apples, cranberries, cucumbers, and numerous
other crops (Delaplane and Mayer, 2000).
Although the pollination service of U.S. agricultural crops is by managed honey bees of
commercial origin, it is important to realize that substantial “within-species” variation occurs in
the honey bee across its original range of Europe, Africa, and western/central Asia. This variation
reects the adaptation of populations of honey bees throughout this vast geographic range to a large
set of climatic differences. One might expect, for example, that honey bees of sub-Saharan Africa
and those of Scandinavia might have evolved somewhat different behaviors related to foraging,
overwintering, and swarming. Given that the honey bee across this range is only a single species
(Apis mellifera), they can and will interbreed when placed together in common apiaries. However,
geographic differences among honey bee populations led scientists to further differentiate Apis
mellifera into a number of “sub-species”, sometimes referred to as “geographic races” (Ruttner
1975, 1988). Subspecies are designated by adding a third name to the species name and are referred
to by a “trinomial”. Examples include Apis mellifera mellifera, Apis mellifera ligustica, and Apis
mellifera carnica, which refer to the Dark Bee of Northern Europe, the Italian honey bee, and the
Carniolan honey bee, respectively.
The importance of having subspecies designations is primarily one of convenience
in having a common vernacular to describe or refer to specic groups or populations of honey
bees. Within the world of beekeeping, various subspecies have been reported to express specic
tendencies or traits of apicultural interest, such as the tendency for defensiveness and high
swarming rate in a subspecies from sub-Saharan Africa (Apis mellifera scutellata) or the tendency
toward gentleness and high propolis use in Apis mellifera caucasica (a subspecies endemic to the

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Caucasus Mountains).
The history of honey bee introductions into the United States is a fascinating story in itself
and, in part, is also reective of the personalities of leading beekeepers and bee scientists of the
time. The rst records of honey bees existing in what is now the U.S. was in 1622, at the Jamestown
colony (present day Virginia; Oertel, 1976). These bees were imported from within the range of A.
m. mellifera in England and became well-established in the eastern part of the country. Interestingly,
these bees quickly spread out in front of the advancing European settlers in subsequent decades.
By 1788, Thomas Jefferson wrote that the native people referred to these insects as “White Man’s
ies”, indicating their role as foretelling the impending arrival of European settlers wherever they
were found (Jefferson, 1788). A. m. mellifera (the Dark Bee of Northern Europe) was apparently
well-suited for North America and was, in fact, the only honey bee present in the U.S. for the next
239 years (1622 until 1861).
By the 1850’s, steamship service was established between the U.S. and Europe, reducing
the time required to cross the Atlantic Ocean and opening the door to affordable and secure
shipments of bees. In 1859, Italian honey bees were introduced to the U.S. from Dzierzon’s
apiary in Germany and by 1860 a shipment of Italian queens were received directly from Italy
(Anonymous 1859; Langstroth 1860 reprinted in Naile 1942). The American beekeeping public
was enamored with the newly available yellow and relatively gentle bees. As a result, Italian
type honey bees form the basis for most present day commercial beekeeping stocks in the U.S.
Following the arrival and success of honey bees from Italy, U.S. beekeepers developed an interest
to try other honey bee subspecies. From 1859 until 1922, efforts were made to import and introduce
a number of additional subspecies. When surveys indicated that the newly discovered tracheal mite
(Acarapis woodi Rennie) was not present in the U.S., the U.S. Honeybee Act was passed in 1922
to restrict further honey bee importations. However, prior to the passage of the Act, a number of
subspecies of European, Middle Eastern, and African origin were imported. Following the Italian
honey bee introductions of the early 1860’s, the Egyptian honey bee (Apis mellifera lamarackii)
was introduced in 1869. This honey bee was soon dismissed by beekeepers, although remnant
genetic markers of this subspecies could still be detected in feral honey bee populations sampled
in the U.S. in the 1990’s (Schiff et al. 1994, Magnus and Szalanski 2010). In 1877, the initial
importations of the Carniolan honey bee (A. m. carnica) were made by Charles Dadant (Dadant
1877). Larger and more sustained importations of Carniolan honey bees were made by Frank
Benton, who imported substantial numbers of queens into Canada and the U.S., starting in 1883
(Norris, 1884). Interestingly, Frank Benton later became the rst Apiculturist of the forerunner of
the U.S. Department of Agriculture, a post he held until 1905.
Frank Benton was also the most likely the initial importer of the Cyprian and Syrian
honey bee subspecies (A. m. cypria and A. m. syriaca, respectively) in the early 1880’s. These
subspecies were imported into both the U.S. and Canada during this time and one particularly large
importation consisted of 150 Cyprian queens made in 1880 (Jones 1880). Neither of these Middle
Eastern subspecies found favor with U.S. beekeepers, although genetic markers indicating some
relictual inuence on the U.S. feral population have been reported (Magnus and Szalanski 2010).
In addition to the Italian and Carniolan honey bees, the Caucasian honey bee (A. m. caucasica) was
a subspecies that came to have enduring interest to U.S. beekeepers. The initial importation details
of this subspecies are less certain than for some of the other subspecies, but there were reports
of importation in the 1880’s and the subspecies was clearly present by 1890 (Hoffman, in York
1906, Tefft 1890). Direct importations of Caucasian honey bees were made into Colorado in 1903

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(Benton 1905). Another African subspecies, A. m. intermissa, from northern Africa was introduced
and established by 1891, although details of the importation are lacking. In any case, this bee was
very quickly dismissed by U.S. beekeepers, especially following the publication of an article by
Benton noting that the bees were “small, very black and spiteful stingers” (Shepherd, 1892).
Based on publications of the time, historical evidence points to the introduction of at least
eight recognized subspecies of honey bee into the U.S. by 1922. In 1990, the descendants of a sub-
Saharan African subspecies, A. m. scutellata, (introduced into Brazil in 1956) traversed the U.S.-
Mexico border and became established in Texas. Twenty years later, these “Africanized” honey
bees are found in a number of southern states, ranging from California through Texas and Florida
(USDA 2007). The imported populations that were derived from these nine subspecies therefore
represent the “starting material” available for genetic selection and breeding within the U.S. Some
additional importations of particular selected stocks have been made through the efforts of the
USDA or queen package resellers (Bourgeois et al. 2010). In recent years, the USDA has imported
“Russian” bees to increase tolerance to Varroa. Large numbers of Australian package bees and
queens (primarily Italian type) have been imported into the U.S., to assure an uninterrupted supply
of pollinators for the almond crop. However, this Australian importation will be stopped in 2011
due to concerns of importing Asian honey bees and a new parasitic mite.
Genetic Bottlenecks and Diversity of U.S. Honey Bee Populations
The honey bee originated in the Old World (Whiteld et al. 2007), where it diverged into
more than two dozen recognized subspecies (Ruttner, 1987, Sheppard et al. 1997, Sheppard and
Meixner 2003). Initial introduction of the honey bee (subspecies A. m. mellifera) to North America
occurred in the 17th century and records indicate that another seven subspecies were introduced by
1922, when further importations were restricted (Sheppard, 1989). With the notable exception of
the introduction of African A. m. scutellata into Brazil in 1957 (Michener, 1975) and subsequent
expansion of descendant Africanized populations into parts of the southern U.S., no additional
subspecies have been introduced into these existing New World honey bee populations.
In considering genetic diversity, it is instructive to realize that the honey bee populations
originally introduced into North America were ltered through two structural genetic “bottlenecks”
(Figure 1). First, the initial “sampling” of each subspecies chosen for importation consisted of a
few tens to hundreds of queens, representing only a small fraction of the genetic diversity within
each subspecies. Secondly, only nine of the more than two dozen named Old World subspecies
found within the species Apis mellifera were ever introduced into the Americas. Thus, overall
“sampling” of the within-species diversity was only partial, with 2/3 of the named subspecies
never having been introduced into the Americas. Subsequent to the initial importations, additional
losses of genetic diversity could have been expected due to “genetic drift.” Genetic drift can be
thought of as changes in gene frequencies across generations due to chance or as the effect of
inbreeding in small populations, both of which can lead to loss of allelic diversity.
Prior to the establishment of parasitic mites in the U.S., there was a rather robust population
of feral honey bees containing genetic markers that reected their diverse origins from some of
the original importations (Schiff and Sheppard 1993, Schiff et al. 1994). Further, comparison
with existing commercial honey bee stocks showed that this feral population contained genetic
diversity that might be useful to supplement existing commercial honey bee stocks. However, the
feral population of honey bees was largely decimated by Varroa mites (Kraus and Page, 1995) and

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Fig. 1. The honey bee population in the U.S. has undergone three distinct genetic bottlenecks
that have reduced genetic diversity. Modied from T. Lawrence.
only limited examples suggest recovery of feral populations (with the exception of Africanized
honey bees in the southern U.S.; Seeley 2007). Consequently, the potential for feral honey bees
to contribute substantial additional genetic variation to U.S. commercial stocks for selection and
breeding proposes may be limited.
Currently available U.S. honey bees are primarily derived from two European subspecies, A.
m. carnica and A. m ligustica. Aside from the aforementioned bottlenecks attributable to sampling,
importation and subsequent genetic consequences in small populations, breeding practices within
the U.S. are also relevant to the question of genetic diversity within U.S. honey bee populations. In
studies conducted in 1993-1994 and in 2004-2005, U.S. commercial queen producers self-reported
the production of close to 1 million queens for sale from around 600 and 500 queen “mothers”,
respectively (Schiff and Sheppard 1995, 1996; Delaney et al 2009). Whether this apparent decline
in the number of queen mothers being used for annual queen production is a trend that will continue
is unknown. However, coupled with high losses of colonies that have been reported in recent years
(averaging 30% annually), declining breeding population sizes would be an additional concern.
Genetic markers studies suggest that while commercial honey bee populations have relatively
limited amounts of genetic diversity, there were genetic differences between the eastern and
western U.S. breeding populations that could potentially be used by bee breeders to contribute to
overall sex allele diversity.
Bee Breeding Practices in the U.S.
Most economically valued livestock species are not native to the U.S. and are derived
from selected strains as a result of well-designed, scientic stock improvement programs. These

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programs are dependent upon long-range breeding programs, as well as the routine and systematic
importation and evaluation of additional resources (mostly germplasm) from within the original
ranges of the species under consideration. The beekeeping industry does not have access to stocks of
origin or standardized evaluation and stock improvement programs. Consequently, the beekeeping
industry does not share the increased productivity that result from such programs, as have served
the poultry, dairy, and swine industries.
Bee-breeding programs must be based upon selection of behavioral traits at the colony level.
Consideration must include the high mating frequency of queens, the complex and dynamic social
structure of the colony, sensitivity to inbreeding, and environmental inuences. Of the selection
criteria and methods used, there is a lack of standardization to measure traits and selection is often
limited to too few traits at the expense of productivity. Inter- and intra-colony genetic diversity has
clearly been demonstrated to increase colony tness, survival, and lessen the impact of pests and
diseases (Fuchs & Schade, 1994; Jones et al, 2004; Mattila et al , 2007; Olroyd et al, 1991; Richard
et al, 2007; Tarpy, 2003; and Seeley & Tarpy, 2007). Maintaining a high level of genetic diversity
is critical and challenging in any stock improvement program, which especially applies to honey
bees.
Scientic bee-breeding programs have largely been dependent upon institution and
government support. Frequently subject to short-term funding, programs that have been turned
over to the industry have historically lacked oversight and soon become unrecognizable. Without
a long-term commitment and supporting resources, selection efforts are relaxed and the gains are
quickly lost.
The U.S. beekeeping industry is built upon the development of large-scale queen and
package bee production, in which it today excels. Historically, private sector breeding efforts have
been largely limited to choosing a few top-performing colonies with little regard for control of
mating or performance over generations. Traditionally, the terms “queen rearing” (the propagation
of queens) and the term “bee breeding” (the evaluation and selection of breeding stock) have
been used interchangeably in the beekeeping community. These are two very different aspects and
require different skills, knowledge, and practices.
Queen producers represent a small, specialized, yet critical aspect of the beekeeping
industry, many of which have been built upon family businesses. Production requires high
overhead, is labor intensive, and the high demand of queens and package bees does not provide
incentive for expensive breeding programs. The applied nature and lack of publications targeted
at bee-breeding programs do not adequately foster an environment for researchers. While this
situation is changing, industry support will determine the viability of such programs.
The U.S. queen and package bee industry provides about one million queens annually to replace
and restock the estimated 2.4 million colonies nationwide. Of commercially managed colonies,
some honey producers and pollinators rear their own queens in addition to those purchased. Some
re-queen their colonies annually, others every other year or as needed depending upon queen
performance. Queen-rearing operations range in size and production, mostly between 5,000 to
150,000 queens produced annually. Often, only a few queen mothers are used for propagation
and with little control of mating areas. Concentrated in northern California and the southwest,
completely isolated mating is not an option and producers depend upon each other to supply
adequate drone sources for mating yards.
Traditionally, commercial breeding stocks in the U.S. are based upon selection of a few
queen mothers from among thousands of colonies within commercial operations. Potential breeder

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colonies are often followed throughout the year, others are selected during early spring. Colonies
that stand out for several valued traits are selected and notations are generally recorded on hive
lids. The criteria selected vary among producers, generally include: large populations, good laying
patterns, fast spring buildup, temperament, consistent color, weight gain, and overwintering ability.
Low prevalence of pests and disease symptoms may also be noted. Increasingly and more recently,
selection also includes monitoring for pest and disease levels, especially Nosema and Varroa.
Testing for hygienic behavior, one known mechanism of resistance to pests and diseases, is also
becoming more common. The beekeeper methods used, choosing the few best colonies within
their apiaries for breeding stock, has been successful in maintaining distinct lines, yet progress in
selection for resistance to pests and diseases has not been realized. Lack of controlled mating and
record keeping remains a handicap.
Most producers in the U.S. augment their programs with purchase of breeder queens from
the limited available specialty breeding stocks, including USDA ‘Varroa Sensitive Hygiene’,
‘Minnesota Hygienic’, ‘New World Carniolan’, and USDA ‘Russian’. Queen producers generally
use a combination of breeders selected from their own colonies and those that they purchased.
Some producers prefer not to use progeny of specialty breeding stocks in their own hives, limiting
these as drone sources for mating yards.
An interest in selection of locally adapted stocks is increasing. Among hobbyist beekeepers
and local beekeeping organizations, the desire to move away from use of miticides and antibiotics
and the frustration in the tightening availability and increased expense of queens promotes this.
These “microbreeder” programs (sensu D. Tarpy, in Connor 2008) are often based upon collection
of “survivor stock” (the collection of swarms). Results are often unpredictable and disappointing
due to lack rigorous selection criteria and controlled mating. Although, hopefully this may change
as these programs develop.
The U.S. queen and package bee industry—concentrated in northern California, the
southeast, and Hawaii—is at full capacity with growing demand. Maintaining healthy rigorous
colonies, controlling Varroa, and avoiding sub-lethal chemical residues in colonies is required
for queen and drone production and is increasingly demanding of labor and costs. The impact of
small hive beetle, SHB (Aethina tumida), is reducing queen production in the southeastern U.S.
Mating nucleus colonies are vulnerable to beetles that are highly attracted to the small colonies and
intermittent state of queenlessness between rounds. Hawaii, once a haven for Varroa-free queen
production, must now deal with the recent introduction and impact of both Varroa and SHB. The
SHB is also expected to spread throughout northern California queen mating areas, despite control
and monitoring efforts.
The high colony demand for pollination of almonds in February and concern over the
high winter loss of colonies resulted in an amendment to the Honey Bee Act of 1922 to allow the
importation hundreds of thousands of package bees from Australia and New Zealand from 2005 to
2010. Due to increasing industry concern over the risk of introducing pests and diseases, as well as
the potential impact of quick spread across the U.S. as colonies are trucked nationwide, the boarder
has since been closed.
Quality of Commercially Produced Queens
The primary perceived problem for beekeepers is a diminished quality of queens, and
recent survey results from beekeeping operations in the U.S. conrms this view. VanEngelsdorp

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et al. (2008) surveyed 305 beekeeping operations in the U.S. accounting for a total of 324,571
beehives. According to the interviewed beekeepers, their primary perceived problem was ‘poor
queens’, with 31% of the dead colonies as a result of one or more issues with the mother queen. By
contrast, starvation (28%), varroa mites (24%), and CCD (9%) were signicant but less prevalent
causes of mortality. “Poor” queens encompass many different problems, but most of these reports
document premature supersedure (queen replacement), inconsistent brood patterns, early drone
laying (indicative of sperm depletion), and failed requeening as indicative of low queen quality. It
is helpful, therefore, to place into an historical context the current quality of the commercial queen
population.
Several studies have surveyed commercially produced queens, either directly or by sampling
queens shipped in packages (Table 1). Farrar (1947) studied queens deriving from packaged bees
over several years. Furgala (1962) collected queens from beekeepers in Canada that were ordered
from either CA or MS, but these queens might represent a biased sample since they were either
dead on arrival or queens that were lost in the rst month. Jay and Dixon (1984) sampled a very
large number of US queens shipped in packages to Western Canada in the mid-1960’s and early
1980’s. Liu et al. (1987) also measured queens sent to Canada from the US for various infections,
as did Burgett and Kitprasert (1992) directly obtained from a commercial beekeeping operation.
Camazine et al. (1998) purchased sets of 15 naturally mated ‘Italian’ queens from 13 different
commercial sources across the US. Similarly, Delaney et al. (2010) purchased 12 ‘Italian’ queens
from each of 12 different breeders either in the Southeast or Western US, two in each set being
temporarily introduced to colonies while the others were banked before processing.
Table 1. Historical evaluations of queen reproductive potential, or “quality”, from various
commercial sources. * = data may not be comparable to previous studies because of different
measurement methods; Jackson et al., in press. Data from: Farrar, 1947; Furgala, 1962; Jay and
Dixon, 1984; Liu et al., 1987; Burgett and Kitprasert, 1992; Camazine et al., 1998; Delaney et
al., 2010.
1947 1962 1984 1987 1992 1998 2010
No. queens 835 465 777 53 200 325 136
Under-developed ovaries - 17% - - - 12% 7.5%*
Nosema 14% 11% 8% 38% - 7% 0%
Tracheal mites NA NA - - 21% 20% 2%
Sperm counts (< 3 million) - 29% 11% - - 19% 19%
Mating number NA NA - - - - 16.0
Physical quality - There are many measures that can serve as proxies for queen reproductive
potential, or “quality”. The most intuitive perhaps are standard morphological measures of
individual adult insects, such as wet or dry weight, thorax width, head width, and wing lengths
(Weaver, 1957; Fischer and Maul, 1991; Dedej et al., 1998; Hatch et al., 1999; Gilley et al., 2003;
Dodologlu et al., 2004; Kahya et al., 2008), several of which are signicantly correlated with
queen reproductive success or fecundity (Eckert, 1934; Avetisyan, 1961; Woyke, 1971; Nelson and
Gary, 1983).

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Weight is often used as a proxy for overall queen quality. In fact, beekeepers often use
size and weight as a rough indicator of the relative quality of a queen. This association may be
predicated on the fact that virgin queens are smaller and weigh less than mated queens because
mated queens have larger, fully developed ovaries. Nelson and Gary (1983) showed that honey
productivity of colonies increased with heavier queens, although other studies have failed to show
a signicant relationship (e.g., Eckert, 1934). Other measures of queen size, such as thorax width,
have also been used and show less variation due to environmental or colony conditions. Delaney
et al. (2010) found that thorax width, but not queen weight, was signicantly positively correlated
with both stored sperm and effective paternity frequency.
Potential fecundity - Queen ovaries are highly developed compared to workers, with
each queen containing approximately 300 or more individual ovarioles (Eckert, 1934). Ovary
development occurs soon after mating and is association with profound genomic, physiological,
and behavioral changes in the queen (Richard et al., 2007; Kocher et al., 2008). Hoopingarner
and Farrar (1959) found a very strong correlation between queen weight and ovariole number,
but others have not shown this same relationship (Eckert, 1934; Hatch et al., 1999; Jackson et
al., in press), thus it is unclear if weight is a good proxy for potential fecundity. The important
glycolipoprotein vitellogenin (Vg) is also a potential indicator of fecundity since it is the yolk
precursor associated with egg production (Tanaka and Hartfelder, 2004). Transcript levels of Vg
appear to be associated with queen weight independently of active egg-laying by queens (Delaney
et al., 2010).
Parasites - While many parasites and pathogens either cannot or do not infect honey bee
queens (in large part because of their faster development time, infrequent availability, or both), there
are some notable exceptions that have been shown to diminish queen bee health and productivity.
There have been several efforts to monitor and measure the gut microsporidian Nosema apis in
commercial queens (Farrar, 1947; Furgala, 1962; Jay and Dixon, 1984; Liu et al., 1987; Camazine
et al., 1998), with some studies showing as many as 38% being infested (Table 1). Most recently,
however, Delaney et al. (2010) did not detect any newly mated queens infested with nosema,
suggesting signicant changes in management practices within the industry. With the introduction
and apparent selection sweep of N. ceranae (Higes et al., 2006; Chen et al., 2008), it is unclear
how this sister taxa may affect the quality of commercial queens. Since the mid-1980’s, queens
have also been subject to infestation from tracheal mites Acarapis woodi (Burgett and Kitprasert,
1992; Camazine et al., 1998; Villa and Danka, 2005). However, this parasite also seems to have
diminished in frequency among commercial stock as well as commercial queens (Table 1; Delaney
et al., 2010). Finally, queens may be infected with any number of viruses (Chen et al., 2005;
Yang and Cox-Foster, 2005), some of which have been shown to be transmitted vertically from
queen to worker offspring (Chen et al., 2006). These pathogens, however, do not seem to have any
direct association with queen quality (Delaney et al., 2010), although they may have some indirect
effects that have yet to be quantied.
Mating success - Another important characteristic that determines a queen’s quality is the
degree to which she is inseminated, since queens with greater sperm stores can live longer and
fertilize more eggs. Queens take mating ights early in life when they are approximately one week
old (Koeniger, 1988), mating with multiple males on one or several ights away from their natal
hive. Sperm is temporarily deposited in the median and lateral oviducts, then a small proportion
migrate and are stored in the spermatheca (Woyke, 1983; Collins, 2000). Many researchers have
assessed the number of stored sperm in a queen’s spermatheca (Mackensen, 1947; Koeniger et

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al., 1990; Lodesani et al., 2004), and a fully mated queen stores approximately 5-7 million sperm
(Woyke, 1962) that gives the spermatheca a tan, marbled coloration (as opposed to whitish and
opaque for partially mated queens and totally clear for unmated queens; Cobey, 2003).
Early studies of the commercial queen population assessed queen spermathecae but did not
perform sperm counts. Furgala (1962) reported that 24 out of 229 (10.5%) queens that had died
upon arrival had few or no sperm in their spermathecae based on visual observation, as did 34
out of 236 (12.9%) queens that died within their rst month. Jay and Dixon (1984) found similar
results, with 11% of the queens having fewer than 3 million sperm (termed “poorly mated”). Using
the same arbitrary cutoff as dened by Woyke (1962), Camazine et al. (1998) found that 19% of the
queens were poorly mated. Most recently, Delaney et al. (2010) also found 19% of commercially
produced queens had fewer than 3 million sperm (“poorly inseminated”), but they also found that
80% of the queens had fewer than 5 million sperm (“inadequately inseminated”), with an average
of 4 million sperm. These numbers are consistent with commercially tested queens in CA in the
mid-1980’s (Harizanis and Gary, 1984).
Insemination is one measure of a queen’s mating success, but emerging evidence suggests
that mating diversity is also important for queen and colony productivity. The genetic diversity
within a colony is a direct reection of the number of drones that sire worker offspring (Tarpy
et al., 2004), and several empirical studies have demonstrated that genetically diverse colonies
increase the behavioral function of the worker force, reduce the likelihood for detrimental levels
of inviable brood due to the csd locus, and lower the prevalence of various parasites and pathogens
(reviewed by Palmer and Oldroyd, 2000). A meta-analysis of studies using molecular techniques
to quantify effective paternity frequency of queens concludes that open-mated queens mate
with approximately 12 drones (Tarpy and Nielsen, 2002). However, only one recent study fully
quantied a cross section of mated queens. Delaney et al. (2010) found that queens mated with an
average of 25 drones, with an effective average paternity frequency of 16.0 ± 9.48.
Overall, the current status of commercial U.S. queens seems to be of high quality when
viewed from an historical perspective. It is clear, therefore, that the current perception of diminished
queen productivity stems from alternate factors. Future research should investigate potential
mechanisms that affect queen quality both prior to mating (e.g., reproductive capacity of drones)
and those after queen introduction (i.e., hive environment). In doing so, it will also be important to
determine the genetic diversity of commercial queen and drone populations.
Future Directions
Worldwide, the apiculture community is focused on nding sustainable solutions
to the multifaceted factors contributing to the current honey bee decline. The crisis has
stimulated collaborative efforts on a global scale. These collaboration include major
efforts to compare and document changes in honey bee populations from many geographic
areas. Programs designed to select stocks for increased resistance to pests and diseases are
increasingly gaining support as well, given the near unanimity among honey bee scientists
that a genetic approach is necessary to ensure a long-term, sustainable managed population.
There have been several national and international collaborative efforts to help implement
such goals. Perhaps the most notable international effort was the formation of COLOSS (Prevention
of honeybee COLony LOSSes), a collaborative network of 17 European countries. Collaborators
are working to identify honey bee populations, track changes for conservation and selection

-49-
purposes, and develop certication programs for local strains and ecotypes of honey bees. While
numerous studies of morphometric characteristics, behavioural traits, and molecular analysis have
been conducted, there is a strategic need to establish a standard protocol to identify, record change,
and preserve diverse honey bee populations in their native ranges.
In the U.S., the recognized need to increase genetic diversity and strengthen selection
programs of commercial breeding stocks has resulted in collaborative efforts among universities,
government researchers, and the queen industry. Honey bee semen of several subspecies of European
honey bees has recently been imported and inseminated to virgin queens of domestic breeding
stocks. Diagnostic programs to assist beekeepers to assess colony health are being established,
as are programs to transfer technology transfer programs to provide hands-on assistance and
instruction in evaluation and selection of commercial breeding stocks.
The current challenges facing the beekeeping industry and new technologies being
developed are pushing beekeeping into a new era. With the sequencing of the honey bee genome
and advancements in molecular techniques, powerful markers for evolutionary and population
genetics studies are increasingly available. Discrimination of honey bee populations and subspecies
may contribute to selection programs through the utilization of these technologies. Furthermore,
the use of molecular techniques can assist in the identication and selection of specic traits of
resistance to pests and disease in breeding stocks. Technologies to perfect the cryopreservation
of honey bee semen and facilitate the safe international exchange of honey bee germplasm are
priorities for development.
Finally, there is a great need to document and track the genetic diversity within and
among honey bee populations in the U.S., particularly both the managed and feral (non-managed)
populations. Determining how such genetic diversity impacts colony phenotype and productivity,
is affected by gene ow among populations (especially the Africanized population in the southern
tier of the country), and is manifest by management and other breeding techniques; this must be
prioritized by future research. In addition, new investigations into the mating behavior, pedigree
relatedness within and among breeding populations, and population genetic structure of current
populations will greatly inform such research. By doing so, these approaches will together enable
genetic solutions to the many problems currently facing the apiculture industry.
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