Pollen Harvest by Honey Bees: Conservation Implications for Native Bees and Flowering

Item Type Article

Authors Buchmann, Steven L.; Shipman, Charles W.

Publisher University of (Tucson, AZ)

Journal Desert Plants

Rights Copyright © Arizona Board of Regents. The University of Arizona.

Download date 08/10/2021 03:05:24

Link to Item http://hdl.handle.net/10150/554244 Pollen HarvestBuchmann and Shipman 3 on its host plants, it would have been available for transport by co- adapted insect, bird and bat pollinators which are of- ten better at depositing viable pollen, effecting subsequent fertilization, fruit and seed set on native flowering plants. Sonoran Desert bees are predominantly specialist feeders Pollen Harvest by Sonoran and depend upon certain plants more than honey bees which can switch hosts at will and have a highly mixed diet. Thus, Desert Honey Bees: in direct competition with these alien social bees living in Conservation Implications forlarge colonies, native desert bees are often at a disadvantage in acquiring pollen and producing replacement offspring. Native Bees and FloweringDesert flowering plants, especially rare, threatened and en- Plants dangered species are also adversely affected since honey bees remove most of the pollen and often are responsible for setting fewer seeds or dispersing pollen at different distances than their original pollinators once did.

Introduction Honey bees (Apis mellifera L.) live in eusocial matriarchal colonies usually founded and headed by one long -lived queen. Because of their ability to produce a new queen from Stephen L. Buchmann a young fertilized egg of the previous queen, the process USDA -ARS Carl Hayden Bee Research Center known as reproductive swarming, colonies may persist for 2000 East Allen Road many years. A single colony, living in deciduous forests in Tucson, Arizona 85719 New York state, has been estimated to have an average lon- gevity of 5.6 years (Seeley, 1986). Mature colonies are com- Charles W. Shipman prised of 20,000 to 60,000 individuals, of which at any time Arizona - Desert Museum there may be a few thousand drone bees (males) present. 2021 North Kinney Road The collective biomass of the adult bees in such a hypotheti- Tucson, Arizona 85743 -8918 cal colony may be from one to six kg. In one year, during 10 to 15 brood -rearing cycles, the colony may produce a total of 150,000 to 250,000 individuals. The food consumed by the "superorganism" colony in one year's time is staggering. A colony may easily collect and collectively ingest as much as 20 to 50 kg of pollen (the floral equivalent of tens of millions Abstract of flowers), 40 -60 kg of stored honey and perhaps 0.1 kg of Managed and feral honey bee colonies (Apis mellifera) har- resins, saps and gums, known to beekeepers and herbal vest immense quantities of nectar and pollen within kilome- medicine practicioners as propolis. To amass such floral re- ters of their nests whether they live in relatively undisturbed sources the bees may have made as many as 1.3 to 2.0 million or agricultural habitats. Within the Sonoran Desert of south-trips for pollen and perhaps three million foraging sorties in ern Arizona, pollen collection by European honey bee colo-search of nectar (Seeley, 1986; Buchmann, unpubl.). During nies was monitored by the use of apicultural pollen traps.its first year of life a new bee colony will produce approxi- Managed colonies near Tucson, Arizona routinely collectedmately 9,900 cm' of comb area containing about 4,100 double - from 20 to 50 kg of pollen each year. Flowering pulses (phe-sided hexagonal cells in which to raise their larvae along nology) in the local flora was closely tracked by the colonies,with storing pollen and floral nectar, processed into honey. and pollen influx into their nests usually occurred as three to four distinct seasonal peaks, although some pollen was ac-Only four resources - pollen, nectar, water and plant resins tively harvested during 48 or more weeks every year. The - are required by the honey bee colony to support all life range of flowers visited for pollen by the honey bee is likelyfunctions. Floral and extrafloral- derived nectar contains sug- the most diverse for any social or solitary bee yet studied, ars (mainly sucrose, glucose and fructose) which are the en- largely due to their massive food requirements, efficient scout-ergy -rich nutrients necessary for individual metabolism, part ing and recruitment to ephemeral flower patches, and persis- of the larval diet, a thermoregulatory and flight "fuel ", and tence of their colonies as perennial units for many years. Atthe material hoarded, as honey, in capped combs to support most Sonoran Desert sites, honey bee colonies took pollenlife during periods of extranidal nectar dearths or over the from at least 12 and as many as 40 -50 dominant angiospermlong cold confinement during winter. Pollen, the collective taxa. Additionally, pollen diet breadth of feral honey bee colo- term for the individual sperm cell- containing male gameto- nies was determined microscopically from blackened below - phytes of angiospermous plants provides the major dietary nest refuse deposits known as bee middens. One such de-source of proteins, amino acids, lipids, minerals, vitamins posit from the Arizona -Mexico borderlands is thought to rep- and other essential nutrients for larval growth and adult resent more than a half century of accumulated materials.physiological maintenance. Honey bees are dominant invertebrate herbivores in desert regions taking pollen and nectar in massive amounts from atA honey bee colony can thus be visualized as a highly spe- least 25 percent of the local flora. Had this pollen remained cialized foraging "machine" able to locate through the initia- 4 Desert Plants1996 tive of scout bees and their recruits, the richest floral patches delimited by using palynological methods (O'Rourke and for pollen and nectar, and rapidly and efficiently communi- Buchmann, 1991) to assess residual pollen in old brood cate these discoveries. These resources are exploited usingcombs, honey, propolis, or debris middens below feral colo- olfactory and the so- called "dance language" communica-nies. Honey bee colonies are ideally suited to this type of tion. Individual foragers are essentially constant to one plant"forensic palynology" since their nests are virtual "sinks" species during a foraging trip, but over time are directed, or for ingested pollen grains which can be sampled quantita- locate on their own, better or newly available flowers. Thistively. Probably the best single source of multiyear pollen shifting of bees from poorer floral resources to better floralplant dietary records are several year old, darkened brood patches has been termed the "information- center foragingcombs. These contain a representative subsample of all the strategy" (Seeley, 1995). pollen grains found in the larval feces (meconia). These ma- terials become "fossilized" in strata within the cell bases of Mature colonies, with 40,000 adult workers for example, mayold brood comb as the colony ages. Further, pollen contribu- have from 10,000 to 20,000 or more foragers actively engagedtions from nectar- producing plants can be separated from in daily flights to collect pollen, nectar, water and resin. Flightpollen plant records through the use of melissopalynology distances by honey bee workers in natural ecosystems havewhereby pollen grains left in stored honey reveal which an- been little studied, but indications for Apis mellifera colo-giosperm species were visited for nectar. nies living in New York forests are that 99 percent of all flights are to flowers less than eight km from the nest, with almost 90During the mid 1980's the author made a surprising discov- percent of the colony's foraging effort taking place withinery in shallow mountain caves within the Organ Pipe four km (Visscher and Seeley, 1982). National Monument on the Arizona/Mexico border. Large deposits of blackened asphalt -like waxy materials were found Calculations of the effective total area foraged, averaged overbelow extant and old dead feral honey bee colonies. Upon a season or during one year and estimated as concentricexamination, these deposits were found to contain honey circular foraging bands, indicate an immense floral landscape bee corpses, beeswax, corbicular pollen loads, cocoons, bee controlled by even one honey bee colony. Roubik (1989)parts and larval feces along with unidentified materials. I've estimated that a single Africanized honey bee (Apis mellifera called these "debris middens" and they hold great poten- scutellata) colony may forage from an area of 100 or evential-as palynological samples- to infer the vegetation of 300 km2 in Panamanian rainforests. In the Sonoran Desert ofthe surrounding area along with information on honey bee Arizona, colonies appear to forage within an area estimatedpollen diet breadth. Unlike packrat middens (indurated de- to be 80 -100 km2 in extent (Southwick and Buchmann, unpubl; posits from white -throated packrats and other species in the Southwick and Buchmann, 1995). area), the honey bees travel great distances from their nests giving a more regional vegetative reconstruction than pos- Honey Bee Colonies as Biological and Chemical Monitoring Units sible with the rodent middens. If such middens are present in With their remarkable foraging abilities, it is surprising toAfrica in dry caves, produced belowApis mellifera scutellata learn that honey bees have been underutilized as "biological colonies, they may hold invaluable information for future monitoring agents" for the study (on an hourly, daily, sea-paleocologists who find and exploit their pollen -rich infor- sonal, annual and multiyear basis) of events occurring within mation. environments found inside their immense foraging domains. It is common for beekeepers to be aware of honey yields perBy using such palynological sampling and analysis tech- hive when apiaries are established in different plant commu-niques, it is possible to reconstruct major and minor bloom- nities. It is quite rare, however, for beekeepers or apiculturaling events at distances of several kilometers from the nest scientists to examine and analyze materials collected by honey within the floral resource landscape. If sampling using pollen bees or to assess local plant community flowering activity,traps is conducted on a weekly or daily basis, fine resolution relate bee food preferences to floral abundance, or some-tracking of blooming events for individual plant species can what cryptically, use their foraging behavior to examine nestbe determined. materials for possible environmental contaminants. The branch of palynology known as melissopalynology is pos- Honey bees are polylectic, and have perhaps the greatest sible because honey made from diverse nectars containspollen dietary breadth of any eusocial insect. Honey bees pollen grains from the parental plants. Thus nectar sources eagerly harvest pollen from a wide diversity of angiosperm can be qualitatively, and sometimes quantitatively determined and other spermatophyte groups. Pollen from wind- polli- to the genus and species level. Similarly, using pollen trapsnated taxa including many gymnosperms in addition to fun- placed on manmade hives, or by analyzing pollen grains left gal and fern spores are also collected. in propolis, larval meconia within old brood combs or found below in debris "middens ", (see O'Rourke and Buchmann,Recently, honey bee colonies have even been used as 1991 for standardized palynological techniques for bee nestbiomonitoring agents for measuring enviornmental pollution materials), the identity of plants utilized as food sources can beby hazardous substances (e.g. pesticides and herbicides, readily determined by ecologists or conservation biologists. heavy metals, radioactive isotopes) since these materials also accumulate via biological magnification, within the beeswax Thus, plant community seasonal flowering activity (pheno-combs and stored pollen and honey within the nest logical patterns) can be indirectly monitored with honey bee (Bromenshenk et al., 1985 ). colonies by using pollen traps (O'Neal and Waller, 1984). Such patterns representing mulityear averages can also be Pollen HarvestBuchmann and Shipman Pollen Harvest By Honey Bee Colonies in the Sonoran Desert this 11 year period, a total of five large colonies of European The author along with numerous colleagues has conductedhoney bees housed in Langstroth hives and fitted with O.A.C. long -term pollen -trap studies with managed European honey bottom type traps, were studied. The pollen traps remained bees at various sites in southern Arizona. These studies have on the colonies at all times and pollen was harvested weekly. utilized so- called modified O.A.C. (Waller, 1980) pollen traps On average, 26.5 kg of pollen (on a fresh weight basis) was that force returning foragers to pass between offset wirerecovered from each colony during this eleven year period. screens, which dislodge about 65 percent of the incomingAt a trap recovery/efficiency ratio of 65 percent, this indi- pollen. These corbicular pollen pellets are then simply re- cated that each colony had actually amassed about 42.5 kg moved from the trap for weighing (as pollen influx per day orof pollen each year. This staggering amount of pollen would per week) or can be color -sorted or mixed then resampled for translate into the production of about 327,000 worker bee various palynological procedures. Some of the results from aequivalents (assuming 130 mg is needed to make a bee) each few sites near Tucson, Arizona will be summarized to demon-year by these colonies (Buchmann, unpublished; Buchmann, strate the magnitude of the pollen harvest by Apis colonies 1996). Another study, in the eastern forests of New York in the desert and its potential impact on native bees which(Visscher and Seeley, 1982; Seeley, 1986; Seeley, 1994 ) dem- also must forage for pollen and nectar in the same environ-onstrated that bees there utilized only 20 kg of pollen, but 60 ments. (See Schmalzel, 1980 for previous study of pollen pref-kg of honey during a one year period. By comparison, colo- erences by honey bees in the Sonoran Desert.) nies at the Pima Canyon site collected and hoarded at least 43 kg of honey (of which about 24.2 kg was consumed during One such study was begun in late 1980 on the upper bajada the year). The variablility in the amount of pollen trapped annu- at the mouth of Pima Canyon in the Santa Catalina Moun- ally at the Pima Canyon location can be seen in Figure 1. tains. The study was terminated at the end of 1991. During

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1981' 1983 1985 1987 1989 1991 Year Figure 1. The annual amounts of pollen trapped (means for three large Langstroth European honey bee colonies as kilograms/year) at the Pima Canyon apiary in the Santa Catalina Mountains north of Tucson, Arizona (1981 -1991) based on 60 %pollen trap efficiency. 6 Desert Plants1996 The pollen availability for honey bees, and presumably othernectar sources, such as saguaro or mesquite blossoms, are bee species, at Pima Canyon on the bajada slopes, and ring-closely monitored and tracked by colonies (Schmidt and ing all the desert "sky islands" like verdant bathtub rings, is Buchmann, 1986). perhaps as great or greater here than for pollen harvest esti- mates anywhere else. It is little wonder then, that these midThese short-term, daily or hourly shifts in the colony's allo- elevation sites so floristically rich may host more species ofcation of foragers amongst competing simultaneously bloom- native bees than any comparable study plot within any other ing and sympatric plants can be seen in Figure 2. Here we see biogeographic region (Buchmann, unpubl.). It is likely that the amounts of pollen collected daily by a honey bee colony as many as 1,000 species of native ground and twig- nesting as well as the number of pollen taxa (plant species) harvested bees live within 100 km of Tucson, compared to perhaps by that colony during the year 1985. This colony was located 4,000 to 5,000 species known to occur within the continental within the rich flora of the Tucson Mountains, which is known United States. Competition for such limited floral resourcesto host about 600 species of flowering plants (Bowers and between introduced honey bees and native nectar and pol-McLaughlin, 1987; Turner and Brown, 1982). Notice that some len- feeding animals, especially native bees, can be intenseforaging peaks for pollen collection are as short as a single (Schaffer, Jensen, et al., 1979, and Schaffer, Zeh, et al., 1983). day, while others may last for several weeks. It should also The amounts of pollen and nectar produced by these plantbe noted that this colony routinely foraged daily from three communities is not only finite but produced in discrete nar- to eight ( ?) plant species during this twelve month period. row or broad "pulses" during a year, but total floral resource production may vary widely especially comparing droughtThe Pima Canyon pollen trap decade plus record is represen- with unusually wet El Niño Southern Oscillation years in the tative of other similar elevation Sonoran Desert sites where Sonoran Desert region (see Figure 1). pollen trap studies have been conducted. Spectral analysis of the 11 year dataset (Buchmann and Thoenes, unpubl.; Typically, most of the native Sonoran desert plants bloom Buchmann, O'Rourke and Shipman, 1990) indicates that there either following the spring or summer monsoon precipitationare four major peaks (Figure 3) of pollen collection by honey events. Some flowering plants, such as Larrea, may bloombees at this site. These four broad episodes of pollen- forag- twice in response to these rains, but most only flower once. ing activity presumably correlate fairly closely with the ac- With these two major precipitation seasons, it is not surpris-tual amounts of pollen available in the environment, although ing therefore that we have guilds of spring and summer -ac-this point has not been examined empiricially at the commu- tive native bees. Many bees in the region are extremely spe-nity level. From Figure 3 we see that pollen harvesting by cialized/limited to using the pollen and nectar resources of ahoney bee colonies occurs twice during the spring and once few related congeners or even single plant species. This isduring or slightly after the summer monsoons. Finally, there the case for the widespread genus fruitfly -sized Perditais a very sharp predictable harvest event that occurs in the (Andrenidae) or the "cactus bee" genus Diadasia which spe-fall with the very last flowers to bloom. This event is domi- cialize on mallows and cactus blossoms. Other native bees,nated by fall- flowering sunflowers in the family Compositae including our largest bee-the bumblebee Bombus sonorus - or(especially the genera Ambrosia, Baccharis, Happlopappus the equally impressive giant black carpenter bees -Xylocopa andHymenothrix). In fact, from examining pollen trap records spp. - are polylectic. When a bee is said to be polylectic it from numerous sites in the fall or early winter months in many simply means that they are non -discriminating in their choice north temperate localities, a terminal community flowering of food plants and forage from a phylogenetic potpourri across event of composites seems to be quite dependable. This is the floral landscape. likely extremely important to the success of honey bees which often prefer to forage from such "weedy" elements of the Palynological studies conducted on old brood combs from flora, especially ones which provide nutritious pollen and managedApis mellifera colonies in Arizona and from debrishoney that can be stored within the brood combs to enhance middens below feral colonies reveal a highly diverse pollenwinter survival. diet over a multiyear period. Buchmann and O'Rourke (1988) and O'Rourke and Buchmann (1991) have determined thatCompetition Between Honey Bees and Native Sonoran honey bees collect pollen from at least 15 and usually 25Desert Bees dominant plant taxa from most Sonoran desert sites. In someIt is difficult if not impossible to demonstrate a strong case cases, up to 40 or 50 species may be used as pollen host plants. for competition between exotic honey bees and native bees, ants, wasps, beetles, flies, butterflies, moths and humming- Bees Detect the "Pulse" of the Floral Community birds on native or exotic flowering plants. One would like to Scout bees and recruits emanating from their Sonoran Desertfind a smoking gun or at least catch the little nectarivores "en colonies and returning home survey a foraging region of atflagrante delicto" on some gaudy floral bouquet. But this least 80 -100 square kilometers. Within this region, they con- has not proven to be the case when researchers have either stantly find then exploit rich new floral patches while aban-made observations in search of scramble competition for lim- doning ones going out of bloom. This behavior gives honey ited floral resources, or when elaborate controlled experiments bees colonies an almost omniscent knowledge of their floral have been designed to prove the case for competition. environment. Such floral choices and shifts happen very quickly. Pollen trap studies at Pima Canyon reveal that manyUnfortunately, this will always be the case since feral honey foraging choices are made on an hourly or less span of time.bee colonies (both European and now Africanized) are now New floral patches and species coming into bloom are found omnipresent across the southwestern deserts. You can't travel very quickly. Dependable year -to -year preferred pollen and to a remote control site, without honey bees, for your ideal Pollen HarvestBuchmann and Shipman Trapped Pollen in gm /colony /day 7 400 300 1981200 100

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, I I III III ,IIIII I. 0 J .I.,IIII IIIIIIIIIr 300 1983200 100 0 II I 110 Ili.. ti 300 1984200 100 0 ,III u I I lII.II Iii II t 1111111111. 300 1985200 100 o I.I)..IIII1IIIIIIIIIII, 300 1986200 100 0 .IIII.1IIIIIIIIIIIIIIIIII.,,III,,.,,III11I. 300 1987200 100 0,, 1 1 1 1 1 1 1 1 1 1 1 1 1 1 . I 300 1988200 100 o 300 1989200 100 0 ..,.0,1II.QIIIIWIII.(illII, .IIII, 300 1990200 100 0 ...._.11.IIIIIIIIIIItI,IIIIII IIII_ 1991300 200 100 0 .,IIIIIIIIIIIIIIIIIII I , .IIIfI..,,,III,_ f f I 1 1 0 50 100 150 200 250 300 350 Date (Julian Calendar) Figure 2. Amounts of pollen (mean value for three full -sized Langstroth European honey bee colonies as grams /colony/ day) from the Pima Canyon pollen trap apiary during the years from 1981 to 1991. The histogram bars are ordered according to their Julian date of sample collection. study. Similarly, we are faced with the "ghost of ecological and ants responded positively to rising nectar standing crops competition past" since honey bees were introduced, andfollowing the removal of introduced Apis colonies, and that migrated on their own, into this region before any baselineit had occurred on a least a conditional basis in other cases. data was ever collected. Thus, we don't really know whatMost native bee species depend either directly upon flowers pre- contact populations of native bees and other pollinators for pollen and nectar as their sole food, as do the were, or even how many native pollinators may have beensuperorganismic honey bees, although native bees and other diminished in numbers or even pushed over the brink into local pollinators do not always simultaneously exploit the same or total extinction by the pollen -hungry invaders from Mexico.plant species as honey bees do. Remember, earlier we dis- cussed the fact that the majority of native Sonoran Desert Some of the best, and scientifically most rigorous, studiesbees have a narrower diet breadth taking their pollen and were made by William Schaffer and his colleagues at Thenectar from a limited floral smorgasboard. The smallest bees, University of Arizona (Schaffer, Jensen, et al., 1979; Schaffer, such as the genus Perdita, may utilize nectar levels on a per Zeh et al., 1983) during their studies of competition forAgaveflower or per inflorescence basis that is below foraging prof- schottii nectar amongst feral honey bees, introduced geneti-itability threshold for individual honey bee colonies. This cally marked "Cordovan" honey bees and native solitary, was likely the case in the multiyear studies by Schaffer and social bees and ants. These studies gave a strong indicationhis co- workers. From an ecological standpoint, however, most that competition was taking place for nectar, that native beesfloral biologists familiar with introduced honey bees in Desert Plants1996 8 ADC SCALE COLONY

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I A M J A S O N D J F M A 1991 -92 Figure 3. Top: Amount of pollen (grams) harvested daily by one full -sized Langstroth European honey bee colony located within Tucson Mountain Park on the grounds of the Sonoran Arthropod Studies Institute during the years of 1991 -92. Bottom: The corresponding number of species utilized each day by the same colony. This was done by hand - sorting the corbicular pellets while fresh according to their color. They were not examined microscopically. Nonetheless, the daily contribution to colony diet by the local vegetation is evident.

"pristine" landscapes, consider it logical that at least someyou can not only find beekeeping "honey production" re- species of native bees, especially those social species suchserves set aside just for them, but also state and national as our desertBombus or someXylocopa, are polylectic, long - parks where beekeeping is expressly forbidden, so as not to lived as individuals and nests, and therefore highly vulner-impact other native nectar and pollen feeders or potentially able to interference competition with managed and feral honey impact the natural reproduction of native flowering plants. bees for limiting floral foodstuffs. Conservation Biology Implications for Native Bees, Australia is a continent with a rich native bee fauna that isCommon and Rare Flowering Plants skewed toward species richness and diversity in largely oneIt is unfortunate that we do not have baseline data on the family -the Colletidae, which are less common in the Sonoran abundances of native Sonoran Desert bees at any study plots Desert. Further, the great eucalypt forests, stands of Acaciaprior to the introduction of honey bees into Arizona (honey and other nectar- producing flora of Australia practically gushbees were recorded in local newspaper accounts by over- nectar at certain times of the year. This has allowed someland wagon from California in the 1860's). It is likely, how- bizarrely- adapted large animals, honeyeater birds and mar-ever, that they migrated on their own northward from their supials such as the honey possums, to adapt to genera suchmuch earlier 16th century introductions by the Spaniards as Anigozanthos and Banksia. Several authors have docu-into the Mexican plateau near Mexico City (Buchmann, un- mented that introduced honey bees are directly competingpublished; see Brand, 1988). Nevertheless, from their domi- with native birds, mammals and bees for limited nectar, espe-nance across the southern half of the state both as managed cially in the forests and sand heaths of Western Australiaapiaries of the European race (Kunzmann, et. al., 1995) and (see reviews in Sugden, Thorp and Buchman, 1996). Some oflikely another one or two hundred thousand feral colonies the records for greatest honey yields per hive have comewithin the state, it is hard to imagine that these exotic aliens from these eucalypt forests in Australia. Interestingly, con-aren't at least depressing the populations of local native bees servationists there have now begun to examine and enactand other pollinators by removing thousands of metric tons legislation with beekeeping in mind. In Western Australiaof pollen and nectar from this region. Pollen HarvestBuchmann and Shipman 9 Similarly, we must wonder what the actual or potential im-"sides" to come together and discuss the issues at hand) pacts of this alien super- foraging bee have been upon the relative to honey bees and native plants and wildlife. reproduction (both short and long -term) of both common, endangered and threatened native flowering plants. HoneyConclusions bees are polylectic generalists and quite effective pollinatorsIf this paper increases the awareness of the public and land for a majority of crop plants (which are also mostly recentmanagers about the potential dangers of honey bees as flo- immigrants from far corners of the earth) and some nativeral competitors with native Sonoran Desert insect and verte- plants. This does not, however, make them the "bee all" orbrate pollinators, then it has served its purpose. It is not my end all universal pollinator for all crops or all native plants. intention to alienate southwestern beekeepers, many of whom Honey bees cannot be carelessly utilized as a one -to -oneare close friends and colleagues, but rather to get everyone replacement for native Sonoran Desert bees. They simplytalking about the proper place and time to use honey bees for don't fit into many flowers properly or make stigmatic con- and when/where to use alternative non-Apis pol- tact, often act as nectar or pollen thieves, or cause unknownlinators. Similarly, land managers need to be aware of the effects on seed set within fruits, or seed shadows, on native potential ecological effects of alien honey bees upon the flowers in natural environments. plants and wildlife in their care and jurisdiction. Further, I hope I have introduced all parties to the powerful ecological It was recently estimated (Buchmann et al., 1992) that theretools of pollen traps, debris middens and melissopalynology could be as many as 1,358 feralApis mellifera colonies within as a way of peering into "bee pantries" to see what they like the west unit of the Saguaro National Park near Tucson, Ari- to eat. It is only by conducting such long -term research, zona. Now, by early 1996, perhaps 30 -50 percent of theseespecially now to build up datasets for Africanized honey feral colonies have become Africanized. These bees will have bees, that we can ever expect to to know whether the lasting an added impact upon the floral resources and pollinationeffects of long past honey bee introductions will be neutral within the park. They collect more pollen and swarm more or negative upon our native plants and co- adapted endemic frequently than European honey bee races. Of crucial impor-pollinators, especially the specialist solitary bees in the tance, is their tendency to harvest pollen from night- bloom- Sonoran Desert. Hopefully, ecologists will also catch on that ing tropical plants normally pollinated by bats (Roubik et al., honey bee colonies can be incredible "biomonitors" into the 1986; Roubik, 1989). They are also known to intensely visitpulse of phenological events around us, or that they can be plants that are dioecious or that have large inflorescences used aschemo- monitoring sampling units to detect the pres- comprised of minute flowers. Thus, columnar cacti in Ari-ence and distribution of environmental pollutants including zona and Sonora, Mexico as well as other plants with noctur- heavy metals, radioactive materials and pesticides. nal anthesis (but with abundant pollen remnants in flowers the morning after) such as the rare and threatened night -Acknowledgments blooming cereus cacti ( striatus and R greggii)I thank the following people for reviewing or commenting may also be impacted by pollination by Africanized honeyupon an earlier draft ofthis manuscript: Drs. James H. Hagler, bees as non -adapted pollen vectors. Justin O. Schmidt, Hayward G. Spangler and Gary Paul Nabhan. A special thanks is extended to Dr. Steven C. Unfortunately, for modern U.S. agriculture we have come to Thoenes for discussions of these and other matters. depend far too much upon honey bees for our essential crop pollination services (Torchio, 1990). This has been especially Literature Cited clear during the mid 90's when honey bee stocks (numbers ofBowers, Janice E. and Steven P. McLaughlin. 1987. Flora and colonies across the country) have fallen dramatically due toVegetation of the Rincon Mountains, Pima County, Arizona. gargantuan problems facing the beekeeping industry. TheseDesert Plants Volume 8(2): 51 -94. include price competition from cheap foreign honey (Mexico and China), several parasitic mites (Acarapis and Varroa), Brand, D. D. 1988.The honey bee in New Spain and Mexico. waxmoths (Galleria and Achroia), other bee diseases and Journal of Cultural Geography 9: 71 -81. now competition from within their own species the newly- arrived Africanized race ofApis mellifera scutellata. Bromenshenk, J.J., S.R. Carlson, J.C. Simpson and J.M. Tho- mas. 1985. Pollution monitoring of Puget sound with honey Undoubtedly, new legislation will be enacted by towns, cit- bees. Science 227: 632 -634. ies and counties to regulate beekeepers practicing their time - honored beecraft, especially with "ornery" Africanized bees Buchmann, S.L. 1996. Competition between honey bees and inside city limits. Even now conservation biologists, envi- native bees in the Sonoran Desert and global bee conserva- ronmentalists and policy makers are discussing the role oftion issues. In: The Conservation of Bees, Matheson, A., managed and feral honey bee colonies within parklands S.L. Buchmann, C. O'Toole, P. Westrich, and I.H. Williams (county, state, national parks and monuments). Africanized(eds.), Academic Press, London (in press). bees are definitely on their minds for public safety reasons, but many are beginning to wonder about the long -term ef- Buchmann S.L., M.K. O'Rourke, and C.W. Shipman. 1990. fects of honey bees for the future survival of native plantsPollen preferences and dietary breadth of managed and feral and native pollinators including solitary ground and twig - Sonoran honey bees. Proceedings of the American Bee Re- nesting bees. We simply do not have all the answers, or thesearch Conference, Tucson, Arizona (October, 1990). Ameri- datasets, upon which to make an informed decision (see can Bee Journal 130: 797 -798. Sugden et al., 1996 for a review of policies and a call for both 1996 lo Desert Plants

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D. E E Pollen HarvestBuchmann and Shipman 11 Buchmann, S.L., M.K. O'Rourke, C.W. Shipman, S.C. Thoenes, Southwick, E.E. and S.L. Buchmann. 1995/96. Effects ofhori- and J.O. Schmidt. 1992. Pollen harvest by honey bees inzon landmarks on homing success in honey bees. American Saguaro National Monument: Potential effects on plant re- Naturalist 146(5): 748 -764. production. Proceedings of the Symposium on Research in Saguaro National Monument (January 23- 24,1991, Tucson,Sugden, E.A., R.A. Thorp and S.L. Buchmann. 1996. Honey Arizona), Stone, C.P. and E.S. Bellantoni (eds.), pp. 149 -156. bee -native bee competition: focal point for environmental change and apicultural response in Australia. Bee World Buchmann, S.L. and M.K. O'Rourke. 1988. Palynological77(1): 264. analysis of diet breadth by honey bee colonies in Sonoran Desert (1980- 1987). Proceedings XVIII International CongressTorchio, P. 1990. Diversification of pollination strategies for of Entomology, Vancouver, B.C., 238 pp. U.S. crops. Environmental Entomology 19: 1649-1656.

Kunzmann, M.R., S.L. Buchmann, J.F. Edwards, S.C. Thoenes Turner, R.M. and D.E. Brown. 1982. Sonoran desertscrub. and E.H. Erikcon. 1995. Africanized bees in North America. Desert Plants 4: 181-221. In: Our Living Resources. USDI , National Biological Ser- vice, Washington, D.C., pp. 448 -451. Visscher, P.K. and T.D. Seeley. 1982. Foraging strategy of honeybee colonies in a temperate deciduous forest. Ecology O'Neal, R.J. and G.D. Waller. 1984. On the pollen harvest by 63:1790 -1801. the honey bee (Apis mellifera L.) near Tucson, Arizona (1976- 1981). Desert Plants 6(2): 81 -94, 99 -109. Waller, G.D. 1980. A modification of the O.A.C. pollen trap. American Bee Journal 120: 119-121. O'Rourke, M.K. and S.L. Buchmann. 1991. Standardized ana- lytical techniques for bee -collected pollen. Environmental Entomology 20(2): 508 -528. Photographs: Roubik, D.W., J.E. Moreno, C. Vergara and D. Wittmann. 1986. A. Steve Buchmann opening a drawer from a modified O.A.C. Sporadic food competition with the African honey bee: pro bottom type pollen trap used in the studies at the Pima Can- jected impact on neotropical social bees. Journal of Tropicalyon apiary site. Ecology 2: 97 -111. B. Close -up of a typical daily mix of corbicular pollen pellets removed from the hindlegs of returning foragers by the trap- Roubik, D.W. 1989. Ecology and Natural History of Tropicalping screens. The pollen grains are held together by nectar Bees. Cambridge University Press, Cambridge, U.K. 514 pp. added by the worker honey bees. C. Portion of the 1985 reconstituted annual pollen collection Schaffer, W. M., D.B. Jensen, D.E. Hobbs, J. Gurevitch, J.R. by all three Pima Canyon trap colonies. The pollen grains Todd, D.W. Zeh, and M.V. Schaffer. 1979. Competition forag-have been acetolyzed to remove the oily pollenkitt and to ing energetics and the cost of sociality in three species ofreveal their exinal sculpturing. Note the dominance of bees. Ecology 60: 976 -987. Prosopis, Acacia, Ehpedra, hi -spine compositae and other grains which were preferred dietary items by honey bee at Schaffer, W.M., D.W. Zeh, S.L. Buchmann, S. Kleinhaus, M.V.this location. Schaffer, and J. Antrim. 1983. Competition for nectar between D. Buchmann holding the largest known debris midden (over introduced honey bees and native North American bees andfive kg) from a feral European honey bee colony. The sample ants. Ecology 64(3): 564 -577. was collected from the floor of a shallow dry cave on Copper Mountain within the Organ Pipe Cactus National Monument Schmalzel, R..J. 1980. The diet breadth of Apis (Hymenoptera: in Arizona. The block of material contains dropped pollen Apidae). M.S. Thesis, Department of Entomology, Univer-pellets and dead bees and is held together in a soil and bees- sity of Arizona, 79 pp. wax matrix. E. Typical aggregation nestsite of a solitary ground- nesting Schmidt, J.O. and S.L. Buchmann. 1986. Floral biology of thebee, Diadasia rinconis, an oligolege (specialist) that feeds saguaro (Cereus giganteus) I. Pollen harvest by Apis entirely upon Opuntia and Carnegiea pollen and nectar. Each mellifera. Oecologia 69: 491 -498. dark mound is the tumulus of soil excavated from the bee burrows belowground. Seeley, T.D. 1986. Social foraging by honeybees: How colo-F. The strange pillow- shaped orange provision masses "bee nies allocate foragers among patches of flowers. Behavioralbread" made by female giant black carpenter bees belonging Ecology and Sociobiology 24:181 -199. to the species Xylocopa californica arizonensis. The provi- sions consist of pollen mixed with floral nectar. Seeley, T. D. 1994. Honey bee foragers as sensory units of their colonies. Behavioral Ecology and Sociobiology. 34: 51 -62.

Seeley, T.D. 1995. The wisdom ofthe hive: the social physiol- ogy of honey bee colonies. Harvard University Press, Cam- bridge, Massachusetts, 295 pp.