Status Review of Three Formerly Common Species of Bumble Bee ...

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eetles use commercial honey bee colonies as hosts, and continue to spread throughoutNorth America as commercial honey bees are transported for crop pollination. Small hivebeetles have a great destructive capability and could cause great harm to native bumblebee populations.Although most honey bee diseases are specific to honey bees, there is evidence of honeybees being carriers for bumble bee diseases, as well as there being the possibility ofshared disease between honey bees and bumble bees. Honey bees are possible vectors forthe trypansomatid Crithidia bombi (Ruiz-González and Brown 2006) although honeybees are not infected by this gut parasite. Deformed wing virus (DWV), a honey beepathogen that results in crippled wings, was thought to be specific to honey bees.However, there is evidence of this disease in European commercial bumble bee breedingoperations (Genersch et al. 2006). Although commercial bumble bee rearing operationsare the likely cause of the spread of DWV to bumble bees, honey bees have the potentialto spread this disease and possibly others to wild bumble bee populations through contactat shared floral resources.There is potential for non-native commercially raised bumble bees to naturalize and outcompetenative bumble bees for limited resources such as nesting sites and forage. Astudy comparing reproductive output of native Japanese bumble bees with non-native B.terrestris colonies, founded by bees that had escaped from commercially producedcolonies, found B. terrestris to have over four times the reproductive output of nativeJapanese bumble bees (Matsumra et al. 2004). A study in England comparing the nectarforagingand reproductive output of a native subspecies of B. terrestris withcommercially raised B. terrestris colonies found that the commercially raised colonieshad higher nectar-foraging rates and greater reproductive output (Ings et al. 2006).Commercial bumble bee producers have likely selected for colonies that are highlyproductive to ensure strong colony populations for use in pollination. While this is adesirable quality for commercial rearing, it could prove to aid invasion of non-nativespecies, subspecies, or varieties of bumble bees that would outcompete native bumble beepopulations.F. Other ThreatsIncreased inbreeding and haplodiploidy:Bumble bees may be particularly susceptible to inbreeding due to low effectivepopulation size (Packer and Owen 2001). As with all other hymenopterans, their sexdetermination system is haplodiploidy. The sex of offspring is determined by whether ornot the egg is fertilized. Unfertilized, or haploid, eggs become males and fertilized, ordiploid, eggs become females. This sex determination system may result in lower levelsof genetic diversity than diploid-diploid sex determination. Some bumble bees have beenfound to have particularly low levels of genetic diversity (Darvill et al. 2006; Ellis et al.2006). Inbreeding depression has been shown to negatively affect bumble bee colony size(Herrmann et al. 2007), a key factor in a colony’s reproductive success. Low geneticdiversity may also increase the risks these bees face from threats such as parasites,diseases, and habitat loss. In haplodiploid organisms, such as bumble bees, lowpopulation levels and resulting inbreeding depression may also increase the risk of32
population extinction by resulting in sterile diploid male production (Zayed and Packer2005).Bumble bees have many natural enemies including spiders, mites, flies, wasps, fungi, anddiseases (Macfarlane et al. 1995). The impact of these natural enemies on bumble beecolony success varies depending on their prevalence. The prevalence and distribution ofthese natural enemies is not known for most of North America. When populations arevery small, perhaps due to other factors, the impact of natural enemies would beheightened.Climate change:Global climate change will likely bring northward recession of the cold adapted speciesof bumble bees and expansion of ranges of warmer adapted species. Similar changes havebeen observed in other species of insects (reviewed in National Research Council 2007).Increased variability in the climate could also cause declines in an even broader range ofspecies (Williams et al. 2007). Kirilenko and Hanley (2007a, 2007b) combine the resultsof four models to predict how climate change will impact Bombus terricola. Their modelsindicate that this bee will shift its range northward by approximately 220 km by 2030,550 km by 2050, and 980 km by 2080. They predict that the range of Bombus moderatus(=lucorum), also in the subgenus Bombus sensu stricto, will shrink by 42%. They predictthat Bombus pensylvanicus will expand its range by 16%.Localized studies in the eastern U.S. have shown that some plants are flowering earlierthan they were in the past, presumably due to climate change (Abu-Asab et al. 2001;Primack et al. 2004). Other studies have demonstrated changes in pollinator phenologycorrelated with regional changes in temperature (Roy and Sparks 2000; Forister andShapiro 2003); if the phenology of plants and their pollinators do not changesynchronously, it is possible that plant-pollinator relationships will be disrupted (NationalResearch Council 2007).An increase in atmospheric CO 2 from global climate change may alter plant nectarproduction, which could negatively impact bumble bees (reviewed by Davis 2003). Anadditional impact of climate change, increased amounts of UV-B radiation from areduction in ozone, could delay flowering in plants and reduce the amount of flowers thatplants produce (National Research Council 2007). These impacts could have negativeeffects on bumble bees.Air pollution:Air pollution destroys volatile hydrocarbons released from flowers that serve as signals topotential pollinators (McFrederick et al. 2008). Increases in air pollutants such as ozonemay therefore interfere with the foraging efficiency of pollinators, especially infragmented landscapes.VII. CONCLUSIONThere are a number of threats facing bumble bees, any of which may be leading to thedecline of these species. The major threats to bumble bees include: spread of pests and33
Page 1 and 2: Status Review of Three Formerly Com
Page 4 and 5: use as commercial pollinators. Dr.
Page 6 and 7: B. Habitat requirementsB. affinis,
Page 8 and 9: and with black hairs extending rear
Page 10 and 11: Although this species was formerly
Page 12 and 13: September 2007).RegionSouthernOntar
Page 14 and 15: B. Pollination EcologyBombus terric
Page 16 and 17: as recently as 2007, Massachusetts
Page 18 and 19: Variety 1: As nominate form above,
Page 20 and 21: the Rocky Mountains. Below are find
Page 22 and 23: Historical records from within San
Page 24 and 25: VI. CURRENT AND POTENTIAL THREATS -
Page 26 and 27: impatiens to be transported into th
Page 28 and 29: equest is made to APHIS, APHIS will
Page 30 and 31: Insecticides are used in wild lands
Page 34 and 35: diseases by the commercial bumble b
Page 36 and 37: Brown, M. J. F., R. Schmid-Hempel,
Page 38 and 39: Fitzpatrick, U., T. E. Murray, R. J
Page 40 and 41: Holm, S. N. 1966. The utilization a
Page 42 and 43: Leonard, M. D. 1928. A list of the
Page 44 and 45: Medler, J. T. and D. W. Carney. 196
Page 46 and 47: Plowright, R. C., B. A. Pendrel, an
Page 48 and 49: 48: 543-548.Stephen, W. P. 1957. Bu
Page 50 and 51: Williams, P. H., M. B. Arau ́jo, a
Page 52 and 53: Abbreviations for museums are as fo
Page 54 and 55: Tennessee: Sugarlands, 12-Apr-1949,
Page 56 and 57: H.C. Manis, Strange, U of ID; 2: Bu
Page 58 and 59: Montrose, 5-Aug-1960, F., P., & M.
Page 60 and 61: Lick Cr. 28 mi SE Union 4280 ft, 3-
Page 62 and 63: N.E. Woodley, Strange, WSU; Richlan

Status Review of Three Formerly Common Species of Bumble Bee ...

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