Bombus bohemicus 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Arthropoda Insecta Hymenoptera Apidae

Scientific Name: Bombus bohemicus Seidl, 1838
Regional Assessments:
Common Name(s):
English Ashton's Cuckoo Bumblebee
Bombus ashtoni Cresson, 1864
Taxonomic Source(s): Cameron, S. A., Hines, H. M. and Williams, P. H. 2007. A comprehensive phylogeny of the bumble bees (Bombus). . Biological Journal of the Linnean Society 91: 161-188.
Taxonomic Notes:

Bombus ashtoni Cresson, 1864 from North America was previously considered to be a species separate from B. bohemicus, but Cameron et al. (2007) suggested it may be conspecific and this was supported by Williams et al. (2014).

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2016
Date Assessed: 2014-08-19
Assessor(s): Hatfield, R., Jepsen, S., Thorp, R., Richardson, L. & Colla, S.
Reviewer(s): Ascher, J., Jha, S., Williams, P., Lozier, J., Cannings, S., Inouye, D., Yanega, D. & Woodard, H.
Contributor(s): Antweiler, G., Arduser, M., Ascher, J., Bartomeus, N., Beauchemin, A., Beckham, J., Cromartie, J., Day, L., Droege, S., Evans, E., Fiscus, D., Fraser, D., Gadallah, Z., Gall, L., Gardner, J., Gill, D., Golick, D., Heinrich, B., Hinds, P., Hines, H., Irwin, R., Jean, R., Klymko, J., Koch, J., MacPhail, V., Martineau, R., Martins, K., Matteson, K., McFarland, K., Milam, J., Moisan-DeSerres, J., Morrison, F., Ogden, J., Packer, L., Richardson, L., Savard, M., Scott, V., Scully, C., Sheffield, C., Sikes, D., Strange, J., Surrette, S., Thomas, C, Thompson, J., Veit, M., Wetherill, K., Williams, N., Williams, P., Winfree, R., Yanega, D. & Zahendra, S.
Facilitator/Compiler(s): Foltz Jordan, S., Hatfield, R., Colla, S. & MacPhail, V.
In North America, this species is declining rapidly, currently occurring in only approximately seven known sites. Its population reduction in North America is suspected to have been >80% in the past decade based on a 97.18% decline in relative abundance between recent (2002-2012) and historic (1805-2001) time periods and a 96.28% decline in extent of occurrence (EOO) has been observed between recent and historic time periods. Since this Psithyrus species uses both Bombus terricola and B. affinis as hosts, and there has been a decline in the availability of these hosts, we can apply criterion A2c (decline in habitat quality). We are not comfortable using either criterion C or D since historic sites have not been revisited and we lack population level data. This review includes Bombus ashtoni (Hatfield et al. 2014.). Based on the above calculations and trends, along with published reports of bumble bee decline and the assessors' best professional judgement, this species meets the criteria for the Critically Endangered Red List Category under criterion A2bc in its North American range. 

In Europe, this species is common to abundant over most of its range, and population seems to be stable (Rasmont et al. 2014). This species is listed as Least Concern in Europe, in view of its wide distribution, presumed large overall population with a stable population trend and no major threats (Rasmont et al. 2014). In Asia, the species has a broad distribution (Williams 1991) but in the south at least it is scattered and uncommon in the mountains, e.g. in Kashmir (Williams 1991), in North China (An et al. 2014) and in Sichuan (Williams et al. 2009).

Because of the widely disparate status of this species globally, and the lack of sufficient data to conduct a world wide assessment at present, we have assessed this species as Data Deficient. While the data are insufficient globally, this species is Critically Endangered in North America, and has been lost from over 90% of its range, and has experienced a greater than 90% drop in relative abundance. 

For further information about this species, see 13152926_Bombus_bohemicus.pdf.
A PDF viewer such as Adobe Reader is required.

Geographic Range [top]

Range Description:In North America, Bombus bohemicus is found in eastern and midwestern United States and Canada in Eastern Temperate Forest and Boreal Forest regions, south in a narrow band at higher elevations along the Appalachian Mountains and extending northwest through the Canadian Great Plains, Mountain West, and Tundra/Taiga to Alaska (Williams et al. 2014; see Figure 1 in the Supplementary Information).

In Europe, this species is widespread from the north of Spain, the south of Italy and the Balkans in the south to beyond the Arctic Circle in the north (Rasmont et al. 2014). It extends eastwards to the Far East of Asia (Williams 1991) and south into China in Sichuan (Williams et al. 2009), where it is uncommon. Bombus bohemicus is one of the most common cuckoo-bumblebees of Europe (Rasmont et al. 2014).

This species is also widespread in many parts of China (Rasmont et al. 2014).
For further information about this species, see 13152926_Bombus_bohemicus.pdf.
A PDF viewer such as Adobe Reader is required.
Countries occurrence:
Andorra; Austria; Belarus; Belgium; Bulgaria; Canada (Alberta, British Columbia, Labrador, Manitoba, New Brunswick, Newfoundland I, Northwest Territories, Nova Scotia, Ontario, Prince Edward I., Québec, Saskatchewan, Yukon); China; Czech Republic; Denmark; Estonia; Finland; France (France (mainland)); Germany; Hungary; Ireland; Italy (Italy (mainland)); Latvia; Lithuania; Luxembourg; Macedonia, the former Yugoslav Republic of; Montenegro; Netherlands; Norway; Poland; Romania; Russian Federation; Serbia (Serbia); Slovakia; Slovenia; Spain (Spain (mainland)); Sweden; Switzerland; Ukraine (Ukraine (main part)); United Kingdom (Great Britain, Northern Ireland); United States (Alaska, Connecticut, Idaho, Illinois, Indiana, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, North Dakota, Ohio, Oregon, Pennsylvania, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin)
Additional data:
Continuing decline in extent of occurrence (EOO):Unknown
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:North America
Despite an increase in bumblebee surveys, and re-sampling of historic locations in North America, there have been very few individuals of this species collected. At the regional level, surveys in southern Ontario (Colla and Packer 2008) and New York State (Giles and Ascher 2006) did not detect this species despite it being present at the same sites historically. Colla et al. (2012) found significant declines in relative abundance across this species Canada and United States range. The species was also found to only persist in 35% of historical sites which were re-sampled between 1991-2009 (Colla et al. 2012). In the past few years, the only specimens collected were in Alaska.

Host species of this bee have also experienced widespread declines (e.g., Bombus affinis (COSEWIC 2010)), which suggests this parasitic species would also be negatively affected.

We evaluated this species’ spatial distribution in North America over time using a measure of change in the extent of occurrence (EOO) and a measure of change in persistence (analytical methods described in Hatfield et al. 2014). We also assessed changes in the species’ relative abundance, which we consider to be an index of abundance relevant to the taxon, as specified by the IUCN Red List Categories and Criteria (IUCN 2012). For all three calculations we divided the database into historical (1805-2001, N=128,572) and current (2002-2012, N=74,682) records. This time frame was chosen to meet the IUCN criteria stipulation that species decline must have been observed over the longer of three generations or 10 years. Average decline for this species was calculated by averaging the change in abundance, persistence, and EOO. This analysis yielded the following results (see also the attached graph of relative abundance and map of change in EOO over time):
  • Persistence in current range relative to historic occupancy: 9.16%
  • Current range size relative to historic range: 3.72%
  • Current relative abundance relative to historic values: 2.82%
  • Average decline: 94.77%
This analysis suggests sharp declines in both relative abundance and persistence over the last ten years. This species had a large historical range in North America, but now appears to be absent from most of it (Hatfield et al. 2014).

In Europe, this species is common to abundant over most of its range, and populations seem to be stable (Rasmont et al. 2014), despite declining rapidly in North America (Williams et al. 2014).

Little information is available about the changes in abundance of this species in Asia.

For further information about this species, see 13152926_Bombus_bohemicus.pdf.
A PDF viewer such as Adobe Reader is required.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:UnknownPopulation severely fragmented:Unknown
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:UnknownAll individuals in one subpopulation:Unknown

Habitat and Ecology [top]

Habitat and Ecology:

Bombus bohemicus is a cuckoo bee, a term used for a specialized lineage of bumble bees (subgenus Psithyrus) that has lost the ability to collect pollen and to rear their brood. As such, these bees do not found their own nests, but instead, usurp the colonies and worker forces of other bumble bee species. To do this, a mated female enters the nest of another bumble bee species, kills or subdues the queen of that colony, and forcibly (using pheromones and/or physical attacks) "enslaves" the workers of that colony to feed her and her developing young. Since all of the resulting cuckoo bee offspring are reproductive (not workers), they leave the colony to mate, and then they hibernate.  The next year, after emerging from hibernation, the mated females seek out other nests to attack.  Males of this species patrol circuits in search of mates. Before finding and invading a host colony, females feed directly from flowers. The food plants of this species include Cirsium, Melilotus, Rubus, Rudbeckia, Solidago, Symphyotrichum, Trifolium and Vaccinium (Williams et al. 2014). 

This bee is a social parasite, and thus is found in association with its host species (Antonovics and Edwards 2011, Williams et al. 2014). Cuckoo bees often attack a broad range of host species, but some specialize in attacking the members of just one species or subgenus. In Europe, Bombus bohemicus is an inquiline primarily in the nests of B. lucorum (Rasmont et al. 2014). In North America, known hosts include Bombus affinis and B. terricola, and potentially B. occidentalis and B. cryptarum (Plath 1934, Owen et al. 2012, Williams et al. 2014).  Habitat types are variable, and likely depend on host species. In Europe, like its primary host, B. bohemicus can be found in a wide variety of habitats, from open grasslands, to sand dunes, heather moorland, woodland edge and subalpine grasslands (Rasmont et al. 2014). In North America, this species' hosts nest in abandoned, underground, rodent burrows. Although overwintering specifics of this bee are unknown, most bumblebees overwinter in mulch, rotting logs, or loose soil (Plath 1934, Macfarlane 1974).  

Generation Length (years):1
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: From European assessment: This species is not traded or exploited commercially.
From North American assessment: This species was used for scientific study (e.g. Fisher 1983), but is no longer commonly used.

Threats [top]

Major Threat(s):

As this bee is a parasitic species, it is dependent on its host species throughout its large range in North America (most of Canada, northern US), some of which are now in decline (e.g. Bombus affinis, B. occidentalis, B. terricola). Although there are still areas where the host species remain detectable, this species has rarely been found over more than a decade. This suggests hosts are declining to an abundance which does not support healthy populations of B. bohemicus in North America (Threat 12.1). In addition, this species is likely vulnerable to environmental stressors such as climate change, habitat loss and pesticide exposure however the extent of this is unknown given the sparsity of recent information for this species.

Natural wildfires and prescribed burning may benefit bees by creating open forage in otherwise unsuitable habitat. As such, the suppression of natural fires can result in habitat loss for bees and other grassland species, particularly in forested regions. In light of this, prescribed burning is frequently used as a conservation management tool to restore natural ecosystems (e.g. grasslands), increase biodiversity (particularly plant species), and control invasive species (e.g. Brockway et al. 2002; Hatch et al. 2002). However, depending on fire intensity, duration, season, frequency, and patchiness, prescribed fire may result in population loss for pollinators, particularly at sites where few individuals of a species exist (e.g. Swengel 1996). As such, both fire suppression and fire itself may threaten this species in some areas.

Bumble bee species that occupy very specialized climatic niches are considered to be at the greatest risk of climate change-driven extinction (Williams et al. 2007, 2009; Williams & Osborne 2009, Rasmont et al. 2014). Given this species’ restricted occurrence in high elevation and high latitude habitats, climate change is a primary threat, however, there are currently no studies indicating which of many possible mechanisms are likely to be having the most effect on this species. In general, climate change may adversely affect bumble bees in three main ways (reviewed in Cameron et al. 2011, final report for the 2010 North American Bumble Bee Species Conservation Planning Workshop):

1. Life history changes (including variable/unpredictable environmental cues; changes in the length of the nesting season, changes in timing of emergence & caste production; and increased overwintering mortality)
2. Changes in community interactions and resources (including asynchrony in resident rodent population phenology, and changes in timing, availability, quantity, and quality of flora resources (Memmott et al. 2007; Hegland et al. 2009)
3. Habitat structure changes (including reduction in effective population size of bumble bees, and range shifts of climatically narrow bumble bees and resources).

Reduced genetic diversity resulting from climate change or other threats can be particularly concerning for bumble bees, since their method of sex-determination  haplodiploidy) can be disrupted by inbreeding) (Goulson 2010, Hatfield et al. 2012).

Conservation Actions [top]

Conservation Actions: Actions should focus on conservation management of host species in North America as captive rearing of this species is likely not an option. Due to the lack of recent specimens across this species large range, a priority conservation measure for this species is targeted surveys to locate extant populations. Additionally, extant populations, if located, should be protected from habitat loss, pesticide exposure and pathogen spillover.

Citation: Hatfield, R., Jepsen, S., Thorp, R., Richardson, L. & Colla, S. 2016. Bombus bohemicus. The IUCN Red List of Threatened Species 2016: e.T13152926A46440141. . Downloaded on 17 August 2018.
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