|Scientific Name:||Bombus terricola Kirby, 1837|
|Taxonomic Source(s):||Williams, P.H., Brown, M.J.F., Carolan, J.C., An, J., Goulson, D., Aytekin, A.M., Best, L.R., Byvaltsev, A.M., Cederberg, B., Dawson, R., Huang, J., Ito, M., Monfared, A., Raina, R.H., Schmid-Hempel, P., Sheffield, C.S., Šima, P. and Xie, Z. 2012. Unveiling cryptic species of the bumblebee subgenus Bombus s. str. worldwide with COI barcodes (Hymenoptera: Apidae). Systematics and Biodiversity 10: 21-56.|
While there has been some debate over whether this species is conspecific with Bombus occidentalis (e.g. Cameron et al. 2007), recent morphological and molecular work (e.g. Bertsch et al. 2010, Williams et al. 2012, Owen and Whidden 2013) support the separate taxa.
|Red List Category & Criteria:||Vulnerable A2b ver 3.1|
|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.|
According to our analysis, this North American species has declined over 30% in both range and persistence across its entire range, with particularly high (>80%) declines in relative abundance over the time period examined (Hatfield et al. 2014). Moreover, examination of long-term trends reveals that the species' relative abundance in the current decade is lower than any other decade, and the relative abundance change from the mean relative abundance has been greater than 66% in the past decade. Our metric that is least sensitive to variation in collection effort is persistence, and to a lesser degree relative abundance, and both of those metrics suggest that this species should at least be classified as Vulnerable, if not Endangered (Hatfield et al. 2014). The average decline of 49.94% (including relative abundance, persistence, and range) suggests a Vulnerable Red List Category. These results are consistent with other studies, discussed in the Population section of this assessment. Based on the above calculations and trends, along with published reports of bumble bee decline and the assessors' best professional judgement, we recommend this species for the Vulnerable Red List category at this time.
|Range Description:||This species has a large range including Newfoundland and the Eastern Temperate and Boreal forest regions, south along higher elevations of the Appalachians, west through North Dakota and the Canadian Great Plains, to the Tundra and Taiga of Canada and the Mountain West, especially in British Columbia (Williams et al. 2014).|
For a graph and map of relative abundance and range changes of this species over time see the Supplementary Material.
Native:Canada (Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland I, Northwest Territories, Nova Scotia, Ontario, Prince Edward I., Québec, Saskatchewan, Yukon); United States (Alaska, Arizona, Colorado, Connecticut, Georgia, Idaho, Illinois - Possibly Extinct, Indiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Montana, Nevada, New Hampshire, New Jersey, New York, North Carolina, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming)
|Range Map:||Click here to open the map viewer and explore range.|
Numerous studies indicate that this species has declined, both regionally and locally, especially in the southern portion of its range. A study examining changes in bumble bee community composition throughout Illinois found that although B. terricola made up 1.2% relative abundance of the bumble bees from collections from 1900-1949, it was not present in state collections from 1950-2007 or from extensive surveys performed at 56 sites across the state in 2007, and is now considered locally extirpated (Grixti et al. 2009). Although this species was historically rare in Illinois (15 bees collected from three sites between 1894 and 1929), records from multiple geographic regions and years indicate that it was not a transient species (Grixti et al. 2009). In a study in Guelph, Ontario, a comparison of relative abundances of bumble bees collected from 1971-1973 and from 2004-2006 found that B. terricola significantly declined in relative abundance from 3% to 0% between the two time periods (Colla and Packer 2008). Also in Ontario, Dr. Paul Williams reports that while this species was one of the most common in Toronto and Algonquin in 1983, Dr. Williams saw only two individuals in Toronto and none in the eastern United States during surveys between 2002 and 2008 (P. Williams pers. comm. 2014). In Manitoba, Turnock et al. (2006) reported declining abundance of this species in the period of 1986-1993, based on bycatch in baited armyworm traps.
A recent long-term study in the Northeastern United States examining historical changes in bees (including both Bombus and non-Bombus bees) found that although this species did not exhibit the rapid and drastic population declines seen in B. ashtoni, B. pensylvanicus and B. affinis, it did exhibit significant declines in relative abundance across its northeastern U.S. range (Bartomeus et al. 2013). In another study comparing current and historical distributions of eight bumble bee species in the United States using museum records and nationwide survey data, Cameron et al. (2011) found that the relative abundances of B. terricola had sharply declined in recent years, from ~10% relative abundance to <1%, in comparison with the codistributed B. impatiens, B. bimaculatus, B. pensylvanicus and B. affinis. In this study, intensive survey efforts of >16,000 bees in 40 states (2007-2009) identified only 32 specimens of B. terricola at nine sites (in North Carolina, Maine, Vermont, Pennsylvania and South Dakota), and the quantified range reduction of this species compared to historical records was estimated at 31% (Cameron et al. 2011). In another comprehensive study of bumble bee decline across both the United States and Canada, Colla et al. (2012) found this species persisted in approximately 52% of re-sampled historically occupied 50 x 50 km grid cells throughout its United States and Canada range, and although abundance had a downward slope, this trend was not significant. This study notes that although previous studies found B. terricola to be among the most sharply declining species (Cameron et al. 2011, Colla and Packer 2008), declines are not as striking when the northernmost parts of the range are considered (Colla et al. 2012).
We evaluated this species’ spatial distribution range-wide over time using a measure of change in the extent of occurrence (EOO; see Figure 2 in the Supplementary Material) and a measure of change in persistence (analytical methods described in Hatfield et al. 2014). We also assessed changes in the species’ relative abundance (see Figure 1 in the Supplementary Material), 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 timeframe 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 graph of relative abundance and map of change in EOO over time in the Supplementary Material):
This analysis indicates that across its entire range, this species has declined over 30% in both range and persistence, with particularly high (>80%) declines in relative abundance over the time period examined. Examination of long-term trends reveals that the species' relative abundance in the current decade is lower than any other decade, and the relative abundance change from the mean relative abundance has been greater than 66% in the past decade. Note that search effort has been low in the northern parts of its range in Canada, but where there has been good search effort the species shows signs of decline (Hatfield et al. 2014).
These results are consistent with other studies, discussed above. Overall, the species has declined dramatically in parts of its historic range, sometimes to the point of local extirpation. Where it remains detectable it typically occurs at lower abundances than historically.
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|| |
Bumble bees, as a whole, are eusocial insects that live in colonies composed of a queen, workers and reproductives (males and new queens). Colonies are annual and only the new, mated queens overwinter. These queens emerge from hibernation in the early spring and immediately start foraging for pollen and nectar and begin to search for a nest site. Nests are often located underground in abandoned rodent nests, or above ground in tufts of grass, old bird nests, rock piles, or cavities in dead trees. Initially, the queen does all of the foraging and care for the colony until the first workers emerge and assist with these duties. Bumble bees collect both nectar and pollen of the plants that they pollinate. In general, bumble bees forage from a diversity of plants, although bumble bee species in a given area can vary greatly in their plant preferences, largely due to differences in tongue length. Bumble bees are well-known to engage in “buzz pollination,” a very effective foraging technique in which they sonicate the flowers to vibrate the pollen loose from the anthers.
Bombus terricola inhabits a wide variety of habitats, including woodlands, farmlands, urban areas, meadows, grasslands, wetlands and other areas (Hobbs 1968, Laverty and Harder 1988, Williams et al. 2014). Queens overwinter in loose ground or rotting logs, and colonies nest underground in vacant rodent burrows (Hobbs 1968, Laverty and Harder 1988, Williams et al. 2014). Males patrol circuits in search of mates (Williams et al. 2014). This species is a frequent nectar robber of long-corolla flowers. Example food plants include Crocus, Eupatorium, Linaria, Melilotus, Monarda, Ribes, Rosa, Rubus, Spirea, Taraxacum, Vaccinium and Vicia (Williams et al. 2014). It is a known host to the cuckoo bumble bee Bombus bohemicus (=B. ashtoni), and a probable host to B. suckleyi and B. insularis (Williams et al. 2014).
|Generation Length (years):||1|
|Movement patterns:||Not a Migrant|
|Use and Trade:||There is no trade or commercialization of this species.|
Like many other bees, this declining species is likely affected by a variety of factors independently and in combination throughout its large range. These factors include loss or fragmentation of habitat, particularly from agricultural expansion (Kosior et al. 2007, Grixti et al. 2009), pathogen spillover, particularly from greenhouse bumblebee pollinators (Colla et al. 2006, Otterstatter and Thomson 2008), pesticides, particularly a relatively new class known as neonicotinoids (Marletto et al. 2003; see review by Hopwood et al. 2012), as well as climate change and severe weather (Williams et al. 2007, Williams and Osborne 2009). Another possible factor is high infection by the pathogen Nosema bombi, which has a high prevalence in B. terricola (11 of 44 specimens examined) compared to stable co-distributed species (<1% infection) (Cameron et al. 2011). According to this study, declining bumble bee populations have significantly higher infection levels of the microsporidian pathogen Nosema bombi and lower genetic diversity compared with co-occurring populations of the stable (non-declining) species, suggesting that higher pathogen prevalence and reduced genetic diversity are realistic predictors of the alarming patterns of bumble bee decline in North America, although cause and effect remain uncertain (Cameron et al. 2011).
Szabo et al. (2012) found that declines in this species throughout its North American range were correlated with the density of vegetable greenhouses, indicating pathogen spillover from managed greenhouse bees may be a significant threat for this species. In addition to the potential spread of disease, competition with managed bees may cause reduced fitness at local levels. In some parts of its range, habitat loss due to agricultural intensification, invasive species, pesticide use and logging may also be threats. In addition, both fire suppression and fire itself may threaten this species in some areas; the suppression of natural fires can result in habitat loss for bees and other grassland species, particularly in forested regions. However, depending on fire intensity, duration, season, frequency, and patchiness, prescribed fire (e.g., for conservation purposes) may result in population loss for pollinators, particularly at sites where few individuals of a species exist (e.g. Swengel 1996).
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 and Osborne 2009). Given this species’ restricted occurrence in high elevation and primarily in the boreal ecozone, 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):
Research Needs: Research needs for North American bumble bees (as a whole) are summarized in Cameron et al. (2011), the final report for the 2010 North American Bumble Bee Species Conservation Planning Workshop.
|Citation:||Hatfield, R., Jepsen, S., Thorp, R., Richardson, L. & Colla, S. 2015. Bombus terricola. The IUCN Red List of Threatened Species 2015: e.T44937505A46440206.Downloaded on 23 June 2018.|
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