|Scientific Name:||Bombus fraternus (Smith, 1854)|
Apathus fraternus Smith, 1854
|Taxonomic Source(s):||Smith, F. 1854. Catalogue of hymenopterous insects in the collection of the British Museum. Part II. Apidae. London, UK.|
|Red List Category & Criteria:||Endangered A2bc 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 exhibited declines in relative abundance and EOO over the past decade (Hatfield et al. 2014). In addition, this species' long-term downward trend in relative abundance is near significant; if the same rate of decline in relative abundance continues, this species could potentially go extinct within 80-90 years. There are huge gaps in recent (as well as historic) collection effort, especially in Oklahoma, Kansas, Nebraska, western Texas, and the Dakotas, yet there has been significant range loss in the northern and southern parts of its range where collection effort has been more consistent. Thus, we have high confidence in the EOO decline of 28.62%, probably due to habitat alterations. We selected criterion A2bc based on a decline in Relative Abundance, EOO, and habitat quality. Habitat modification over the past 10 years (insecticide use, grassland conversion to agriculture) has been severe in the region where this species occurs (Hatfield et al. 2014.). These results are consistent with other findings of decline in this species (e.g. Colla et al. 2012). 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 Endangered Red List category at this time.
|Previously published Red List assessments:|
|Range Description:||Bombus fraternus is found in the Eastern Temperate Forest region on the coastal plain of the southeastern United States from central Florida north to New Jersey, Ohio west throughout the United States Great Plains (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:United States (Alabama, Arkansas, Colorado, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Louisiana, Massachusetts, Minnesota, Mississippi, Missouri, Nebraska, New Jersey, New Mexico, North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Tennessee, Texas, Virginia)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Colla et al. (2012) found this species persisted in only 27% of its re-sampled historic range, and also showed a significant decline in relative abundance. Grixti et al. (2009) located the species during a statewide study in Illinois but found it had declined in distribution from the southern portion of the state. |
We evaluated this species’ spatial distribution 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 species' long-term downward trend in relative abundance is near significant; if the same rate of decline in relative abundance continues, this species could potentially go extinct within 80-90 years. There are huge gaps in recent (as well as historic) collection effort, especially in Oklahoma, Kansas, Nebraska, western Texas and the Dakotas, yet there has been significant range loss in the northern and southern parts of its range where collection effort has been more consistent. Habitat modification over the past 10 years (insecticide use, grassland conversion to agriculture) has been severe in the region where this species occurs.
|Current Population Trend:||Decreasing|
|Habitat and Ecology:|
Bumblebees, 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. Bumblebees collect both nectar and pollen of the plants that they pollinate. In general, bumblebees 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. Bumblebees 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 fraternus is a short-tongued bee associated with grasslands and urban gardens (Williams et al. 2014). It nests underground, and males perch and chase moving objects in search of mates (Williams et al. 2014). Example food plants include Asclepias, Cassia, Dalea, Liatris, Melilotus, Ratibida, and Solidago (Williams et al. 2014).
|Generation Length (years):||1|
Generally, bumble bees (Bombus spp.) are threatened by a number of factors including habitat loss, pesticide use, pathogens from managed pollinators, competition with non-native bees, and climate change (reviewed in Goulson 2010, Williams et al. 2009, Williams and Osborne 2009, Fürst et al. 2014, Cameron et al. 2011, Hatfield et al. 2012). Reduced genetic diversity resulting from any of these threats can be particularly concerning for bumble bees, since their method of sex-determination can be disrupted by inbreeding, and since genetic diversity already tends to be low in this group due to the colonial life cycle (i.e., large numbers of bumble bees found locally may represent only one or a few queens) (Goulson 2010, Hatfield et al. 2012, but see Cameron et al. 2011 and Lozier et al. 2011).Habitat loss due to the conversion of grasslands to agriculture is likely the major threat to this species. Much its range overlaps with prime agricultural areas, particularly for corn production (e.g. Midwest USA). Grixti et al. (2009) found it had declined in Illinois, a state with extensive natural habitat loss. Pesticide exposure in suitable habitat may also be causing declines. Corn seed is now almost entirely treated with neonicotinoids, a pesticide group known to negatively impact bees (Hopwood et al. 2012). Parasite levels in the wild have not been studied in this species thus the threat of pathogen spillover to this species is unknown. 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.
With the exception of the above, specific conservation and research needs for this species have not been identified. 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. 2014. Bombus fraternus. The IUCN Red List of Threatened Species 2014: e.T44937623A69001851.Downloaded on 22 May 2018.|
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