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Ambient Air Temperature Does Not Predict whether Small or Large Workers Forage in Bumble Bees (Bombus impatiens).

Couvillon MJ, Fitzpatrick G, Dornhaus A - Psyche (Camb Mass) (2010)

Bottom Line: We found no significant effect of ambient or nest temperature on the average size of bees flying to and foraging from a suspended feeder.Instead, bees of all sizes successfully flew and foraged between 16°C and 36°C.Size variation therefore could not be explained in terms of niche specialization for foragers at different temperatures.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA ; Laboratory of Apiculture and Social Insects, Department of Biological and Environmental Science, University of Sussex, Falmer, Brighton BN1 9QG, UK.

ABSTRACT

Bumble bees are important pollinators of crops and other plants. However, many aspects of their basic biology remain relatively unexplored. For example, one important and unusual natural history feature in bumble bees is the massive size variation seen between workers of the same nest. This size polymorphism may be an adaptation for division of labor, colony economics, or be nonadaptive. It was also suggested that perhaps this variation allows for niche specialization in workers foraging at different temperatures: larger bees might be better suited to forage at cooler temperatures and smaller bees might be better suited to forage at warmer temperatures. This we tested here using a large, enclosed growth chamber, where we were able to regulate the ambient temperature. We found no significant effect of ambient or nest temperature on the average size of bees flying to and foraging from a suspended feeder. Instead, bees of all sizes successfully flew and foraged between 16°C and 36°C. Thus, large bees foraged even at very hot temperatures, which we thought might cause overheating. Size variation therefore could not be explained in terms of niche specialization for foragers at different temperatures.

No MeSH data available.


Foraging activity, measured as the number of trips per bee in one observation period, declined at higher temperatures. Shown is the average (with standard deviation) of all bees in the respective category across all days with the respective temperature (total N = 339 bees*days).
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Figure 3: Foraging activity, measured as the number of trips per bee in one observation period, declined at higher temperatures. Shown is the average (with standard deviation) of all bees in the respective category across all days with the respective temperature (total N = 339 bees*days).

Mentions: Overall, we found that all forager body sizes were measured at all temperatures (Figure 2). The number of trips made per observation period decreased at higher temperatures and was on average lower in larger foragers (defined here as foragers over 4.75 mm thorax width, Figure 3; ANOVA, df = 9, R2 = 0.86, ambient temperature P = .002, body size P = .028, interaction P = .61). It is not clear why larger bees made fewer trips; perhaps because they needed longer to fill their crop on each visit. This result is the same if, instead of the average number of trips across bees in the respective category, each bee’s number of trips is entered in the analysis separately (df = 338, R2 = 0.07, ambient temperature P = .004, body size P = .0002, interaction P = .43).


Ambient Air Temperature Does Not Predict whether Small or Large Workers Forage in Bumble Bees (Bombus impatiens).

Couvillon MJ, Fitzpatrick G, Dornhaus A - Psyche (Camb Mass) (2010)

Foraging activity, measured as the number of trips per bee in one observation period, declined at higher temperatures. Shown is the average (with standard deviation) of all bees in the respective category across all days with the respective temperature (total N = 339 bees*days).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440703&req=5

Figure 3: Foraging activity, measured as the number of trips per bee in one observation period, declined at higher temperatures. Shown is the average (with standard deviation) of all bees in the respective category across all days with the respective temperature (total N = 339 bees*days).
Mentions: Overall, we found that all forager body sizes were measured at all temperatures (Figure 2). The number of trips made per observation period decreased at higher temperatures and was on average lower in larger foragers (defined here as foragers over 4.75 mm thorax width, Figure 3; ANOVA, df = 9, R2 = 0.86, ambient temperature P = .002, body size P = .028, interaction P = .61). It is not clear why larger bees made fewer trips; perhaps because they needed longer to fill their crop on each visit. This result is the same if, instead of the average number of trips across bees in the respective category, each bee’s number of trips is entered in the analysis separately (df = 338, R2 = 0.07, ambient temperature P = .004, body size P = .0002, interaction P = .43).

Bottom Line: We found no significant effect of ambient or nest temperature on the average size of bees flying to and foraging from a suspended feeder.Instead, bees of all sizes successfully flew and foraged between 16°C and 36°C.Size variation therefore could not be explained in terms of niche specialization for foragers at different temperatures.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA ; Laboratory of Apiculture and Social Insects, Department of Biological and Environmental Science, University of Sussex, Falmer, Brighton BN1 9QG, UK.

ABSTRACT

Bumble bees are important pollinators of crops and other plants. However, many aspects of their basic biology remain relatively unexplored. For example, one important and unusual natural history feature in bumble bees is the massive size variation seen between workers of the same nest. This size polymorphism may be an adaptation for division of labor, colony economics, or be nonadaptive. It was also suggested that perhaps this variation allows for niche specialization in workers foraging at different temperatures: larger bees might be better suited to forage at cooler temperatures and smaller bees might be better suited to forage at warmer temperatures. This we tested here using a large, enclosed growth chamber, where we were able to regulate the ambient temperature. We found no significant effect of ambient or nest temperature on the average size of bees flying to and foraging from a suspended feeder. Instead, bees of all sizes successfully flew and foraged between 16°C and 36°C. Thus, large bees foraged even at very hot temperatures, which we thought might cause overheating. Size variation therefore could not be explained in terms of niche specialization for foragers at different temperatures.

No MeSH data available.