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ARS Home » Pacific West Area » Pullman, Washington » Animal Disease Research Unit » Research » Publications at this Location » Publication #426419
Research Project: Identifying Effective Immune Responses and Vaccine Development for Bovine Anaplasmosis

Location: Animal Disease Research Unit

Title: High thermal tolerance in high-elevation species and laboratory-reared colonies of tropical bumble bees

Author
item GONZALEZ, VICTOR - University Of Kansas
item Oyen, Kennan
item AGUILAR, MARLENE - New Granada Military University
item HERRERA, ANDRES - University Of Kansas
item MARTIN, RUBEN - New Granada Military University
item OSPINA, RODULFO - National University Of Colombia

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2022
Publication Date: 12/30/2022
Citation: Gonzalez, V.H., Oyen, K.J., Aguilar, M.L., Herrera, A., Martin, R.D., Ospina, R. 2022. High thermal tolerance in high-elevation species and laboratory-reared colonies of tropical bumble bees. Ecology and Evolution. 12(12). Article 9560. https://doi.org/10.1002/ece3.9560.
DOI: https://doi.org/10.1002/ece3.9560

Interpretive Summary: Little is known about the thermal tolerance of tropical bees. Bumble bees are in decline and one explanation is that environmental temperatures exceed the tolerance of bees. To test this, we measured bumble bee thermal tolerance from warmer and cooler regions across an altitudinal gradient. We found that heat tolerance was invariant between populations and cold tolerance decreased with decreasing environmental temperatures. This matches other studies and suggests that other aspects besides temperature may impact bumble bee populations in the tropics.

Technical Abstract: Bumble bees are key pollinators with some species reared in captivity at a commercial scale, but with significant evidence of population declines and with alarming predictions of substantial impacts under climate change scenarios. While studies on the thermal biology of temperate bumble bees are still limited, they are entirely absent from the tropics where the effects of climate change are expected to be greater. Herein, we test whether bees' thermal tolerance decreases with elevation and whether the stable optimal conditions used in laboratory-reared colonies reduces their thermal tolerance. We assessed changes in the lower (CTMin) and upper (CTMax) critical thermal limits of four species at two elevations (2600 and 3600'm) in the Colombian Andes, examined the effect of body size, and evaluated the thermal tolerance of wild-caught and laboratory-reared individuals of Bombus pauloensis. We also compiled information on bumble bees' thermal limits and assessed potential predictors for broadscale patterns of variation. We found that CTMin decreased with increasing elevation, while CTMax was similar between elevations. CTMax was slightly higher (0.84°C) in laboratory-reared than in wild-caught bees while CTMin was similar, and CTMin decreased with increasing body size while CTMax did not. Latitude is a good predictor for CTMin while annual mean temperature, maximum and minimum temperatures of the warmest and coldest months are good predictors for both CTMin and CTMax. The stronger response in CTMin with increasing elevation, and similar CTMax, supports Brett's heat-invariant hypothesis, which has been documented in other taxa. Andean bumble bees appear to be about as heat tolerant as those from temperate areas, suggesting that other aspects besides temperature (e.g., water balance) might be more determinant environmental factors for these species. Laboratory-reared colonies are adequate surrogates for addressing questions on thermal tolerance and global warming impacts.