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United States Department of Agriculture

Agricultural Research Service

Research Project: INSECT GENOMIC BIODIVERSITY AND MOLECULAR REGULATION OF DIAPAUSE Title: Effect of temperature on post-wintering development and total lipid content of alfalfa leafcutting bees

Authors
item O'Neill, Kevin -
item O'Neill, Ruth -
item Kemp, William
item Delphia, Casey -

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 23, 2011
Publication Date: August 1, 2011
Citation: O'Neill, K.M., O'Neill, R.P., Kemp, W.P., Delphia, C.M. 2011. Effect of temperature on post-wintering development and total lipid content of alfalfa leafcutting bees. Environmental Entomology. 40(4):917-930.

Interpretive Summary: The alfalfa leafcutting bee is the single most important commercial-scale pollinator of seed alfalfa in North America, and understanding the thermal environment of brood and adult bees is central to efficient and effective management of large populations of this species. Much of the previous work on the effects of temperature on alfalfa leafcutting bee post-wintering development has involved a relatively limited range of temperatures as well as simplified statistical models. In this study, we examined the effect of temperature on post-wintering development, in alfalfa leafcutting bee adults, by using a greater number of temperature treatments than used in previous studies (19 versus eight or fewer) and analytical tools formulated to model non-linear relationships between temperature and development in insects. We also tested the hypothesis that rearing temperature influences adult body lipid content at emergence, which could affect adult survival, establishment and performance as a pollinator, and reproductive success. We found that two of the non-linear models tested (Lactin-2 and Briere-2) provided the best fits to the data and generated reasonable estimates of upper (36-39°C) and lower (16-18°C) developmental thresholds and optimum (33-34°C) rearing temperatures for maximizing the rate of development. We also found that bees successfully emerged over a broad range of temperatures (22-35°C). However, variation in the rate of development among individuals reared at the same temperature was lowest at 31-33°C. With respect to adult condition, we found that the optimum rearing temperature to maximize the proportion of body lipids was 27-29°C. Our results expand upon previous findings and contribute to our understanding of designing practical rearing guidelines that simultaneously maximize development rate, survival, and adult condition, while synchronizing adult emergence with alfalfa bloom.

Technical Abstract: Temperature plays an important role in effective management of the alfalfa leafcutting bee (Megachile rotundata L.), the major commercial pollinator of seed alfalfa (Medicago sativa L.) in North America. Previous studies of the effects of temperature on post-wintering development of M. rotundata have been limited by the range of temperatures examined and by the use of linear regression models to describe non-linear relationships. To improve our understanding of threshold and optimum rearing temperatures of M. rotundata, we examined the effect of temperature on post-wintering development using a greater number of temperature treatments than used in previous studies (19 versus eight or fewer) and analytical tools formulated to model non-linear relationships between temperature and development in insects. We also tested the hypothesis that rearing temperature influences adult body lipid content at emergence, which could affect adult survival, establishment and performance as a pollinator, and reproductive success. We found that the Lactin-2 and Briere-2 models provided the best fits to the data and, based on our observations, gave reasonable estimates of upper (36-39°C) and lower (16-18°C) developmental thresholds and optimum (33-34°C) rearing temperatures for maximizing the rate of development. We also found that bees successfully emerged over a broad range of temperatures (22-35°C). However, variation in the rate of development among individuals reared at the same temperature was lowest at 31-33°C. With respect to adult condition, we found that the optimum rearing temperature to maximize the proportion of body lipids was 27-29°C. Our results are discussed in relation to previous findings and speak to the difficulties in designing practical rearing guidelines that simultaneously maximize development rate, survival, and adult condition, while synchronizing adult emergence with alfalfa bloom.

Last Modified: 12/20/2014
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