Effects of developmental state on low-temperature physiology of the alfalfa leafcutting bee, Megachile rotundata

Authors: BENNETT, MEGHAN - North Dakota State University; Debardlabon, Korie; Rinehart, Joe; Yocum, George; GREENLEE, KENDRA - North Dakota State University

Submitted to: Bulletin of Entomological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2021
Publication Date: 3/8/2023
Citation: Bennett, M.M., Debardlabon, K.M., Rinehart, J.P., Yocum, G.D., Greenlee, K.J. 2023. Effects of developmental state on low-temperature physiology of the alfalfa leafcutting bee, Megachile rotundata. Bulletin of Entomological Research. https://doi.org/10.1017/S0007485321001103.
DOI: https://doi.org/10.1017/S0007485321001103

Interpretive Summary: An insect’s ability to withstand low temperatures is called “cold tolerance.” Cold tolerance is difficult to quantity because it cannot be obtained by a single measure. Rather, a collective assessment of insect’s responses to cold must be collected to make inferences about its tolerance to cold. Although the alfalfa leafcutting bee, Megachile rotundata, is the most intensively managed solitary bee species, and cold temperatures are used extensively during their management, their cold tolerance has not yet been characterized. Researchers with the USDA-ARS Insect Genetics and Biochemistry Research Unit in Fargo, ND, in collaboration with researchers at the North Dakota State University, Department of Biology worked to fill this important knowledge gap. They characterized important thermal thresholds, below which bees rapidly succumbed, deciphered how responses to cold stress changed during development, and discovered that some injuries as a result of cold stress during early life stages were not seen until the bees became adults. This last result is of special importance because it demonstrates that how a bee is managed early in life can affect its ability to pollinate in the field. Taken together, these results provide critical information to develop improved management practices of commercially reared M. rotundata to improve both survival and eventual field performance.

Technical Abstract: Cold tolerance is difficult to measure because it requires multiple assessments of an insect’s physiology. Temperatures experienced during development can affect adult morphology and physiology. Less is known about how exposure to cold during development affects adult thermal performance. Sensitivity to low temperatures can vary across development. We found that cold exposure during development affects recovery from chill coma but not critical thermal minimum. Furthermore, we saw that cold tolerance varies across development with respect to supercooling point. The post-diapause quiescent stage was more tolerant to cold than stages in active development. Furthermore, assessing the presence of sub-lethal effects is essential to understanding the consequences of low temperatures during development. We observed some red-eye pupae who were exposed to cold resulted in adults with wing deformities. We comprehensively assessed cold tolerance using multiple assays and responses of adults to developmental cold stress.