|BENNETT, MEGHAN - North Dakota State University|
|Rinehart, Joseph - Joe|
|GREENLEE, KENDRA - North Dakota State University|
Submitted to: Journal of Experimental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2018
Publication Date: 5/1/2018
Citation: Bennett, M.M., Rinehart, J.P., Yocum, G.D., Greenlee, K.J. 2018. Cues for cavity nesters: investigating relevant zeitgebers for emerging leafcutting bees, Megachile rotundata. Journal of Experimental Biology. 221(10):jeb175406. https://doi.org/10.1242/jeb.175406.
Interpretive Summary: Animals rely on cues to synchronize their biological rhythms to daily and seasonal fluctuations of the environment. We know very little about what cues pollinators are using to synchronize adult emergence, which is important for mating and resource availability. The alfalfa leafcutting bee, Megachile rotundata is a major pollinator used in commercial farming, and it is unknown how bees know what time to emerge. We examined how emerging bees respond to temperature cues, because we hypothesize these are important due to their development within a light restricted nest and cavity. We found that bees are highly sensitive to temperature fluctuations, and we have evidence that these fluctuations interact with their biological rhythm pathways. Furthermore, M. rotundata can quickly respond to a changing environment. This knowledge is crucial for understanding how emergence is mediated by the environment when animals develop in darkness. The majority of wild bee species share a similar life history; thus this study was crucial to better understanding how emergence of pollinators is mediated.
Technical Abstract: Emerging insects rely on external cues to synchronize themselves with the environment. Thermoperiod has been identified as an important cue and may be important for insects that emerge from light-restricted habitats. The alfalfa leafcutting bee, Megachile rotundata, a cavity-nesting bee, undergoes development within a brood cell inside a cavity. Emerging M. rotundata respond to a thermoperiod, but it is unclear if the thermoperiod interacts with circadian feedback loops. To determine how a thermoperiod mediates emergence, we exposed emerging bees to changing conditions and measured emergence rhythms in response. We observed free-running emergence rhythms after exposure to a thermoperiod. Furthermore, how quickly bees can respond to thermal changes and how sensitive they are to the environment is unknown. When environmental conditions were switched during bee emergence, bees responded to that change within one day. We found emerging bees were sensitive to increases in temperature, entraining to slow (0.33°C) temperature ramp speeds. Together these data suggest that M. rotundata have underlying circadian mechanisms that can be synchronized by daily fluctuations in temperature. The response and sensitivity to a thermoperiod imply that M. rotundata evolved temperature-mediated oscillators.