Meeting Abstract
Organisms live in complex worlds where environmental stresses can be more or less intense, occur for longer or shorter periods, and repeat more or less frequently. Yet while single stress events have been well-studied, the physiological and fitness effects of these more complex patterns of stress are not well understood. The eastern spruce budworm, Choristoneura fumiferana, is an important forest pest of the boreal forest and previous studies have shown the importance of low temperature stress in regulating its population and range. In this study we manipulated the number of low temperature exposures budworm received, while controlling the intensity and total length of time of exposure. We found that while spruce budworm that received repeated low temperature events had significantly greater cryoprotectant content (at a cost to glycogen reserves), survival to eclosion was significantly impacted. We also examined transcriptomic responses to low temperature stress, and found that while only a few transcripts were significantly differentially regulated following a single low temperature stress event, hundreds were differentially regulated following repeated low temperature stresses. These included transcripts for antifreeze proteins, several heat shock proteins, and electron transport chain proteins. We also modelled the spatial distribution of spruce budworm and found that species range was significantly impacted by retaining terms related to number of cold stress events. These results suggest that current studies that focus on single stress events may be missing the full range of potential stress responses, and that fluctuating stress may be an important determinant of species ranges.
