Potential impacts of climate change on the phenological synchrony between a consumer and its resource: The example of the spruce budworm and its tree host

Sebastien Portalier, Biology, University of Ottawa, Montreal, QC, Canada, Jean-Noël Candau, Natural Resources Canada, ON, Canada and Frithjof Lutscher, Department of Mathematics and Statistics, University of Ottawa, Ottawa, ON, Canada

Background/Question/Methods
The ongoing anthropogenic climate change increasingly affects species phenology. Especially, the resting period, when organisms remain inactive during part of the year, is often driven by temperature. In the case of a consumer and a resource, the synchrony of the end of their respective resting period is fundamental for the persistence of their interaction. Since the consumer and its resource are likely to respond differently to a change in temperature regime, the synchrony between them will likely be altered. However, a mechanistic approach that investigates the effects of climate change on the phenological synchrony of consumer – resource systems is still missing. In this study, we propose a general theoretical model that determines the duration of the resting period according to temperature, and its effects on synchrony or mismatch between phenological stages of two interacting species. We then illustrate our approach using the spruce budworm – balsam fir system in Eastern Canada as a case study.
Results/Conclusions
We found that an increase in temperature would usually advance phenology. However, the effects of a warm or cold spell during the resting period would strongly vary according to the time and the duration of the spell for a given species. Depending on the way each species reacts to the same temperature shift, the mismatch between the consumer and its resource may increase or decrease. For the spruce budworm – balsam fir system, our model predicts that an increase in temperature may increase the mismatch between the insect and the tree in Southern sites, but may increase the synchrony in Northern sites. This kind of modelling approach is of primer importance to investigate potential effects of climate change on consumer – resource systems. Among ecological interactions, consumer-resource relationships are fundamental to the functioning of terrestrial and marine ecosystems. The study of synchrony between interacting species is fundamental to predict future species distribution.