In fact, climate change can accelerate the spread of these insects, which can reduce ecosystem resilience and negatively impact biodiversity. One example of a destructive insect species is the eastern spruce budworm (SBW), a moth native to North America that has huge impacts on the coniferous forests of Canada. The population of SBW shows large oscillations, and large-scale outbreaks that occur approximately every 60 years, causing major economic and ecological damage in eastern North American boreal forests. Recent work indicates that a key driver of population outbreaks are dispersal dynamics – yet the mechanisms behind the dispersal process (e.g., weather, behaviour, physiology) are only partially understood, in part due to lack of fine scale data on their dispersal trajectories. Professor Clément Bataille’s group has entered into a partnership with the Invasive Species Centre, which will generate new methods and data that will investigate the dispersal of this insect in eastern Canada.
How do researchers go about tracking the spruce budworm? The answer lies in the main food source of the moths, which is usually balsam fir needles as well as any spruce needles. Depending on their location, these trees contain different proportions of isotopes (isotopes are different forms of an element with different masses). Depending on the local geology or climate, trees retain this isotope “fingerprint”, which is then incorporated into the tissues of the spruce budworm that consumes the needles. The variation of isotope composition across the landscape can be mapped on the landscape using machine-learning statistical approaches. For example, maps predicting strontium isotope variations are produced using variations in the underlying bedrock geology whereas those predicting hydrogen isotopes are based on modeling the water cycle. Once these maps are created, researchers can analyze the isotopes of hydrogen, strontium and sulfur in the moth tissues. The isotope composition in the moth tissues reflects the location where the larvae grew up. By comparing the isotope in the moth tissue with that of the isoscape, the researchers can identify the place of natal origin of these moths. The location of natal origin is key to understand dispersal strategy, pathways, and infestation stage.
More broadly, all methods and data generated by this project will be shared with the Invasive Species Centre and the Healthy Forest Partnership, and through them, with other potential end-users. The ultimate applied goal of this project is to allow early intervention strategies to limit infestation and to develop preventive approaches to protect the boreal forest.
