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Using semiochemicals to predict biotic resistance and facilitation of invading phytophagous insects
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Isitt, Rylee; Økland, Bjørn; Krokene, Paal; Sweeney, Jon; Heard, Stephen; Pureswaran, Deepa — 2022-10-14 <p>Invasive species are leading causes of biodiversity loss and economic damage. Allocating limited resources towards prevention and management of invasions requires risk assessments based on ecological knowledge for species of potential concern. Interactions of potentially invasive species with heterospecifics in a novel community will contribute to biotic resistance and facilitation experienced by the invader, and thus the likelihood of establishment. To experimentally predict heterospecific interactions, we conducted field experiments using synthetic aggregation-pheromone lures to measure the response of ecologically relevant species (possible predators, competitors, and facilitators) to the simulated presence of two potentially invasive spruce bark beetles, the North American <em>Dendroctonus rufipennis</em> (tested in Norway) and the European <em>Ips typographus</em> (tested in eastern Canada). The Canadian beetle community responded strongly to <em>I. typographus</em> lures, suggesting potential for considerable biotic resistance, whereas <em>D. rufipennis</em> lures prompted little response by the Norwegian beetle community. <em>D. rufipennis</em> was attracted to <em>I. typographus </em>lures, suggesting potential facilitation between these species through cooperative mass attack on trees. Our findings will inform invasive-species risk assessments for <em>I. typographus</em> and <em>D. rufipennis</em> and highlight useful methods for assessing interactions among other taxa that rely heavily on semiochemical communication.</p>
Concordia Spectrum Research Repository Translation missing: fr.blacklight.search.logo
Improved performance of the eastern spruce budworm on black spruce as warming temperatures disrupt phenological defenses
Bellemin-noel, Bastien; Bourassa, Stéphane; Despland, Emma; De Grandpré, Louis; Pureswaran, Deepa — 2020-12-21 Phenological shifts, induced by global warming, can lead to mismatch between closely interacting species. The eastern spruce budworm, Choristoneura fumiferana, an important outbreaking insect defoliator in North America, mainly feeds on balsam fir, Abies balsamea, which has historically been well synchronized with the insect. But as climate change pushes the northern range limit of the budworm further north towards the boreal forest, the highly valuable black spruce, Picea mariana, historically protected against the budworm by its late budburst phenology, is suffering increased defoliation during the current outbreak. We tested the hypothesis that rising temperatures can lead, not to a mismatch, but to an improved match between the budworm and black spruce through differential phenological advancement. For three years, eastern spruce budworm larvae were reared from instar 2 to pupae, on both black spruce and balsam fir, in a temperature free-air enhancement experiment (T-FACE) consisting in 24 field plots, half of which were heated at +2°C from March to October. Our results show that every year, larval development was faster on heated trees and pupation was earlier than on unheated trees. Bud development was also accelerated in heated trees of both species. However, there was no difference in mass between pupae that developed at +2°C and controls at the end of the season. Finally, we found no difference either in development rate or pupal mass between larvae reared on black spruce and those reared on balsam fir. This suggests that under higher temperature eastern spruce budworm will be as successful on black spruce as on balsam fir, as black spruce budburst becomes better synchronized with the insect’s emergence from diapause. This could lead to critical changes in outbreak dynamics and severity with important ecological state shifts at the landscape level.

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(auteur : Pureswaran, Deepa)

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