Leaf toughness as a mechanism of defence against spruce budworm

Fuentealba, Álvaro; Sagne, Solène; Legendre, Gaspar; Bauce, Éric; Despland, Emma

doi:10.1007/s11829-020-09761-w

Cited by 12 publications

(18 citation statements)

References 46 publications

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“…Ontogenetic changes in foliage quality thus limit the period when the foliage is suitable for herbivorous insects, promoting tight phenological host–herbivore relationships that define a window of opportunity [ 12 , 13 , 14 ]. The magnitude of these differences between young and old foliage defines the strictness of the window of opportunity for insect herbivores on evergreen trees [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

“…We first summarize past work on ontogenetic progression of defense traits in expanding white spruce foliage and highlight knowledge gaps for future research. Review of the literature highlights that toughness is one trait that has received relatively little attention, despite evidence for an important role in defense against the spruce budworm [ 15 ]. Therefore, we measured white spruce leaf toughness during the growing season in both expanding and mature foliage in order to improve understanding of the ontogenetic trajectory of mechanical defense during the window of opportunity for herbivores.…”

Section: Introductionmentioning

confidence: 99%

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Defensive Traits during White Spruce (Picea glauca) Leaf Ontogeny

Lirette

Despland

2021

Insects

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Changes during leaf ontogeny affect palatability to herbivores, such that many insects, including the eastern spruce budworm (Choristoneura fumiferana (Clem.)), are specialist feeders on growing conifer leaves and buds. Developmental constraints imply lower toughness in developing foliage, and optimal defense theory predicts higher investment in chemical defense in these vulnerable yet valuable developing leaves. We summarize the literature on the time course of defensive compounds in developing white spruce (Picea glauca (Moench) Voss) needles and report original research findings on the ontogeny of white spruce needle toughness. Our results show the predicted pattern of buds decreasing in toughness followed by leaves increasing in toughness during expansion, accompanied by opposite trends in water content. Toughness of mature foliage decreased slightly during the growing season, with no significant relationship with water content. Toughness of sun-grown leaves was slightly higher than that of shade-grown leaves. However, the literature review did not support the expected pattern of higher defensive compounds in expanding leaves than in mature leaves, suggesting that white spruce might instead exhibit a fast-growth low-defense strategy.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Defensive Traits during White Spruce (Picea glauca) Leaf Ontogeny

Lirette

Despland

2021

Insects

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“…In the present study, we provide evidence for the importance of phenological synchrony on the performance of an outbreaking defoliator of evergreen conifers. Under poor synchrony, spruce budworm on black spruce exhibits high mortality rates early in larval development because they are often unable to mine the foliage (Fuentealba et al, 2018) due to its toughness (Fuentealba et al, 2020), but those that do survive show similar performance as on balsam fir (Fuentealba et al, 2017). When insect and plant phenology are well synchronized, mortality on black spruce is no higher than on fir, and pupal mass and development time are similar (Fuentealba et al, 2017).…”

Section: Discussionmentioning

confidence: 99%

“…Black spruce budburst occurs later in the season (roughly 2 weeks after balsam fir) greatly extending the period of starvation of second‐instar larvae (Blais, 1957; Nealis & Régnière, 2004). Moreover, while waiting for new buds to open, young larvae are for the most part unable to mine mature black spruce needles from previous years due to their greater toughness than those of balsam fir (Fuentealba et al, 2020). Elevated levels of secondary metabolites have traditionally also been considered among black spruce's defences against defoliation, but these are mostly expressed in mature foliage (Fuentealba et al, 2017; Parent et al, 2020) such that they contribute to the window of opportunity for insect feeding.…”

Section: Introductionmentioning

confidence: 99%

Improved performance of the eastern spruce budworm on black spruce as warming temperatures disrupt phenological defences

Bellemin-Noël

Bourassa

Despland

et al. 2021

Global Change Biology

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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 into 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 3 years, eastern spruce budworm larvae were reared from instar 2 to pupae, on both black spruce and balsam fir, in a temperature free‐air controlled 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 regimes, 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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“…In addition, plant structural components of cell walls, cellulose and lignin, play essential roles in plant defenses as constitutive barriers. For instance, plant cellulose content can effectively predict plant defense traits (i.e., leaf toughness) and is negatively associated with some types of insect feeding, such as leaf miners ( Kitajima et al, 2012 ; Fuentealba et al, 2020 ). Therefore, understanding of how these phytochemicals affect invasive insect performance is critical in predicting invasive insect invasiveness.…”

Section: Introductionmentioning

confidence: 99%

Plant Chemistry Determines Host Preference and Performance of an Invasive Insect

et al. 2020

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Understanding how host plant chemistry affects invasive insects is crucial for determining the physiological mechanism of host use and predicting invasive insect outbreak and damage on hosts. Here, we examined the effects of plant nutrition and defensive chemicals on host preference and performance of adults and larvae of the invasive potato tuberworm, Phthorimaea operculella (Zeller; Lepidoptera: Gelechiidae), on four native (Solanum tuberosum, Nicotiana tabacum, Datura stramonium, and Solanum lycopersicum) and three new (Solanum melongena, Physalis alkekengi, and Lycium barbarum) host plants. We found that adults preferred to oviposit on S. tuberosum and N. tabacum leaves and the soil around these native host plants over other hosts. Larvae performed well on S. tuberosum and N. tabacum, reaching higher pupa weight and having better survival. Larvae performed poorly on S. melongena, S. lycopersicum, P. alkekengi, D. stramonium, and L. barbarum, with lower pupa weight and lower survival. Solanum tuberosum and N. tabacum had higher leaf soluble proteins than other plants and lower leaf total phenolics than S. lycopersicum, D. stramonium, and L. barbarum. Moreover, carbon content and soluble protein were positively associated with larval survival, while defensive traits (lignin and total phenolics) negatively affected larval survival. These findings provide insights into understanding of biochemical mechanisms of interactions between invasive insects and host plants, indicating the importance of considering plant chemistry when assessing invasive insect host use and damage.

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Leaf toughness as a mechanism of defence against spruce budworm

Cited by 12 publications

References 46 publications

Defensive Traits during White Spruce (Picea glauca) Leaf Ontogeny

Defensive Traits during White Spruce (Picea glauca) Leaf Ontogeny

Improved performance of the eastern spruce budworm on black spruce as warming temperatures disrupt phenological defences

Plant Chemistry Determines Host Preference and Performance of an Invasive Insect

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