Defensive Traits during White Spruce (Picea glauca) Leaf Ontogeny

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 optim...

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Bibliographic Details
Published in:Insects (Basel, Switzerland) Switzerland), 2021-07, Vol.12 (7), p.644
Main Authors: Lirette, Antoine-Olivier, Despland, Emma
Format: Article
Language:English
Subjects:
Buds
Carbon
Chemical defense
Coniferous trees
Conifers
Feeders
Foliage
Growing season
Herbivores
herbivory
Insects
leaf defensive traits
leaf physical traits
Leaves
Literature reviews
Moisture content
Nitrogen
Ontogeny
Palatability
Phenology
Picea glauca
Pine needles
plant-insect interactions
Shade
spruce budworm
Toughness
Trees
Water content
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Summary: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.
ISSN:2075-4450
2075-4450
DOI:10.3390/insects12070644