Do Offspring of Insects Feeding on Defoliation-Resistant Trees Have Better Biological Performance When Exposed to Nutritionally-Imbalanced Food?

Abstract

White spruce (Picea glauca (Moench) Voss) trees that are resistant or susceptible to spruce budworm (Choristoneura fumiferana (Clem.)) attack were identified in a southern Quebec plantation. Due to high mortality-induced selective pressures imposed by resistant trees on spruce budworm larvae, insects that survive on resistant trees exhibited greater biological performance than those on susceptible trees. We tested the hypothesis that this better biological performance is maintained across generations when progeny were subjected to nutritional stress. We collected pupae from resistant and susceptible trees (phenotype). Adults were reared under controlled laboratory conditions. Progeny were subsequently reared on two types of artificial diet (high vs. low quality). Low quality diet simulated food quality deterioration during outbreak conditions. Results confirmed that surviving insects collected from resistant trees have better performance than those from susceptible trees. Offspring performance (pupal mass, developmental time) was affected only by diet quality. These results suggest that adaptive advantages that would be acquired from parents fed on resistant trees are lost when progeny are exposed to nutritionally-imbalanced food, but the effects persist when larvae are fed a balanced diet. Offspring mortality, fecundity and fertility were positively influenced by parental origin (tree phenotype).