Phenotypic variation in food utilization in an outbreak insect herbivore

Area of Science:

• Ecology
• Evolutionary Biology
• Insect Science

Background:

• Nutrition profoundly influences insect evolution by shaping phenotypic traits.
• Understanding how nutritional conditions affect additive and nonadditive phenotypic components is crucial for evolutionary insights, especially in outbreaking insect populations.

Purpose of the Study:

• To investigate the additive and nonadditive variation in food utilization traits of the spruce budworm (Choristoneura fumiferana).
• To assess the impact of chronic nutritional stress on these traits across three generations.

Main Methods:

• 160 full-sib families of spruce budworm were reared under laboratory conditions on high and low-energy diets for three generations.
• Key traits measured included pupal mass, consumption rate (RCR), growth rate (RGR), approximate digestibility (AD), efficiency of conversion of digested food (ECD), and efficiency of conversion of ingested food (ECI).

Main Results:

• All tested food utilization traits exhibited a high proportion of nonadditive genetic effects influencing phenotype expression.
• Significant family × diet interactions were observed for pupal mass, RGR, and ECD, with these traits also showing the highest heritability.
• No maternal effects were detected.

Conclusions:

• Food utilization traits in spruce budworm may evolve via epigenetic mechanisms, including phenotypic plasticity.
• Findings offer valuable data for ecological models aiming to improve population dynamics forecasts for this pest insect.