Diapause survival requires a temperature-sensitive preparatory period

Area of Science:

• Insect physiology
• Ecology
• Environmental science

Background:

• Diapause is a crucial survival strategy for insects facing environmental stress.
• Cold-adapted insects like the Eastern spruce budworm (Choristoneura fumiferana) initiate diapause before winter, but early fall temperatures can negatively affect energy reserves and survival.
• Understanding the impact of pre-diapause conditions is vital for predicting insect population dynamics.

Purpose of the Study:

• To investigate how fall temperature and duration influence diapause initiation and overwintering survival in Eastern spruce budworm larvae.
• To identify the metabolic changes associated with different fall conditions.
• To determine the optimal fall conditions for maximizing post-diapause survival.

Main Methods:

• Second instar larvae of Choristoneura fumiferana were subjected to a factorial design of varying fall temperatures (10-25°C) and exposure durations (1-10 weeks).
• Metabolite levels (glycogen, glycerol, protein) were measured before and during diapause.
• Post-diapause survival was assessed by quantifying adult emergence.

Main Results:

• Extended exposure to warm fall temperatures led to significant depletion of larval glycogen stores.
• Both prolonged warm conditions and short, cool fall periods negatively impacted post-diapause survival.
• Optimal fall conditions for survival involved a balance between temperature and exposure duration.

Conclusions:

• Fall environmental conditions have profound fitness consequences for overwintering insects.
• Early diapause onset in Choristoneura fumiferana may be linked to a temperature-sensitive process essential for successful overwintering.
• These findings are critical for understanding insect resilience to climate change and for pest management strategies.