Modeling cold tolerance in the mountain pine beetle, Dendroctonus ponderosae.

Area of Science:

• Ecology
• Entomology
• Climate Change Biology

Background:

• Cold-induced mortality is a primary driver of mountain pine beetle (Dendroctonus ponderosae) population dynamics.
• The supercooling point (SCP) quantifies acute cold exposure mortality in this species.
• SCP and mortality rates vary significantly throughout the beetle's life cycle, particularly around winter.

Purpose of the Study:

• To develop a mechanistic model predicting mountain pine beetle supercooling point (SCP) distribution.
• To link SCP fluctuations to temperature-dependent cold hardening and dehardening processes.
• To understand how seasonal and geographic climate variations influence beetle cold tolerance.

Main Methods:

• Utilized field-collected Dendroctonus ponderosae larvae SCP data across the developmental season.
• Incorporated phloem temperatures and a three-state insect model (feeding, intermediate, cold-hardened).
• Modeled daily changes in cold tolerance gain and loss rates based on temperature variables.

Main Results:

• The model accurately predicts SCP distribution and cold-induced mortality, aligning with field and lab observations.
• Predicted cold tolerance variability across seasons and geographic locations based on local climate.
• Demonstrated that shifts between cold-hardened states are driven by temperature-dependent gain and loss rates.

Conclusions:

• The developed model provides a robust framework for understanding seasonal and geographic variation in mountain pine beetle cold tolerance.
• Findings highlight the importance of considering intra-seasonal and inter-annual climate variability in predicting beetle population dynamics.
• Emphasized the need to integrate this cold tolerance model with other biological models for comprehensive climate change impact assessments on Dendroctonus ponderosae.