Temperature affects phenological synchrony in a tree-killing bark beetle

Area of Science:

• Ecology
• Entomology
• Population Dynamics

Background:

• Phenological synchrony can enhance population growth in species exhibiting positive density dependence.
• Life stage-specific thermal thresholds for development can promote synchrony under fluctuating temperatures.
• The southern pine beetle (Dendroctonus frontalis) shows shifts in abundance at its northern range limits.

Purpose of the Study:

• To test if cooler winter temperatures in the northern range of the southern pine beetle converge its life stage structure, synchronizing spring flight.
• To understand the role of temperature variation in the phenological synchrony of insect populations.

Main Methods:

• In situ laboratory experiments to determine thermal thresholds for southern pine beetle development.
• Development rate modeling to simulate population convergence under different thermal regimes.
• Field trapping of wild southern pine beetles to assess spring flight synchrony across geographic locations.

Main Results:

• Laboratory experiments revealed a higher thermal threshold for pupation than larval development, with cooler temperatures synchronizing larval development and adult emergence.
• Development rate models indicated population convergence at the late larval stage under northern temperatures, but not southern or null models.
• Field trapping showed greater spring flight synchrony in New Jersey compared to Georgia and Mississippi, consistent with cooler winter temperatures.

Conclusions:

• Cooler winter temperatures in northern regions can lead to phenological synchrony in southern pine beetle emergence.
• This synchrony creates positive feedback loops, potentially increasing the frequency and intensity of southern pine beetle outbreaks in northern pine forests.
• Understanding thermal influences on insect development is crucial for predicting population dynamics and outbreak potential.