Variation in complex semiochemical signals arising from insects and host plants

Area of Science:

• Chemical Ecology
• Insect Behavior
• Forest Entomology

Background:

• Insect chemical communication relies on signals from both insects and plants.
• Understanding variation sources is crucial for evolutionary theory and pest management.
• Pine engraver beetles (Ips pini) use complex chemical signals for communication.

Purpose of the Study:

• To investigate variation in chemical signaling of pine engraver beetles at multiple scales: host tree, tree-within-host, and beetle-on-tree.
• To analyze the sources of variation in monoterpene and pheromone volatile profiles.
• To assess the implications of this variation for behavioral ecology.

Main Methods:

• Studied Ips pini tunneling in jack, red, and white pines.
• Utilized linear mixed-effects models to analyze chemical profiles.
• Determined volatile profiles using gas chromatography.

Main Results:

• White pine phloem had the highest monoterpene concentration, but beetles produced lower monoterpene-to-pheromone ratios.
• Beetle-to-beetle variation in plume composition was substantially greater (2-9 times) than inter-tree variation.
• Stereoisomeric ratios of the pheromone ipsdienol were consistent, with variation primarily at the beetle level.

Conclusions:

• Variation in chemical plumes is largely driven by individual beetle differences rather than host tree species.
• Significant beetle-to-beetle variation in pheromone plumes has implications for communication strategies, including cheating and predator avoidance.
• Findings highlight the importance of considering individual variation in insect chemical ecology research.