Leaf trichomes affect caterpillar feeding in an instar-specific manner

Area of Science:

• Plant-insect interactions
• Chemical ecology
• Evolutionary biology

Background:

• Leaf trichomes are plant structures that deter insect herbivores through physical and chemical defenses.
• The impact of different trichome types on herbivore feeding at various developmental stages remains underexplored.
• Solanaceous species exhibit diverse trichome densities and types, offering a model for studying plant defense mechanisms.

Purpose of the Study:

• To investigate how caterpillar instar and leaf trichome type (glandular vs. non-glandular) influence feeding initiation by Manduca sexta.
• To assess the differential effectiveness of trichome types in deterring herbivory across early and later caterpillar developmental stages.
• To understand the role of trichome variation in Solanaceous species on herbivore host-plant selection.

Main Methods:

• Experimental study using 11 Solanaceous plant species with varying trichome characteristics.
• Controlled feeding trials with different instars of the specialist herbivore Manduca sexta.
• Quantification of feeding initiation success based on caterpillar instar and trichome type encountered.

Main Results:

• Non-glandular trichomes significantly deterred feeding initiation in first- and second-instar Manduca sexta caterpillars.
• Glandular trichomes showed less deterrence compared to non-glandular trichomes against early instar caterpillars.
• Neither glandular nor non-glandular trichomes significantly impacted feeding initiation by third-instar caterpillars.

Conclusions:

• Non-glandular trichomes are crucial deterrents for early-stage caterpillar feeding on Solanaceous plants.
• The defensive role of trichomes against Manduca sexta diminishes in later instars, suggesting post-initiation feeding factors are important.
• Trichome type and density variation influences herbivore behavior, with implications for plant defense evolution.