Abstract
1. In the evolutionary arms race between plants and herbivores,
sophisticated mechanisms of indirect defense play a pivotal role. This
study investigated the intricate ecological dynamics between
Aristolochia contorta, Sericinus montela, and Ooencyrtus
spp., with a special focus on the role of volatile organic compounds
(VOCs) in plant. 2. This study utilized field surveys, olfactometer
experiments, and Gas Chromatography-Mass Spectrometry (GC-MS) analysis
to investigate the role of volatile organic compounds. 3. Field surveys
showed a 54.6% egg parasitism rate, with quadrats containing A.
contorta and larvae attracting more Ooencyrtus spp. than those
with the plant alone. In olfactometer bioassays, Ooencyrtus spp.
demonstrated a notable preference for leaves damaged by a pattern wheel,
attracting 46.8% of Ooencyrtus spp. compared to undamaged
controls. Moreover, leaves treated with larval saliva were found to be
similarly attractive, drawing in 48.7% of Ooencyrtus spp.. In
addition, the difference in attraction between leaves with and without
larval saliva did not reach statistical significance. GC-MS analysis
identified essential VOCs in the damaged leaves, including hexyl
acetate, cyclohexene, δ-cadinene, α-pinene, and β-caryophyllene.
Additionally, leaves treated with larval saliva revealed the presence of
exo-isocitral (0.61%), and β-pinene (0.14%), though in minimal
amounts. Despite these complex responses, our analysis suggests that the
compounds introduced or increased in concentration by larval saliva do
not significantly boost the attraction of Ooencyrtus spp. 4. This
finding implies that while the VOCs response to damage and saliva
application is multifaceted, serving multiple defensive functions, the
quantities of these saliva-induced compounds could be insufficient to
substantially influence the behavior of Ooencyrtus spp. towards
the damaged leaves. This research furthers our understanding of the
indirect defense strategies of plants, particularly highlighting the
vital roles of VOCs in A. contorta. Moreover, our findings
suggest new avenues for exploring the ecological and evolutionary roles
of chemical signals, shedding light on the complex interactions
facilitated by these chemical cues in plant defense mechanisms.