Species-Specific Recognition in Fig-Wasp Mutualism: The Role of Volatile Blends and Seasonal Shifts in Olfactory Responses.

Volatile organic compounds (VOCs) mediate host recognition in the obligate fig-fig wasp mutualism, but studies on the chemical mechanisms maintaining pollinator host specificity in sympatric, phylogenetically distant fig species remain scarce. We investigated two sympatric dioecious fig species from different subgenera: Ficus hispida (pollinated by Ceratosolen solmsi marchali), and Ficus hirta (pollinated by Valisia javana), integrating behavioral assays, GC-MS, and GC-EAD to distinguish physiological perception from behavioral outcome. Both fig wasp species were attracted to host VOCs but showed species-specific responses to non-host odors: V. javana actively avoided non-host volatiles, whereas C. solmsi marchali showed no preference. GC-MS identified 44 compounds in F. hispida and 47 in F. hirta, with significant interspecific divergence (PERMANOVA, p = 0.001) but minimal seasonal variation within F. hispida. GC-EAD revealed that C. solmsi marchali perceived 15 host compounds in spring and 12 in summer; V. javana perceived 8 in spring and 5 in summer. Both species consistently perceived Linalool and 1,8-Cineole, but these ubiquitous plant volatiles alone cannot explain host specificity. Instead, specificity is likely conferred by the specific ratios in which common compounds and host-unique volatiles are combined-for example Indole and (E, E)-Cosmene in F. hispida, and α-Cedrene epoxide in F. hirta. By distinguishing perception from behavior, we show that host fidelity is maintained through species-specific VOC blends, with seasonal modulation of olfactory sensitivity further shaping pollinator responses. These findings contribute to understanding chemical communication evolution under sympatry and seasonal environmental variability.