Conserved herbivore-induced volatile signalling despite divergent VOC-life-history associations in two locally adapted Arabidopsis thaliana populations

O_LIVolatile organic compounds (VOCs) mediate plant-plant signalling and may contribute to phenotypic differentiation among populations. However, the extent to which VOC-mediated signalling varies among locally adapted populations, and how VOC traits relate to major fitness-related traits, remain poorly understood. C_LIO_LIWe conducted a greenhouse experiment using two genetically and phenologically divergent Iberian populations of Arabidopsis thaliana. Plants were exposed to herbivory by Spodoptera exigua, after which we quantified herbivore-induced VOC emissions, VOC-mediated signalling effects on neighbouring conspecifics, and relationships between VOC traits, flowering time, and seed germination. C_LIO_LIHerbivory altered VOC composition, but overall VOC profiles remained broadly similar between populations despite strong divergence in life-history strategies, constitutive resistance to herbivory, and genetic structure. In contrast, correlations between VOC traits and fitness-related traits differed between populations and herbivory treatments. Nevertheless, receiver plants from both populations exhibited reduced herbivore damage after exposure to herbivore-induced emitters, indicating conserved VOC-mediated signalling. C_LIO_LIOur results suggest that herbivore-induced volatile signalling may represent a relatively conserved component of plant defence across locally adapted populations. In contrast, relationships between VOC traits and life-history variation may reflect population-specific integration of defence and fitness-related traits. C_LI