Diversity of Volatile Emissions From Cork Oak: Quantity and Quality Vary Independently Across Its Range

Knowledge of the intraspecific variability of volatiles produced by plants is central for estimating their fluxes from ecosystems and for understanding their evolution in an ecological and phylogenetic context. Past studies suggested that volatile emissions from Cork oak (Quercus suber L.) exhibit a high degree of qualitative and quantitative polymorphism. However, the extent of inherent emission variability across its range is not known. We investigated leaf emissions, photosynthetic, and morphological traits of 241 Cork oak seedlings from ten provenances. To minimize environmental influences, emissions were determined at 30°C and saturating light on seed-grown saplings of similar age grown under the same conditions. All individuals, except for three apparent non-emitters, released the same five monoterpenes at a mean rate of 2559 ± 120 ng m^-2 s^-1. Northern provenances tended to develop more sclerophyllous leaves with higher emission rates and lower photosynthetic rates than southern populations, resulting in significant different carbon losses by emissions. Independently, the emission composition varied discontinuously among individuals according to three distinct chemotypes, indicating inherent differences in the activity of two types of monoterpene synthases: one producing α-, β-pinene and sabinene, and the other limonene. Chemotype frequencies differed among provenances, particularly between South-Eastern Mediterranean and South-Western Atlantic provenances. Regarding leaf traits, we found no differences between chemotypes. The study confirms that Cork oak is a strong emitter of monoterpenes, the quality and quantity of which vary independently within its range. A comparison of the emission variability with that of other oak species suggests that a Pinene/sabinene chemotype is the ancestral form within the oak subgenus Cerris, which diversified during species radiation. This diversification is less pronounced in Cork oak than in other sympatric oaks, likely due to differential fragmentation and expansion of their ranges in the past.