Format: ORAL

Miquel Cap1, Antoni J. Far2, Pere M. Mir-Rossell2,3, Carles Cardona3,4, Brigida Fernndez de Simn5, Ramn Perea1, Ismael Aranda5, Jaume Flexas2, Marc Carriqu2,5

1 Plant and Animal Ecology Lab. Centro para la Conservación de la Biodiversidad y el Desarrollo Sostenible. Departamento de Sistemas y Recursos Naturales, Universidad Politécnica de Madrid, 28040, Madrid, Spain. 2 Grup de recerca en Biologia de les Plantes en Condicions Mediterrànies, Departament de Biologia, Universitat de les Illes Balears, Institut d'Investigacions Agroambientals i d'Economia de l'Aigua (INAGEA), 07122 Palma, Illes Balears, Spain 3 Grup d’Ecologia Interdisciplinar, Departament de Biologia, Universitat de les Illes Balears, 07122, Palma, Spain 4 Centre Forestal de les Illes Balears (CEFOR-Finca de Menut), Institut Balear de la Natura, C/Gremi de Corredors 10 (Polígon Son Rossinyol), 07009, Palma, Spain 5 Instituto de Ciencias Forestales (ICIFOR-INIA), CSIC, Carretera de La Coruña k.m. 7.5, 28040, Madrid, Spain

Plant responses to herbivory play a crucial role in maintaining ecosystem functionality. While a trade-off between resistance and tolerance to herbivory has been theorized, recent studies challenged this dichotomy, as they showed that species might possess in-between behaviour. Additionally, the study of enemy release processes suggests that plant responses to herbivory ameliorate after herbivore disappearance. Based on these premises, we set an experiment with the non-palatable insular-endemic shrub Hypericum balearicum to assess its capacity to respond to herbivores. We conducted a comprehensive assessment of real herbivore interaction with H. balearicum in natural areas and examined plant responses following simulated herbivory. For this, we cultivated H. balearicum individuals at the Forestal Centre of the Balearic Islands. From all, we planted 90 in each of two natural areas inhabited by feral goats and sheep. To isolate the impact of herbivores, half of the plants at each site were excluded. Simultaneously, 90 individuals were maintained in a plant nursery for a simulated experiment involving two induced herbivory treatments: moderate and severe. After 45 days, we measured various physiological, biochemical and growth parameters associated with herbivory response. Plants in natural areas showed no signs of herbivore predation, indicating an absence of herbivory on this species. Nevertheless, the response capacity remained evident. Following induced herbivory, we observed maintained net photosynthesis but increased chlorophyll concentration, specific leaf area and Root:Shoot ratio in response to increasing treatment intensity. Severe herbivory simulation induced oxidative stress, and variations in the concentration of 47 leaf secondary compounds were reported across all treatments. Our findings challenge the conventional notion that resistant plants lack mechanisms to respond after herbivory when evolutionary pressures are absent. This study underscores the importance of considering historical factors, such as the presence of extinct herbivores or traits originated by exaptation, in the assessment of plant-herbivore interactions.