Effects of biodiversity on plant chemical profiles and its eco-evolutionary significance

The rapid decline of global biodiversity raises urgent concerns about its causes and ecological impacts. Beyond reducing species richness, biodiversity loss can disrupt ecological interactions. This thesis investigates how plant metabolic profiles are shaped by the plant diversity of the surrounding community and proposes a framework to further reveal their ecological and evolutionary functions, such as mediating species interactions and driving co-evolutionary dynamics in diverse communities. Using an eco-metabolomic approach that combines targeted and untargeted analyses of volatile and non-volatile compounds in Plantago lanceolata, we integrated long-term field experiments with greenhouse studies to disentangle the complex environmental and evolutionary drivers shaping plant metabolic profiles. The results show that plant diversity shapes both community-level VOC emissions and the VOC profiles of focal plants, and also influences the overall metabolome, with contrasting responses between volatile and non-volatile compounds. These patterns reflect both phenotypic plasticity and adaptation, which strengthen as plant and soil communities mature, highlighting the importance of shared community history in addition to species richness. Finally, this thesis shows that the establishment of P. lanceolata across ranges far from its native origin leads to metabolomic changes and that environmental factors at the origin of the population also play an important role in shaping these responses. Individuals from introduced ranges maintain or even enhance their chemical defences against generalist herbivores, suggesting that plant metabolic changes may contribute to the establishment of P. lanceolata across the world. Overall, this work demonstrates that plant metabolic profiles are shaped by both immediate community context and long-term eco-evolutionary dynamics, advancing our understanding of plant metabolic trait variation in a changing world.