Increasing intraspecific plant chemical diversity at plot and plant level affects herbivorous, predatory, and pollinating arthropod communities

Plant chemistry mediates interactions between plants and their environment. While intraspecific chemodiversity at the plant level is well-studied, the effects of groups of plants differing in chemistry on interactions need more attention. To test how intraspecific chemodiversity affects plant-arthropod interactions, we manipulated plots of Tanacetum vulgare L., differing in chemotype richness and composition. Over three seasons, we monitored four arthropod groups (herbivores, flower visitors, predators, and ants). We hypothesized that higher plot-level chemotype richness enhances occurrence across all studied arthropod groups and that the effect on abundance would be negative for herbivore and ant abundance and positive for flower visitors and predators. Mixed models revealed that with increasing plot-level chemotype richness, herbivore abundance decreased, flower visitor abundance increased, and predatory arthropods and ants remained largely unaffected. Specific chemotypes influenced community assembly within arthropod groups over time, emphasizing that plant chemical diversity shapes insect communities and contributes to ecosystem dynamics.