Nitrogen overfertilization: Impact on ecological interactions and floral morphology in a peri‐urban environment

Abstract Nitrogen is a crucial element that affects plant metabolic processes and indirectly influences the structure and dynamics of ecological interactions in terrestrial ecosystems. Since the invention of the Haber–Bosch process, human activity has significantly influenced the amount of nitrogen released into the environment. However, how do these overfertilization processes affect flora and fauna in urban ecosystems? In our experiments, we used elevated nitrogen concentrations to simulate terrestrial eutrophication processes in Nicotiana tabacum L. We evaluated reproductive traits such as floral morphology using geometric morphometrics. Additionally, nectar volume and solute concentration, along with other vegetative traits, were quantified. Subsequently, the impacts of these modifications on herbivory and pollination interactions in a peri‐urban environment were measured. Overfertilization resulted in notable modifications to the floral shape of the lobes, as well as a significant increase in percentage of herbivory by chewing insects, without affecting floral visitation rates. We also observed that elevated herbivory on fertilised plants did not show a direct correlation with overall pollination rates per plant or seed set. In contrast, the reduction in leaf size during the second phase of the experiment, owing to overfertilization effects, affected seed production. The roles of potential pollinators and their influence on seed quantity in control plants are discussed. Nitrogen is a crucial element not only for plants in natural terrestrial ecosystems but also plays a fundamental role in the modification and shaping of reproductive and vegetative structures. Moreover, it affects the functionality of ecological interactions of pollination and herbivory in anthropogenic environments, such as peri‐urban areas.