Overfertilization alters the ecological interactions and floral morphology in peri-urban environment

Abstract

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. But, how might these processes of overfertilization impact flora and fauna within urban ecosystems? In our experiment, we employed elevated nitrogen concentrations to simulate terrestrial eutrophication in Nicotiana tabacum. We assessed the floral morphology through geometric morphometrics and quantified the nectar volume and the concentration of solutes. Subsequently, we investigated the impact of these modifications on herbivory and pollination interactions in a peri-urban setting. Overfertilization resulted in notable modifications to the floral shape of the lobes, along with a significant increase in herbivory rates due to chewing insects and daily pollination rates. However, we observed that herbivory intensity in fertilized plants and reduction in leaf size at the end of the experiments were not directly correlated with the overall pollination rate per plant. Furthermore, our findings indicate that the daily pollination rates were influenced by overfertilization. However, this increase was not attributed to the energetic content of nectar (including volume, concentration, and energy), but probably to other factors, such as the presence of nitrogen compounds in the nectar. 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 under potential terrestrial eutrophication scenarios.