Phenolic content of invasive and non-invasive emergent wetland plants

• Invasive plants were associated with higher soil nutrients and fewer neighboring species.
• Foliar phenolic concentrations (FPC) varied seasonally for invasive wetland plants.
• FPC did not differ between noninvasive and invasive wetland plants.
• FPC of closely related Typha species responded to different environmental factors.
• Nutrient availability may lead to lower phenolic content in fast growing species.

Secondary chemical production is a potential mechanism of invasive plant success, but little is known about the prevalence of these compounds in wetland species. High concentrations of phenolic compounds, with their diverse functionality, may confer an advantage to plants in response to environmental conditions. We surveyed 19 plant species from ten sites in New York State and explored the relationship between foliar phenolic content (FPC), soil nitrogen, soil phosphorus, herbivory, neighboring plant cover, and sampling date. We also evaluated the responsiveness and variability of FPC between Typha latifolia and T. angustifolia by manipulating nutrient availability and herbivore pressure in the field. We found no consistent difference in FPC between invasive and non-invasive species and no relationship with environmental factors for non-invasive plants. However, invasive plants differed significantly among sites, suggesting spatial variability is influenced by local environmental factors. Sampling date, soil nutrients and herbivory were among the most important predictive factors for FPC in invasive populations of T. latifolia, T. angustifolia, L. salicaria and P. arundinacea, implying plasticity for some invaders. Although nutrient availability was negatively associated with FPC for some Typha species, we failed to reproduce this effect in our manipulative experiment. Generalities regarding intra- and interspecific differences in phenolic compound production in wetland plants and their role in invasion success remain elusive. However, our work provides a comprehensive accounting of relative FPC in wetland plants and its relationship to environmental variation that serves as a foundation for future manipulative studies.