Polystyrene seedling trays used as substrate by native plants.

Among polymers, expanded polystyrene (EPS) is increasingly abundant as a form of anthropogenic litter in natural environments, particularly along waterways. Nevertheless, there is still no research focusing on the interaction between this type of litter and biodiversity components. In this note, we reported the first evidence of an interaction between EPS and living native plants along an artificial drainage channel in a land reclaimed area of Tyrrhenian central Italy. We sampled a number of EPS seedling trays, deriving from agricultural activities, obtaining evidence for an interaction between this polymer and plants: on a total of 231 available seedling holes, 16.88% have been occupied from six species (Lycopus europaeus, Poa cfr. trivialis, Stachys palustris, Silene sp., Phragmites australis, Parietariajudaica). The set of species occurring on floating polystyrene trays appears comparable to that occurring on the sides of the land reclaimed channels (locally, L. europaeus and S. palustris are among the most common species of the riverine vegetation). Therefore, it is very probable that floating trays are a random sample of the seed rain of the vegetation of the sides of the channels. However, more research is needed to assess if the plant assemblage growing on EPS is random process or if peculiar substrate exerts some sort of selection on the plant community.