Composition and phylogenetic structure of Pampean grasslands under distinct land use and presence of alien species

Alien species can modify ecosystem functions and ecological processes in natural communities, and potentially become invasive. In the Brazilian Pampean grasslands, reports of changes in land use and invasions of alien plant species are becoming more frequent. This study aimed to investigate species composition and phylogenetic relationships between native and alien plants across four sites of Brazilian Pampean grasslands under distinct land uses (NOM: no agricultural management; GRZ: grazed pastures; AGR: agrarian crops; ROAD: roadside). The phylogenetic relationship between native and alien species was analyzed at two scales: inter-site (large scale) and intra-site (small scale). We found inter-site differences in phylogenetic diversity. Overall, across all sites we found random phylogenetic relationships among alien and native species. In the most disturbed site (ROAD) we found significant phylogenetic clustering among all species (alien and natives), while at the small scale, clustering was only found among natives. We conclude that clustering of phylogenetic relationships among alien and native species is only evident at small sampling scales in environments subject to high levels of disturbance (i.e., road sides) in the studied Pampean Grasslands, suggesting that environmental filtering plays an important role in local community assembly. Keywords: disturbance, land use, phylogenetic pattern, plant invasion, native communities