The role of population source and dominance on plant community diversity in a newly restored prairie

Ecological restoration provides an opportunity to test how abiotic and biotic filters influence community assembly and biodiversity.  Filters on community assembly that may be unique to restoration include human selection of: 1) relative abundance and composition of species in seed mixes and 2) population sources of seeds (i.e., local or selected genotypes) to be re-introduced.   We established experimental restorations using a split-plot design in two sites located at the same latitude but across a longitudinal precipitation gradient from Kansas to Illinois.  The whole plot treatment was source population (cultivar and non-cultivar) of the dominant grasses Andropogon gerardii, Schizachyrium scoparium, and Sorghastrum nutans.  Each whole plot contained a gradient of seeded diversity established by varying dominance of the grasses, with no change in species richness.  This framework was used to test whether population source and dominance of prairie grasses influence initial floristic composition during restoration.  In Kansas, seed source and dominance interacted (P=0.063) to affect diversity, and dominance of cultivars was inversely related to diversity (P<0.001, R²=0.28).  In Illinois, seeded dominance affected establishing plant diversity (P<0.001), but an opposite pattern between source population and diversity was observed.  Furthermore, dominance of the local ecotypes of native prairie grasses was inversely related to diversity (P=0.017, R²=0.19).  Overall, results indicate that anthropogenic filters of population source and introduced dominance can influence community structure even at the onset of restoration.