Effects of Manipulated Rainfall and Intraspecific Variation Within Dominant Species on Community Assembly: Insights From a Long-Term Grassland Restoration Experiment.

Grasslands converted to agricultural land use can be reestablished by sowing seeds of native species and temporal dynamics of diversity under altered climate can inform community assembly in the context of global change. We quantified three aspects of diversity (species richness, phylogenetic diversity, and functional diversity) in restored prairie plots sown with different ecotypes of two dominant grass species and manipulated rainfall to understand the relative importance of abiotic filtering and population source of dominant species on community assembly. We also evaluated the contributions of intra- and interspecific variations in functional traits across plots sown with different ecotypes of dominant species. Since the fourth year of community establishment, species richness decreased over time as dominant species gradually established. Phylogenetic and functional diversity was unaffected by the ecotypic sources of dominant species during restoration. Experimental drought did not affect species richness, phylogenetic, or functional diversity. Community structure in the grasslands was mainly shaped by intraspecific, within-population variation in the dominant species rather than by differences in traits among species. Our results showed that intraspecific biotic interactions contribute more than environmental filtering to community assembly in a tallgrass-dominated prairie ecosystem.