Essential attributes of plant diversity and invasion studies

Most studies of plant diversity carefully evaluate species-environment relationships for a given set of plots and environmental gradients in a study area. Many investigators are now considering the effects of spatial autocorrelation on diversity patterns in an attempt to isolate the effects of “space” from other abiotic or biotic factors. A few studies are now investigating the role of habitat heterogeneity around their study plots or the effects of gamma diversity on alpha diversity in their plots. Here, we demonstrate that all of the factors above influence native and non-native species richness, and that all must be considered as essential elements of plant diversity and invasion studies. We present case studies that show: (1) how plot size affects our understanding of species-environment relationships; (2) how the spatial extent at which landscape heterogeneity is quantified affects species richness; (3) how gamma diversity (the regional species pool) affects local species accumulation; and (4) how all of these factors are influenced by spatial autocorrelation. In addition to considering each of these factors, there are significant interactions among the factors above that must be considered simultaneously if we are to effectively quantify native and non-native plant species patterns.