Worldwide evidence of a unimodal relationship between productivity and plant species richness

AbstractThe search for predictions of species diversity across environmental gradients has challenged ecologists for decades. The humped-back model (HBM) suggests that plant diversity peaks at intermediate productivity; at low productivity few species can tolerate the environmental stresses, and at high productivity a few highly competitive species dominate. Over time the HBM has become increasingly controversial, and recent studies claim to have refuted it. Here, by using data from coordinated surveys conducted throughout grasslands worldwide and comprising a wide range of site productivities, we provide evidence in support of the HBM pattern at both global and regional extents. The relationships described here provide a foundation for further research into the local, landscape, and historical factors that maintain biodiversity., Usage notesraw plot data from globally distributed sitesfraser_plotdata.csvR script for within_site_GLMs_Fig2A_TableS2within_site_GLMs_Fig2A_TableS2.RR script for Table_1_analyses_FigS1Table_1_analyses_FigS1.RR script for varied_grain_analyses_FigS2varied_grain_analyses_FigS2.RR script for HBmodels_FigS3HBmodels_FigS3.RR script for max_richness_FigS4max_richness_FigS4.RR script for within_site_GLMs_reduced_data_Figs_S5_2B_S6within_site_GLMs_reduced_data_Figs_S5_2B_S6.R