Species–area curves indicate the importance of habitats’ contributions to regional biodiversity

We examined species–area curves, species composition and similarity (Jaccardʹs coefficients), and species richness in 17 vegetation types to develop a composite index of a vegetation typeʹs contribution to regional species richness. We collected data from 1 to 1000 m2 scales in 147 nested plots in Rocky Mountain National Park, Colorado, USA to compare three species–area curve models’ abilities to estimate the number of species observed in each vegetation type. The log(species)–log(area) curve had the largest adjusted coefficients of determination (r2 values) in 12 of the 17 types, followed by the species–log(area) curve with five of the highest values. When the slopes of the curves were corrected for species overlap among plots with Jaccardʹs coefficients, the species–log(area) curves estimated values closest to those observed. We combined information from species–area curves and measures of heterogeneity with information on the area covered by each vegetation type and found that the types making the greatest contributions to regional biodiversity covered the smallest areas. This approach may provide an accurate and relatively rapid way to rank hotspots of plant diversity within regions of interest.