Fig. 2 Pairwise compositional dissimilarity among plant communities (turnover component, βturnover, based on Simpson index) along the 3200-km environmental gradient. These results were generated from the generalized dissimilarity model (GDM, for details see methods) based on presence/absence data. (a) Relationship between βturnover and environmental dissimilarity based on all the environmental variables (MAP, MAT, altitude, soil N, and soil P). (b) Relative importance of variables for explaining variation in βturnover. (c-h) Partial ecological distances (i.e. effects on βturnover) showing the individual effects of each variable on βturnover for species with large (blue) and small (yellow) genomes. The separation of plants into groups by genome size was based on the global median genome size value of terrestrial plants (2.5 pg/1C value) in the Kew database (seeMaterials and Methods ). Results for separation into groups based on the median value of our studied species (1.59 pg/1C value) are supplied in Fig. S3 . Locations on each line associated with larger values on the y-axis indicate an increased likelihood of observing that genome-size group at that value along the x-axis, and higher maxima in curves indicate larger effects associated with that variable overall.