Global fern and lycophyte richness explained: how regional and local factors shape plot richness

Aim To disentangle the influence of environmental factors at different spatial grains (regional and local) on fern and lycophyte species richness and ask how regional and plot-level richness are related to each other. Location Global. Time Period Present. Major Taxa studied Ferns and lycophytes. Methods We explored fern and lycophyte species richness at two spatial grains, regional (hexagonal grid cells of 7666 km2) and plot-level (300–500 m2), in relation to environmental data at regional and local grains (the 7666-km2 hexagonal grid cells and 4-km2 square grid cells, respectively). For the regional grain, we obtained species richness data for 1243 spatial units and used them together with climatic, and topographical predictors to model global fern richness. For the plot-level grain, we collated a global dataset of nearly 83,000 vegetation plots with surface area in the range 300–500 m2 in which all fern and lycophyte species had been counted. We used structural equation model...