Using Large-Scale Integrative Analyses to Understand Global Patterns of Fern Diversity

It is well-known that the distribution of species diversity is spatially heterogeneous, but understanding the factors contributing to the formation of biodiversity hotspots remains a challenge. In this study, we quantify diversity and identify hotspots of species richness and endemism in ferns. We evaluate the drivers of global fern diversity by integrating over 800,000 georeferenced species occurrence records, a time-calibrated phylogeny of nearly 4,000 species, and seven climate and environmental layers. We find that Tropical and subtropical mountains harbor a disproportionate number of species relative to the land area they occupy; 58% of global species richness occur in eight principally montane hotspots together comprising just 7% of Earth's land area. Areas of high environmental heterogeneity harbor a disproportionate amount of fern species, and global patterns of extant fern diversity reflect the distribution of these areas, especially in mountains at lower latitudes. Persistence of ancient lineages in areas with long-term climatic stability helps explain exceptional endemism in regions such as Malasia.