Towards revealing the global diversity and community assembly of soil eukaryotes.

Soil fungi, protists, and animals (i.e., the eukaryome) play a critical role in key ecosystem functions in terrestrial ecosystems. Yet, we lack a holistic understanding of the processes shaping the global distribution of the eukaryome. We conducted a molecular analysis of 193 composite soil samples spanning the world's major biomes. Our analysis showed that the importance of selection processes was higher in the community assemblage of smaller-bodied and wider niche breadth organisms. Soil pH and mean annual precipitation were the primary determinants of the community structure of eukaryotic microbes and animals, respectively. We further found contrasting latitudinal diversity patterns and strengths for soil eukaryotic microbes and animals. Our results point to a potential link between body size and niche breadth of soil eukaryotes and the relative effect of ecological processes and environmental factors in driving their biogeographic patterns.