Scaling laws predict global microbial diversity
Scaling laws underpin unifying theories of biodiversity and are among the most predictively powerful relationships in biology. However, scaling laws developed for plants and animals often go untested or fail to hold for microorganisms. As a result, it is unclear whether scaling laws of biodiversity span evolutionarily distant domains of life that encompass all modes of metabolism and scales of abundance. Using a global-scale compilation of ~35,000 sites and ~5.6·106 species, we demonstrate similar rates of scaling in commonness and rarity across microorganisms and macroscopic plants and animals. We document a universal dominance scaling law that holds across 30 orders of magnitude, an unprecedented expanse that predicts the abundance of dominant ocean bacteria. In combining this scaling law with the lognormal model of species abundance, we predict that Earth is home to ~1012 microbial species. This estimate is also supported by the microbial richness scaling relationship we derive from the largest ever inventory of high-throughput molecular data. Microbial biodiversity seems greater than ever anticipated yet predictable from the smallest to the largest microbiome.